Breakdown resistance of refractory metals compared to copper

CERN Document Server

Taborelli, M; Kildemo, M

2004-01-01

The behaviour of Mo, W and Cu with respect to electrical breakdown in ultra high vacuum has been investigated by means of a capacitor discharge method. The maximum stable electric field without breakdown and the field enhancement factor, beta have been measured between electrodes of the same material in a sphere/plane geometry for anode and cathode, respectively. The maximum stable field increases as a function of the number of breakdown events for W and Mo. In contrast, no systematic increase is observed for Cu. The highest values obtained are typically 500 MV/m for W, 350 MV/m for Mo and only 180 MV/m for Cu. This conditioning, found for the refractory metals, corresponds to a simultaneous decrease of beta and is therefore related to the field emission properties of the surface and their modification upon sparking. Accordingly, high beta values and no applicable field increase occur for Cu even after repeated breakdown. The results are compared with RF breakdown experiments [1] performed on prototype 30 GHz...

Atmospheric pressure He-air plasma jet: Breakdown process and propagation phenomenon

International Nuclear Information System (INIS)

Begum, Asma; Laroussi, Mounir; Pervez, Mohammad Rasel

2013-01-01

In this paper He-discharge (plasma jet/bullet) in atmospheric pressure air and its progression phenomenon has been studied experimentally using ICCD camera, optical emission spectroscopy (OES) and calibrated dielectric probe measurements. The repetitive nanosecond pulse has applied to a plasma pencil to generate discharge in the helium gas channel. The discharge propagation speed was measured from the ICCD images. The axial electric field distribution in the plasma jet is inferred from the optical emission spectroscopic data and from the probe measurement. The correlation between the jet velocities, jet length with the pulse duration is established. It shows that the plasma jet is not isolated from the input voltage along its propagation path. The discharge propagation speed, the electron density and the local and average electric field distribution along the plasma jet axis predicted from the experimental results are in good agreement with the data predicted by numerical simulation of the streamer propagation presented in different literatures. The ionization phenomenon of the discharge predicts the key ionization parameters, such as speed, peak electric field in the front, and electron density. The maximum local electric field measured by OES is 95 kV/cm at 1.3 cm of the jet axis, and average EF measured by probe is 24 kV/cm at the same place of the jet. The average and local electron density estimated are in the order of 10 11 cm -3 and it reaches to the maximum of 10 12 cm -3 .

Breakdown voltage reduction by field emission in multi-walled carbon nanotubes based ionization gas sensor

Energy Technology Data Exchange (ETDEWEB)

Saheed, M. Shuaib M.; Muti Mohamed, Norani; Arif Burhanudin, Zainal, E-mail: zainabh@petronas.com.my [Centre of Innovative Nanostructures and Nanodevices, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia)

2014-03-24

Ionization gas sensors using vertically aligned multi-wall carbon nanotubes (MWCNT) are demonstrated. The sharp tips of the nanotubes generate large non-uniform electric fields at relatively low applied voltage. The enhancement of the electric field results in field emission of electrons that dominates the breakdown mechanism in gas sensor with gap spacing below 14 μm. More than 90% reduction in breakdown voltage is observed for sensors with MWCNT and 7 μm gap spacing. Transition of breakdown mechanism, dominated by avalanche electrons to field emission electrons, as decreasing gap spacing is also observed and discussed.

Atmospheric pressure He-air plasma jet: Breakdown process and propagation phenomenon

Energy Technology Data Exchange (ETDEWEB)

Begum, Asma [Independent University, Bangladesh, School of Engineering and Computer Science, Bashundhara, Dhaka (Bangladesh); Laroussi, Mounir [Old Dominion University, Department of Electrical and Computer Engineering, Norfolk, Virginia (United States); Pervez, Mohammad Rasel [Master Mind College, Department of Physics, Dhanmondi, Dhaka (Bangladesh)

2013-06-15

In this paper He-discharge (plasma jet/bullet) in atmospheric pressure air and its progression phenomenon has been studied experimentally using ICCD camera, optical emission spectroscopy (OES) and calibrated dielectric probe measurements. The repetitive nanosecond pulse has applied to a plasma pencil to generate discharge in the helium gas channel. The discharge propagation speed was measured from the ICCD images. The axial electric field distribution in the plasma jet is inferred from the optical emission spectroscopic data and from the probe measurement. The correlation between the jet velocities, jet length with the pulse duration is established. It shows that the plasma jet is not isolated from the input voltage along its propagation path. The discharge propagation speed, the electron density and the local and average electric field distribution along the plasma jet axis predicted from the experimental results are in good agreement with the data predicted by numerical simulation of the streamer propagation presented in different literatures. The ionization phenomenon of the discharge predicts the key ionization parameters, such as speed, peak electric field in the front, and electron density. The maximum local electric field measured by OES is 95 kV/cm at 1.3 cm of the jet axis, and average EF measured by probe is 24 kV/cm at the same place of the jet. The average and local electron density estimated are in the order of 10{sup 11} cm{sup -3} and it reaches to the maximum of 10{sup 12} cm{sup -3}.

Ionizing gas breakdown waves in strong electric fields.

Science.gov (United States)

Klingbeil, R.; Tidman, D. A.; Fernsler, R. F.

1972-01-01

A previous analysis by Albright and Tidman (1972) of the structure of an ionizing potential wave driven through a dense gas by a strong electric field is extended to include atomic structure details of the background atoms and radiative effects, especially, photoionization. It is found that photoionization plays an important role in avalanche propagation. Velocities, electron densities, and temperatures are presented as a function of electric field for both negative and positive breakdown waves in nitrogen.

A model of breakdown in parallel-plate detectors

International Nuclear Information System (INIS)

Fonte, P.

1996-01-01

Parallel-plate avalanche chambers (PPAC's) have many desirable properties, such as a fast, large area particle detector. However, the maximum gain is limited by a form of violent breakdown that limits the usefulness of this detector, despite its other evident qualities. The exact nature of this phenomenon is not yet sufficiently clear to sustain possible improvements. A previous experimental study is complemented in the present work by a quantitative model of the breakdown phenomenon in PPAC's, based on the streamer theory. The model reproduces well the peculiar behavior of the external current observed in PPAC's and resistive-plate chambers. Other breakdown properties measured in PPAC's are also well reproduced

Analysis of the modulation mechanisms of the electric field and breakdown performance in AlGaN/GaN HEMT with a T-shaped field-plate

Science.gov (United States)

Mao, Wei; Fan, Ju-Sheng; Du, Ming; Zhang, Jin-Feng; Zheng, Xue-Feng; Wang, Chong; Ma, Xiao-Hua; Zhang, Jin-Cheng; Hao, Yue

2016-12-01

A novel AlGaN/GaN high electron mobility transistor (HEMT) with a source-connected T-shaped field-plate (ST-FP HEMT) is proposed for the first time in this paper. The source-connected T-shaped field-plate (ST-FP) is composed of a source-connected field-plate (S-FP) and a trench metal. The physical intrinsic mechanisms of the ST-FP to improve the breakdown voltage and the FP efficiency and to modulate the distributions of channel electric field and potential are studied in detail by means of two-dimensional numerical simulations with Silvaco-ATLAS. A comparison to the HEMT and the HEMT with an S-FP (S-FP HEMT) shows that the ST-FP HEMT could achieve a broader and more uniform channel electric field distribution with the help of a trench metal, which could increase the breakdown voltage and the FP efficiency remarkably. In addition, the relationship between the structure of the ST-FP, the channel electric field, the breakdown voltage as well as the FP efficiency in ST-FP HEMT is analyzed. These results could open up a new effective method to fabricate high voltage power devices for the power electronic applications. Project supported by the National Natural Science Foundation of China (Grant Nos. 61574112, 61334002, 61306017, 61474091, and 61574110) and the Natural Science Basic Research Plan in Shaanxi Province, China (Grant No. 605119425012).

dc breakdown conditioning and breakdown rate of metals and metallic alloys under ultrahigh vacuum

CERN Document Server

Descoeudres, A; Calatroni, S; Taborelli, M; Wuensch, W

2009-01-01

RF accelerating structures of the Compact Linear Collider (CLIC) require a material capable of sustaining high electric field with a low breakdown rate and low induced damage. Because of the similarity of many aspects of DC and RF breakdown, a DC breakdown study is underway at CERN in order to test candidate materials and surface preparations, and have a better understanding of the breakdown mechanism under ultra-high vacuum in a simple setup. Conditioning speeds and breakdown fields of several metals and alloys have been measured. The average breakdown field after conditioning ranges from 100 MV/m for Al to 850 MV/m for stainless steel, and is around 170 MV/m for Cu which is the present base-line material for CLIC structures. The results indicate clearly that the breakdown field is limited by the cathode. The presence of a thin cuprous oxide film at the surface of copper electrodes significantly increases the breakdown field. On the other hand, the conditioning speed of Mo is improved by removing oxides at t...

High breakdown voltage quasi-two-dimensional β-Ga2O3 field-effect transistors with a boron nitride field plate

Science.gov (United States)

Bae, Jinho; Kim, Hyoung Woo; Kang, In Ho; Yang, Gwangseok; Kim, Jihyun

2018-03-01

We have demonstrated a β-Ga2O3 metal-semiconductor field-effect transistor (MESFET) with a high off-state breakdown voltage (344 V), based on a quasi-two-dimensional β-Ga2O3 field-plated with hexagonal boron nitride (h-BN). Both the β-Ga2O3 and h-BN were mechanically exfoliated from their respective crystal substrates, followed by dry-transfer onto a SiO2/Si substrate for integration into a high breakdown voltage quasi-two-dimensional β-Ga2O3 MESFETs. N-type conducting behavior was observed in the fabricated β-Ga2O3 MESFETs, along with a high on/off current ratio (>106) and excellent current saturation. A three-terminal off-state breakdown voltage of 344 V was obtained, with a threshold voltage of -7.3 V and a subthreshold swing of 84.6 mV/dec. The distribution of electric fields in the quasi-two-dimensional β-Ga2O3 MESFETs was simulated to analyze the role of the dielectric h-BN field plate in improving the off-state breakdown voltage. The stability of the field-plated β-Ga2O3 MESFET in air was confirmed after storing the MESFET in ambient air for one month. Our results pave the way for unlocking the full potential of β-Ga2O3 for use in a high-power nano-device with an ultrahigh breakdown voltage.

dc breakdown conditioning and breakdown rate of metals and metallic alloys under ultrahigh vacuum

Directory of Open Access Journals (Sweden)

A. Descoeudres

2009-03-01

Full Text Available The rf accelerating structures of the Compact Linear Collider (CLIC require a material capable of sustaining high electric field with a low breakdown rate and low induced damage. Because of the similarity of many aspects of dc and rf breakdown, a dc breakdown study is underway at CERN in order to test candidate materials and surface preparations, and have a better understanding of the breakdown mechanism under ultrahigh vacuum in a simple setup. Conditioning speeds and breakdown fields of several metals and alloys have been measured. The average breakdown field after conditioning ranges from 100  MV/m for Al to 850  MV/m for stainless steel, and is around 170  MV/m for Cu which is the present base-line material for CLIC structures. The results indicate clearly that the breakdown field is limited by the cathode. The presence of a thin cuprous oxide film at the surface of copper electrodes significantly increases the breakdown field. On the other hand, the conditioning speed of Mo is improved by removing oxides at the surface with a vacuum heat treatment, typically at 875°C for 2 hours. Surface finishing treatments of Cu samples only affect the very first breakdowns. More generally, surface treatments have an effect on the conditioning process itself, but not on the average breakdown field reached after the conditioning phase. In analogy to rf, the breakdown probability has been measured in dc with Cu and Mo electrodes. The dc data show similar behavior as rf as a function of the applied electric field.

New mechanism of cluster-field evaporation in rf breakdown

Directory of Open Access Journals (Sweden)

Z. Insepov

2004-12-01

Full Text Available Using a simple field evaporation model and molecular dynamics simulations of nanoscale copper tip evolution in a high electric field gradient typical for linacs, we have studied a new mechanism for rf-field evaporation. The mechanism consists of simultaneous (collective field evaporation of a large group of tip atoms in high-gradient fields. Thus, evaporation of large clusters is energetically more favorable when compared with the conventional, “one-by-one” mechanism. The studied mechanism could also be considered a new mechanism for the triggering of rf-vacuum breakdown. This paper discusses the mechanism and the experimental data available for electric field evaporation of field-emission microscopy tips.

Localization of rf breakdowns in a standing wave cavity

Directory of Open Access Journals (Sweden)

Faya Wang

2009-04-01

Full Text Available At SLAC, a five-cell, normal-conducting, L-band (1.3 GHz, standing-wave (SW cavity was built as a prototype positron capture accelerator for the ILC. The structure met the ILC gradient goal but required extensive rf processing. When rf breakdowns occurred, a large variation was observed in the decay rate of the stored energy in the cavity after the input power was shut off. It appeared that the breakdowns were isolating sections of the cavity, and that the trapped energy in those sections was then partitioned among its natural modes, producing a distinct beating pattern during the decay. To explore this phenomenon further, an equivalent circuit model of cavity was created that reproduces well its normal operating characteristics. The model was then used to compute the spectra of trapped energy for different numbers of isolated cells. The resulting modal patterns agree well with those of the breakdown data, and thus such a comparison appears to provide a means of identifying the irises on which the breakdowns occurred.

Experimental Study of Magnetic Field Production and Dielectric Breakdown of Auto-Magnetizing Liners

Science.gov (United States)

Shipley, Gabriel; Awe, Thomas; Hutchinson, Trevor; Hutsel, Brian; Slutz, Stephen; Lamppa, Derek

2017-10-01

AutoMag liners premagnetize the fuel in MagLIF targets and provide enhanced x-ray diagnostic access and increased current delivery without requiring external field coils. AutoMag liners are composite liners made with discrete metallic helical conduction paths separated by insulating material. First, a low dI/dt ``foot'' current pulse (1 MA in 100 ns) premagnetizes the fuel. Next, a higher dI/dt pulse with larger induced electric field initiates breakdown on the composite liner's; surface, switching the current from helical to axial to implode the liner. Experiments on MYKONOS have tested the premagnetization and breakdown phases of AutoMag and demonstrate axial magnetic fields above 90 Tesla for a 550 kA peak current pulse. Electric fields of 17 MV/m have been generated before breakdown. AutoMag may enhance MagLIF performance by increasing the premagnetization strength significantly above 30 T, thus reducing thermal-conduction losses and mitigating anomalous diffusion of magnetic field out of hotter fuel regions, by, for example, the Nernst thermoelectric effect. This project was funded in part by Sandia's Laboratory Directed Research and Development Program (Projects No. 200169 and 195306).

Statistics of vacuum breakdown in the high-gradient and low-rate regime

Science.gov (United States)

Wuensch, Walter; Degiovanni, Alberto; Calatroni, Sergio; Korsbäck, Anders; Djurabekova, Flyura; Rajamäki, Robin; Giner-Navarro, Jorge

2017-01-01

In an increasing number of high-gradient linear accelerator applications, accelerating structures must operate with both high surface electric fields and low breakdown rates. Understanding the statistical properties of breakdown occurrence in such a regime is of practical importance for optimizing accelerator conditioning and operation algorithms, as well as of interest for efforts to understand the physical processes which underlie the breakdown phenomenon. Experimental data of breakdown has been collected in two distinct high-gradient experimental set-ups: A prototype linear accelerating structure operated in the Compact Linear Collider Xbox 12 GHz test stands, and a parallel plate electrode system operated with pulsed DC in the kV range. Collected data is presented, analyzed and compared. The two systems show similar, distinctive, two-part distributions of number of pulses between breakdowns, with each part corresponding to a specific, constant event rate. The correlation between distance and number of pulses between breakdown indicates that the two parts of the distribution, and their corresponding event rates, represent independent primary and induced follow-up breakdowns. The similarity of results from pulsed DC to 12 GHz rf indicates a similar vacuum arc triggering mechanism over the range of conditions covered by the experiments.

High breakdown electric field in β-Ga2O3/graphene vertical barristor heterostructure

Science.gov (United States)

Yan, Xiaodong; Esqueda, Ivan S.; Ma, Jiahui; Tice, Jesse; Wang, Han

2018-01-01

In this work, we study the high critical breakdown field in β-Ga2O3 perpendicular to its (100) crystal plane using a β-Ga2O3/graphene vertical heterostructure. Measurements indicate a record breakdown field of 5.2 MV/cm perpendicular to the (100) plane that is significantly larger than the previously reported values on lateral β-Ga2O3 field-effect-transistors (FETs). This result is compared with the critical field typically measured within the (100) crystal plane, and the observed anisotropy is explained through a combined theoretical and experimental analysis.

A Model for the Onset of Vortex Breakdown

Science.gov (United States)

Mahesh, K.

1996-01-01

A large body of information exists on the breakdown of incompressible streamwise vortices. Less is known about vortex breakdown at high speeds. An interesting example of supersonic vortex breakdown is the breakdown induced by the interaction of vortices with shock waves. The flow in supersonic engine inlets and over high-speed delta wings constitute technologically important examples of this phenomenon, which is termed 'shock-induced vortex breakdown'. In this report, we propose a model to predict the onset of shock-induced vortex breakdown. The proposed model has no adjustable constants, and is compared to both experiment and computation. The model is then extended to consider two other problems: the breakdown of a free compressible vortex, and free incompressible vortex breakdown. The same breakdown criterion is used in all three problems to predict the onset of breakdown. Finally, a new breakdown map is proposed that allows the simultaneous comparison of data from flows ranging from incompressible breakdown to breakdown induced by a shock wave.

The inception of pulsed discharges in air: simulations in background fields above and below breakdown

Science.gov (United States)

Sun, Anbang; Teunissen, Jannis; Ebert, Ute

2014-11-01

We investigate discharge inception in air, in uniform background electric fields above and below the breakdown threshold. We perform 3D particle simulations that include a natural level of background ionization in the form of positive and \\text{O}2- ions. In background fields below breakdown, we use a strongly ionized seed of electrons and positive ions to enhance the field locally. In the region of enhanced field, we observe the growth of positive streamers, as in previous simulations with 2D plasma fluid models. The inclusion of background ionization has little effect in this case. When the background field is above the breakdown threshold, the situation is very different. Electrons can then detach from \\text{O}2- and start ionization avalanches in the whole volume. These avalanches together create one extended discharge, in contrast to the ‘double-headed’ streamers found in many fluid simulations.

The Multistability of Technological Breakdowns in Education

DEFF Research Database (Denmark)

Andersen, Bjarke Lindsø; Tafdrup, Oliver Alexander

2017-01-01

Introduction Everyone who is involved with modern technological artefacts such as computers, software and tablets has experienced situations where the artefacts suddenly cease to function properly. This is commonly known as a technological breakdown. Within education and the praxis of teaching...... technological breakdowns become a more and more ubiquitous phenomenon due to the rapid increase of technological artefacts utilized for educational purposes (Riis, 2012). The breakdowns impact the educational practice with consequences ranging from creating small obstacles to rendering it impossible to conduct...... successful teaching. Thus, knowing how to cope with technological breakdowns is a pivotal part of being a technological literate....

Pulsed and streamer discharges in air above breakdown electric field

NARCIS (Netherlands)

A.B. Sun (Anbang); H.J. Teunissen (Jannis); U. M. Ebert (Ute)

2013-01-01

htmlabstractA 3D particle model is developed to investigate the streamer formation in electric fields above the breakdown threshold, in atmospheric air (1bar, 300 Kelvin). Adaptive particle management, adaptive mesh refinement and parallel computing techniques are used in the code. Photoionization

Influence of temperature on current-induced domain wall motion and its Walker breakdown

International Nuclear Information System (INIS)

Fan, Lvchao; Hu, Jingguo; Su, Yuanchang; Zhu, Jinrong

2016-01-01

The current-driven domain wall propagation along a thin ferromagnetic strip with thermal field is studied by means of micromagnetic simulations. The results show that the velocity of domain wall is almost independent of temperature until Walker breakdown happened. However the thermal field can suppress Walker breakdown and makes domain wall move faster. Further analysis indicates that the thermal field tends to keep the out-of-plane magnetic moment of the domain wall stay in high value, which can promote domain wall motion and suppress the Walker breakdown by breaking the period of domain wall transformation. - Highlights: • Influences of temperature on the displacement and the velocity of DW are shown. • The suppression of Walker breakdown by temperature is given. • The reason for suppressing Walker breakdown is analyzed. • The breaking transformation period of Walker breakdown by temperature is given.

Statistics of vacuum breakdown in the high-gradient and low-rate regime

Directory of Open Access Journals (Sweden)

Walter Wuensch

2017-01-01

Full Text Available In an increasing number of high-gradient linear accelerator applications, accelerating structures must operate with both high surface electric fields and low breakdown rates. Understanding the statistical properties of breakdown occurrence in such a regime is of practical importance for optimizing accelerator conditioning and operation algorithms, as well as of interest for efforts to understand the physical processes which underlie the breakdown phenomenon. Experimental data of breakdown has been collected in two distinct high-gradient experimental set-ups: A prototype linear accelerating structure operated in the Compact Linear Collider Xbox 12 GHz test stands, and a parallel plate electrode system operated with pulsed DC in the kV range. Collected data is presented, analyzed and compared. The two systems show similar, distinctive, two-part distributions of number of pulses between breakdowns, with each part corresponding to a specific, constant event rate. The correlation between distance and number of pulses between breakdown indicates that the two parts of the distribution, and their corresponding event rates, represent independent primary and induced follow-up breakdowns. The similarity of results from pulsed DC to 12 GHz rf indicates a similar vacuum arc triggering mechanism over the range of conditions covered by the experiments.

Lowering effect of radioactive irradiation on breakdown voltage and electron avalanche pulse characteristics

International Nuclear Information System (INIS)

Kawahashi, Akira; Nakano, Toru; Hosokawa, Tatsuzo; Miyoshi, Yosinori.

1976-01-01

In the time resolving measurement of the growing process and breakdown of electron avalanche in a gap of uniform electric field, the phenomenon that DC breakdown voltage slightly lowered was observed when β ray was irradiated as the initial electron source, as compared with unirradiated condition. Beta source used is 90 Sr- 90 Y of 2 mCi in radiative equilibrium. The experimental results and the examination are described in detail. In brief, the remarkable superposition of succeeding avalanche pulse over the preceeding avalanche pulse waveform was observed under the gap condition in which the breakdown voltage decreased in β-ray irradiation. Thus this superposition of avalanche pulses is considered as one of the causes of the breakdown voltage reduction. When β source is used as the initial electron source, the number of supplied initial electrons is very large as compared with unity, and at the same time, a great number of initial electrons can be supplied within the diffusion radius r of avalanche. Then the effect of initial electron number n 0 was considered by employing a diagram for breakdown scheme. The transition from Townsend type breakdown to streamer type breakdown occurs owing to increasing n 0 , and in that condition, the breakdown voltage lowers slightly. (Wakatsuki, Y)

High frequency breakdown voltage

International Nuclear Information System (INIS)

Chu, Thanh Duy.

1992-03-01

This report contains information about the effect of frequency on the breakdown voltage of an air gap at standard pressure and temperature, 76 mm Hg and O degrees C, respectively. The frequencies of interest are 47 MHz and 60 MHz. Additionally, the breakdown in vacuum is briefly considered. The breakdown mechanism is explained on the basis of collision and ionization. The presence of the positive ions produced by ionization enhances the field in the gap, and thus determines the breakdown. When a low-frequency voltage is applied across the gap, the breakdown mechanism is the same as that caused by the DC or static voltage. However, when the frequency exceeds the first critical value f c , the positive ions are trapped in the gap, increasing the field considerably. This makes the breakdown occur earlier; in other words, the breakdown voltage is lowered. As the frequency increases two decades or more, the second critical frequency, f ce , is reached. This time the electrons start being trapped in the gap. Those electrons that travel multiple times across the gap before reaching the positive electrode result in an enormous number of electrons and positive ions being present in the gap. The result is a further decrease of the breakdown voltage. However, increasing the frequency does not decrease the breakdown voltage correspondingly. In fact, the associated breakdown field intensity is almost constant (about 29 kV/cm).The reason is that the recombination rate increases and counterbalances the production rate, thus reducing the effect of the positive ions' concentration in the gap. The theory of collision and ionization does not apply to the breakdown in vacuum. It seems that the breakdown in vacuum is primarily determined by the irregularities on the surfaces of the electrodes. Therefore, the effect of frequency on the breakdown, if any, is of secondary importance

Interpretation of Mason's equation in terms of measurable electrochemical-etching parameters governing the dielectric breakdown phenomenon

International Nuclear Information System (INIS)

Al-Najjar, S.A.R.; Durrani, S.A.

1986-01-01

A new interpretation of Mason's equation, as applicable to the electrochemical etching (ECE) of tracks in polymers, is presented in terms of physically meaningful track-etching parameters. The values of these parameters have been experimentally obtained by irradiating CR-39 foils with heavy ions ( 238 U and 129 Xe) and α-particles of various energies, and applying chemical pre-etching (CPE), followed by ECE in steps, with increasing electric field until the 'treeing' breakdown is initiated. A value of 1.19 MV cm -1 is obtained for the intrinsic electrical breakdown stress of CR-39. It is found that the track radius r used in Mason's equation is related to the radius rsub(Θ) of a sphere, inscribed within the etch cone, whose lowest point is at a fixed distance lsub(o) above the cone tip, with lsub(o) ≅ 1.75 μm for α-particle tracks of energies 2-5.5 MeV, such that r = 0.43 + rsub(Θ) (in μm). (author)

Analysis of low-pressure dc breakdown in nitrogen between two spherical iron electrodes

International Nuclear Information System (INIS)

Pejovic, Momcilo M.; Nesic, Nikola T.; Pejovic, Milic M.

2006-01-01

The influence of afterglow period τ, voltage increase rate k, and electrode gap d on breakdown voltage U b for a nitrogen-filled tube with spherical electrodes of diameter D>>d and p=6.5 mbar has been investigated. The data for the breakdown voltage were obtained for the case when there is a presence of N( 4 S) atoms, which release secondary electrons via recombination on the cathode. By fitting the experimental data of breakdown voltage mean values as a function of the voltage increase rate, the static breakdown voltages for afterglow periods of 15 and 100 s were estimated. The electrical field as a function of the electrode gap using breakdown voltage mean values was also determined. It is shown that experimental results of the breakdown voltage mean value as a function of pd in the interval of d from 0.82 to 1.62 mm can be very well described with Paschen's law, valid for the case of parallel-plate electrodes

New phenomenology of gas breakdown in DC and RF fields

Science.gov (United States)

Petrović, Zoran Lj; Sivoš, Jelena; Savić, Marija; Škoro, Nikola; Radmilović Radenović, Marija; Malović, Gordana; Gocić, Saša; Marić, Dragana

2014-05-01

This paper follows a review lecture on the new developments in the field of gas breakdown and low current discharges, usually covered by a form of Townsend's theory and phenomenology. It gives an overview of a new approach to identifying which feedback agents provide breakdown, how to model gas discharge conditions and reconcile the results with binary experiments and how to employ that knowledge in modelling gas discharges. The next step is an illustration on how to record volt-ampere characteristics and use them on one hand to obtain the breakdown voltage and, on the other, to identify the regime of operation and model the secondary electron yields. The second aspect of this section concerns understanding the different regimes, their anatomy, how those are generated and how free running oscillations occur. While temporal development is the most useful and interesting part of the new developments, the difficulty of presenting the data in a written form precludes an easy publication and discussion. Thus, we shall only mention some of the results that stem from these measurements. Most micro discharges operate in DC albeit with complex geometries. Thus, parallel plate micro discharge measurements were needed to establish that Townsend's theory, with all its recent extensions, is still valid until some very small gaps. We have shown, for example, how a long-path breakdown puts in jeopardy many experimental observations and why a flat left-hand side of the Paschen curve often does not represent good physics. We will also summarize a kinetic representation of the RF breakdown revealing a somewhat more complex picture than the standard model. Finally, we will address briefly the breakdown in radially inhomogeneous conditions and how that affects the measured properties of the discharge. This review has the goal of summarizing (rather than developing details of) the current status of the low-current DC discharges formation and operation as a discipline which, in spite of

Rf breakdown studies in room temperature electron linac structures

International Nuclear Information System (INIS)

Loew, G.A.; Wang, J.W.

1988-05-01

This paper is an overall review of studies carried out by the authors and some of their colleagues on RF breakdown, Field Emission and RF processing in room temperature electron linac structure. The motivation behind this work is twofold: in a fundamental way, to contribute to the understanding of the RF breakdown phenomenon, and as an application, to determine the maximum electric field gradient that can be obtained and used safely in future e/sup +-/ linear colliders. Indeed, the next generation of these machines will have to reach into the TeV (10 12 eV) energy range, and the accelerating gradient will be to be of the crucial parameters affecting their design, construction and cost. For a specified total energy, the gradient sets the accelerator length, and once the RF structure, frequency and pulse repetition rate are selected, it also determines the peak and average power consumption. These three quantities are at the heart of the ultimate realizability and cost of these accelerators. 24 refs., 19 figs., 4 tabs

Voltage breakdown on niobium and copper surfaces

International Nuclear Information System (INIS)

Werner, G.R.; Padamsee, H.; Betzwieser, J.C.; Liu, Y.G.; Rubin, K.H.R.; Shipman, J.E.; Ying, L.T.

2003-01-01

Experiments have shown that voltage breakdown in superconducting niobium RF cavities is in many ways similar to voltage breakdown on niobium cathodes in DC voltage gaps; most striking are the distinctive starburst patterns and craters that mark the site of voltage breakdown in both superconducting cavities and DC vacuum gaps. Therefore, we can learn much about RF breakdown from simpler, faster DC experiments. We have direct evidence, in the form of before'' and ''after'' pictures, that breakdown events caused by high surface electric fields occur with high probability at contaminant particles on surfaces. Although the pre-breakdown behavior (field emission) seems to depend mostly on the contaminant particles present and little on the substrate, the breakdown event itself is greatly affected by the substrate-niobium, heavily oxidized niobium, electropolished copper, and diamond-machined copper cathodes lead to different kinds of breakdown events. By studying DC voltage breakdown we hope to learn more details about the processes involved in the transition from field emission to catastrophic arcing and the cratering of the surface; as well as learning how to prevent breakdown, we would like to learn how to cause breakdown, which could be important when ''processing'' cavities to reduce field emission. (author)

Heavy-ion interactions in relativistic mean-field models

International Nuclear Information System (INIS)

Rashdan, M.

1996-01-01

The interaction potential between spherical nuclei and the elastic scattering cross section are calculated within relativistic mean-field (linear and non-linear) models, using a generalized relativistic local density approximation. The nuclear densities are calculated self-consistently from the solution of the relativistic mean-field equations. It is found that both the linear and non-linear models predict the characteristic switching-over phenomenon of the heavy-ion nuclear potential, where the potential gets attraction with increasing energy up to some value where it reverses this behaviour. The non-linear NLC model predicts a deeper potential than the linear LW model. The elastic scattering cross section calculated within the non-linear NLC model is in better agreement with experiments than that calculated within the linear LW model. (orig.)

Acoustic emission and magnification of atomic lines resolution for laser breakdown of salt water in ultrasound field

International Nuclear Information System (INIS)

Bulanov, Alexey V.; Nagorny, Ivan G.

2015-01-01

Researches of the acoustic effects accompanying optical breakdown in a water, generated by the focused laser radiation with power ultrasound have been carried out. Experiments were performed by using 532 nm pulses from Brilliant B Nd:YAG laser. Acoustic radiation was produced by acoustic focusing systems in the form hemisphere and ring by various resonance frequencies of 10.7 kHz and 60 kHz. The experimental results are obtained, that show the sharply strengthens effects of acoustic emission from a breakdown zone by the joint influence of a laser and ultrasonic irradiation. Essentially various thresholds of breakdown and character of acoustic emission in fresh and sea water are found out. The experimental result is established, testifying that acoustic emission of optical breakdown of sea water at presence and at absence of ultrasound essentially exceeds acoustic emission in fresh water. Atomic lines of some chemical elements like a Sodium, Magnesium and so on were investigated for laser breakdown of water with ultrasound field. The effect of magnification of this lines resolution for salt water in ultrasound field was obtained

Electrical breakdown in vacuum

International Nuclear Information System (INIS)

Beukema, G.P.

1980-01-01

The main part of this thesis is dedicated to the field enhancement factor; in particular to the study of the origin, alteration and influence on the breakdown properties of different materials. This work required the examination of large surface areas on the same microscopic scale on which the relevant phenomena occur. (Pre)-breakdown measurements are described in which the anode condition does not play a role in the initiation of a breakdown, while the cathode can be considered as a broad-area electrode. The influence of adsorbed gases on pre-breakdown currents is investigated. It is shown that ions, released by field emission electrons from adsorbed layers on the anode change the emitting properties of a well-conditioned cathode if the current density at the anode is small. A new experimental arrangement is outlined to better distinguish between the different parameters which are important for the initiation of electrical breakdown. Comparative measurements between stainless steel and titanium electrodes are described to study the influence of either the cathode or the anode upon the initiation of a breakdown. (Auth.)

Discharge breakdown in the EXTRAP configuration

International Nuclear Information System (INIS)

Drake, J.R.

1982-02-01

The breakdown of a discharge in a linear EXTRAP configuration has been studied experimentally. In this configuration the breakdown occurs along the zero B-field line, which is the axis of the linear octupole magnetic field, between the anode and cathode which constitute the ends of the linear device. Breakdown could be described by a modified Townsend criterion which included additional electron losses due to the presence of the B-field transverse to the discharge. (author)

Comparative Studies of High-Gradient Rf and Dc Breakdowns

CERN Document Server

Kovermann, Jan Wilhelm; Wuensch, Walter

2010-01-01

The CLIC project is based on normal-conducting high-gradient accelerating structures with an average accelerating gradient of 100 MV/m. The maximum achievable gradient in these structures is limited by the breakdown phenomenon. The physics of breakdowns is not yet fully understood quantitatively. A full knowledge could have strong impact on the design, material choice and construction of rf structures. Therefore, understanding breakdowns has great importance to reaching a gradient of 100MV/m with an acceptable breakdown probability. This thesis addresses the physics underlying the breakdown effect, focusing on a comparison of breakdowns in rf structures and in a dc spark setup. The dc system is simpler, easier to benchmark against simulations, with a faster turnaround time, but the relationship to rf breakdown must be established. To do so, an experimental approach based on optical diagnostics and electrical measurements methods was made. Following an introduction into the CLIC project, a general theoretical ...

Experimental study of DC vacuum breakdown and application to high-gradient accelerating structures for CLIC

CERN Document Server

Shipman, Nicholas; Jones, Roger

2016-01-01

The compact linear collider (CLIC) is a leading candidate for the next generation high energy linear collider. As any breakdown would result in a partial or full loss of luminosity for the pulse in which it occurs, obtaining a low breakdown rate in CLIC accelerating structures is a critical requirement for the successful operation of the proposed collider. This thesis presents investigations into the breakdown phenomenon primarily in the low breakdown rate regime of interest to CLIC, performed using the CERN DC spark systems between 2011 and 2014. The design, construction and commissioning of several new pieces of hardware, as well as the development of improved techniques to measuring the inter-electrode gap distance are detailed. These hardware improvements were fundamental in enabling the exciting new experiments mentioned below, which in turn have provided significant additional insight into the phenomenon of breakdown. Experiments were performed to measure fundamental parameters of individual breakdowns...

Superconductivity and electronic structure of superpure niobium. 3. Magnetoconductivity and magnetic breakdown in large magnetic fields

International Nuclear Information System (INIS)

Alekseevskij, N.E.; Nizhankovskij, V.I.; Bertel', K.-X.

1976-01-01

Measurements have been of electric conductivity and magnetoresistance of niobium monocrystals with various orientations in helium and hydrogen temperature regions in steady-state magnetic fields of up to 175 ke. At helium temperatures the resistance is shown to be proportional to the square of temperature. A significant longitudinal magnetoresistance of niobium has been established, depending on the sample orientation. Its initiation is attributed to the open nature of the niobium Fermi surface. As a result of studying the lateral magnetoresistance in fields of up to 92 ke, a stereographic projection of niobium open directions has been constructed. Open trajectories exist both in two-dimensional regions around the directions [100] and [111] and along the symmetry lines. Studies conducted in fields of up to 175 ke have revealed a magnetic break- own leading to the conversion of the open trajectories to the closed ones. A comprehensive picture of the magnetic break-down in niobium has been obtained, and on the basis of the coherent model an expression has been derived describing the impact of this break-down on the resistance. Comparison between experimental and theoretical dependences of the magnetoresistance on the field characteristics has provided the value of the break-down field H 0 =280 ke

Initiation of vacuum breakdown and failure mechanism of the carbon nanotube during thermal field emission

Science.gov (United States)

Dan, Cai; Lie, Liu; Jin-Chuan, Ju; Xue-Long, Zhao; Hong-Yu, Zhou; Xiao, Wang

2016-04-01

The carbon nanotube (CNT)-based materials can be used as vacuum device cathodes. Owing to the excellent field emission properties of CNT, it has great potentials in the applications of an explosive field emission cathode. The falling off of CNT from the substrate, which frequently appears in experiments, restricts its application. In addition, the onset time of vacuum breakdown limits the performance of the high-power explosive-emission-cathode-based diode. In this paper, the characteristics of the CNT, electric field strength, contact resistance and the kind of substrate material are varied to study the parameter effects on the onset time of vacuum breakdown and failure mechanism of the CNT by using the finite element method. Project supported by the National Natural Science Foundation of China (Grant Nos. 11305263 and 61401484).

Gauge theories as theories of spontaneous breakdown

International Nuclear Information System (INIS)

Ivanov, E.A.; Ogievetsky, V.I.

1976-01-01

Any gauge theory is proved to arise from spontaneous breakdown of symmetry under certain infinite parameter group, the corresponding gauge field being the Goldstone field by which this breakdown is accompanied

Effect of neutron irradiation on the breakdown voltage of power MOSFET's

International Nuclear Information System (INIS)

Hasan, S.M.Y.; Kosier, S.L.; Schrimpf, R.D.; Galloway, K.F.

1994-01-01

The effect of neutron irradiation on power metal-oxide-semiconductor field effect transistor (power MOSFET) breakdown voltage has been investigated. Transistors with various breakdown voltage ratings were irradiated in a TRIGA nuclear reactor with cumulative fluence levels up to 5 x 10 14 neutrons/cm 2 (1 MeV equivalent). Noticeable increases in the breakdown voltages are observed in n-type MOSFET's after 10 13 neutrons/cm 2 and in p-type MOSFETs after 10 12 neutrons/cm 2 . An increase in breakdown voltage of as much as 30% is observed after 5 x 10 14 neutrons/cm 2 . The increase in breakdown voltage is attributed to the neutron-irradiation-induced defects which decrease the mean free path and trap majority carriers in the space charge region. The effect of positive trapped oxide charge due to concomitant gamma radiation and the effect of the termination structure on the increase in breakdown voltage are considered. An empirical model is presented to predict the value of the breakdown voltage as a function of neutron fluence

A Coaxial Vortex Ring Model for Vortex Breakdown

OpenAIRE

Blackmore, Denis; Brons, Morten; Goullet, Arnaud

2008-01-01

A simple - yet plausible - model for B-type vortex breakdown flows is postulated; one that is based on the immersion of a pair of slender coaxial vortex rings in a swirling flow of an ideal fluid rotating around the axis of symmetry of the rings. It is shown that this model exhibits in the advection of passive fluid particles (kinematics) just about all of the characteristics that have been observed in what is now a substantial body of published research on the phenomenon of vortex breakdown....

Pre-breakdown processes in a dielectric fluid in inhomogeneous pulsed electric fields

Energy Technology Data Exchange (ETDEWEB)

Shneider, Mikhail N., E-mail: m.n.shneider@gmail.com [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Pekker, Mikhail [MMSolution, 6808 Walker Street, Philadelphia, Pennsylvania 19135 (United States)

2015-06-14

We consider the development of pre-breakdown cavitation nanopores appearing in the dielectric fluid under the influence of the electrostrictive stresses in the inhomogeneous pulsed electric field. It is shown that three characteristic regions can be distinguished near the needle electrode. In the first region, where the electric field gradient is greatest, the cavitation nanopores, occurring during the voltage nanosecond pulse, may grow to the size at which an electron accelerated by the field inside the pores can acquire enough energy for excitation and ionization of the liquid on the opposite pore wall, i.e., the breakdown conditions are satisfied. In the second region, the negative pressure caused by the electrostriction is large enough for the cavitation initiation (which can be registered by optical methods), but, during the voltage pulse, the pores do not reach the size at which the potential difference across their borders becomes sufficient for ionization or excitation of water molecules. And, in the third, the development of cavitation is impossible, due to an insufficient level of the negative pressure: in this area, the spontaneously occurring micropores do not grow and collapse under the influence of surface tension forces. This paper discusses the expansion dynamics of the cavitation pores and their most probable shape.

Dispersion of breakdown voltage of liquid helium

International Nuclear Information System (INIS)

Ishii, Itaru; Noguchi, Takuya

1978-01-01

As for the electrical insulation characteristics of liquid helium, the discrepancy among the measured values by each person is very large even in the fundamental DC breakdown voltage in uniform electric field. The dispersion of experimental values obtained in the experiments by the same person is also large. Hereafter, the difference among the mean values obtained by each experimenter will be referred to as ''deviation of mean values'', and the dispersion of measured values around the mean value obtained by the same person as ''deviation around the man value''. The authors have mainly investigated on the latter experimentally. The cryostat was made of stainless steel, and the innermost helium chamber was of 500 mm I.D. and approximately 1200 mm deep. The high voltage electrode was of brass sphere of 25 mm diameter, and the low voltage electrode was of brass plate. The experiment was conducted for liquid helium boiling at 4.2 K and 1 atm, and the breakdown voltage and time lag were measured by applying the approximately square wave impulses of fast rise and long tail, ramp and DC voltages. The cause of the deviation of mean values may be the presence of impurity particles or the effect of electrode shape. As for the deviation around the mean value, the dispersion is large, and its standard deviation may amount to 10 to 20% of the man value. The dispersion is not due to the statistical time lag, but is due to parameters that vary with breakdown. (Wakatsuki, Y.)

A new SOI high-voltage device with a step-thickness drift region and its analytical model for the electric field and breakdown voltage

International Nuclear Information System (INIS)

Luo Xiaorong; Zhang Wei; Zhang Bo; Li Zhaoji; Yang Shouguo; Zhan Zhan; Fu Daping

2008-01-01

A new SOI high-voltage device with a step-thickness drift region (ST SOI) and its analytical model for the two-dimension electric field distribution and the breakdown voltage are proposed. The electric field in the drift region is modulated and that of the buried layer is enhanced by the variable thickness SOI layer, thereby resulting in the enhancement of the breakdown voltage. Based on the Poisson equation, the expression for the two-dimension electric field distribution is presented taking the modulation effect into account, from which the RESURF (REduced SURface Field) condition and the approximate but explicit expression for the maximal breakdown voltage are derived. The analytical model can explain the effects of the device parameters, such as the step height and the step length of the SOI layer, the doping concentration and the buried oxide thickness, on the electric field distribution and the breakdown voltage. The validity of this model is demonstrated by a comparison with numerical simulations. Improvement on both the breakdown voltage and the on-resistance (R on ) for the ST SOI is obtained due to the variable thickness SOI layer

Runaway breakdown in strong electric field as a source of terrestrial gamma flashes and gamma bursts in lightning leader steps

Energy Technology Data Exchange (ETDEWEB)

Gurevich, A.V. [P.N. Lebedev Physical Institute, Russian Academy of Sciences, 119991 Moscow (Russian Federation)]. E-mail: alex@lpi.ru; Zybin, K.P. [P.N. Lebedev Physical Institute, Russian Academy of Sciences, 119991 Moscow (Russian Federation); Medvedev, Yu.V. [Joint Institute for High Temperature, Russian Academy of Sciences, 127412 Moscow (Russian Federation)

2007-01-22

The new model of lightning step leader is proposed. It includes three main processes developing simultaneously in a strong electric field: conventional breakdown, effect of runaway electrons and runaway breakdown (RB). The theory of RB in strong electric field is developed. Comparison with the existing observational data shows that the model can serve as a background for the explanation of gamma bursts in step leader and TGF.

Runaway breakdown in strong electric field as a source of terrestrial gamma flashes and gamma bursts in lightning leader steps

International Nuclear Information System (INIS)

Gurevich, A.V.; Zybin, K.P.; Medvedev, Yu.V.

2007-01-01

The new model of lightning step leader is proposed. It includes three main processes developing simultaneously in a strong electric field: conventional breakdown, effect of runaway electrons and runaway breakdown (RB). The theory of RB in strong electric field is developed. Comparison with the existing observational data shows that the model can serve as a background for the explanation of gamma bursts in step leader and TGF

Time-odd mean fields in covariant density functional theory: Rotating systems

International Nuclear Information System (INIS)

Afanasjev, A. V.; Abusara, H.

2010-01-01

Time-odd mean fields (nuclear magnetism) and their impact on physical observables in rotating nuclei are studied in the framework of covariant density functional theory (CDFT). It is shown that they have profound effect on the dynamic and kinematic moments of inertia. Particle number, configuration, and rotational frequency dependencies of their impact on the moments of inertia have been analyzed in a systematic way. Nuclear magnetism can also considerably modify the band crossing features such as crossing frequencies and the properties of the kinematic and dynamic moments of inertia in the band crossing region. The impact of time-odd mean fields on the moments of inertia in the regions away from band crossing only weakly depends on the relativistic mean-field parametrization, reflecting good localization of the properties of time-odd mean fields in CDFT. The moments of inertia of normal-deformed nuclei considerably deviate from the rigid-body value. On the contrary, superdeformed and hyperdeformed nuclei have the moments of inertia which are close to rigid-body value. The structure of the currents in rotating frame, their microscopic origin, and the relations to the moments of inertia have been systematically analyzed. The phenomenon of signature separation in odd-odd nuclei, induced by time-odd mean fields, has been analyzed in detail.

Cluster analysis of polymers using laser-induced breakdown spectroscopy with K-means

Science.gov (United States)

Yangmin, GUO; Yun, TANG; Yu, DU; Shisong, TANG; Lianbo, GUO; Xiangyou, LI; Yongfeng, LU; Xiaoyan, ZENG

2018-06-01

Laser-induced breakdown spectroscopy (LIBS) combined with K-means algorithm was employed to automatically differentiate industrial polymers under atmospheric conditions. The unsupervised learning algorithm K-means were utilized for the clustering of LIBS dataset measured from twenty kinds of industrial polymers. To prevent the interference from metallic elements, three atomic emission lines (C I 247.86 nm , H I 656.3 nm, and O I 777.3 nm) and one molecular line C–N (0, 0) 388.3 nm were used. The cluster analysis results were obtained through an iterative process. The Davies–Bouldin index was employed to determine the initial number of clusters. The average relative standard deviation values of characteristic spectral lines were used as the iterative criterion. With the proposed approach, the classification accuracy for twenty kinds of industrial polymers achieved 99.6%. The results demonstrated that this approach has great potential for industrial polymers recycling by LIBS.

A 12 kV, 1 kHz, Pulse Generator for Breakdown Studies of Samples for CLIC RF Accelerating Structures

CERN Document Server

Soares, R H; Kovermann, J; Calatroni, S; Wuensch, W

2012-01-01

Compact Linear Collider (CLIC) RF structures must be capable of sustaining high surface electric fields, in excess of 200 MV/m, with a breakdown (BD) rate below 3×10-7 breakdowns/pulse/m. Achieving such a low rate requires a detailed understanding of all the steps involved in the mechanism of breakdown. One of the fundamental studies is to investigate the statistical characteristics of the BD rate phenomenon at very low values to understand the origin of an observed dependency of the surface electric field raised to the power of 30. To acquire sufficient BD data, in a reasonable period of time, a high repetition rate pulse generator is required for an existing d.c. spark system at CERN. Following BD of the material sample the pulse generator must deliver a current pulse of several 10’s of Amperes for ~2 μs. A high repetition rate pulse generator has been designed, built and tested; this utilizes pulse forming line technology and employs MOSFET switches. This paper describes the design of the pulse generat...

Breakdown concepts for contingency tables

NARCIS (Netherlands)

Kuhnt, S.

2010-01-01

Loglinear Poisson models are commonly used to analyse contingency tables. So far, robustness of parameter estimators as well as outlier detection have rarely been treated in this context. We start with finite-sample breakdown points. We yield that the breakdown point of mean value estimators

Radiative processes as a condensation phenomenon and the physical meaning of deformed canonical structures

International Nuclear Information System (INIS)

Gamboa, J.; Mendez, F.; Grigorio, L.S.; Guimaraes, M.S.; Wotzasek, C.

2008-01-01

We study the radiative corrections of QED 3 from the dual point of view and show that this process is the exact dual to the Julia-Toulouse mechanism introduced by Quevedo and Trugenberger [F. Quevedo, C.A. Trugenberger, Nucl. Phys. B 501 (1997) 143] some years ago. We discuss the physics behind this mechanism that involves condensation of topological defects. It is shown that the dual Stuckelberg mechanism is responsible for the 'rank-jump' phenomenon that transforms the scalar field (dual to Maxwell in this dimensionality) into the vectorial self-dual field. This phenomenon is studied using the ideas of noncommutative fields theory that examines possible deformations of the canonical structure of some well-known models in (2+1)D. A deformation is constructed linking the massless scalar field theory with the self-dual theory. This is the exact dual of the known deformation connecting the Maxwell theory with the Maxwell-Chern-Simons theory. Duality, radiative corrections, the Julia-Toulouse mechanism and canonical deformations are then used to establish a web of relations between the mentioned theories and to propose a physical picture of the deformation procedure adopted

Dark current, breakdown, and magnetic field effects in a multicell, 805 MHz cavity

Directory of Open Access Journals (Sweden)

J. Norem

2003-07-01

Full Text Available We present measurements of dark currents and x rays in a six cell 805 MHz cavity, taken as part of an rf development program for muon cooling, which requires high power, high stored energy, low frequency cavities operating in a strong magnetic field. We have done the first systematic study of the behavior of high power rf in a strong (2.5–4 T magnetic field. Our measurements extend over a very large dynamic range in current and provide good fits to the Fowler-Nordheim field emission model assuming mechanical structures produce field enhancements at the surface. The locally enhanced field intensities we derive at the tips of these emitters are very large, (∼10  GV/m, and should produce tensile stresses comparable to the tensile strength of the copper cavity walls and should be capable of causing breakdown events. We also compare our data with estimates of tensile stresses from a variety of accelerating structures. Preliminary studies of the internal surface of the cavity and window are presented, which show splashes of copper with many sharp cone shaped protrusions and wires which can explain the experimentally measured field enhancements. We discuss a “cold copper” breakdown mechanism and briefly review alternatives. We also discuss a number of effects due to the 2.5 T solenoidal fields on the cavity such as altered field emission due to mechanical deformation of emitters, and dark current ring beams, which are produced from the irises by E×B drifts during the nonrelativistic part of the acceleration process.

String-theoretic breakdown of effective field theory near black hole horizons

Science.gov (United States)

Dodelson, Matthew; Silverstein, Eva

2017-09-01

We investigate the validity of the equivalence principle near horizons in string theory, analyzing the breakdown of effective field theory caused by longitudinal string spreading effects. An experiment is set up where a detector is thrown into a black hole a long time after an early infalling string. Light cone gauge calculations, taken at face value, indicate a detectable level of root-mean-square longitudinal spreading of the initial string as measured by the late infaller. This results from the large relative boost between the string and detector in the near-horizon region, which develops automatically despite their modest initial energies outside the black hole and the weak curvature in the geometry. We subject this scenario to basic consistency checks, using these to obtain a relatively conservative criterion for its detectability. In a companion paper, we exhibit longitudinal nonlocality in well-defined gauge-invariant S-matrix calculations, obtaining results consistent with the predicted spreading albeit not in a direct analog of the black hole process. We discuss applications of this effect to the firewall paradox, and estimate the time and distance scales it predicts for new physics near black hole and cosmological horizons.

First order mean field games - explicit solutions, perturbations and connection with classical mechanics

KAUST Repository

Gomes, Diogo A.

2016-01-06

We present recent developments in the theory of first-order mean-field games (MFGs). A standard assumption in MFGs is that the cost function of the agents is monotone in the density of the distribution. This assumption leads to a comprehensive existence theory and to the uniqueness of smooth solutions. Here, our goals are to understand the role of local monotonicity in the small perturbation regime and the properties of solutions for problems without monotonicity. Under a local monotonicity assumption, we show that small perturbations of MFGs have unique smooth solutions. In addition, we explore the connection between first-order MFGs and classical mechanics and KAM theory. Next, for non-monotone problems, we construct non-unique explicit solutions for a broad class of first-order mean-field games. We provide an alternative formulation of MFGs in terms of a new current variable. These examples illustrate two new phenomena: the non-uniqueness of solutions and the breakdown of regularity.

First order mean field games - explicit solutions, perturbations and connection with classical mechanics

KAUST Repository

Gomes, Diogo A.; Nurbekyan, Levon; Prazeres, Mariana

2016-01-01

We present recent developments in the theory of first-order mean-field games (MFGs). A standard assumption in MFGs is that the cost function of the agents is monotone in the density of the distribution. This assumption leads to a comprehensive existence theory and to the uniqueness of smooth solutions. Here, our goals are to understand the role of local monotonicity in the small perturbation regime and the properties of solutions for problems without monotonicity. Under a local monotonicity assumption, we show that small perturbations of MFGs have unique smooth solutions. In addition, we explore the connection between first-order MFGs and classical mechanics and KAM theory. Next, for non-monotone problems, we construct non-unique explicit solutions for a broad class of first-order mean-field games. We provide an alternative formulation of MFGs in terms of a new current variable. These examples illustrate two new phenomena: the non-uniqueness of solutions and the breakdown of regularity.

Water surface deformation in strong electrical fields and its influence on electrical breakdown in a metal pin-water electrode system

International Nuclear Information System (INIS)

Bruggeman, Peter; Graham, Leigh; Groote, Joris de; Vierendeels, Jan; Leys, Christophe

2007-01-01

Electrical breakdown and water surface deformation in a metal pin-water electrode system with dc applied voltages is studied for small inter-electrode distances (2-12 mm). The radius of curvature of the metal pin is 0.5 cm to exclude corona before breakdown at these small inter-electrode spacings. Calculations of the water surface deformation as a function of the applied voltage and initial inter-electrode spacing are compared with measurements of the water elevation. For distances smaller than 7 mm the calculated stability limit of the water surface corresponds with the experimentally obtained breakdown voltage. It is proved with fast CCD images and calculations of the electrical field distribution that the water surface instability triggers the electrical breakdown in this case. The images show that at breakdown the water surface has a Taylor cone-like shape. At inter-electrode distance of 7 mm and larger the breakdown voltage is well below the water stability limit and the conductive channel at breakdown is formed between the pin electrode and the static water surface. Both cases are discussed and compared

Magnetic-breakdown oscillations of the thermoelectric field in layered conductors

Energy Technology Data Exchange (ETDEWEB)

Peschanskii, V. G., E-mail: vpeschansky@ilt.kharkov.ua [Karazin Kharkov National University (Ukraine); Galbova, O. [St. Cyril and Methodium University (Macedonia, The Former Yugoslav Republic of); Hasan, R. [Karazin Kharkov National University (Ukraine)

2016-12-15

The response of an electron system to nonuniform heating of layered conductors with an arbitrary quasi-two-dimensional electron energy spectrum in a strong magnetic field B is investigated theoretically in the case when cyclotron frequency ω{sub c} is much higher than the frequency 1/τ of collisions between charge carriers. In the case of a multisheet Fermi surface (FS), we calculate the dependence of the thermoelectric coefficients on the magnitude and orientation of the magnetic field in the vicinity of the Lifshitz topological transition when the FS connectivity changes under the action of an external force (e.g., pressure) on the conductor. Upon a decrease in the spacing between individual pockets (sheets) of the FS, conduction electrons can tunnel as a result of the magnetic breakdown from one FS sheet to another; their motion over magneticbreakdown trajectories becomes complicated and entangled. The thermoelectric field exhibits a peculiar dependence on the magnetic field: for a noticeable deviation of vector B from the normal through angle ϑ to the layers, the thermoelectric field oscillates as a function of tanϑ. The period of these oscillations contains important information on the distance between individual FS sheets and their corrugation.

Fast Breakdown as Coronal/Ionization Waves?

Science.gov (United States)

Krehbiel, P. R.; Petersen, D.; da Silva, C. L.

2017-12-01

Studies of high-power narrow bipolar events (NBEs) have shown they are produced by a newly-recognized breakdown process called fast positive breakdown (FPB, Rison et al., 2016, doi:10.1038/ncomms10721). The breakdown was inferred to be produced by a system of positive streamers that propagate at high speed ( ˜3-6 x 107 m/s) due to occurring in a localized region of strong electric field. The polarity of the breakdown was determined from broadband interferometer (INTF) observations of the propagation direction of its VHF radiation, which was downward into the main negative charge region of a normally-electrified storm. Subsequent INTF observations being conducted in at Kennedy Space Center in Florida have shown a much greater incidence of NBEs than in New Mexico. Among the larger dataset have been clear-cut instances of some NBEs being produced by upward breakdown that would be of negative polarity. The speed and behavior of the negative breakdown is the same as that of the fast positive, leading to it being termed fast negative breakdown (FNB). The similarity (not too mention its occurrence) is surprising, given the fact that negative streamers and breakdown develops much differently than that of positive breakdown. The question is how this happens. In this study, we compare fast breakdown characteristics to well-known streamer properties as inferred from laboratory experiments and theoretical analysis. Additionally, we begin to explore the possibility that both polarities of fast breakdown are produced by what may be called coronal or ionization waves, in which the enhanced electric field produced by streamer or coronal breakdown of either polarity propagates away from the advancing front at the speed of light into a medium that is in a metastable condition of being at the threshold of hydrometeor-mediated corona onset or other ionization processes. The wave would develop at a faster speed than the streamer breakdown that gives rise to it, and thus would be

Visualization of the structure of vortex breakdown in free swirling jet flow

NARCIS (Netherlands)

Vanierschot, M.; Perçin, M.; van Oudheusden, B.W.

2016-01-01

In this paper we investigate the three dimensional flow structures in a free annular swirling jet flow undergoing vortex breakdown. The flow field is analyzed by means of time-resolved Tomographic Particle Image Velocimetry measurements. Both time-averaged and instantaneous flow structures are

Breakdown properties of irradiated MOS capacitors

International Nuclear Information System (INIS)

Paccagnella, A.; Candelori, A.; Pellizzer, F.; Fuochi, P.G.; Lavale, M.

1996-01-01

The authors have studied the effects of ionizing and non-ionizing radiation on the breakdown properties of different types of MOS capacitors, with thick (200 nm) and thin (down to 8 nm) oxides. In general, no large variations of the average breakdown field, time-to-breakdown at constant voltage, or charge-to-breakdown at constant voltage, or charge-to-breakdown values have been observed after high dose irradiation (20 Mrad(Si) 9 MeV electrons on thin and thick oxides, 17(Si) Mrad Co 60 gamma and 10 14 neutrons/cm 2 only on thick oxides). However, some modifications of the cumulative failure distributions have been observed in few of the oxides tested

Suppressing RF breakdown of powerful backward wave oscillator by field redistribution

Directory of Open Access Journals (Sweden)

W. Song

2012-03-01

Full Text Available An over mode method for suppressing the RF breakdown on metal surface of resonant reflector cavity in powerful backward wave oscillator is investigated. It is found that the electric field is redistributed and electron emission is restrained with an over longitudinal mode cavity. Compared with the general device, a frequency band of about 5 times wider and a power capacity of at least 1.7 times greater are obtained. The results were verified in an X-band high power microwave generation experiment with the output power near 4 gigawatt.

Finite-State Mean-Field Games, Crowd Motion Problems, and its Numerical Methods

KAUST Repository

Machado Velho, Roberto

2017-09-10

In this dissertation, we present two research projects, namely finite-state mean-field games and the Hughes model for the motion of crowds. In the first part, we describe finite-state mean-field games and some applications to socio-economic sciences. Examples include paradigm shifts in the scientific community and the consumer choice behavior in a free market. The corresponding finite-state mean-field game models are hyperbolic systems of partial differential equations, for which we propose and validate a new numerical method. Next, we consider the dual formulation to two-state mean-field games, and we discuss numerical methods for these problems. We then depict different computational experiments, exhibiting a variety of behaviors, including shock formation, lack of invertibility, and monotonicity loss. We conclude the first part of this dissertation with an investigation of the shock structure for two-state problems. In the second part, we consider a model for the movement of crowds proposed by R. Hughes in [56] and describe a numerical approach to solve it. This model comprises a Fokker-Planck equation coupled with an Eikonal equation with Dirichlet or Neumann data. We first establish a priori estimates for the solutions. Next, we consider radial solutions, and we identify a shock formation mechanism. Subsequently, we illustrate the existence of congestion, the breakdown of the model, and the trend to the equilibrium. We also propose a new numerical method for the solution of Fokker-Planck equations and then to systems of PDEs composed by a Fokker-Planck equation and a potential type equation. Finally, we illustrate the use of the numerical method both to the Hughes model and mean-field games. We also depict cases such as the evacuation of a room and the movement of persons around Kaaba (Saudi Arabia).

Optical breakdown threshold investigation of 1064 nm laser induced air plasmas

International Nuclear Information System (INIS)

Thiyagarajan, Magesh; Thompson, Shane

2012-01-01

We present the theoretical and experimental measurements and analysis of the optical breakdown threshold for dry air by 1064 nm infrared laser radiation and the significance of the multiphoton and collisional cascade ionization process on the breakdown threshold measurements over pressures range from 10 to 2000 Torr. Theoretical estimates of the breakdown threshold laser intensities and electric fields are obtained using two distinct theories namely multiphoton and collisional cascade ionization theories. The theoretical estimates are validated by experimental measurements and analysis of laser induced breakdown processes in dry air at a wavelength of 1064 nm by focusing 450 mJ max, 6 ns, 75 MW max high-power 1064 nm IR laser radiation onto a 20 μm radius spot size that produces laser intensities up to 3 - 6 TW/cm 2 , sufficient for air ionization over the pressures of interest ranging from 10 to 2000 Torr. Analysis of the measured breakdown threshold laser intensities and electric fields are carried out in relation with classical and quantum theoretical ionization processes, operating pressures. Comparative analysis of the laser air breakdown results at 1064 nm with corresponding results of a shorter laser wavelength (193 nm) [M. Thiyagarajan and J. E. Scharer, IEEE Trans. Plasma Sci. 36, 2512 (2008)] and a longer microwave wavelength (10 8 nm) [A. D. MacDonald, Microwave Breakdown in Gases (Wiley, New York, 1966)]. A universal scaling analysis of the breakdown threshold measurements provided a direct comparison of breakdown threshold values over a wide range of frequencies ranging from microwave to ultraviolet frequencies. Comparison of 1064 nm laser induced effective field intensities for air breakdown measurements with data calculated based on the collisional cascade and multiphoton breakdown theories is used successfully to determine the scaled collisional microwave portion. The measured breakdown threshold of 1064 nm laser intensities are then scaled to

Persistence and failure of mean-field approximations adapted to a class of systems of delay-coupled excitable units

Science.gov (United States)

Franović, Igor; Todorović, Kristina; Vasović, Nebojša; Burić, Nikola

2014-02-01

We consider the approximations behind the typical mean-field model derived for a class of systems made up of type II excitable units influenced by noise and coupling delays. The formulation of the two approximations, referred to as the Gaussian and the quasi-independence approximation, as well as the fashion in which their validity is verified, are adapted to reflect the essential properties of the underlying system. It is demonstrated that the failure of the mean-field model associated with the breakdown of the quasi-independence approximation can be predicted by the noise-induced bistability in the dynamics of the mean-field system. As for the Gaussian approximation, its violation is related to the increase of noise intensity, but the actual condition for failure can be cast in qualitative, rather than quantitative terms. We also discuss how the fulfillment of the mean-field approximations affects the statistics of the first return times for the local and global variables, further exploring the link between the fulfillment of the quasi-independence approximation and certain forms of synchronization between the individual units.

Effective masses and the nuclear mean field

International Nuclear Information System (INIS)

Mahaux, C.; Sartor, R.

1985-01-01

The effective mass characterizes the energy dependence of the empirical average nuclear potential. This energy dependence has two different sources, namely the nonlocality in space of the microscopic mean field on the one hand, and its true energy dependence on the other hand. Correspondingly it is convenient to divide the effective mass into two components, the k-mass and the ω-mass. The latter is responsible for the existence of a peak in the energy dependence of the effective mass. This peak is located near the Fermi energy in nuclear matter and in nuclei, as well as in the electron gas, the hard sphere Fermi gas and liquid helium 3. A related phenomenon is the existence of a low energy anomaly in the energy dependence of the optical model potential between two heavy ions. (orig.)

Experimental research for vacuum gap breakdown in high voltage multi-pulse

International Nuclear Information System (INIS)

Huang Ziping; He Jialong; Chen Sifu; Deng Jianjun; Wang Liping

2008-01-01

Base on the breakdown theory of vacuum gaps, experiments have been done to find out the breakdown electric field intensities in high voltage single-and triple-pulse for 26 vacuum gaps with different shapes. The experimental results match up to the theory and confirm the effect of the pulse-number increase on the breakdown electric field intensity. The key point to decide the macroscopical breakdown electric field intensity of a vacuum gap has been pointed out with some advises about the design of a multi-pulse linear inductive accelerator's accelerate gap. (authors)

Laser-induced breakdown spectroscopy analysis of asbestos

International Nuclear Information System (INIS)

Caneve, L.; Colao, F.; Fabbri, F.; Fantoni, R.; Spizzichino, V.; Striber, J.

2005-01-01

Laser-induced breakdown spectroscopy was applied to test the possibility of detecting and identifying asbestos in different samples in view of the perspective at field operation without sample preparation which is peculiar to this technique. Several like-resin materials were first investigated by laser-induced breakdown spectroscopy, in order to find an asbestos container assuring safe laboratory operation during the material characterization aimed to identify indicators suitable for a quick identification on field. Successively, spectra of asbestos samples of both in serpentine and amphibole forms were measured and the variability in elemental composition was calculated from the emission spectra. Ratios of intensities of characteristic elements were tested as indicators for asbestos recognition. Laser-induced breakdown spectroscopy results were compared with those obtained by analyzing the same asbestos samples with a scanning electron microscopy equipped with an energy dispersive X-ray spectroscopy, a good correlation was found for Mg/Si and Fe/Si, thus showing the capability of laser-induced breakdown spectroscopy as a diagnostic tool for this category of materials. In particular, it was demonstrated that the method based on two indicators derived from laser-induced breakdown spectroscopy intensity ratios allows to discriminate between asbestos and cements in single shot measurements suitable to field operation

Mean field games

KAUST Repository

Gomes, Diogo A.

2014-01-06

In this talk we will report on new results concerning the existence of smooth solutions for time dependent mean-field games. This new result is established through a combination of various tools including several a-priori estimates for time-dependent mean-field games combined with new techniques for the regularity of Hamilton-Jacobi equations.

Mean field games

KAUST Repository

Gomes, Diogo A.

2014-01-01

In this talk we will report on new results concerning the existence of smooth solutions for time dependent mean-field games. This new result is established through a combination of various tools including several a-priori estimates for time-dependent mean-field games combined with new techniques for the regularity of Hamilton-Jacobi equations.

Three-dimensional simulation of vortex breakdown

Science.gov (United States)

Kuruvila, G.; Salas, M. D.

1990-01-01

The integral form of the complete, unsteady, compressible, three-dimensional Navier-Stokes equations in the conservation form, cast in generalized coordinate system, are solved, numerically, to simulate the vortex breakdown phenomenon. The inviscid fluxes are discretized using Roe's upwind-biased flux-difference splitting scheme and the viscous fluxes are discretized using central differencing. Time integration is performed using a backward Euler ADI (alternating direction implicit) scheme. A full approximation multigrid is used to accelerate the convergence to steady state.

Double helix vortex breakdown in a turbulent swirling annular jet flow

Science.gov (United States)

Vanierschot, M.; Percin, M.; van Oudheusden, B. W.

2018-03-01

In this paper, we report on the structure and dynamics of double helix vortex breakdown in a turbulent annular swirling jet. Double helix breakdown has been reported previously for the laminar flow regime, but this structure has rarely been observed in turbulent flow. The flow field is investigated experimentally by means of time-resolved tomographic particle image velocimetry. Notwithstanding the axisymmetric nature of the time-averaged flow, analysis of the instantaneous three-dimensional (3D) vortical structures shows the existence of a vortex core along the central axis which breaks up into a double helix downstream. The winding sense of this double helix is opposite to the swirl direction (m =-2 ) and it is wrapped around a central vortex breakdown bubble. This structure is quite different from double helix breakdown found in laminar flows where the helix is formed in the wake of the bubble and not upstream. The double helix precesses around the central axis of the jet with a precessing frequency corresponding to a Strouhal number of 0.27.

Pressurized-helium breakdown at very low temperatures

Energy Technology Data Exchange (ETDEWEB)

Metas, R J

1972-06-01

An investigation of the electrical-breakdown behavior of helium at very low temperatures has been carried out to assist the design and development of superconducting power cables. At very high densities, both liquid and gaseous helium showed an enhancement in electric strength when pressurized to a few atmospheres; conditioned values of breakdown fields then varied between 30 and 45 MV/m. Breakdown processes occurring over a wide range of helium densities are discussed. 24 references.

Pre-breakdown phenomena and discharges in a gas-liquid system

Science.gov (United States)

Tereshonok, D. V.; Babaeva, N. Yu; Naidis, G. V.; Panov, V. A.; Smirnov, B. M.; Son, E. E.

2018-04-01

In this paper, we investigate pre-breakdown and breakdown phenomena in gas-liquid systems. Cavitation void formation and breakdown in bubbles immersed in liquids are studied numerically, while complete breakdown of bubbled water is studied in experiments. It is shown that taking into account the dependence of water dielectric constant on electric field strength plays the same important role for cavitation void appearance under the action of electrostriction forces as the voltage rise time. It is also shown that the initial stage of breakdown in deformed bubbles immersed in liquid strongly depends on spatial orientation of the bubbles relative to the external electric field. The effect of immersed microbubbles, distributed in bulk water, on breakdown time and voltage is studied experimentally. At the breakdown voltage, the slow ‘thermal’ mechanism is changed by the fast ‘streamer-leader’ showing a decrease in breakdown time by two orders of magnitude by introducing microbubbles (0.1% of volumetric gas content) into the water. In addition, the plasma channel is found to pass between nearby microbubbles, exhibiting some ‘guidance’ effect.

Influence of water trees on breakdown voltage of polymeric cables insulations

Energy Technology Data Exchange (ETDEWEB)

Stancu, Cristina [INCDIE ICPE CA, Bucharest (Romania); Notingher, Petru V.; Plopeanu, Mihai Gabriel [Politehnica University of Bucharest, Bucharest (Romania)

2011-07-01

In a previous paper was shown that water trees development modifies considerably the electric field repartition, which increases significantly in the vicinity of treed areas. In order to find the water trees influence on the breakdown voltage, in the present paper, an experimental study on model cables insulated with low density polyethylene is done. In insulation samples, water trees with various dimensions and densities were developed. For the reduction of the test duration, an electric field with a higher frequency (3-5 kHz) was used. For breakdown voltage measurement an automatic setup was realized. For each value of the ageing time the dimensions and densities of water trees and breakdown voltage were measured and the dependency of the breakdown voltage with these quantities were analysed. The results show a significant reduction of the breakdown voltage of treed cables insulations compared to un-treed ones. Key words: polyethylene, water treeing, electric field, breakdown, power cables.

Breakdown characteristics of xenon HID Lamps

Science.gov (United States)

Babaeva, Natalia; Sato, Ayumu; Brates, Nanu; Noro, Koji; Kushner, Mark

2009-10-01

The breakdown characteristics of mercury free xenon high intensity discharge (HID) lamps exhibit a large statistical time lag often having a large scatter in breakdown voltages. In this paper, we report on results from a computational investigation of the processes which determine the ignition voltages for positive and negative pulses in commercial HID lamps having fill pressures of up to 20 atm. Steep voltage rise results in higher avalanche electron densities and earlier breakdown times. Circuit characteristics also play a role. Large ballast resistors may limit current to the degree that breakdown is quenched. The breakdown voltage critically depends on cathode charge injection by electric field emission (or other mechanisms) which in large part controls the statistical time lag for breakdown. For symmetric lamps, ionization waves (IWs) simultaneously develop from the bottom and top electrodes. Breakdown typically occurs when the top and bottom IWs converge. Condensed salt layers having small conductivities on the inner walls of HID lamps and on the electrodes can influence the ignition behavior. With these layers, IWs tend to propagate along the inner wall and exhibit a different structure depending on the polarity.

Voltage-stabilised elastomers with increased relative permittivity and high electrical breakdown strength by means of phase separating binary copolymer blends of silicone elastomers

DEFF Research Database (Denmark)

A Razak, Aliff Hisyam; Yu, Liyun; Skov, Anne Ladegaard

2017-01-01

Increased electrical breakdown strength and increased dielectric permittivity of silicone-based dielectric elastomers are achieved by means of the addition of so-called voltage-stabilisers prepared from PDMS–PPMS copolymers as well as PDMS–PEG copolymers in order to compensate for the negative...... effect of softness on electrical stability of silicone elastomers. The voltage-stabilised elastomer, incorporating a high-permittivity PDMS–PEG copolymer, possesses increased relative permittivity, high electrical breakdown strength, excellent network integrity and low dielectric loss and paves the way...

DC breakdown characteristics of silicone polymer composites for HVDC insulator applications

Science.gov (United States)

Han, Byung-Jo; Seo, In-Jin; Seong, Jae-Kyu; Hwang, Young-Ho; Yang, Hai-Won

2015-11-01

Critical components for HVDC transmission systems are polymer insulators, which have stricter requirements that are more difficult to achieve compared to those of HVAC insulators. In this study, we investigated the optimal design of HVDC polymer insulators by using a DC electric field analysis and experiments. The physical properties of the polymer specimens were analyzed to develop an optimal HVDC polymer material, and four polymer specimens were prepared for DC breakdown experiments. Single and reverse polarity breakdown tests were conducted to analyze the effect of temperature on the breakdown strength of the polymer. In addition, electric fields were analyzed via simulations, in which a small-scale polymer insulator model was applied to prevent dielectric breakdown due to electric field concentration, with four DC operating conditions taken into consideration. The experimental results show that the electrical breakdown strength and the electric field distribution exhibit significant differences in relation to different DC polarity transition procedures.

Accoustic Localization of Breakdown in Radio Frequency Accelerating Cavities

Energy Technology Data Exchange (ETDEWEB)

Lane, Peter Gwin [IIT, Chicago

2016-07-01

Current designs for muon accelerators require high-gradient radio frequency (RF) cavities to be placed in solenoidal magnetic fields. These fields help contain and efficiently reduce the phase space volume of source muons in order to create a usable muon beam for collider and neutrino experiments. In this context and in general, the use of RF cavities in strong magnetic fields has its challenges. It has been found that placing normal conducting RF cavities in strong magnetic fields reduces the threshold at which RF cavity breakdown occurs. To aid the effort to study RF cavity breakdown in magnetic fields, it would be helpful to have a diagnostic tool which can localize the source of breakdown sparks inside the cavity. These sparks generate thermal shocks to small regions of the inner cavity wall that can be detected and localized using microphones attached to the outer cavity surface. Details on RF cavity sound sources as well as the hardware, software, and algorithms used to localize the source of sound emitted from breakdown thermal shocks are presented. In addition, results from simulations and experiments on three RF cavities, namely the Aluminum Mock Cavity, the High-Pressure Cavity, and the Modular Cavity, are also given. These results demonstrate the validity and effectiveness of the described technique for acoustic localization of breakdown.

Risk-sensitive mean-field games

KAUST Repository

Tembine, Hamidou

2014-04-01

In this paper, we study a class of risk-sensitive mean-field stochastic differential games. We show that under appropriate regularity conditions, the mean-field value of the stochastic differential game with exponentiated integral cost functional coincides with the value function satisfying a Hamilton -Jacobi- Bellman (HJB) equation with an additional quadratic term. We provide an explicit solution of the mean-field best response when the instantaneous cost functions are log-quadratic and the state dynamics are affine in the control. An equivalent mean-field risk-neutral problem is formulated and the corresponding mean-field equilibria are characterized in terms of backward-forward macroscopic McKean-Vlasov equations, Fokker-Planck-Kolmogorov equations, and HJB equations. We provide numerical examples on the mean field behavior to illustrate both linear and McKean-Vlasov dynamics. © 1963-2012 IEEE.

Risk-sensitive mean-field games

KAUST Repository

Tembine, Hamidou; Zhu, Quanyan; Başar, Tamer

2014-01-01

In this paper, we study a class of risk-sensitive mean-field stochastic differential games. We show that under appropriate regularity conditions, the mean-field value of the stochastic differential game with exponentiated integral cost functional coincides with the value function satisfying a Hamilton -Jacobi- Bellman (HJB) equation with an additional quadratic term. We provide an explicit solution of the mean-field best response when the instantaneous cost functions are log-quadratic and the state dynamics are affine in the control. An equivalent mean-field risk-neutral problem is formulated and the corresponding mean-field equilibria are characterized in terms of backward-forward macroscopic McKean-Vlasov equations, Fokker-Planck-Kolmogorov equations, and HJB equations. We provide numerical examples on the mean field behavior to illustrate both linear and McKean-Vlasov dynamics. © 1963-2012 IEEE.

Appropriate Educational Means of Dealing with the Phenomenon of Smoking among Zarqa University Students

Science.gov (United States)

hatamleh, habes Moh'd; al Khaza'leh, Mohammed Salman

2016-01-01

The study aimed to identify the (appropriate educational means of dealing with the phenomenon of smoking among Zarqa University students), and to achieve this goal, the descriptive approach has been used, also used a questionnaire submitted to (800) students of the sample, and a couple of open questions has been submitted to 70 members of the…

Kinetic parameters, collision rates, energy exchanges and transport coefficients of non-thermal electrons in premixed flames at sub-breakdown electric field strengths

KAUST Repository

Bisetti, Fabrizio

2014-01-02

The effects of an electric field on the collision rates, energy exchanges and transport properties of electrons in premixed flames are investigated via solutions to the Boltzmann kinetic equation. The case of high electric field strength, which results in high-energy, non-thermal electrons, is analysed in detail at sub-breakdown conditions. The rates of inelastic collisions and the energy exchange between electrons and neutrals in the reaction zone of the flame are characterised quantitatively. The analysis includes attachment, ionisation, impact dissociation, and vibrational and electronic excitation processes. Our results suggest that Townsend breakdown occurs for E/N = 140 Td. Vibrational excitation is the dominant process up to breakdown, despite important rates of electronic excitation of CO, CO2 and N2 as well as impact dissociation of O2 being apparent from 50 Td onwards. Ohmic heating in the reaction zone is found to be negligible (less than 2% of peak heat release rate) up to breakdown field strengths for realistic electron densities equal to 1010 cm-3. The observed trends are largely independent of equivalence ratio. In the non-thermal regime, electron transport coefficients are insensitive to mixture composition and approximately constant across the flame, but are highly dependent on the electric field strength. In the thermal limit, kinetic parameters and transport coefficients vary substantially across the flame due to the spatially inhomogeneous concentration of water vapour. A practical approach for identifying the plasma regime (thermal versus non-thermal) in studies of electric field effects on flames is proposed. © 2014 Taylor & Francis.

Weibull Analysis of Electrical Breakdown Strength as an Effective Means of Evaluating Elastomer Thin Film Quality

DEFF Research Database (Denmark)

Silau, Harald; Stabell, Nicolai Bogø; Petersen, Frederik Riddersholm

2018-01-01

To realize the commercial potential of dielectric elastomers, reliable, large-scale film production is required. Ensuring proper mixing and subsequently avoiding demixing after, for example, pumping and coating of elastomer premix in an online process is not facile. Weibull analysis...... of the electrical breakdown strength of dielectric elastomer films is shown to be an effective means of evaluating the film quality. The analysis is shown to be capable of distinguishing between proper and improper mixing schemes where similar analysis of ultimate mechanical properties fails to distinguish....

Improving breakdown voltage performance of SOI power device with folded drift region

Science.gov (United States)

Qi, Li; Hai-Ou, Li; Ping-Jiang, Huang; Gong-Li, Xiao; Nian-Jiong, Yang

2016-07-01

A novel silicon-on-insulator (SOI) high breakdown voltage (BV) power device with interlaced dielectric trenches (IDT) and N/P pillars is proposed. In the studied structure, the drift region is folded by IDT embedded in the active layer, which results in an increase of length of ionization integral remarkably. The crowding phenomenon of electric field in the corner of IDT is relieved by the N/P pillars. Both traits improve two key factors of BV, the ionization integral length and electric field magnitude, and thus BV is significantly enhanced. The electric field in the dielectric layer is enhanced and a major portion of bias is borne by the oxide layer due to the accumulation of inverse charges (holes) at the corner of IDT. The average value of the lateral electric field of the proposed device reaches 60 V/μm with a 10 μm drift length, which increases by 200% in comparison to the conventional SOI LDMOS, resulting in a breakdown voltage of 607 V. Project supported by the Guangxi Natural Science Foundation of China (Grant Nos. 2013GXNSFAA019335 and 2015GXNSFAA139300), Guangxi Experiment Center of Information Science of China (Grant No. YB1406), Guangxi Key Laboratory of Wireless Wideband Communication and Signal Processing of China, Key Laboratory of Cognitive Radio and Information Processing (Grant No. GXKL061505), Guangxi Key Laboratory of Automobile Components and Vehicle Technology of China (Grant No. 2014KFMS04), and the National Natural Science Foundation of China (Grant Nos. 61361011, 61274077, and 61464003).

RF Breakdown in Normal Conducting Single-Cell Structures

International Nuclear Information System (INIS)

Dolgashev, V.A.; Nantista, C.D.; Tantawi, S.G.; Higashi, Y.; Higo, T.

2006-01-01

Operating accelerating gradient in normal conducting accelerating structures is often limited by rf breakdown. The limit depends on multiple parameters, including input rf power, rf circuit, cavity shape and material. Experimental and theoretical study of the effects of these parameters on the breakdown limit in full scale structures is difficult and costly. We use 11.4 GHz single-cell traveling wave and standing wave accelerating structures for experiments and modeling of rf breakdown behavior. These test structures are designed so that the electromagnetic fields in one cell mimic the fields in prototype multicell structures for the X-band linear collider. Fields elsewhere in the test structures are significantly lower than that of the single cell. The setup uses matched mode converters that launch the circular TM 01 mode into short test structures. The test structures are connected to the mode launchers with vacuum rf flanges. This setup allows economic testing of different cell geometries, cell materials and preparation techniques with short turn-around time. Simple 2D geometry of the test structures simplifies modeling of the breakdown currents and their thermal effects

Effect of high solenoidal magnetic fields on breakdown voltages of high vacuum 805 MHz cavities

International Nuclear Information System (INIS)

Moretti, A.; Bross, A.; Geer, S.; Qian, Z.; Norem, J.; Li, D.; Zisman, M.; Torun, Y.; Rimmer, R.; Errede, D.

2005-01-01

There is an on going international collaboration studying the feasibility and cost of building a muon collider or neutrino factory [1,2]. An important aspect of this study is the full understanding of ionization cooling of muons by many orders of magnitude for the collider case. An important muon ionization cooling experiment, MICE [3], has been proposed to demonstrate and validate the technology that could be used for cooling. Ionization cooling is accomplished by passing a high-emittance muon beam alternately through regions of low Z material, such as liquid hydrogen, and very high accelerating RF Cavities within a multi-Tesla solenoidal field. To determine the effect of very large solenoidal magnetic fields on the generation of dark current, x-rays and on the breakdown voltage gradients of vacuum RF cavities, a test facility has been established at Fermilab in Lab G. This facility consists of a 12 MW 805 MHz RF station and a large warm bore 5 T solenoidal superconducting magnet containing a pill box type cavity with thin removable window apertures. This system allows dark current and breakdown studies of different window configurations and materials. The results of this study will be presented. The study has shown that the peak achievable accelerating gradient is reduced by a factor greater than 2 when solenoidal field of greater than 2 T are applied to the cavity

Mean-field lattice trees

NARCIS (Netherlands)

Borgs, C.; Chayes, J.T.; Hofstad, van der R.W.; Slade, G.

1999-01-01

We introduce a mean-field model of lattice trees based on embeddings into d of abstract trees having a critical Poisson offspring distribution. This model provides a combinatorial interpretation for the self-consistent mean-field model introduced previously by Derbez and Slade [9], and provides an

The Electrical Breakdown of Thin Dielectric Elastomers

DEFF Research Database (Denmark)

Zakaria, Shamsul Bin; Morshuis, Peter H. F.; Yahia, Benslimane Mohamed

2014-01-01

Dielectric elastomers are being developed for use in actuators, sensors and generators to be used in various applications, such as artificial eye lids, pressure sensors and human motion energy generators. In order to obtain maximum efficiency, the devices are operated at high electrical fields....... This increases the likelihood for electrical breakdown significantly. Hence, for many applications the performance of the dielectric elastomers is limited by this risk of failure, which is triggered by several factors. Amongst others thermal effects may strongly influence the electrical breakdown strength....... In this study, we model the electrothermal breakdown in thin PDMS based dielectric elastomers in order to evaluate the thermal mechanisms behind the electrical failures. The objective is to predict the operation range of PDMS based dielectric elastomers with respect to the temperature at given electric field...

Impact of a drain field plate on the breakdown characteristics of AlInN/GaN MOSHEMT

Science.gov (United States)

Jena, Kanjalochan; Swain, Raghunandan; Lenka, T. R.

2015-11-01

In this paper, a novel AlInN/GaN metal oxide semiconductor high electron mobility transistor (MOSHEMT) employing the drain field plate technique is proposed and the effect of a drain field plate on the breakdown voltage (BV) is investigated. A reduction of the peak electric field is required to achieve AlInN/GaN MOSHEMTs with a high BV. The proposed AlInN/GaN MOSHEMT with both gate and drain field plates simultaneously reduces the electric field concentration at the gate and the drain edge by decreasing the potential gradient along the channel for the 2 dimensional electron gas (2DEG). The reduction in the peak electric field at the drain edge of the proposed device leads to a 57% increase in BV compared with the BV for an AlInN/GaN MOSHEMT with a gate field plate only. A significantly higher BV can be achieved by optimizing the gate-to-drain distance (L gd ), the length of the drain field plate (L dfp ) and the thickness of the SiN passivation layer thickness (T SiN ). A detailed breakdown analysis of the device was carried out using Silvaco Technology Computer Aided Design (TCAD). The detailed numerical simulations were done by using the non-local energy balance (EB) transport model, which was calibrated with the previously published experimental results. The results showed a great potential for applications of the drain-field-plated AlInN/GaN MOSHEMT to deliver high currents and high powers in microwave technologies.

Ionizing potential waves and high-voltage breakdown streamers.

Science.gov (United States)

Albright, N. W.; Tidman, D. A.

1972-01-01

The structure of ionizing potential waves driven by a strong electric field in a dense gas is discussed. Negative breakdown waves are found to propagate with a velocity proportional to the electric field normal to the wavefront. This causes a curved ionizing potential wavefront to focus down into a filamentary structure, and may provide the reason why breakdown in dense gases propagates in the form of a narrow leader streamer instead of a broad wavefront.

Mechanism of the free charge carrier generation in the dielectric breakdown

Science.gov (United States)

Rahim, N. A. A.; Ranom, R.; Zainuddin, H.

2017-12-01

Many studies have been conducted to investigate the effect of environmental, mechanical and electrical stresses on insulator. However, studies on physical process of discharge phenomenon, leading to the breakdown of the insulator surface are lacking and difficult to comprehend. Therefore, this paper analysed charge carrier generation mechanism that can cause free charge carrier generation, leading toward surface discharge development. Besides, this paper developed a model of surface discharge based on the charge generation mechanism on the outdoor insulator. Nernst’s Planck theory was used in order to model the behaviour of the charge carriers while Poisson’s equation was used to determine the distribution of electric field on insulator surface. In the modelling of surface discharge on the outdoor insulator, electric field dependent molecular ionization was used as the charge generation mechanism. A mathematical model of the surface discharge was solved using method of line technique (MOL). The result from the mathematical model showed that the behaviour of net space charge density was correlated with the electric field distribution.

The effect of external visible light on the breakdown voltage of a long discharge tube

Science.gov (United States)

Shishpanov, A. I.; Ionikh, Yu. Z.; Meshchanov, A. V.

2016-06-01

The breakdown characteristics of a discharge tube with a configuration typical of gas-discharge light sources and electric-discharge lasers (a so-called "long discharge tube") filled with argon or helium at a pressure of 1 Torr have been investigated. A breakdown has been implemented using positive and negative voltage pulses with a linear leading edge having a slope dU/ dt ~ 10-107 V/s. Visible light from an external source (halogen incandescent lamp) is found to affect the breakdown characteristics. The dependences of the dynamic breakdown voltage of the tube on dU/ dt and on the incident light intensity are measured. The breakdown voltage is found to decrease under irradiation of the high-voltage anode of the tube in a wide range of dU/ dt. A dependence of the effect magnitude on the light intensity and spectrum is obtained. Possible physical mechanisms of this phenomenon are discussed.

Electrical breakdown phenomena of dielectric elastomers

DEFF Research Database (Denmark)

Mateiu, Ramona Valentina; Yu, Liyun; Skov, Anne Ladegaard

2017-01-01

Silicone elastomers have been heavily investigated as candidates for dielectric elastomers and are as such almost ideal candidates with their inherent softness and compliance but they suffer from low dielectric permittivity. This shortcoming has been sought optimized by many means during recent...... years. However, optimization with respect to the dielectric permittivity solely may lead to other problematic phenomena such as premature electrical breakdown. In this work, we investigate the electrical breakdown phenomena of various types of permittivity-enhanced silicone elastomers. Two types...... of silicone elastomers are investigated and different types of breakdown are discussed. Furthermore the use of voltage stabilizers in silicone-based dielectric elastomers is investigated and discussed....

Mean-Field Games for Marriage

Science.gov (United States)

Bauso, Dario; Dia, Ben Mansour; Djehiche, Boualem; Tembine, Hamidou; Tempone, Raul

2014-01-01

This article examines mean-field games for marriage. The results support the argument that optimizing the long-term well-being through effort and social feeling state distribution (mean-field) will help to stabilize marriage. However, if the cost of effort is very high, the couple fluctuates in a bad feeling state or the marriage breaks down. We then examine the influence of society on a couple using mean-field sentimental games. We show that, in mean-field equilibrium, the optimal effort is always higher than the one-shot optimal effort. We illustrate numerically the influence of the couple’s network on their feeling states and their well-being. PMID:24804835

Mean-field games for marriage.

Directory of Open Access Journals (Sweden)

Dario Bauso

Full Text Available This article examines mean-field games for marriage. The results support the argument that optimizing the long-term well-being through effort and social feeling state distribution (mean-field will help to stabilize marriage. However, if the cost of effort is very high, the couple fluctuates in a bad feeling state or the marriage breaks down. We then examine the influence of society on a couple using mean-field sentimental games. We show that, in mean-field equilibrium, the optimal effort is always higher than the one-shot optimal effort. We illustrate numerically the influence of the couple's network on their feeling states and their well-being.

Mean-field games for marriage

KAUST Repository

Bauso, Dario

2014-05-07

This article examines mean-field games for marriage. The results support the argument that optimizing the long-term well-being through effort and social feeling state distribution (mean-field) will help to stabilize marriage. However, if the cost of effort is very high, the couple fluctuates in a bad feeling state or the marriage breaks down. We then examine the influence of society on a couple using mean-field sentimental games. We show that, in mean-field equilibrium, the optimal effort is always higher than the one-shot optimal effort. We illustrate numerically the influence of the couple\\'s network on their feeling states and their well-being. © 2014 Bauso et al.

Mean-field games for marriage

KAUST Repository

Bauso, Dario; Dia, Ben Mansour; Djehiche, Boualem; Tembine, Hamidou; Tempone, Raul

2014-01-01

This article examines mean-field games for marriage. The results support the argument that optimizing the long-term well-being through effort and social feeling state distribution (mean-field) will help to stabilize marriage. However, if the cost of effort is very high, the couple fluctuates in a bad feeling state or the marriage breaks down. We then examine the influence of society on a couple using mean-field sentimental games. We show that, in mean-field equilibrium, the optimal effort is always higher than the one-shot optimal effort. We illustrate numerically the influence of the couple's network on their feeling states and their well-being. © 2014 Bauso et al.

High gradient RF breakdown study

International Nuclear Information System (INIS)

Laurent, L.; Luhmann, N.C. Jr.; Scheitrum, G.; Hanna, S.; Pearson, C.; Phillips, R.

1998-01-01

Stanford Linear Accelerator Center and UC Davis have been investigating high gradient RF breakdown and its effects on pulse shortening in high energy microwave devices. RF breakdown is a critical issue in the development of high power microwave sources and next generation linear accelerators since it limits the output power of microwave sources and the accelerating gradient of linacs. The motivation of this research is to find methods to increase the breakdown threshold level in X-band structures by reducing dark current. Emphasis is focused on improved materials, surface finish, and cleanliness. The test platform for this research is a traveling wave resonant ring. A 30 MW klystron is employed to provide up to 300 MW of traveling wave power in the ring to trigger breakdown in the cavity. Five TM 01 cavities have previously been tested, each with a different combination of surface polish and/or coating. The onset of breakdown was extended up to 250 MV/m with a TiN surface finish, as compared to 210 MV/m for uncoated OFE copper. Although the TiN coating was helpful in depressing the field emission, the lowest dark current was obtained with a 1 microinch surface finish, single-point diamond-turned cavity

Jerky-type phenomena at nanocomposite surfaces : The breakdown of the coulomb friction law

NARCIS (Netherlands)

Hosson, Jeff T.M. De; Pei, Yutao; Chen, Changqiang

This article concentrates on the jerky-type phenomenon of surfaces in relative motion (i.e., a breakdown of the Coulomb friction law) in nanocomposite materials. Physical arguments are provided to understand the dependence of friction on sliding velocity in the sense of self-lubrication. Also

DOE Task Force meeting on Electrical Breakdown of Insulating Ceramics in a High Radiation Field

International Nuclear Information System (INIS)

Green, P.H.

1991-08-01

This volume contains the abstracts and presentation material from the Research Assistance Task Force Meeting ''Electrical Breakdown of Insulating Ceramics in a High-Radiation Field.'' The meeting was jointly sponsored by the Office of Basic Energy Sciences and the Office of Fusion Energy of the US Department of Energy in Vail, Colorado, May 28--June 1, 1991. The 26 participants represented expertise in fusion, radiation damage, electrical breakdown, ceramics, and semiconductor and electronic structures. These participants came from universities, industries, national laboratories, and government. The attendees represented eight nations. The Task Force meeting was organized in response to the recent discovery that a combination of temperature, electric field, and radiation for an extended period of time has an unexplained adverse effect in ceramics, termed radiation-enhanced electrical degradation (REED). REED occurs after an incubation period and continues to accelerate with irradiation until the ceramics can no longer be regarded as insulators. It appears that REED is irreversible and the ceramic insulators cannot be readily annealed or otherwise repaired for future services. This effect poses a serious threat for fusion reactors, which require electrical insulators in diagnostic devices, in radio frequency and neutral beam systems, and in magnetic assemblies. The problem of selecting suitable electrical insulating materials in thus far more serious than previously anticipated

Simulation of a three-dimensional vortex breakdown

Science.gov (United States)

Liu, C. H.; Menne, Stefan

1989-01-01

The breakdown of a vortex flow in a tube is studied for a slightly diverging tube by means of a numerical solution of the Navier-Stokes equations for a quasi-stationary, incompressible, laminar flow. Numerical results are compared to experiments of Faler and Leibovich. The numerical data display features similar to the experimental results concerning breakdown conditions, location, and structure.

Linear entropy and collapse–revival phenomenon for a general formalism N-type four-level atom interacting with a single-mode field

Science.gov (United States)

Eied, A. A.

2018-05-01

In this paper, the linear entropy and collapse-revival phenomenon through the relation ( -{\\bar{n}}) in a system of N-configuration four-level atom interacting with a single-mode field with additional forms of nonlinearities of both the field and the intensity-dependent atom-field coupling functional are investigated. A factorization of the initial density operator is assumed, considering the field to be initially in a squeezed coherent states and the atom initially in its most upper excited state. The dynamical behavior of the linear entropy and the time evolution of ( -{\\bar{n}}) are analyzed. In particular, the effects of the mean photon number, detuning, Kerr-like medium and the intensity-dependent coupling functional on the entropy and the evolution of ( -{\\bar{n}}) are examined.

Extended Deterministic Mean-Field Games

KAUST Repository

Gomes, Diogo A.

2016-04-21

In this paper, we consider mean-field games where the interaction of each player with the mean field takes into account not only the states of the players but also their collective behavior. To do so, we develop a random variable framework that is particularly convenient for these problems. We prove an existence result for extended mean-field games and establish uniqueness conditions. In the last section, we consider the Master Equation and discuss properties of its solutions.

Extended Deterministic Mean-Field Games

KAUST Repository

Gomes, Diogo A.; Voskanyan, Vardan K.

2016-01-01

In this paper, we consider mean-field games where the interaction of each player with the mean field takes into account not only the states of the players but also their collective behavior. To do so, we develop a random variable framework that is particularly convenient for these problems. We prove an existence result for extended mean-field games and establish uniqueness conditions. In the last section, we consider the Master Equation and discuss properties of its solutions.

Impulse breakdown of small air gap in electric field Part I: Influence ...

African Journals Online (AJOL)

The influence of barrier position on breakdown voltage in air dielectric has been investigated. Needle and Cone positive point electrodes were used and the effects of electrode curvature on barrier position for maximum breakdown voltage were compared, with air gap for the point to plane electrode fixed at 10 cm for all the ...

Effect of High Solenoidal Magnetic Fields on Breakdown Voltages of High Vacuum 805 MHz Cavities

CERN Document Server

Moretti, A; Geer, S; Qian, Z

2004-01-01

The demonstration of muon ionization cooling by a large factor is necessary to demonstrate the feasilibility of a collider or neutrino factory. An important cooling experiment, MICE [1], has been proposed to demonstrate 10 % cooling which will validate the technology. Ionization cooling is accomplished by passing a high-emittance beam in a multi-Tesla solenoidal channel alternately through regions of low Z material and very high accelerating RF Cavities. To determine the effect of very large solenoidal magnetic fields on the generations of Dark current, X-Rays and breakdown Voltage gradients of vacuum RF cavities, a test facility has been established at Fermilab in Lab G. This facility consists of a 12 MW 805 MHz RF station, and a large bore 5 T solenoidal superconducting magnet containing a pill box type Cavity with thin removable window apertures allowing dark current studies and breakdown studies of different materials. The results of this study will be presented. The study has shown that the peak achievab...

RF Breakdown in Normal Conducting Single-cell Structures

CERN Document Server

Dolgashev, Valery A; Higo, Toshiyasu; Nantista, Christopher D; Tantawi, Sami G

2005-01-01

Operating accelerating gradient in normal conducting accelerating structures is often limited by rf breakdown. The limit depends on multiple parameters, including input rf power, rf circuit, cavity shape and material. Experimental and theoretical study of the effects of these parameters on the breakdown limit in full scale structures is difficult and costly. We use 11.4 GHz single-cell traveling wave and standing wave accelerating structures for experiments and modeling of rf breakdown behavior. These test structures are designed so that the electromagnetic fields in one cell mimic the fields in prototype multicell structures for the X-band linear collider. Fields elsewhere in the test structures are significantly lower than that of the single cell. The setup uses matched mode converters that launch the circular TM01 mode into short test structures. The test structures are connected to the mode launchers with vacuum rf flanges. This setup allows economic testing of different cell geometries, cell materials an...

Source-Drain Punch-Through Analysis of High Voltage Off-State AlGaN/GaN HEMT Breakdown

Science.gov (United States)

Jiang, H.; Li, X.; Wang, J.; Zhu, L.; Wang, H.; Liu, J.; Wang, M.; Yu, M.; Wu, W.; Zhou, Y.; Dai, G.

2017-06-01

AlGaN/GaN high-electron mobility transistor’s (HEMT’s) off-state breakdown is investigated using conventional three-terminal off-state breakdown I-V measurement. Competition between gate leakage and source-injection buffer leakage (SIBL) is discussed in detail. It is found that the breakdown is dominated by source-injection which is sensitive to gate voltage and gate length at large gate-to-drain spacing (Lgd > 7μm), where a threshold drain voltage of the occurrence of the SIBL current in GaN buffer exists, and after this threshold voltage the SIBL current continually increased till the buffer breakdown. Our analysis showed that due to the punch-through effect in the buffer, a potential barrier between 2DEG and GaN buffer at the source side mainly controlled by the drain voltage determines the buffer leakage current and the occurrence of the following buffer breakdown, which could explain the experimentally observed breakdown phenomenon.

THE METHODS OF CALCULATIONS OF THE TEMPERATURE BREAKDOWN FIELD IN THE LINE OF THE MODEM HIGH-SPEED WIRE MILL

Directory of Open Access Journals (Sweden)

S. M. Zhuchkov

2007-01-01

Full Text Available The calculation methods of the temperature field of the breakdown, being rolled in lines of the modern high-speed wire mill, is developed on the basis of solving of problem of the contact exchange of hot metal with cold rollers.

Abnormal breakdown characteristic in a two-phase mixture

International Nuclear Information System (INIS)

Ye Qizheng; Li Jin; Lu Fei

2006-01-01

A two-phase mixture (TPM) is a mixture of gas and macroparticles of high concentration. Based on Townsend's theory, a new cell-iterative model in analytical form for the breakdown mechanism in TPM is presented. Compared with the original cell-iterative model in our previous paper, the obstructive factor of the macroparticles that influences the electron avalanche propagation is considered, except for the macroparticles distorting the electrical field and capture of the electrons. The cell attractive parameter k is presented according to the classical continuum theory for field charging. The modified Paschen law for a TPM is presented to calculate the breakdown voltage. The breakdown voltage of the TPM, U TPM , increases gradually with an increase in the macroparticle number density (m). The voltage U TPM is lower than that of the pure gas at low m values and larger at high m values. With a decrease of the macroparticle volume fraction and the dielectric mismatch, the voltage U TPM increases gradually at low m values and decreases gradually at high m values. The voltage U TPM at pd 200 cm Torr is lower than that at pd = 760 cm Torr for low m values and larger for high m values. This kind of abnormal breakdown characteristic in the TPM occurs in the case of high macroparticle volume fraction. On the other hand, the minimum of the TPM's Paschen curve increases with increase in m. It provides the possibility and the conditions of greatly increasing the breakdown voltage in a nearly uniform field

Abnormal breakdown characteristic in a two-phase mixture

Energy Technology Data Exchange (ETDEWEB)

Ye Qizheng; Li Jin; Lu Fei [College of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan, 430074 (China)

2006-05-21

A two-phase mixture (TPM) is a mixture of gas and macroparticles of high concentration. Based on Townsend's theory, a new cell-iterative model in analytical form for the breakdown mechanism in TPM is presented. Compared with the original cell-iterative model in our previous paper, the obstructive factor of the macroparticles that influences the electron avalanche propagation is considered, except for the macroparticles distorting the electrical field and capture of the electrons. The cell attractive parameter k is presented according to the classical continuum theory for field charging. The modified Paschen law for a TPM is presented to calculate the breakdown voltage. The breakdown voltage of the TPM, U{sub TPM}, increases gradually with an increase in the macroparticle number density (m). The voltage U{sub TPM} is lower than that of the pure gas at low m values and larger at high m values. With a decrease of the macroparticle volume fraction and the dielectric mismatch, the voltage U{sub TPM} increases gradually at low m values and decreases gradually at high m values. The voltage U{sub TPM} at pd 200 cm Torr is lower than that at pd = 760 cm Torr for low m values and larger for high m values. This kind of abnormal breakdown characteristic in the TPM occurs in the case of high macroparticle volume fraction. On the other hand, the minimum of the TPM's Paschen curve increases with increase in m. It provides the possibility and the conditions of greatly increasing the breakdown voltage in a nearly uniform field.

Experimental and theoretical study of breakdown mechanisms in a gas in an uniform electric field

Energy Technology Data Exchange (ETDEWEB)

Bayle, P

1975-01-01

The theoretical study of breakdown mechanisms in a gas with an applied electric field has been made on the basis of a deterministic model built on continuity equations governing the evolution of electronic and ionic densities. With this purpose, the breakdown formation has been simulated in electronegative gases (air, oxygen) taking into account the space charge effects on initial applied electric field, the electronic emission on the cathode by photonic or ionic impact, the delayed electrons processes (attachment, detachment) and charge exchange processes. Without space charge, the influence of photoionization in the gas on the electronic and ionic population has been pointed out in a discharge in nitrogen. Then the problem of external electrode discharges has been approached for the study of plasma visualization pannel cells, and the fundamental role of the charges deposed on dielectrics has been manifested. In the experimental study, the discharge formation has been analysed in rare gases and nitrogen for high over voltages (more than 100%) and for pressures of about hundred torrs. Using high-speed cinematographic techniques, the discharge propagation has been studied with a one nanosecond time resolution. The ultra-fast propagation zone of anode-directed streamer has been linked with the intervention of distance ionization process. The arrival of the streamers on the anode induces the beginning of an ionization front propagating towards the cathode.

Experimental and theoretical study of breakdown mechanisms in a gas in an uniform electric field

International Nuclear Information System (INIS)

Bayle, Pierre.

1975-01-01

The theoretical study of breakdown mechanisms in a gas with an applied electric field has been made on the basis of a deterministic model built on continuity equations governing the evolution of electronic and ionic densities. With this purpose, the breakdown formation has been simulated in electronegative gases (air, oxygen) taking into account the space charge effects on initial applied electric field, the electronic emission on the cathode by photonic or ionic impact, the delayed electrons processes (attachment, detachment) and charge exchange processes. Without space charge, the influence of photoionization in the gas on the electronic and ionic population has been pointed out in a discharge in nitrogen. Then the problem of external electrode discharges has been approached for the study of plasma visualization pannel cells, and the fundamental role of the charges deposed on dielectrics has been manifested. In the experimental study, the discharge formation has been analysed in rare gases and nitrogen for high over voltages (more than 100%) and for pressures of about hundred torrs. Using high-speed cinematographic techniques, the discharge propagation has been studied with a one nanosecond time resolution. The ultra-fast propagation zone of anode-directed streamer has been linked with the intervention of distance ionization process. The arrival of the streamers on the anode induces the beginning of an ionization front propagating towards the cathode [fr

Breakdown in ZnO Varistors by High Power Electrical Pulses; TOPICAL

International Nuclear Information System (INIS)

PIKE, GORDON E.

2001-01-01

This report documents an investigation of irreversible electrical breakdown in ZnO varistors due to short pulses of high electric field and current density. For those varistors that suffer breakdown, there is a monotonic, pulse-by-pulse degradation in the switching electric field. The electrical and structural characteristics of varistors during and after breakdown are described qualitatively and quantitatively. Once breakdown is nucleated, the degradation typically follows a well-defined relationship between the number of post-initiation pulses and the degraded switching voltage. In some cases the degraded varistor has a remnant 20(micro)m diameter hollow track showing strong evidence of once-molten ZnO. A model is developed for both electrical and thermal effects during high energy pulsing. The breakdown is assumed to start at one electrode and advance towards the other electrode as a thin filament of conductive material that grows incrementally with each successive pulse. The model is partially validated by experiments in which the varistor rod is cut at several different lengths from the electrode. Invariably one section of the cut varistor has a switching field that is not degraded while the other section(s) are heavily degraded. Based on the experiments and models of behavior during breakdown, some speculations about the nature of the nucleating mechanism are offered in the last section

Conditions for electron runaway under leader breakdown of long gaps

International Nuclear Information System (INIS)

Ul'yanov, K. N.

2008-01-01

An original hydrodynamic model in which inelastic collisions in the equations of motion and energy balance play a decisive role is developed and applied to simulate electron avalanches in strong electric fields. The mean energy and drift velocity of electrons, as well as the ionization coefficient and electric field in a wide range of mean electron energies, are determined for helium and xenon. A criterion is derived for the runaway of the average electron in discharges with ionization multiplication. It is shown that runaway can take place at any value of E/p, provided that the momentum mean free path exceeds the gap length. The voltage corresponding to electron runaway is found for helium, xenon, and air as a function of the electric field, the electron mean energy, and the parameter pd. Conditions for the formation of a precursor in electronegative gases are analyzed. It is shown that the presence of a precursor with a high electric conductance is necessary for the formation of a new leader step. The voltage and time ranges corresponding to efficient electron runaway and X-ray generation during leader breakdown in air are determined

Gas breakdown in tokamaks

International Nuclear Information System (INIS)

Abramov, V.A.; Pogutse, O.P.; Yurchenko, Eh.I.

1975-01-01

The initial stage of the charge development in a tokomak is considered theoretically. It is supposed that all electrons produced in neutral gas ionisation process are in the regime of an almost continuous acceleration. The production time of a given electron density is calculated as a function of the neutral gas density and of parameters of the vortex electric field. The mechanism of plasma escape on walls is considered. It is shown that the escaping time is defined by a specific inertial flow of plasma and depends on whether chamber walls are metal or dielectric. The criterion of the gas breakdown in a toroidal system is formulated. The developed theory is shown to explain a strong dependence of the breakdown on the gas initial density [ru

Electron drift velocity in SF{sub 6} in strong electric fields determined from rf breakdown curves

Energy Technology Data Exchange (ETDEWEB)

Lisovskiy, V; Yegorenkov, V [Department of Physics and Technology, Kharkov National University, Svobody sq.4, Kharkov 61077 (Ukraine); Booth, J-P [Laboratoire de Physique des Plasmas, Ecole Polytechnique, Palaiseau 91128 (France); Landry, K [Unaxis Displays Division France SAS, 5, Rue Leon Blum, Palaiseau 91120 (France); Douai, D [Physical Sciences Division, Institute for Magnetic Fusion Research, CEA Centre de Cadarache, F-13108 Saint Paul lez Durance Cedex (France); Cassagne, V, E-mail: lisovskiy@yahoo.co [Developpement Photovoltaique Couches Minces, Total, 2, place Jean Millier, La Defense 6, 92400 Courbevoie (France)

2010-09-29

This paper presents measurements of the electron drift velocity V{sub dr} in SF{sub 6} gas for high reduced electric fields (E/N = 330-5655 Td (1 Td = 10{sup -17} V cm{sup 2})). The drift velocities were obtained using the method of Lisovskiy and Yegorenkov (1998 J. Phys. D: Appl. Phys. 31 3349) based on the determination of the pressure and voltage of the turning points of rf capacitive discharge breakdown curves for a range of electrode spacings. The V{sub dr} values thus obtained were in good agreement with those calculated from the cross-sections of Phelps and Van Brunt (1988 J. Appl. Phys. 64 4269) using the BOLSIG code. The validity of the Lisovskiy-Yegorenkov method is discussed and we show that it is applicable over the entire E/N range where rf discharge ignition at breakdown occurs for rf frequencies of 13.56 MHz or above.

Breakdown Characteristics Study on an 18 Cell X-band Structure

International Nuclear Information System (INIS)

Wang, F

2008-01-01

A CLIC designed 18 cells, low group velocity (2.4% to 1.0% c), X-band (11.4 GHz) accelerator structure (denoted T18) was designed at CERN, its cells were built at KEK, and it was assembled and tested at SLAC. An interesting feature of this structure is that the gradient in the last cell is about 50% higher than that in the first cell. This structure has been RF conditioned at SLAC NLCTA for about 1400 hours where it incurred about 2200 breakdowns. This paper presents the characteristics of these breakdowns, including (1) the breakdown rate dependence on gradient, pulse width and conditioning time, (2) the breakdown distribution along the structure, (3) relation between breakdown and pulsed heating dependence study and (4) electric field decay time for breakdown changing over the whole conditioning time. Overall, this structure performed very well, having a final breakdown rate of less than 1e-6/pulse/m at 106 MV/m with 230 ns pulse width

Breakdown Characteristics Study on an 18 Cell X-band Structure

International Nuclear Information System (INIS)

Wang Faya

2009-01-01

A CLIC designed 18 cells, low group velocity (2.4% to 1.0% c), X-band (11.4 GHz) accelerator structure (denoted T18) was designed at CERN, its cells were built at KEK, and it was assembled and tested at SLAC. An interesting feature of this structure is that the gradient in the last cell is about 50% higher than that in the first cell. This structure has been RF conditioned at SLAC NLCTA for about 1400 hours where it incurred about 2200 breakdowns. This paper presents the characteristics of these breakdowns, including 1) the breakdown rate dependence on gradient, pulse width and conditioning time, 2) the breakdown distribution along the structure, 3) relation between breakdown and pulsed heating dependence study and 4) electric field decay time for breakdown changing over the whole conditioning time. Overall, this structure performed very well, having a final breakdown rate of less than 1e-6/pulse/m at 106 MV/m with 230 ns pulse width.

Measurements of electron avalanche formation time in W-band microwave air breakdown

International Nuclear Information System (INIS)

Cook, Alan M.; Hummelt, Jason S.; Shapiro, Michael A.; Temkin, Richard J.

2011-01-01

We present measurements of formation times of electron avalanche ionization discharges induced by a focused 110 GHz millimeter-wave beam in atmospheric air. Discharges take place in a free volume of gas, with no nearby surfaces or objects. When the incident field amplitude is near the breakdown threshold for pulsed conditions, measured formation times are ∼0.1-2 μs over the pressure range 5-700 Torr. Combined with electric field breakdown threshold measurements, the formation time data shows the agreement of 110 GHz air breakdown with the similarity laws of gas discharges.

Measurements of electron avalanche formation time in W-band microwave air breakdown

Science.gov (United States)

Cook, Alan M.; Hummelt, Jason S.; Shapiro, Michael A.; Temkin, Richard J.

2011-08-01

We present measurements of formation times of electron avalanche ionization discharges induced by a focused 110 GHz millimeter-wave beam in atmospheric air. Discharges take place in a free volume of gas, with no nearby surfaces or objects. When the incident field amplitude is near the breakdown threshold for pulsed conditions, measured formation times are ˜0.1-2 μs over the pressure range 5-700 Torr. Combined with electric field breakdown threshold measurements, the formation time data shows the agreement of 110 GHz air breakdown with the similarity laws of gas discharges.

Mean-field magnetohydrodynamics and dynamo theory

CERN Document Server

Krause, F

2013-01-01

Mean-Field Magnetohydrodynamics and Dynamo Theory provides a systematic introduction to mean-field magnetohydrodynamics and the dynamo theory, along with the results achieved. Topics covered include turbulence and large-scale structures; general properties of the turbulent electromotive force; homogeneity, isotropy, and mirror symmetry of turbulent fields; and turbulent electromotive force in the case of non-vanishing mean flow. The turbulent electromotive force in the case of rotational mean motion is also considered. This book is comprised of 17 chapters and opens with an overview of the gen

Continuous Time Finite State Mean Field Games

International Nuclear Information System (INIS)

Gomes, Diogo A.; Mohr, Joana; Souza, Rafael Rigão

2013-01-01

In this paper we consider symmetric games where a large number of players can be in any one of d states. We derive a limiting mean field model and characterize its main properties. This mean field limit is a system of coupled ordinary differential equations with initial-terminal data. For this mean field problem we prove a trend to equilibrium theorem, that is convergence, in an appropriate limit, to stationary solutions. Then we study an N+1-player problem, which the mean field model attempts to approximate. Our main result is the convergence as N→∞ of the mean field model and an estimate of the rate of convergence. We end the paper with some further examples for potential mean field games

Continuous Time Finite State Mean Field Games

Energy Technology Data Exchange (ETDEWEB)

Gomes, Diogo A., E-mail: dgomes@math.ist.utl.pt [Instituto Superior Tecnico, Center for Mathematical Analysis, Geometry, and Dynamical Systems, Departamento de Matematica (Portugal); Mohr, Joana, E-mail: joana.mohr@ufrgs.br; Souza, Rafael Rigao, E-mail: rafars@mat.ufrgs.br [UFRGS, Instituto de Matematica (Brazil)

2013-08-01

In this paper we consider symmetric games where a large number of players can be in any one of d states. We derive a limiting mean field model and characterize its main properties. This mean field limit is a system of coupled ordinary differential equations with initial-terminal data. For this mean field problem we prove a trend to equilibrium theorem, that is convergence, in an appropriate limit, to stationary solutions. Then we study an N+1-player problem, which the mean field model attempts to approximate. Our main result is the convergence as N{yields}{infinity} of the mean field model and an estimate of the rate of convergence. We end the paper with some further examples for potential mean field games.

RF BREAKDOWN STUDIES USING PRESSURIZED CAVITIES

Energy Technology Data Exchange (ETDEWEB)

Johnson, Rolland

2014-09-21

Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Part of the problem is that RF breakdown in an evacuated cavity involves a complex mixture of effects, which include the geometry, metallurgy, and surface preparation of the accelerating structures and the make-up and pressure of the residual gas in which plasmas form. Studies showed that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas, as needed for muon cooling channels, without the need for long conditioning times, even in the presence of strong external magnetic fields. This positive result was expected because the dense gas can practically eliminate dark currents and multipacting. In this project we used this high pressure technique to suppress effects of residual vacuum and geometry that are found in evacuated cavities in order to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of magnetic field, frequency, and surface preparation. One of the interesting and useful outcomes of this project was the unanticipated collaborations with LANL and Fermilab that led to new insights as to the operation of evacuated normal-conducting RF cavities in high external magnetic fields. Other accomplishments included: (1) RF breakdown experiments to test the effects of SF6 dopant in H2 and He gases with Sn, Al, and Cu electrodes were carried out in an 805 MHz cavity and compared to calculations and computer simulations. The heavy corrosion caused by the SF6 components led to the suggestion that a small admixture of oxygen, instead of SF6, to the hydrogen would allow the same advantages without the corrosion in a practical muon beam line. (2) A

Junction depth dependence of breakdown in silicon detector diodes

International Nuclear Information System (INIS)

Beck, G.A.; Carter, A.A.; Carter, J.R.; Greenwood, N.M.; Lucas, A.D.; Munday, D.J.; Pritchard, T.W.; Robinson, D.; Wilburn, C.D.; Wyllie, K.

1996-01-01

The high voltage capability of detector diodes fabricated in the planar process is limited by the high field generated at the edge of the junction.We have fabricated diodes with increased junction depth with respect to our standard process and find a significantly higher breakdown voltage,in reasonable agreement with previous studies of junction breakdown. (orig.)

Numerical investigation of MHD heat transfer in a vertical round tube affected by transverse magnetic field

Energy Technology Data Exchange (ETDEWEB)

Zikanov, Oleg [University of Michigan - Dearborn, MI 48128-1491 (United States); Listratov, Yaroslav [Moscow Power Engineering Institute, 14 Karsnokazarmennaya St., Moscow 111250 (Russian Federation)

2016-12-15

Numerical simulations of the flow of a liquid metal in a vertical pipe are performed. The configuration reproduces the test section of the recent experiment . The mean flow is directed downward, a half of the pipe's wall is heated, and a strong horizontal magnetic field perpendicular to the temperature gradient is imposed. The simulations produce results in good agreement with the experiment and lead us to an explanation of the observed phenomenon of anomalous high-amplitude temperature fluctuations. The fluctuations are caused by growth and quasi-periodic breakdown of the pairs of ascending and descending jets related to the elevator-mode thermal convection. Implications for operation of liquid metal blankets with poloidal ducts are discussed.

Continuous time finite state mean field games

KAUST Repository

Gomes, Diogo A.; Mohr, Joana; Souza, Rafael Rigã o

2013-01-01

In this paper we consider symmetric games where a large number of players can be in any one of d states. We derive a limiting mean field model and characterize its main properties. This mean field limit is a system of coupled ordinary differential equations with initial-terminal data. For this mean field problem we prove a trend to equilibrium theorem, that is convergence, in an appropriate limit, to stationary solutions. Then we study an N+1-player problem, which the mean field model attempts to approximate. Our main result is the convergence as N→∞ of the mean field model and an estimate of the rate of convergence. We end the paper with some further examples for potential mean field games. © 2013 Springer Science+Business Media New York.

Continuous time finite state mean field games

KAUST Repository

Gomes, Diogo A.

2013-04-23

In this paper we consider symmetric games where a large number of players can be in any one of d states. We derive a limiting mean field model and characterize its main properties. This mean field limit is a system of coupled ordinary differential equations with initial-terminal data. For this mean field problem we prove a trend to equilibrium theorem, that is convergence, in an appropriate limit, to stationary solutions. Then we study an N+1-player problem, which the mean field model attempts to approximate. Our main result is the convergence as N→∞ of the mean field model and an estimate of the rate of convergence. We end the paper with some further examples for potential mean field games. © 2013 Springer Science+Business Media New York.

An LOD with improved breakdown voltage in full-frame CCD devices

Science.gov (United States)

Banghart, Edmund K.; Stevens, Eric G.; Doan, Hung Q.; Shepherd, John P.; Meisenzahl, Eric J.

2005-02-01

In full-frame image sensors, lateral overflow drain (LOD) structures are typically formed along the vertical CCD shift registers to provide a means for preventing charge blooming in the imager pixels. In a conventional LOD structure, the n-type LOD implant is made through the thin gate dielectric stack in the device active area and adjacent to the thick field oxidation that isolates the vertical CCD columns of the imager. In this paper, a novel LOD structure is described in which the n-type LOD impurities are placed directly under the field oxidation and are, therefore, electrically isolated from the gate electrodes. By reducing the electrical fields that cause breakdown at the silicon surface, this new structure permits a larger amount of n-type impurities to be implanted for the purpose of increasing the LOD conductivity. As a consequence of the improved conductance, the LOD width can be significantly reduced, enabling the design of higher resolution imaging arrays without sacrificing charge capacity in the pixels. Numerical simulations with MEDICI of the LOD leakage current are presented that identify the breakdown mechanism, while three-dimensional solutions to Poisson's equation are used to determine the charge capacity as a function of pixel dimension.

Vortex breakdown in a cylinder with a rotating bottom and a flat stress-free surface

International Nuclear Information System (INIS)

Serre, E.; Bontoux, P.

2007-01-01

Vortex breakdown and transition to time-dependent regimes are investigated in a cylinder (H/R = 4) with a rotating disk and a free-surface. The aim of this study is to show how, by changing upstream conditions it is possible to alter on the flow, particularly the vortex breakdown process. The understanding of such effects on vortex breakdown is very useful in the development of a control strategy in order to intensify or remove the phenomenon. The flow dynamics are explored through numerical solution of the three-dimensional Navier-Stokes equations based on high-order spectral approximations. The use of a flat, stress-free model for the air/water interface is shown to be entirely satisfactory at least for moderate Reynolds numbers. A particular interest of these results is to show how the bubble related to the vortex breakdown becomes attached to the free-surface and grows in diameter as the Reynolds number is increased, Re ≥ 2900. Such a phenomenon removes the cylindrical vortex core upstream of the breakdown which is usually included in classical theories based on idealized models of vortex flows. The flow is shown to be unstable to three-dimensional perturbations for sufficiently large rotation rates. The bifurcated state takes the form of a k = 3 rotating wave at Re = 3000. The existence of the free-surface promotes the onset of periodicity, with a critical Reynolds number about 15% lower than in the case with a rigid cover. Moreover, the successive bifurcations occur over a much shorter range of Reynolds numbers and lead rapidly to a multi-frequency regime with more than five different frequencies. In the unsteady regime, the vortex breakdown is characterized by an elongated, asymmetric recirculation zone, attached to the free-surface and precessing around the axis of the container. By increasing the rotation, the circular stagnation line on the free-surface takes a more irregular form and starts to move around the axis of the cylinder in the same sense as

Mean field interaction in biochemical reaction networks

KAUST Repository

Tembine, Hamidou; Tempone, Raul; Vilanova, Pedro

2011-01-01

In this paper we establish a relationship between chemical dynamics and mean field game dynamics. We show that chemical reaction networks can be studied using noisy mean field limits. We provide deterministic, noisy and switching mean field limits

Mean Field Games Models-A Brief Survey

KAUST Repository

Gomes, Diogo A.

2013-11-20

The mean-field framework was developed to study systems with an infinite number of rational agents in competition, which arise naturally in many applications. The systematic study of these problems was started, in the mathematical community by Lasry and Lions, and independently around the same time in the engineering community by P. Caines, Minyi Huang, and Roland Malhamé. Since these seminal contributions, the research in mean-field games has grown exponentially, and in this paper we present a brief survey of mean-field models as well as recent results and techniques. In the first part of this paper, we study reduced mean-field games, that is, mean-field games, which are written as a system of a Hamilton-Jacobi equation and a transport or Fokker-Planck equation. We start by the derivation of the models and by describing some of the existence results available in the literature. Then we discuss the uniqueness of a solution and propose a definition of relaxed solution for mean-field games that allows to establish uniqueness under minimal regularity hypothesis. A special class of mean-field games that we discuss in some detail is equivalent to the Euler-Lagrange equation of suitable functionals. We present in detail various additional examples, including extensions to population dynamics models. This section ends with a brief overview of the random variables point of view as well as some applications to extended mean-field games models. These extended models arise in problems where the costs incurred by the agents depend not only on the distribution of the other agents, but also on their actions. The second part of the paper concerns mean-field games in master form. These mean-field games can be modeled as a partial differential equation in an infinite dimensional space. We discuss both deterministic models as well as problems where the agents are correlated. We end the paper with a mean-field model for price impact. © 2013 Springer Science+Business Media New York.

Mean Field Games Models-A Brief Survey

KAUST Repository

Gomes, Diogo A.; Saú de, Joã o

2013-01-01

The mean-field framework was developed to study systems with an infinite number of rational agents in competition, which arise naturally in many applications. The systematic study of these problems was started, in the mathematical community by Lasry and Lions, and independently around the same time in the engineering community by P. Caines, Minyi Huang, and Roland Malhamé. Since these seminal contributions, the research in mean-field games has grown exponentially, and in this paper we present a brief survey of mean-field models as well as recent results and techniques. In the first part of this paper, we study reduced mean-field games, that is, mean-field games, which are written as a system of a Hamilton-Jacobi equation and a transport or Fokker-Planck equation. We start by the derivation of the models and by describing some of the existence results available in the literature. Then we discuss the uniqueness of a solution and propose a definition of relaxed solution for mean-field games that allows to establish uniqueness under minimal regularity hypothesis. A special class of mean-field games that we discuss in some detail is equivalent to the Euler-Lagrange equation of suitable functionals. We present in detail various additional examples, including extensions to population dynamics models. This section ends with a brief overview of the random variables point of view as well as some applications to extended mean-field games models. These extended models arise in problems where the costs incurred by the agents depend not only on the distribution of the other agents, but also on their actions. The second part of the paper concerns mean-field games in master form. These mean-field games can be modeled as a partial differential equation in an infinite dimensional space. We discuss both deterministic models as well as problems where the agents are correlated. We end the paper with a mean-field model for price impact. © 2013 Springer Science+Business Media New York.

Mean-field theory and solitonic matter

International Nuclear Information System (INIS)

Cohen, T.D.

1989-01-01

Finite density solitonic matter is considered in the context of quantum field theory. Mean-field theory, which provides a reasonable description for single-soliton properties gives rise to a crystalline description. A heuristic description of solitonic matter is given which shows that the low-density limit of solitonic matter (the limit which is presumably relevant for nuclear matter) does not commute with the mean-field theory limit and gives rise to a Fermi-gas description of the system. It is shown on the basis of a formal expansion of simple soliton models in terms of the coupling constant why one expects mean-field theory to fail at low densities and why the corrections to mean-field theory are nonperturbative. This heuristic description is tested against an exactly solvable 1+1 dimensional model (the sine-Gordon model) and found to give the correct behavior. The relevance of these results to the program of doing nuclear physics based on soliton models is discussed. (orig.)

The limits of the mean field

International Nuclear Information System (INIS)

Guerra, E.M. de

2001-01-01

In these talks, we review non relativistic selfconsistent mean field theories, their scope and limitations. We first discuss static and time dependent mean field approaches for particles and quasiparticles, together with applications. We then discuss extensions that go beyond the non-relativistic independent particle limit. On the one hand, we consider extensions concerned with restoration of symmetries and with the treatment of collective modes, particularly by means of quantized ATDHF. On the other hand, we consider extensions concerned with the relativistic dynamics of bound nucleons. We present data on nucleon momentum distributions that show the need for relativistic mean field approach and probe the limits of the mean field concept. Illustrative applications of various methods are presented stressing the role that selfconsistency plays in providing a unifying reliable framework to study all sorts of properties and phenomena. From global properties such as size, mass, lifetime,.., to detailed structure in excitation spectra (high spin, RPA modes,..), as well as charge, magnetization and velocity distributions. (orig.)

Collision and diffusion in microwave breakdown of nitrogen gas in and around microgaps

International Nuclear Information System (INIS)

Campbell, J. D.; Lenters, G. T.; Bowman, A.; Remillard, S. K.

2014-01-01

The microwave induced breakdown of N 2 gas in microgaps was modeled using the collision frequency between electrons and neutral molecules and the effective electric field concept. Low pressure breakdown at the threshold electric field occurs outside the gap, but at high pressures it is found to occur inside the microgap with a large threshold breakdown electric field corresponding to a very large electron oscillation amplitude. Three distinct pressure regimes are apparent in the microgap breakdown: a low pressure multipactor branch, a mid-pressure Paschen branch, both of which occur in the space outside the microgap, and a high pressure diffusion-drift branch, which occurs inside the microgap. The Paschen and diffusion-drift branches are divided by a sharp transition and each separately fits the collision frequency model. There is evidence that considerable electron loss to the microgap faces accompanies the diffusion-drift branch in microgaps

Mean field interaction in biochemical reaction networks

KAUST Repository

Tembine, Hamidou

2011-09-01

In this paper we establish a relationship between chemical dynamics and mean field game dynamics. We show that chemical reaction networks can be studied using noisy mean field limits. We provide deterministic, noisy and switching mean field limits and illustrate them with numerical examples. © 2011 IEEE.

Breakdown characteristics of SF6/N2 in severely non-uniform electric fields at low temperatures

Science.gov (United States)

Wang, Y.; Gao, Z. W.; Li, G. X.; Zhu, X. C.; Yu, C. L.; Liang, J. Q.; Li, L.

2018-01-01

SF6 has good electrical insulating properties, which is widely used as an insulating medium of GIS, GIL and other electrical equipment. However, the reliability of electrical equipments´ insulated gas is greatly challenged in cold areas, since SF6 more readily liquefies. To solve the problem, SF6 can be mixed with N2 to maintain the insulating properties, and reduce its liquefaction temperature. Such practice has certain application prospect. In this paper, a breakdown experimental platform was built to study the insulating property of SF6/N2 at low temperature, wherein the temperature of the platform can be adjusted. A severely non-uniform electric field was generated by a rod-plate electrode. The breakdown characteristics of SF6/N2 with different mixing proportions at low pressures and low temperatures were measured. The result showed that the mixed gas was not liquefied within the temperature range. Temperature had insignificant influence on the insulating property thereof. The result in the paper has certain guiding significance for applying SF6/N2 mixed gas in high latitude areas.

Exploration of transnationalism as a concept and phenomenon in Public Administration

Directory of Open Access Journals (Sweden)

Barry Hanyane

2015-12-01

Full Text Available Transnationalism as both a phenomenon and a concept has received negligible attention in modern times in relation to the practice of public administration and its corresponding field of study. This article provides an account of the meaning and the relevance of both the concept and phenomenon as received and applied by practitioners and scholars in the said practice and field of study. From the latter, a deliberate approach towards policy matters is undertaken in relation to the concept and phenomenon of transnationalism. In this article policies used by the national Department of Home Affairs in South Africa form the basis from which a case is made relevant to this topic in p(Public a(Administration. Additionally, case studies in the SADC region are considered. This article therefore argues that transnationalism is as much local as global issues such as immigration, citizenship, global economy, service delivery, government (inefficiency and (ineffectiveness and such other matters of public interest.

X- and O-mode ECH breakdown and startup in TCA

International Nuclear Information System (INIS)

Whaley, D.R.; Goodman, T.P.; Pochelon, A.; Behn, R.; Cardinali, A.; Duval, B.P.; Joye, B.; Tran, M.Q.

1992-02-01

We have performed a comparative study of X- and O-mode high field side launch for ECH breakdown and startup of tokamak plasmas. We observe that X-mode power is not absorbed at the cyclotron resonance but uniquely at the upper hybrid resonance, displaced to the lower field side of the cyclotron resonance. O-mode power, however, is absorbed at the cyclotron resonance as well. We also observe that the displacement of the upper hybrid resonance to the low field side with O-mode launch is significantly smaller than with X-mode launch due to the lower densities produced at the same microwave power level. The result is a more central and less localized breakdown with O-mode launch. The breakdown characteristics of X- and O-mode launch are seen to affect the position of the initial plasma current centroid in the poloidal cross section. We observe a strong correlation between the initial current ramp and the initial plasma current position which is most likely due to the dependence of the plasma inductance, toroidal electric field, and field-line connection lengths on the plasma major radius. X-mode startup occurs further to the low field side where current ramp rates are observed to be poor. (author) 18 figs., 23 refs

The validity of the general similarity law for electrical breakdown of gases

International Nuclear Information System (INIS)

Osmokrovic, Predrag; Zivic, Tamara; Loncar, Boris; Vasic, Aleksandra

2006-01-01

This paper investigates the validity of the similarity law in cases of dc and pulse breakdown of gases. Geometrically similar systems insulated with SF 6 gas were used during experiments. It is shown that the similarity law is valid for dc breakdown voltage if the electron mean free path is included in geometrical parameters of the system, but not for pulse breakdown voltages. The explanation for this is the mechanism of the pulse discharge. The similarity law was expanded to take into account mechanisms of pulse breakdown initiation. Thus, the general similarity law is obtained, the validity of which in case of a pulse breakdown is established experimentally

Structure of a swirling jet with vortex breakdown and combustion

Science.gov (United States)

Sharaborin, D. K.; Dulin, V. M.; Markovich, D. M.

2018-03-01

An experimental investigation is performed in order to compare the time-averaged spatial structure of low- and high-swirl turbulent premixed lean flames by using the particle image velocimetry and spontaneous Raman scattering techniques. Distributions of the time-average velocity, density and concentration of the main components of the gas mixture are measured for turbulent premixed swirling propane/air flames at atmospheric pressure for the equivalence ratio Φ = 0.7 and Reynolds number Re = 5000 for low- and high-swirl reacting jets. For the low-swirl jet (S = 0.41), the local minimum of the axial mean velocity is observed within the jet center. The positive value of the mean axial velocity indicates the absence of a permanent recirculation zone, and no clear vortex breakdown could be determined from the average velocity field. For the high-swirl jet (S = 1.0), a pronounced vortex breakdown took place with a bubble-type central recirculation zone. In both cases, the flames are stabilized in the inner mixing layer of the jet around the central wake, containing hot combustion products. O2 and CO2 concentrations in the wake of the low-swirl jet are found to be approximately two times smaller and greater than those in the recirculation zone of the high-swirl jet, respectively.

Double helix vortex breakdown in a turbulent swirling annular jet flow

NARCIS (Netherlands)

Vanierschot, M.; Perçin, M.; van Oudheusden, B.W.

2018-01-01

In this paper, we report on the structure and dynamics of double helix vortex breakdown in a turbulent annular swirling jet. Double helix breakdown has been reported previously for the laminar flow regime, but this structure has rarely been observed in turbulent flow. The flow field is

Breakdown of coupling dielectrics for Si microstrip detectors

International Nuclear Information System (INIS)

Candelori, A.; Paccagnella, A.; Padova Univ.; Saglimbeni, G.

1999-01-01

Double-layer coupling dielectrics for AC-coupled Si microstrip detectors have been electrically characterized in order to determine their performance in a radiation-harsh environment, with a focus on the dielectric breakdown. Two different dielectric technologies have been investigated: SiO 2 /TEOS and SiO 2 /Si 3 N 4 . Dielectrics have been tested by using a negative gate voltage ramp of 0.2 MV/(cm·s). The metal/insulator/Si I-V characteristics show different behaviours depending on the technology. The extrapolated values of the breakdown field for unirradiated devices are significantly higher for SiO 2 /Si 3 N 4 dielectrics, but the data dispersion is lower for SiO 2 /TEOS devices. No significant variation of the breakdown field has been measured after a 10 Mrad (Si) γ irradiation for SiO 2 /Si 3 N 4 dielectrics. Finally, the SiO 2 /Si 3 N 4 DC conduction is enhanced if a positive gate voltage ramp is applied with respect to the negative one, due to the asymmetric conduction of the double-layer dielectric

Dramatically enhanced electrical breakdown strength in cellulose nanopaper

Directory of Open Access Journals (Sweden)

Jianwen Huang

2016-09-01

Full Text Available Electrical breakdown behaviors of nanopaper prepared from nanofibrillated cellulose (NFC were investigated. Compared to conventional insulating paper made from micro softwood fibers, nanopaper has a dramatically enhanced breakdown strength. Breakdown field of nanopaper is 67.7 kV/mm, whereas that of conventional paper is only 20 kV/mm. Air voids in the surface of conventional paper are observed by scanning electron microscope (SEM. Further analyses using mercury intrusion show that pore diameter of conventional paper is around 1.7 μm, while that of nanopaper is below 3 nm. Specific pore size of nanopaper is determined to be approximately 2.8 nm by the gas adsorption technique. In addition, theoretical breakdown strengths of nanopaper and conventional paper are also calculated to evaluate the effect of pore size. It turns out that theoretical values agree well with experimental data, indicating that the improved strength in nanopaper is mainly attributed to the decreased pore size. Due to its outstanding breakdown strength, this study indicates the suitability of nanopaper for electrical insulation in ultra-high voltage convert transformers and other electrical devices.

Nonasymptotic mean-field games

KAUST Repository

Tembine, Hamidou

2014-12-01

Mean-field games have been studied under the assumption of very large number of players. For such large systems, the basic idea consists to approximate large games by a stylized game model with a continuum of players. The approach has been shown to be useful in some applications. However, the stylized game model with continuum of decision-makers is rarely observed in practice and the approximation proposed in the asymptotic regime is meaningless for networked systems with few entities. In this paper we propose a mean-field framework that is suitable not only for large systems but also for a small world with few number of entities. The applicability of the proposed framework is illustrated through a dynamic auction with asymmetric valuation distributions.

Nonasymptotic mean-field games

KAUST Repository

Tembine, Hamidou

2014-12-01

Mean-field games have been studied under the assumption of very large number of players. For such large systems, the basic idea consists of approximating large games by a stylized game model with a continuum of players. The approach has been shown to be useful in some applications. However, the stylized game model with continuum of decision-makers is rarely observed in practice and the approximation proposed in the asymptotic regime is meaningless for networks with few entities. In this paper, we propose a mean-field framework that is suitable not only for large systems but also for a small world with few number of entities. The applicability of the proposed framework is illustrated through various examples including dynamic auction with asymmetric valuation distributions, and spiteful bidders.

Dynamical Mean Field Approximation Applied to Quantum Field Theory

CERN Document Server

Akerlund, Oscar; Georges, Antoine; Werner, Philipp

2013-12-04

We apply the Dynamical Mean Field (DMFT) approximation to the real, scalar phi^4 quantum field theory. By comparing to lattice Monte Carlo calculations, perturbation theory and standard mean field theory, we test the quality of the approximation in two, three, four and five dimensions. The quantities considered in these tests are the critical coupling for the transition to the ordered phase and the associated critical exponents nu and beta. We also map out the phase diagram in four dimensions. In two and three dimensions, DMFT incorrectly predicts a first order phase transition for all bare quartic couplings, which is problematic, because the second order nature of the phase transition of lattice phi^4-theory is crucial for taking the continuum limit. Nevertheless, by extrapolating the behaviour away from the phase transition, one can obtain critical couplings and critical exponents. They differ from those of mean field theory and are much closer to the correct values. In four dimensions the transition is sec...

Vortex breakdown in simple pipe bends

Science.gov (United States)

Ault, Jesse; Shin, Sangwoo; Stone, Howard

2016-11-01

Pipe bends and elbows are one of the most common fluid mechanics elements that exists. However, despite their ubiquity and the extensive amount of research related to these common, simple geometries, unexpected complexities still remain. We show that for a range of geometries and flow conditions, these simple flows experience unexpected fluid dynamical bifurcations resembling the bubble-type vortex breakdown phenomenon. Specifically, we show with simulations and experiments that recirculation zones develop within the bends under certain conditions. As a consequence, fluid and particles can remain trapped within these structures for unexpectedly-long time scales. We also present simple techniques to mitigate this recirculation effect which can potentially have impact across industries ranging from biomedical and chemical processing to food and health sciences.

Experimental Study on High Electrical Breakdown of Water Dielectric

International Nuclear Information System (INIS)

Zhang Zicheng; Zhang Jiande; Yang Jianhua

2005-01-01

By means of a coaxial apparatus, pressurized water breakdown experiments with microsecond charging have been carried out with different surface roughness of electrodes and different ethylene glycol concentrations of ethylene glycol/water mixture. The experimental results about the breakdown stress and the effective time are presented. The breakdown stress is normalized to the situation that the effective time is transformed to 1 μs and analyzed. The conclusions are as follows: (1) the breakdown stress formula is modified to E = 0.561M A -1/10 t eff -1/N P 1/8 ; (2) the coefficient M is significantly increased by surface polishing and ethylene glycol additive; (3) it is accumulative for the capacity of improving electrical breakdown strength for surface polishing, ethylene glycol additive, and pressurization, of which pressurization is the most effective method; (4) the highest stress of 235.5 kV/cm is observed in ethylene glycol/water mixture with an ethylene glycol concentration of 80% at a hydrostatic pressure of 1215.9 kPa and is about one time greater than that in pure water at constant pressure; (5) for pressurization and surface polishing, the primary mechanism to improve the breakdown strength of water dielectric is the increase in the breakdown time delay. Research results indicate great potential in the application of the high power pulse conditioning system of water dielectric

HOOLIGANISM – CONTEMPORARY SOCIAL PHENOMENON

Directory of Open Access Journals (Sweden)

MARIA LULESCU

2012-05-01

Full Text Available The proposed scientific theme is going to approach and study the hooliganism phenomenon as a contemporary social matter, in terms of conceptual and etiological. The present work has four main purposes: (1- that of explaining the meaning of hooliganism social phenomenon; (2- that of discovering the origins of hooliganism; (3- that of knowing which are the causes that encourages the occurence of the hooliganism; (4- that of knowing how to control and minimize this phenomenon.

Effect of temperature on the uniform field breakdown strength of electronegative gases

International Nuclear Information System (INIS)

Christophorou, L.G.; Mathis, R.A.; Hunter, S.R.; Carter, J.G.

1987-03-01

In general, the electron attachment rate constant, k/sub a/ ( ,Υ), as a function of the mean electron energy and temperature Υ for electronegative gases which attach electrons nondissociatively decreases greatly with Υ from room temperature to Υ ≤ 600K, while that for electronegative gases which attach electrons dissociatively increases with increasing Υ. Based on recent studies in our laboratory on k/sub a/ ( ,Υ), we investigated the variation with Υ (∼295-575K) of the uniform field breakdown strength, (E/N)/sub lim/, for three classes of electronegative gases: (a) gases such as c-C 4 F 8 (and c-C 4 F 6 , 1-C 3 F 6 ) which attach strongly low-energy (≤ 1 eV) electrons nondissociatively and for which k/sub a/ ( ,Υ), decreases precipitously with Υ above ambient; (b) gases such as C 2 F 6 and CF 3 Cl which attach electrons exclusively dissociatively and whose k/sub a/ ( ,Υ) increases with Υ; and (c) gases such as C 3 F 8 and n-C 4 F 10 which attach electrons both nondissociatively and dissociatively over a common low-energy range and whose k/sub a/ ( ,Υ) first decreases and then increases with Υ above ambient. The (E/N)/sub lim/(Υ) has been found to decrease significantly with Υ for (a), to decrease slowly with Υ for (c), and to increase slightly with Υ for (b). These changes in (E/N)/sub lim/ follow those in k/sub a/ ( ,Υ). A similar behavior is expected for other electronegative gaseous dielectrics in the respective three groups

The Breakdown Mechanisms In Electrical Discharges: The Role Of The Field Emission Effect In Direct Current Discharges In Micro gaps

International Nuclear Information System (INIS)

Radmilovic-Radjenovic, M.; Radjenovic, B.; Bojarov, A.; Klas, M.; Matejcik, S.

2013-01-01

This review represents an attempt to sum up the current state of the research in the field of breakdown phenomena in electrical discharges. The paper provides facts and theories concerning different classes of direct current, radio and microwave frequency discharges, in vacuum, in the gas and in liquids, without and in the presence of the magnetic fields. The emphasize was made on the field emission effects and on the fundamental aspects of the breakdown phenomena in micro discharges via discussions and analysis of the experimental, theoretical and simulation results. It was found that the Paschen's law is not applicable for the micron gap sizes, when deviations from the standard scaling law become evident and modified Paschen curve should be used. The explanation of the deviations from the Paschen law was attributed to the secondary electron emission enhanced by the strong field generated in micro gaps. The experiments were carried out in order to establish scaling law in micro gaps. The volt-ampere characteristics were also recorded and compared with the theoretical predictions based on the Fowler-Nordheim theory. The importance of the enhancement factor and the space charge on results was also considered. On the basis of the experimental breakdown voltage curves, the effective yields in micro gaps have been estimated for different gases which can be served as input data in modeling. The effective yields allow analytically produce modified Paschen curves that predicts the deviations from the Paschen law observed in the experiments. In addition, we present results of computer simulations using a Particle-in-cell/Monte Carlo Collisions (PIC/MCC) code with the secondary emission model in order to include the field emission enhanced secondary electron production in micro gaps. The agreement between simulation and experimental results suggest that computer simulations can be used to improve understanding of the plasma physics as an alternative to analytical

Mean-field models and exotic nuclei

Energy Technology Data Exchange (ETDEWEB)

Bender, M; Buervenich, T; Maruhn, J A; Greiner, W [Inst. fuer Theoretische Physik, Univ. Frankfurt (Germany); Rutz, K [Inst. fuer Theoretische Physik, Univ. Frankfurt (Germany); [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany); Reinhard, P G [Inst. fuer Theoretische Physik, Univ. Erlangen (Germany)

1998-06-01

We discuss two widely used nuclear mean-field models, the relativistic mean-field model and the (nonrelativistic) Skyrme-Hartree-Fock model, and their capability to describe exotic nuclei. Test cases are superheavy nuclei and neutron-rich Sn isotopes. New information in this regime helps to fix hitherto loosely determined aspects of the models. (orig.)

Mean-field models and exotic nuclei

International Nuclear Information System (INIS)

Bender, M.; Buervenich, T.; Maruhn, J.A.; Greiner, W.; Rutz, K.; Reinhard, P.G.

1998-01-01

We discuss two widely used nuclear mean-field models, the relativistic mean-field model and the (nonrelativistic) Skyrme-Hartree-Fock model, and their capability to describe exotic nuclei. Test cases are superheavy nuclei and neutron-rich Sn isotopes. New information in this regime helps to fix hitherto loosely determined aspects of the models. (orig.)

On the breakdown modes and parameter space of Ohmic Tokamak startup

Science.gov (United States)

Peng, Yanli; Jiang, Wei; Zhang, Ya; Hu, Xiwei; Zhuang, Ge; Innocenti, Maria; Lapenta, Giovanni

2017-10-01

Tokamak plasma has to be hot. The process of turning the initial dilute neutral hydrogen gas at room temperature into fully ionized plasma is called tokamak startup. Even with over 40 years of research, the parameter ranges for the successful startup still aren't determined by numerical simulations but by trial and errors. However, in recent years it has drawn much attention due to one of the challenges faced by ITER: the maximum electric field for startup can't exceed 0.3 V/m, which makes the parameter range for successful startup narrower. Besides, this physical mechanism is far from being understood either theoretically or numerically. In this work, we have simulated the plasma breakdown phase driven by pure Ohmic heating using a particle-in-cell/Monte Carlo code, with the aim of giving a predictive parameter range for most tokamaks, even for ITER. We have found three situations during the discharge, as a function of the initial parameters: no breakdown, breakdown and runaway. Moreover, breakdown delay and volt-second consumption under different initial conditions are evaluated. In addition, we have simulated breakdown on ITER and confirmed that when the electric field is 0.3 V/m, the optimal pre-filling pressure is 0.001 Pa, which is in good agreement with ITER's design.

Electrical breakdown studies with Mycalex insulators

International Nuclear Information System (INIS)

Waldron, W.; Greenway, W.; Eylon, S.; Henestroza, E.; Yu, S.

2003-01-01

Insulating materials such as alumina and glass-bonded mica (Mycalex) are used in accelerator systems for high voltage feedthroughs, structural supports, and barriers between high voltage insulating oil and the vacuum beam pipe in induction accelerator cells. Electric fields in the triple points should be minimized to prevent voltage breakdown. Mechanical stress can compromise seals and result in oil contamination of the insulator surface. We have tested various insulator cleaning procedures including ultrasonic cleaning with a variety of aqueous-based detergents, and manual scrubbing with various detergents. Water sheeting tests were used to determine the initial results of the cleaning methods. Ultimately, voltage breakdown tests will be used to quantify the benefits of these cleaning procedures

Gas breakdown at cyclotron resonance with a submillimeter laser

International Nuclear Information System (INIS)

Hacker, M.P.; Temkin, R.J.; Lax, B.

1976-01-01

A pulsed 496-μm CH 3 F laser is used to produce gas breakdown in He at pressures between 1 and 300 Torr in an intense longitudinal magnetic field. Breakdown is detected by the observation of visible light when the electron cyclotron frequency (eB/m) equals the laser frequency, which occurs at B=216 kG for lambda=496 μm. At the lowest helium pressures and near cyclotron resonance, the focused laser intensity of 40 kW/cm 2 gives rise to very large electron heating rates, well beyond the limit of validity of conventional equilibrium breakdown theory. The observed result is an intensity-dependent resonant linewidth, much larger than predicted by equilibrium theories

Effect of RF Parameters on Breakdown Limits in High-Vacuum X-Band Structures

International Nuclear Information System (INIS)

Dolgashev, Valery A.

2003-01-01

RF breakdown is one of the major factors determining performance of high power rf components and rf sources. RF breakdown limits working power and produces irreversible surface damage. The breakdown limit depends on the rf circuit, structure geometry, and rf frequency. It is also a function of the input power, pulse width, and surface electric and magnetic fields. In this paper we discuss multi-megawatt operation of X-band rf structures at pulse width on the order of one microsecond. These structures are used in rf systems of high gradient accelerators. Recent experiments at Stanford Linear Accelerator Center (SLAC) have explored the functional dependence of breakdown limit on input power and pulse width. The experimental data covered accelerating structures and waveguides. Another breakdown limit of accelerating structures was associated with high magnetic fields found in waveguide-to-structure couplers. To understand and quantify these limits we simulated 3D structures with the electrodynamics code Ansoft HFSS and the Particle-In-Cell code MAGIC3D. Results of these simulations together with experimental data will be discussed in this paper

Magnetic field induced augmented thermal conduction phenomenon in magneto-nanocolloids

International Nuclear Information System (INIS)

Katiyar, Ajay; Dhar, Purbarun; Nandi, Tandra; Das, Sarit K.

2016-01-01

Magnetic field induced augmented thermal conductivity of magneto-nanocolloids involving nanoparticles, viz. Fe_2O_3, Fe_3O_4, NiO and Co_3O_4 dispersed in different base fluids have been reported. Experiments reveal the augmented thermal transport under external applied magnetic field. A maximum thermal conductivity enhancement ∼114% is attained at 7.0 vol% concentration and 0.1 T magnetic flux density for Fe_3O_4/EG magneto-nanocolloid. However, a maximum ∼82% thermal conductivity enhancement is observed for Fe_3O_4/kerosene magneto-nanocolloid for the same concentration but relatively at low magnetic flux density (∼0.06 T). Thereby, a strong effect of fluid as well as particle physical properties on the chain formation propensity, leading to enhanced conduction, in such systems is observed. Co_3O_4 nanoparticles show insignificant effect on the thermal conductivity enhancement of MNCs due to their minimal magnetic moment. A semi-empirical approach has been proposed to understand the mechanism and physics behind the thermal conductivity enhancement under external applied magnetic field, in tune with near field magnetostatic interactions as well as Neel relaxivity of the magnetic nanoparticles. Furthermore, the model is able to predict the phenomenon of enhanced thermal conductivity as a function of physical parameters and shows good agreement with the experimental observations. - Highlights: • Heat conduction in magneto-nanocolloids augments tremendously under magnetic field. • Oxide nanoparticles of Fe, Ni and Co dispersed in variant base fluids are used. • Enhancement in heat conduction is due to the formation of thermally conductive chains. • Proposed semi-empirical model shows good agreement with the experimental results.

Family-nurse co-construction of meaning: a central phenomenon of family caring.

Science.gov (United States)

Meiers, Sonja J; Tomlinson, Patricia S

2003-06-01

The purpose of the study was to understand and interpret caring in the family health experience by exploring the interactional phenomenon of family-nurse co-construction of meaning in the paediatric intensive care unit (PICU). A hermeneutic phenomenological method within a framework of existentialism and symbolic interactionism was used in the investigation. The convenience sample for this study was four family-nurse dyads, that is four families of critically ill children (all with positive outcomes) and the four nurses assigned to their care who were participating in a larger study. Data were derived from semi-structured interviews regarding significant interactions throughout the child's illness and subsequent significant interactions of families with other nurses and nurses with other families. Trustworthiness of the study was addressed through the criteria of credibility, dependability, transferability and confirmability. Co-construction of meaning in the family health experience was found to have two dimensions: interdependent and independent. Both families and nurses described being like family as an essential component of the interdependent experience. Independent dimensions for families were journeying through troubled waters of learning the meaning of the illness event and sensing family comfort through the nurse's care. Independent dimensions described by nurses were journeying through troubled waters of learning to care for families and living with another's fear. The family-nurse interaction, the relational connection and the evolution of meanings that families and nurses construct, was affirmed as the major vehicle in the co-construction experience. Family caring is influenced by the existential meaning constructing, process-oriented, interactional nature of the family health experience. Caring in the family health experience is enhanced through actions the nurse performs on behalf of, and with, the family while understanding the family's unique

The electrical breakdown strength of pre-stretched elastomers, with and without sample volume conservation

DEFF Research Database (Denmark)

Zakaria, Shamsul Bin; Morshuis, Peter H. F.; Yahia, Benslimane Mohamed

2015-01-01

In practice, the electrical breakdown strength of dielectric electroactive polymers (DEAPs)determines the upper limit for transduction. During DEAP actuation, the thickness of the elastomer decreases, and thus the electrical field increases and the breakdown process is determined by a coupled...... electro-mechanical failure mechanism. A thorough understanding of the mechanisms behind the electro-mechanical breakdown process is required for developing reliable transducers. In this study, two experimental configurations were used to determine the stretch dependence of the electrical breakdown...

Effects of streamwise vortex breakdown on supersonic combustion.

Science.gov (United States)

Hiejima, Toshihiko

2016-04-01

This paper presents a numerical simulation study of the combustion structure of streamwise vortex breakdown at Mach number 2.48. Hydrogen fuel is injected into a combustor at sonic speed from the rear of a hypermixer strut that can generate streamwise vortices. The results show that the burning behavior is enhanced at the points of the shock waves that are incident on the vortex and therefore the vortex breakdown in the subsonic region occurs due to combustion. The breakdown domain in the mainstream is found to form a flame-holding region suited to combustion and to lead to a stable combustion field with detached flames. In this way, streamwise vortex breakdown has an essential role in combustion enhancement and the formation of flames that hold under supersonic inflow conditions. Finally, the combustion property defined here is shown to coincide with the produced-water mass flow. This property shows that the amount of combustion is saturated at equivalence ratios over 0.4, although there is a slight increase beyond 1.

Space Charge Modulated Electrical Breakdown of Oil Impregnated Paper Insulation Subjected to AC-DC Combined Voltages

Directory of Open Access Journals (Sweden)

Yuanwei Zhu

2018-06-01

Full Text Available Based on the existing acknowledgment that space charge modulates AC and DC breakdown of insulating materials, this investigation promotes the related investigation into the situations of more complex electrical stress, i.e., AC-DC combined voltages. Experimentally, the AC-DC breakdown characteristics of oil impregnated paper insulation were systematically investigated. The effects of pre-applied voltage waveform, AC component ratio, and sample thickness on AC-DC breakdown characteristics were analyzed. After that, based on an improved bipolar charge transport model, the space charge profiles and the space charge induced electric field distortion during AC-DC breakdown were numerically simulated to explain the differences in breakdown characteristics between the pre-applied AC and pre-applied DC methods under AC-DC combined voltages. It is concluded that large amounts of homo-charges are accumulated during AC-DC breakdown, which results in significantly distorted inner electric field, leading to variations of breakdown characteristics of oil impregnated paper insulation. Therefore, space charges under AC-DC combined voltages must be considered in the design of converter transformers. In addition, this investigation could provide supporting breakdown data for insulation design of converter transformers and could promote better understanding on the breakdown mechanism of insulating materials subjected to AC-DC combined voltages.

Nonasymptotic mean-field games

KAUST Repository

Tembine, Hamidou

2014-01-01

a mean-field framework that is suitable not only for large systems but also for a small world with few number of entities. The applicability of the proposed framework is illustrated through various examples including dynamic auction with asymmetric

The wavelength dependence of gold nanorod-mediated optical breakdown during infrared ultrashort pulses

Energy Technology Data Exchange (ETDEWEB)

Davletshin, Yevgeniy R.; Kumaradas, J. Carl [Department of Physics, Ryerson University, Toronto, ON (Canada)

2017-04-15

This paper investigates the wavelength dependence of the threshold of gold nanorod-mediated optical breakdown during picosecond and femtosecond near infrared optical pulses. It was found that the wavelength dependence in the picosecond regime is governed solely by the changes of a nanorod's optical properties. On the other hand, the optical breakdown threshold during femtosecond pulse exposure falls within one of two regimes. When the ratio of the maximum electric field from the outside to the inside of the nanorod is less then 7 (the absorption regime) the seed electrons are initiated by photo-thermal emission, and the wavelength dependence in the threshold of optical breakdown is the result of optical properties of the nanoparticle. When the ratio is greater than 7 (the near-field regime) more seed electrons are initiated by multiphoton ionization, and the wavelength dependence of the threshold of optical breakdown results from a combination of nanorod's optical properties and transitions in the order of multiphoton ionization. The findings of this study can guide the design of nanoparticle based optical breakdown applications. This analysis also deepens the understanding of nanoparticle-mediated laser induced breakdown for picosecond and femtosecond pulses at near infrared wavelengths. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Mean-field theory of nuclear structure and dynamics

International Nuclear Information System (INIS)

Negele, J.W.

1982-01-01

The physical and theoretical foundations are presented for the mean-field theory of nuclear structure and dynamics. Salient features of the many-body theory of stationary states are reviewed to motivate the time-dependent mean-field approximation. The time-dependent Hartree-Fock approximation and its limitations are discussed and general theoretical formulations are presented which yield time-dependent mean-field equations in lowest approximation and provide suitable frameworks for overcoming various conceptual and practical limitations of the mean-field theory. Particular emphasis is placed on recent developments utilizing functional integral techniques to obtain a quantum mean-field theory applicable to quantized eigenstates, spontaneous fission, the nuclear partition function, and scattering problems. Applications to a number of simple, idealized systems are presented to verify the approximations for solvable problems and to elucidate the essential features of mean-field dynamics. Finally, calculations utilizing moderately realistic geometries and interactions are reviewed which address heavy-ion collisions, fusion, strongly damped collisions, and fission

RF Breakdown Studies Using a 1.3 GHZ Test Cell

International Nuclear Information System (INIS)

Sah, R.; Johnson, R.P.; Neubauer, M.; Conde, M.; Gai, W.; Moretti, A.; Popovic, M.; Yonehara, K.; Byrd, J.; Li, D.; BastaniNejad, M.

2009-01-01

Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Recent studies have shown that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas without the need for long conditioning times, because the dense gas can dramatically reduce dark currents and multipacting. In this project we use this high pressure technique to suppress effects of residual vacuum and geometry found in evacuated cavities to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of magnetic field, frequency, and surface preparation. A 1.3-GHz RF test cell with replaceable electrodes (e.g. Mo, Cu, Be, W, and Nb) and pressure barrier capable of operating both at high pressure and in vacuum has been designed and built, and preliminary testing has been completed. A series of detailed experiments is planned at the Argonne Wakefield Accelerator. At the same time, computer simulations of the RF Breakdown process will be carried out to help develop a consistent physics model of RF Breakdown. In order to study the effect of the radiofrequency on RF Breakdown, a second test cell will be designed, fabricated, and tested at a lower frequency, most likely 402.5 MHz.

Nonasymptotic mean-field games

KAUST Repository

Tembine, Hamidou

2014-01-01

propose a mean-field framework that is suitable not only for large systems but also for a small world with few number of entities. The applicability of the proposed framework is illustrated through a dynamic auction with asymmetric valuation distributions.

Fabrication of 4H-SiC Schottky barrier diodes with high breakdown voltages

CERN Document Server

Kum, B H; Shin, M W; Park, J D

1999-01-01

This paper discusses the fabrication and the breakdown characteristics of 4H-SiC Schottky barrier diodes (SBDs). Optimal processing conditions for the ohmic contacts were extracted using the transmission-line method (TLM) and were applied to the device fabrication. The Ti/4H-SiC SBDs with Si sub x B sub y passivation showed a maximum reverse breakdown voltage of 268 V with a forward current density as high as 70 mA/cm sup 2 at a forward voltage of 2 V. The breakdown of the Pt. 4H-SiC SBDs without any passivation occurred at near 110 V. It is concluded that the breakdown enhancement in the Ti/4H-SiC SBDs can be attributed to the passivation; otherwise, excess surface charge near the edge of the Schottky contact would lead to electric fields of sufficient magnitude to cause field emission.

Breakdown-prone volume in terahertz wave beams

Energy Technology Data Exchange (ETDEWEB)

Nusinovich, G. S.; Qiao, F.; Kashyn, D. G.; Pu, R. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742-3511 (United States); Dolin, L. S. [Institute of Applied Physics, Nizhny Novgorod 603600 (Russian Federation)

2013-06-21

This study was motivated by the recently proposed concept of remote detection of concealed radioactive materials by a focused terahertz (THz) radiation [V. L. Granatstein and G. S. Nusinovich, J. Appl. Phys. 108, 063304 (2010)]. According to this concept, a high-power THz radiation should be focused in a small spot where the field intensity exceeds the breakdown threshold. In the presence of free electrons in such a breakdown-prone volume, a THz discharge will occur there. However, this volume should be so small that in the absence of ionizing sources in its vicinity the probability to have there any free electrons is low. Then, the increased breakdown rate in a series of THz pulses would indicate the presence of hidden radioactive materials in the vicinity of the focused spot. For this concept, it is important to accurately determine the breakdown-prone volume created by a focused THz radiation. This problem is analyzed in this paper, first, for the case of a single wave beam and, then, for the case of crossing wave beams of different polarizations. The problem is studied first ignoring the diffraction spread of wave beams in the vicinity of the focal plane and, then, with the account for the diffraction spreading. Then, relations between the THz wave power, the range of such a system and the breakdown-prone volume are analyzed. Finally, the effect of the atmospheric turbulence on propagation and focusing of THz wave beams in air is considered.

Breakdown-prone volume in terahertz wave beams

International Nuclear Information System (INIS)

Nusinovich, G. S.; Qiao, F.; Kashyn, D. G.; Pu, R.; Dolin, L. S.

2013-01-01

This study was motivated by the recently proposed concept of remote detection of concealed radioactive materials by a focused terahertz (THz) radiation [V. L. Granatstein and G. S. Nusinovich, J. Appl. Phys. 108, 063304 (2010)]. According to this concept, a high-power THz radiation should be focused in a small spot where the field intensity exceeds the breakdown threshold. In the presence of free electrons in such a breakdown-prone volume, a THz discharge will occur there. However, this volume should be so small that in the absence of ionizing sources in its vicinity the probability to have there any free electrons is low. Then, the increased breakdown rate in a series of THz pulses would indicate the presence of hidden radioactive materials in the vicinity of the focused spot. For this concept, it is important to accurately determine the breakdown-prone volume created by a focused THz radiation. This problem is analyzed in this paper, first, for the case of a single wave beam and, then, for the case of crossing wave beams of different polarizations. The problem is studied first ignoring the diffraction spread of wave beams in the vicinity of the focal plane and, then, with the account for the diffraction spreading. Then, relations between the THz wave power, the range of such a system and the breakdown-prone volume are analyzed. Finally, the effect of the atmospheric turbulence on propagation and focusing of THz wave beams in air is considered.

Mean-field approximation minimizes relative entropy

International Nuclear Information System (INIS)

Bilbro, G.L.; Snyder, W.E.; Mann, R.C.

1991-01-01

The authors derive the mean-field approximation from the information-theoretic principle of minimum relative entropy instead of by minimizing Peierls's inequality for the Weiss free energy of statistical physics theory. They show that information theory leads to the statistical mechanics procedure. As an example, they consider a problem in binary image restoration. They find that mean-field annealing compares favorably with the stochastic approach

Factors that Influence RF Breakdown in Antenna Systems

Science.gov (United States)

Caughman, J. B. O.; Baity, F. W.; Rasmussen, D. A.; Aghazarian, M.; Castano Giraldo, C. H.; Ruzic, David

2007-11-01

One of the main power-limiting factors in antenna systems is the maximum voltage that the antenna or vacuum transmission line can sustain before breaking down. The factors that influence RF breakdown are being studied in a resonant 1/4-wavelength section of vacuum transmission line terminated with an open circuit electrode structure. Breakdown can be initiated via electron emission by high electric fields and by plasma formation in the structure, depending on the gas pressure. Recent experiments have shown that a 1 kG magnetic field can influence plasma formation at pressures as low as 8x10-5 Torr at moderate voltage levels (LLC, for the U.S. Dept. of Energy under contract DE-AC05-00OR22725. Work supported by USDOE with grant DE-FG02-04ER54765

Linear Quadratic Mean Field Type Control and Mean Field Games with Common Noise, with Application to Production of an Exhaustible Resource

Energy Technology Data Exchange (ETDEWEB)

Graber, P. Jameson, E-mail: jameson-graber@baylor.edu [Baylor University, Department of Mathematics (United States)

2016-12-15

We study a general linear quadratic mean field type control problem and connect it to mean field games of a similar type. The solution is given both in terms of a forward/backward system of stochastic differential equations and by a pair of Riccati equations. In certain cases, the solution to the mean field type control is also the equilibrium strategy for a class of mean field games. We use this fact to study an economic model of production of exhaustible resources.

Mean fields and self consistent normal ordering of lattice spin and gauge field theories

International Nuclear Information System (INIS)

Ruehl, W.

1986-01-01

Classical Heisenberg spin models on lattices possess mean field theories that are well defined real field theories on finite lattices. These mean field theories can be self consistently normal ordered. This leads to a considerable improvement over standard mean field theory. This concept is carried over to lattice gauge theories. We construct first an appropriate real mean field theory. The equations determining the Gaussian kernel necessary for self-consistent normal ordering of this mean field theory are derived. (orig.)

Breakdown criteria due to radio-frequency fields in vacuum. Final report

International Nuclear Information System (INIS)

Reid, D.W.; Lohsen, R.A.

1982-01-01

The factors that affect the voltage at which vacuum gaps break down are analyzed. Based on the literature and some simplifying assumptions, a functional dependence is hypothesized. The hypothesis is related to a proposed experiment using radio-frequency power to generate the breakdown voltage

Liquid argon dielectric breakdown studies with the MicroBooNE purification system

Energy Technology Data Exchange (ETDEWEB)

Acciarri, R.; Carls, B.; James, C.; Johnson, B.; Jostlein, H.; Lockwitz, S.; Lundberg, B.; Raaf, J. L.; Rameika, R.; Rebel, B.; Zeller, G. P.; Zuckerbrot, M.

2014-11-01

The proliferation of liquid argon time projection chamber detectors makes the characterization of the dielectric properties of liquid argon a critical task. To improve understanding of these properties, a systematic study of the breakdown electric field in liquid argon was conducted using a dedicated cryostat connected to the MicroBooNE cryogenic system at Fermilab. An electrode sphere-plate geometry was implemented using spheres with diameters of 1.3 mm, 5.0 mm, and 76 mm. The MicroBooNE cryogenic system allowed measurements to be taken at a variety of electronegative contamination levels ranging from a few parts-per-million to tens of parts-per-trillion. The cathode-anode distance was varied from 0.1 mm to 2.5 cm. The results demonstrate a geometric dependence of the electric field strength at breakdown. This study is the first time that the dependence of the breakdown field on stressed cathode area has been shown for liquid argon.

Magnetic field induced augmented thermal conduction phenomenon in magneto-nanocolloids

Energy Technology Data Exchange (ETDEWEB)

Katiyar, Ajay, E-mail: ajay_cim@rediffmail.com [Research and Innovation Centre (DRDO), Indian Institute of Technology Madras Research Park, Chennai 600 113 (India); Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600 036 (India); Dhar, Purbarun, E-mail: purbarun@iitrpr.ac.in [Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600 036 (India); Nandi, Tandra, E-mail: tandra_n@rediffmail.com [Defence Materials and Stores Research and Development Establishment (DRDO), G.T. Road, Kanpur 208 013 (India); Das, Sarit K., E-mail: skdas@iitrpr.ac.in [Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600 036 (India)

2016-12-01

Magnetic field induced augmented thermal conductivity of magneto-nanocolloids involving nanoparticles, viz. Fe{sub 2}O{sub 3}, Fe{sub 3}O{sub 4}, NiO and Co{sub 3}O{sub 4} dispersed in different base fluids have been reported. Experiments reveal the augmented thermal transport under external applied magnetic field. A maximum thermal conductivity enhancement ∼114% is attained at 7.0 vol% concentration and 0.1 T magnetic flux density for Fe{sub 3}O{sub 4}/EG magneto-nanocolloid. However, a maximum ∼82% thermal conductivity enhancement is observed for Fe{sub 3}O{sub 4}/kerosene magneto-nanocolloid for the same concentration but relatively at low magnetic flux density (∼0.06 T). Thereby, a strong effect of fluid as well as particle physical properties on the chain formation propensity, leading to enhanced conduction, in such systems is observed. Co{sub 3}O{sub 4} nanoparticles show insignificant effect on the thermal conductivity enhancement of MNCs due to their minimal magnetic moment. A semi-empirical approach has been proposed to understand the mechanism and physics behind the thermal conductivity enhancement under external applied magnetic field, in tune with near field magnetostatic interactions as well as Neel relaxivity of the magnetic nanoparticles. Furthermore, the model is able to predict the phenomenon of enhanced thermal conductivity as a function of physical parameters and shows good agreement with the experimental observations. - Highlights: • Heat conduction in magneto-nanocolloids augments tremendously under magnetic field. • Oxide nanoparticles of Fe, Ni and Co dispersed in variant base fluids are used. • Enhancement in heat conduction is due to the formation of thermally conductive chains. • Proposed semi-empirical model shows good agreement with the experimental results.

Investigation of multipactor breakdown in communication satellite microwave co-axial systems

Science.gov (United States)

Nagesh, S. K.; Revannasiddiah, D.; Shastry, S. V. K.

2005-01-01

Multipactor breakdown or multipactor discharge is a form of high frequency discharge that may occur in microwave components operating at very low pressures. Some RF components of multi-channel communication satellites have co-axial geometry and handle high RF power under near-vacuum conditions. The breakdown occurs due to secondary electron resonance, wherein electrons move back and forth in synchronism with the RF voltage across the gap between the inner and outer conductors of the co-axial structure. If the yield of secondary electrons from the walls of the co-axial structure is greater than unity, then the electron density increases with time and eventually leads to the breakdown. In this paper, the current due to the oscillating electrons in the co-axial geometry has been treated as a radially oriented Hertzian dipole. The electric field, due to this dipole, at any point in the coaxial structure, may then be determined by employing the dyadic Green's function technique. This field has been compared with the field that would exist in the absence of multipactor.

Dynamic of microwave breakdown in the localized places of transmitting line driving by Cherenkov-type oscillator

Science.gov (United States)

Xie, Jialing; Chen, Changhua; Chang, Chao; Wu, Cheng; Shi, Yanchao; Cao, Yibing; Song, Zhimin; Zhang, Yuchuan

2018-02-01

A breakdown cavity is designed to study the breakdown phenomena of high-power microwaves in transmission waveguides. The maximum electric field within the cavity varies in amplitude from 400 kV/cm to 1.8 MV/cm and may surpass breakdown thresholds. The breakdown cavities were studied in particle-in-cell simulations and experiments, the results of which yielded waveforms that were consistent. The experimental results indicate that the microwave pulse does not shorten, and the amplitude of the electric field does not fall below 800 kV/cm. Moreover, large numbers of electrons are not emitted in microwaves below 670 kV/cm at 9.75 GHz frequency and 25-ns pulse width transmitted in stainless steel waveguides. The radiation waveforms of breakdown cavity with different materials are compared in experiments, with titanium material performing better.

Obstacle mean-field game problem

KAUST Repository

Gomes, Diogo A.; Patrizi, Stefania

2015-01-01

In this paper, we introduce and study a first-order mean-field game obstacle problem. We examine the case of local dependence on the measure under assumptions that include both the logarithmic case and power-like nonlinearities. Since the obstacle operator is not differentiable, the equations for first-order mean field game problems have to be discussed carefully. Hence, we begin by considering a penalized problem. We prove this problem admits a unique solution satisfying uniform bounds. These bounds serve to pass to the limit in the penalized problem and to characterize the limiting equations. Finally, we prove uniqueness of solutions. © European Mathematical Society 2015.

The influence of the breakdown electric field in the configuration of lightning corona sheath on charge distribution in the channel

Science.gov (United States)

Ignjatovic, Milan; Cvetic, Jovan; Heidler, Fridolin; Markovic, Slavoljub; Djuric, Radivoje

2014-11-01

A model of corona sheath that surrounds the thin core of the lightning channel has been investigated by using a generalized traveling current source return stroke model. The lightning channel is modeled by a charged corona sheath that stretches around a highly conductive central core through which the main current flows. The channel core with the negatively charged outer channel sheath forms a strong electric field, with an overall radial orientation. The return stroke process is modeled as the negative leader charge in the corona sheath being discharged by the positive charge coming from the channel core. Expressions that describe how the corona sheath radius evolves during the return stroke are obtained from the corona sheath model, which predicts charge motion within the sheath. The corona sheath model, set forth by Maslowski and Rakov (2006), Tausanovic et al. (2010), Marjanovic and Cvetic (2009), Cvetic et al. (2011) and Cvetic et al. (2012), divides the sheath onto three zones: zone 1 (surrounding the channel core with net positive charge), zone 2 (surrounding zone 1 with negative charge) and zone 3 (the outer zone, representing uncharged virgin air). In the present study, we have assumed a constant electric field inside zone 1, as suggested by experimental research of corona discharges in coaxial geometry conducted by Cooray (2000). The present investigation builds upon previous studies by Tausanovic et al. (2010) and Cvetic et al. (2012) in several ways. The value of the breakdown electric field has been varied for probing its effect on channel charge distribution prior and during the return stroke. With the aim of investigating initial space charge distribution along the channel, total electric field at the outer surface of the channel corona sheath, just before the return stroke, is calculated and compared for various return stroke models. A self-consistent algorithm is applied to the generalized traveling current source return stroke model, so that the

Kinetic Simulations of Dense Plasma Focus Breakdown

Science.gov (United States)

Schmidt, A.; Higginson, D. P.; Jiang, S.; Link, A.; Povilus, A.; Sears, J.; Bennett, N.; Rose, D. V.; Welch, D. R.

2015-11-01

A dense plasma focus (DPF) device is a type of plasma gun that drives current through a set of coaxial electrodes to assemble gas inside the device and then implode that gas on axis to form a Z-pinch. This implosion drives hydrodynamic and kinetic instabilities that generate strong electric fields, which produces a short intense pulse of x-rays, high-energy (>100 keV) electrons and ions, and (in deuterium gas) neutrons. A strong factor in pinch performance is the initial breakdown and ionization of the gas along the insulator surface separating the two electrodes. The smoothness and isotropy of this ionized sheath are imprinted on the current sheath that travels along the electrodes, thus making it an important portion of the DPF to both understand and optimize. Here we use kinetic simulations in the Particle-in-cell code LSP to model the breakdown. Simulations are initiated with neutral gas and the breakdown modeled self-consistently as driven by a charged capacitor system. We also investigate novel geometries for the insulator and electrodes to attempt to control the electric field profile. The initial ionization fraction of gas is explored computationally to gauge possible advantages of pre-ionization which could be created experimentally via lasers or a glow-discharge. Prepared by LLNL under Contract DE-AC52-07NA27344.

Breakdown characteristics in DC spark experiments of copper focusing on purity and hardness

CERN Document Server

Yokoyama, Kazue; Higashi, Yasuo; Higo, Toshi; Matsumoto, Shuji; Santiago-Kern, Ana Rocia; Pasquino, Chiara; Calatroni, Sergio; Wuensch, Walter

2010-01-01

The breakdown characteristics related to the differences in purity and hardness were investigated for several types of copper using a DC spark test system. Three types of oxygen-free copper (OFC) materials, usual class 1 OFC 7-nine large-grain copper and 6-nine hot-isotropic-pressed (HIP) copper with/without diamond finish, were tested with the DC spark test system. The measurements of the beta, breakdown fields, and breakdown probability are presented and discussed in this paper.

Method of making dielectric capacitors with increased dielectric breakdown strength

Science.gov (United States)

Ma, Beihai; Balachandran, Uthamalingam; Liu, Shanshan

2017-05-09

The invention is directed to a process for making a dielectric ceramic film capacitor and the ceramic dielectric laminated capacitor formed therefrom, the dielectric ceramic film capacitors having increased dielectric breakdown strength. The invention increases breakdown strength by embedding a conductive oxide layer between electrode layers within the dielectric layer of the capacitors. The conductive oxide layer redistributes and dissipates charge, thus mitigating charge concentration and micro fractures formed within the dielectric by electric fields.

The physics of ''vacuum'' breakdown

International Nuclear Information System (INIS)

Schwirzke, F.

1993-01-01

Many discharges form small cathode spots which provide such a high energy density that the cathode material explodes into a dense plasma cloud within a very short time. Despite the fundamental importance of cathode spots for the breakdown process and the formation of a discharge, the structure of the cathode spot plasma and the source of the high energy density were not yet well defined. One model, the whisker explosive emission model, assumes that joule heating by field emitted electrons provides the energy. Current densities of j FE = 10 12 - 10 13 A/m 2 would be required. However, the pre-breakdown j FE is self-limiting. The negative space charge caused by j FE in the cathode-anode gap reduces the effective electric field E on the cathode surface. The maximum current density j CL is space charge limited by Child-Langmuir's law. The field emitting spot cannot deliver j CL without turning itself off, since the negative space charge caused by j CL reduces E congruent 0 at the cathode surface. Hence, it must be that the vacuum j FE CL . The development of a current with j > j FE (vacuum) requires that ions exist in front of the electron emitting spot. Ions cannot be emitted from the surface of the field emitting spot, the enhanced electric field would hold them back. The initial ionization must occur in the cathode-anode gap near the electron emitting spot. Ionization of desorbed neutrals provides the mechanism. This ionization process requires considerably less current than the ionization of solid material by joule heating. Field emission and the impact of ions stimulate desorption of weakly bound adsorbates from the surface of the electron emitting spot. The cross section for ionization of the neutrals has a maximum for ∼ 100 eV electrons

High-speed photography and holography of laser induced breakdown in liquids

International Nuclear Information System (INIS)

Lauterborn, W.

1979-01-01

Optical breakdown phenomena in liquids due to focused ruby laser light are investigated by high-speed photography and holography. Special attention is given the dynamics of the cavities produced in the liquid upon breakdown as they can be expected to become a powerful research tool in cavitation physics. To this end the production of three-dimensional breakdown configurations would be desirable as well as their investigation by high-speed holographic means. Both problems are presently under study. To achieve multiple breakdown at preselected points in the liquid a grating-lens assembly and digital holograms in photoresist are used. To film the motion of the cavities high-speed holocinematographic methods are developed. By now four to eight holograms can be taken at a rate of 10 to 20 kHz. (author)

Mindfulness as a booming, diverse and (non) religious phenomenon

DEFF Research Database (Denmark)

Borup, Jørn

2016-01-01

Mindfulness has become a phenomenon with widespread appeal in many Western countries. Like yoga, it has an Eastern religious origin, but through a long history it has been transformed and adapted to new cultural and social contexts. While the majority of research on mindfulness has been conducted...... within the health sciences, the aim of this article is to investigate the distribution, meaning and function of this practice through quantitative mapping and qualitative interviews with 16 mindfulness providers in the city of Aarhus in Denmark. The analysis reveals not just a booming phenomenon......, but also a field characterized by diversity in terms of authority claims, motivations and uses. The discussion focuses on whether mindfulness can be seen as a religious practice or as a typical expression of an individualized and secularized technique....

Induced dual EIT and EIA resonances with optical trapping phenomenon in near/far fields in the N-type four-level system

Science.gov (United States)

Osman, Kariman I.; Joshi, Amitabh

2017-01-01

The optical trapping phenomenon is investigated in the probe absorptive susceptibility spectra, during the interaction of four-level N-type atomic system with three transverse Gaussian fields, in a Doppler broadened medium. The system was studied under different temperature settings of 87Rb atomic vapor as well as different non-radiative decay rate. The system exhibits a combination of dual electromagnetically induced transparency with electromagnetically induced absorption (EIA) or transparency (EIT) resonances simultaneously in near/far field. Also, the optical trapping phenomenon is considerably affected by the non-radiative decay rate.

On the dynamics of a subnanosecond breakdown in nitrogen below atmospheric pressures

Energy Technology Data Exchange (ETDEWEB)

Shklyaev, V. A., E-mail: shklyaev@to.hcei.tsc.ru, E-mail: beh@loi.hcei.tsc.ru [Laboratory of Theoretical Physics, Institute of High Current Electronics, Russian Academy of Sciences, 2/3 Akademichesky Ave., 634055 Tomsk (Russian Federation); Institute of High Technology Physics, National Research Tomsk Polytechnic University, 30 Lenin Avenue, 634050 Tomsk (Russian Federation); Baksht, E. Kh., E-mail: shklyaev@to.hcei.tsc.ru, E-mail: beh@loi.hcei.tsc.ru; Tarasenko, V. F. [Laboratory of Optical Radiations, Institute of High Current Electronics, Russian Academy of Sciences, 2/3 Akademichesky Ave., 634055 Tomsk (Russian Federation); Belomyttsev, S. Ya.; Grishkov, A. A. [Laboratory of Theoretical Physics, Institute of High Current Electronics, Russian Academy of Sciences, 2/3 Akademichesky Ave., 634055 Tomsk (Russian Federation); Burachenko, A. G. [Laboratory of Optical Radiations, Institute of High Current Electronics, Russian Academy of Sciences, 2/3 Akademichesky Ave., 634055 Tomsk (Russian Federation); Laboratory of Low Temperature Plasma, Tomsk State University, 36 Lenin Ave., 634050 Tomsk (Russian Federation)

2015-12-07

The dynamics of a breakdown in a gas-filled diode with a highly inhomogeneous electric field was studied in experiments at a time resolution of ∼100 ps and in numerical simulation by the 2D axisymmetric particle-in-cell (PIC) code XOOPIC. The diode was filled with nitrogen at pressures of up to 100 Torr. The dynamics of the electric field distribution in the diode during the breakdown was analyzed, and the factors that limit the pulse duration of the runaway electron beam current at different pressures were determined.

Gas Breakdown of Radio Frequency Glow Discharges in Helium at near Atmospheric Pressure

International Nuclear Information System (INIS)

Liu Xinkun; Xu Jinzhou; Cui Tongfei; Guo Ying; Zhang Jing; Shi Jianjun

2013-01-01

A one-dimensional self-consistent fluid model was developed for radio frequency glow discharge in helium at near atmospheric pressure, and was employed to study the gas breakdown characteristics in terms of breakdown voltage. The effective secondary electron emission coefficient and the effective electric field for ions were demonstrated to be important for determining the breakdown voltage of radio frequency glow discharge at near atmospheric pressure. The constant of A was estimated to be 64±4 cm −1 Torr −1 , which was proportional to the first Townsend coefficient and could be employed to evaluate the gas breakdown voltage. The reduction in the breakdown voltage of radio frequency glow discharge with excitation frequency was studied and attributed to the electron trapping effect in the discharge gap

Breakdown Studies for the CLIC Accelerating

CERN Document Server

Calatroni, S; Kovermann, J; Taborelli, M; Timko, H; Wuensch, W; Durabekova, F; Nordlund, K; Pohjonen, A; Kuronen, A

2010-01-01

Optimizing the design and the manufacturing of the CLIC RF accelerating structures for achieving the target value of breakdown rate at the nominal accelerating gradient of 100 MV/m requires a detailed understanding of all the steps involved in the mechanism of breakdown. These include surface modification under RF fields, electron emission and neutral evaporation in the vacuum, arc ignition and consequent surface modification due to plasma bombardment. Together with RF tests, experiments are conducted in a simple DC test set-up instrumented with electrical diagnostics and optical spectroscopy. The results are also used for validating simulations which are performed using a wide range of numerical tools (MD coupled to electrostatic codes, PIC plasma simulations) able to include all the above phenomena. Some recent results are presented in this paper

Trapped Bose gas. Mean-field approximation and beyond

International Nuclear Information System (INIS)

Pitaevskii, L.P.

1998-01-01

The recent realization of Bose-Einstein condensation in atomic gases opens new possibilities for observation of macroscopic quantum phenomena. There are two important features of the system - weak interaction and significant spatial inhomogeneity. Because of this inhomogeneity a non-trivial 'zeroth-order' theory exists, compared to the 'first-order' Bogoliubov theory. This theory is based on the mean-field Gross-Pitaevskii equation for the condensate ψ -function. The equation is classical in its essence but contains the ℎ constant explicitly. Phenomena such as collective modes, interference, tunneling, Josephson-like current and quantized vortex lines can be described using this equation. The study of deviations from the zeroth-order theory arising from zero-point and thermal fluctuations is also of great interest. Thermal fluctuations are described by elementary excitations which define the thermodynamic behaviour of the system and result in Landau-type damping of collective modes. Fluctuations of the phase of the condensate wave function restrict the monochromaticity of the Josephson current. Fluctuations of the numbers of quanta result in the quantum collapse-revival of the collective oscillations. This phenomenon is considered in some details. Collapse time for the JILA experimental conditions turns out to be of the order of seconds. (Copyright (1998) World Scientific Publishing Co. Pte. Ltd)

Breakdowns in collaborative information seeking

DEFF Research Database (Denmark)

Hertzum, Morten

2010-01-01

Collaborative information seeking is integral to many professional activities. In hospital work, the medication process encompasses continual seeking for information and collaborative grounding of information. This study investigates breakdowns in collaborative information seeking through analyses...... of the use of the electronic medication record adopted in a Danish healthcare region and of the reports of five years of medication incidents at Danish hospitals. The results show that breakdowns in collaborative information seeking is a major source of medication incidents, that most of these breakdowns...... are breakdowns in collaborative grounding rather than information seeking, that the medication incidents mainly concern breakdowns in the use of records as opposed to oral communication, that the breakdowns span multiple degrees of separation between clinicians, and that the electronic medication record has...

Observation of Multi-GeV Breakdown Thresholds in Dielectric Wakefield Structures

International Nuclear Information System (INIS)

Thompson, M.C.; Thompson, M.C.; Yoder, R.B.; Hogan, M.J.; Ischebeck, R.; Kirby, N.A.; Siemann, Robert H.; Walz, D.R.; Badakov, H.; Rosenzweig, J.B.; Travish, G.; Scott, A.; Muggli, P.

2008-01-01

An experiment designed to test the breakdown threshold of a dielectric subjected to the GV/m-scale electric-fields of an intense electron-beam has been completed. In this experiment at the Final Focus Test Beam (FFTB) facility, the 28.5 GeV SLAC electron beam was focused down and propagated through short fused-silica capillary-tubes with internal diameters of as little as 100 (micro)m. The electric field at the inner surface of the tubes was varied from about 1 GV/m to 22 GV/m by adjusting the longitudinal compression of the electron bunch. We observed a sharp increase in optical emissions from the capillaries in the middle part of this surface field range which we believe indicates the transition between sustainable field levels and breakdown. If this initial interpretation is correct, the multi-GV/m surfaced fields that were sustained equate to on axis accelerating field of several GV/m

Breakdown localization in the fixed gap system

CERN Document Server

Rajamaki, Robin; Wuensch, Walter

2014-01-01

Accurate localization of breakdowns in vacuum could help shed light on breakdown related processes that are not yet fully understood. At the DC spark lab at CERN, an instrument called the Fixed Gap System (FGS) has been developed partially for this purpose. Among other things, the FGS has four built-in antennas, which are intended for breakdown localization. The capability of this aspect of the FGS was explored in this report. Specifically, the feasibility of using a method similar to that which is used in cavity Beam Position Monitors (BPMs) was investigated. The usable frequency range of the current experimental setup was also studied. Firstly, a modal analysis of the inner geometry of the FGS was done in HFSS. This showed that the two first modes to be expected in the spark gap quite differ from those of the ideal pillbox – both in field pattern and in frequency ( 4 and 6 GHz vs. 0.2 and 3 GHz). Secondly, S-parameters of the system were measured. These showed that the coupling between antennas is weak...

On Social Optima of Non-Cooperative Mean Field Games

Energy Technology Data Exchange (ETDEWEB)

Li, Sen; Zhang, Wei; Zhao, Lin; Lian, Jianming; Kalsi, Karanjit

2016-12-12

This paper studies the social optima in noncooperative mean-field games for a large population of agents with heterogeneous stochastic dynamic systems. Each agent seeks to maximize an individual utility functional, and utility functionals of different agents are coupled through a mean field term that depends on the mean of the population states/controls. The paper has the following contributions. First, we derive a set of control strategies for the agents that possess *-Nash equilibrium property, and converge to the mean-field Nash equilibrium as the population size goes to infinity. Second, we study the social optimal in the mean field game. We derive the conditions, termed the socially optimal conditions, under which the *-Nash equilibrium of the mean field game maximizes the social welfare. Third, a primal-dual algorithm is proposed to compute the *-Nash equilibrium of the mean field game. Since the *-Nash equilibrium of the mean field game is socially optimal, we can compute the equilibrium by solving the social welfare maximization problem, which can be addressed by a decentralized primal-dual algorithm. Numerical simulations are presented to demonstrate the effectiveness of the proposed approach.

The breakdown phase in a coaxial plasma gun

International Nuclear Information System (INIS)

Donges, A.; Herziger, G.; Krompholz, H.; Ruehl, F.; Schoenbach, K.

1980-01-01

The electrical breakdown in a coaxial plasma gun was investigated by means of optical and electrical measurements. The optimum start and operation conditions of the gun turned out to be strongly dependent on material and length of the cylindrical insulator. (orig.)

A breakdown enhanced AlGaN/GaN MISFET with source-connected P-buried layer

Science.gov (United States)

Luo, Xin; Wang, Ying; Cao, Fei; Yu, Cheng-Hao; Fei, Xin-Xing

2017-12-01

This paper presents a breakdown-enhanced AlGaN/GaN MISFET with a source-connected P-buried layer combined with field plates (SC-PBL FPs MISFET). A TCAD tool was used to analyze the breakdown characteristics of the proposed structure, and results show that in comparison to the conventional gate field plate MISFET (GFP-C MISFET), the proposed structure provides a significant increase of breakdown voltage (VBK) due to redistribution of electric field in the gate-drain region induced by the SC-PBL and the FPs. The optimized SC-PBL FPs MISFET with a gate-drain spacing of 6 μm achieved a high Baliga's figure of merit of 2.6 GW cm-2 with a corresponding breakdown voltage (VBK) of 1311.62 V and specific on resistance (RON,sp) of 0.66 mΩ cm2, which demonstrates a good trade-off between RON,sp and VBK compared to the GFP-C MISFET with VBK of 524.27 V and RON,sp of 0.61 mΩ cm2.

Dimensional analysis in field theory

International Nuclear Information System (INIS)

Stevenson, P.M.

1981-01-01

Dimensional Transmutation (the breakdown of scale invariance in field theories) is reconciled with the commonsense notions of Dimensional Analysis. This makes possible a discussion of the meaning of the Renormalisation Group equations, completely divorced from the technicalities of renormalisation. As illustrations, I describe some very farmiliar QCD results in these terms

Grain-Scale Supercharging and Breakdown on Airless Regoliths

Science.gov (United States)

Zimmerman, M. I.; Farrell, W. M.; Hartzell, C.M.; Wang, X.; Horanyi, M.; Hurley, D. M.; Hibbitts, K.

2016-01-01

Interactions of the solar wind and emitted photoelectrons with airless bodies have been studied extensively. However, the details of how charged particles interact with the regolith at the scale of a single grain have remained largely uncharacterized. Recent efforts have focused upon determining total surface charge under photoemission and solar wind bombardment and the associated electric field and potential. In this work, theory and simulations are used to show that grain-grain charge differences can exceed classical sheath predictions by several orders of magnitude, sometimes reaching dielectric breakdown levels. Temperature-dependent electrical conductivity works against supercharging by allowing current to leak through individual grains; the balance between internal conduction and surface charging controls the maximum possible grain-to-grain electric field. Understanding the finer details of regolith grain charging, conductive equilibrium, and dielectric breakdown will improve future numerical studies of space weathering and dust levitation on airless bodies.

Fear of breakdown and the unlived life.

Science.gov (United States)

Ogden, Thomas H

2014-04-01

Winnicott's Fear of breakdown is an unfinished work that requires that the reader be not only a reader, but also a writer of this work which often gestures toward meaning as opposed to presenting fully developed ideas. The author's understanding of the often confusing, sometimes opaque, argument of Winnicott's paper is as follows. In infancy there occurs a breakdown in the mother-infant tie that forces the infant to take on, by himself, emotional events that he is unable to manage. He short-circuits his experience of primitive agony by generating defense organizations that are psychotic in nature, i.e., they substitute self-created inner reality for external reality, thus foreclosing his actually experiencing critical life events. By not experiencing the breakdown of the mother-infant tie when it occurred in infancy, the individual creates a psychological state in which he lives in fear of a breakdown that has already happened, but which he did not experience. The author extends Winnicott's thinking by suggesting that the driving force of the patient's need to find the source of his fear is his feeling that parts of himself are missing and that he must find them if he is to become whole. What remains of his life feels to him like a life that is mostly an unlived life. Copyright © 2014 Institute of Psychoanalysis.

Two Populations Mean-Field Monomer-Dimer Model

Science.gov (United States)

Alberici, Diego; Mingione, Emanuele

2018-04-01

A two populations mean-field monomer-dimer model including both hard-core and attractive interactions between dimers is considered. The pressure density in the thermodynamic limit is proved to satisfy a variational principle. A detailed analysis is made in the limit of one population is much smaller than the other and a ferromagnetic mean-field phase transition is found.

5.0 kV breakdown-voltage vertical GaN p-n junction diodes

Science.gov (United States)

Ohta, Hiroshi; Hayashi, Kentaro; Horikiri, Fumimasa; Yoshino, Michitaka; Nakamura, Tohru; Mishima, Tomoyoshi

2018-04-01

A high breakdown voltage of 5.0 kV has been achieved for the first time in vertical GaN p-n junction diodes by using our newly developed guard-ring structures. A resistance device was inserted between the main diode portion and the guard-ring portion in a ring-shaped p-n diode to generate a voltage drop over the resistance device by leakage current flowing through the guard-ring portion under negatively biased conditions before breakdown. The voltage at the outer mesa edge of the guard-ring portion, where the electric field intensity is highest and the destructive breakdown usually occurs, is decreased by the voltage drop, so the electric field concentration in the portion is reduced. By adopting this structure, the breakdown voltage (V B) is raised by about 200 V. Combined with a low measured on-resistance (R on) of 1.25 mΩ cm2, Baliga’s figure of merit (V\\text{B}2/R\\text{on}) was as high as 20 GW/cm2.

Review of Vortex Methods for Simulation of Vortex Breakdown

National Research Council Canada - National Science Library

Levinski, Oleg

2001-01-01

The aim of this work is to identify current developments in the field of vortex breakdown modelling in order to initiate the development of a numerical model for the simulation of F/A-18 empennage buffet...

Quasiparticle Breakdown and Spin Hamiltonian of the Frustrated Quantum Pyrochlore Yb_{2}Ti_{2}O_{7} in a Magnetic Field.

Science.gov (United States)

Thompson, J D; McClarty, P A; Prabhakaran, D; Cabrera, I; Guidi, T; Coldea, R

2017-08-04

The frustrated pyrochlore magnet Yb_{2}Ti_{2}O_{7} has the remarkable property that it orders magnetically but has no propagating magnons over wide regions of the Brillouin zone. Here we use inelastic neutron scattering to follow how the spectrum evolves in cubic-axis magnetic fields. At high fields we observe, in addition to dispersive magnons, a two-magnon continuum, which grows in intensity upon reducing the field and overlaps with the one-magnon states at intermediate fields leading to strong renormalization of the dispersion relations, and magnon decays. Using heat capacity measurements we find that the low- and high-field regions are smoothly connected with no sharp phase transition, with the spin gap increasing monotonically in field. Through fits to an extensive data set of dispersion relations combined with magnetization measurements, we reevaluate the spin Hamiltonian, finding dominant quantum exchange terms, which we propose are responsible for the anomalously strong fluctuations and quasiparticle breakdown effects observed at low fields.

Quasiparticle Breakdown and Spin Hamiltonian of the Frustrated Quantum Pyrochlore Yb2 Ti2 O7 in a Magnetic Field

Science.gov (United States)

Thompson, J. D.; McClarty, P. A.; Prabhakaran, D.; Cabrera, I.; Guidi, T.; Coldea, R.

2017-08-01

The frustrated pyrochlore magnet Yb2 Ti2 O7 has the remarkable property that it orders magnetically but has no propagating magnons over wide regions of the Brillouin zone. Here we use inelastic neutron scattering to follow how the spectrum evolves in cubic-axis magnetic fields. At high fields we observe, in addition to dispersive magnons, a two-magnon continuum, which grows in intensity upon reducing the field and overlaps with the one-magnon states at intermediate fields leading to strong renormalization of the dispersion relations, and magnon decays. Using heat capacity measurements we find that the low- and high-field regions are smoothly connected with no sharp phase transition, with the spin gap increasing monotonically in field. Through fits to an extensive data set of dispersion relations combined with magnetization measurements, we reevaluate the spin Hamiltonian, finding dominant quantum exchange terms, which we propose are responsible for the anomalously strong fluctuations and quasiparticle breakdown effects observed at low fields.

Regularity theory for mean-field game systems

CERN Document Server

Gomes, Diogo A; Voskanyan, Vardan

2016-01-01

Beginning with a concise introduction to the theory of mean-field games (MFGs), this book presents the key elements of the regularity theory for MFGs. It then introduces a series of techniques for well-posedness in the context of mean-field problems, including stationary and time-dependent MFGs, subquadratic and superquadratic MFG formulations, and distinct classes of mean-field couplings. It also explores stationary and time-dependent MFGs through a series of a-priori estimates for solutions of the Hamilton-Jacobi and Fokker-Planck equation. It shows sophisticated a-priori systems derived using a range of analytical techniques, and builds on previous results to explain classical solutions. The final chapter discusses the potential applications, models and natural extensions of MFGs. As MFGs connect common problems in pure mathematics, engineering, economics and data management, this book is a valuable resource for researchers and graduate students in these fields.

Regularity Theory for Mean-Field Game Systems

KAUST Repository

Gomes, Diogo A.

2016-09-14

Beginning with a concise introduction to the theory of mean-field games (MFGs), this book presents the key elements of the regularity theory for MFGs. It then introduces a series of techniques for well-posedness in the context of mean-field problems, including stationary and time-dependent MFGs, subquadratic and superquadratic MFG formulations, and distinct classes of mean-field couplings. It also explores stationary and time-dependent MFGs through a series of a-priori estimates for solutions of the Hamilton-Jacobi and Fokker-Planck equation. It shows sophisticated a-priori systems derived using a range of analytical techniques, and builds on previous results to explain classical solutions. The final chapter discusses the potential applications, models and natural extensions of MFGs. As MFGs connect common problems in pure mathematics, engineering, economics and data management, this book is a valuable resource for researchers and graduate students in these fields.

Regularity Theory for Mean-Field Game Systems

KAUST Repository

Gomes, Diogo A.; Pimentel, Edgard A.; Voskanyan, Vardan K.

2016-01-01

Beginning with a concise introduction to the theory of mean-field games (MFGs), this book presents the key elements of the regularity theory for MFGs. It then introduces a series of techniques for well-posedness in the context of mean-field problems, including stationary and time-dependent MFGs, subquadratic and superquadratic MFG formulations, and distinct classes of mean-field couplings. It also explores stationary and time-dependent MFGs through a series of a-priori estimates for solutions of the Hamilton-Jacobi and Fokker-Planck equation. It shows sophisticated a-priori systems derived using a range of analytical techniques, and builds on previous results to explain classical solutions. The final chapter discusses the potential applications, models and natural extensions of MFGs. As MFGs connect common problems in pure mathematics, engineering, economics and data management, this book is a valuable resource for researchers and graduate students in these fields.

High power breakdown testing of a photonic band-gap accelerator structure with elliptical rods

Directory of Open Access Journals (Sweden)

Brian J. Munroe

2013-01-01

Full Text Available An improved single-cell photonic band-gap (PBG structure with an inner row of elliptical rods (PBG-E was tested with high power at a 60 Hz repetition rate at X-band (11.424 GHz, achieving a gradient of 128  MV/m at a breakdown probability of 3.6×10^{-3} per pulse per meter at a pulse length of 150 ns. The tested standing-wave structure was a single high-gradient cell with an inner row of elliptical rods and an outer row of round rods; the elliptical rods reduce the peak surface magnetic field by 20% and reduce the temperature rise of the rods during the pulse by several tens of degrees, while maintaining good damping and suppression of high order modes. When compared with a single-cell standing-wave undamped disk-loaded waveguide structure with the same iris geometry under test at the same conditions, the PBG-E structure yielded the same breakdown rate within measurement error. The PBG-E structure showed a greatly reduced breakdown rate compared with earlier tests of a PBG structure with round rods, presumably due to the reduced magnetic fields at the elliptical rods vs the fields at the round rods, as well as use of an improved testing methodology. A post-testing autopsy of the PBG-E structure showed some damage on the surfaces exposed to the highest surface magnetic and electric fields. Despite these changes in surface appearance, no significant change in the breakdown rate was observed in testing. These results demonstrate that PBG structures, when designed with reduced surface magnetic fields and operated to avoid extremely high pulsed heating, can operate at breakdown probabilities comparable to undamped disk-loaded waveguide structures and are thus viable for high-gradient accelerator applications.

Analysis of the pressure fields in a swirling annular jet flow

NARCIS (Netherlands)

Perçin, M.; Vanierschot, M.; van Oudheusden, B.W.

2017-01-01

In this paper, we investigate the flow structures and pressure fields of a free annular swirling jet flow undergoing vortex breakdown. The flow field is analyzed by means of time-resolved tomographic particle image velocimetry measurements, which enable the reconstruction of the three-dimensional

Mean Field Games with a Dominating Player

Energy Technology Data Exchange (ETDEWEB)

Bensoussan, A., E-mail: axb046100@utdallas.edu [The University of Texas at Dallas, International Center for Decision and Risk Analysis, Jindal School of Management (United States); Chau, M. H. M., E-mail: michaelchaumanho@gmail.com; Yam, S. C. P., E-mail: scpyam@sta.cuhk.edu.hk [The Chinese University of Hong Kong, Department of Statistics (Hong Kong, People’s Republic of China) (China)

2016-08-15

In this article, we consider mean field games between a dominating player and a group of representative agents, each of which acts similarly and also interacts with each other through a mean field term being substantially influenced by the dominating player. We first provide the general theory and discuss the necessary condition for the optimal controls and equilibrium condition by adopting adjoint equation approach. We then present a special case in the context of linear-quadratic framework, in which a necessary and sufficient condition can be asserted by stochastic maximum principle; we finally establish the sufficient condition that guarantees the unique existence of the equilibrium control. The proof of the convergence result of finite player game to mean field counterpart is provided in Appendix.

Band mixing effects in mean field theories

International Nuclear Information System (INIS)

Kuyucak, S.; Morrison, I.

1989-01-01

The 1/N expansion method, which is an angular momentum projected mean field theory, is used to investigate the nature of electromagnetic transitions in the interacting boson model (IBM). Conversely, comparison with the exact IBM results sheds light on the range of validity of the mean field theory. It is shown that the projected mean field results for the E2 transitions among the ground, β and γ bands are incomplete for the spin dependent terms and it is essential to include band mixing effect for a correct (Mikhailov) analysis of E2 data. The algebraic expressions derived are general and will be useful in the analysis of experimental data in terms of both the sd and sdg boson models. 17 refs., 7 figs., 8 tabs

Facilitating breakdown in noble gases at near-atmospheric pressure using antennas

Energy Technology Data Exchange (ETDEWEB)

Sobota, A; Van Veldhuizen, E M; Haverlag, M [Eindhoven University of Technology, Department of Applied Physics, Postbus 513, 5600MB Eindhoven (Netherlands); Gendre, M F; Manders, F, E-mail: a.sobota@tue.nl [Philips Lighting, Mathildelaan 1, 5600JM Eindhoven (Netherlands)

2011-04-20

Electrical breakdown in near-atmospheric pressure noble gases requires voltages that are quite high, which is undesirable for a large number of possible applications. Metallic structures (antennas) were used on the outer side of the lamp burner to enhance the electric field locally while keeping the same potential difference across the electrodes. Optical and electrical measurements were performed in an argon or xenon atmosphere at 0.3 or 0.7 bar, with 4 or 7 mm between the electrode tips. We used rod-shaped tungsten electrodes of 0.6 mm in diameter. We found that both active and passive antennas facilitate breakdown, and we demonstrated the differences between the two types and their effects on the breakdown process.

Facilitating breakdown in noble gases at near-atmospheric pressure using antennas

International Nuclear Information System (INIS)

Sobota, A; Van Veldhuizen, E M; Haverlag, M; Gendre, M F; Manders, F

2011-01-01

Electrical breakdown in near-atmospheric pressure noble gases requires voltages that are quite high, which is undesirable for a large number of possible applications. Metallic structures (antennas) were used on the outer side of the lamp burner to enhance the electric field locally while keeping the same potential difference across the electrodes. Optical and electrical measurements were performed in an argon or xenon atmosphere at 0.3 or 0.7 bar, with 4 or 7 mm between the electrode tips. We used rod-shaped tungsten electrodes of 0.6 mm in diameter. We found that both active and passive antennas facilitate breakdown, and we demonstrated the differences between the two types and their effects on the breakdown process.

Dielectric breakdown in silica-amorphous polymer nanocomposite films: the role of the polymer matrix.

Science.gov (United States)

Grabowski, Christopher A; Fillery, Scott P; Westing, Nicholas M; Chi, Changzai; Meth, Jeffrey S; Durstock, Michael F; Vaia, Richard A

2013-06-26

The ultimate energy storage performance of an electrostatic capacitor is determined by the dielectric characteristics of the material separating its conductive electrodes. Polymers are commonly employed due to their processability and high breakdown strength; however, demands for higher energy storage have encouraged investigations of ceramic-polymer composites. Maintaining dielectric strength, and thus minimizing flaw size and heterogeneities, has focused development toward nanocomposite (NC) films; but results lack consistency, potentially due to variations in polymer purity, nanoparticle surface treatments, nanoparticle size, and film morphology. To experimentally establish the dominant factors in broad structure-performance relationships, we compare the dielectric properties for four high-purity amorphous polymer films (polymethyl methacrylate, polystyrene, polyimide, and poly-4-vinylpyridine) incorporating uniformly dispersed silica colloids (up to 45% v/v). Factors known to contribute to premature breakdown-field exclusion and agglomeration-have been mitigated in this experiment to focus on what impact the polymer and polymer-nanoparticle interactions have on breakdown. Our findings indicate that adding colloidal silica to higher breakdown strength amorphous polymers (polymethyl methacrylate and polyimide) causes a reduction in dielectric strength as compared to the neat polymer. Alternatively, low breakdown strength amorphous polymers (poly-4-vinylpyridine and especially polystyrene) with comparable silica dispersion show similar or even improved breakdown strength for 7.5-15% v/v silica. At ∼15% v/v or greater silica content, all the polymer NC films exhibit breakdown at similar electric fields, implying that at these loadings failure becomes independent of polymer matrix and is dominated by silica.

Back-reaction beyond the mean field approximation

International Nuclear Information System (INIS)

Kluger, Y.

1993-01-01

A method for solving an initial value problem of a closed system consisting of an electromagnetic mean field and its quantum fluctuations coupled to fermions is presented. By tailoring the large N f expansion method to the Schwinger-Keldysh closed time path (CTP) formulation of the quantum effective action, causality of the resulting equations of motion is ensured, and a systematic energy conserving and gauge invariant expansion about the electromagnetic mean field in powers of 1/N f is developed. The resulting equations may be used to study the quantum nonequilibrium effects of pair creation in strong electric fields and the scattering and transport processes of a relativistic e + e - plasma. Using the Bjorken ansatz of boost invariance initial conditions in which the initial electric mean field depends on the proper time only, we show numerical results for the case in which the N f expansion is truncated in the lowest order, and compare them with those of a phenomenological transport equation

Partial discharges and breakdown in C3F8

International Nuclear Information System (INIS)

Koch, M; Franck, C M

2014-01-01

Traditional search processes of gases or gas mixtures for replacing SF 6 involve time consuming measurements of partial discharges and breakdown behaviour for several voltage waveforms and different field configurations. Recently a model for prediction of this behaviour for SF 6 was described in literature. The model only requires basic properties of the gas such as the critical field strength and the effective ionization coefficient, which can be obtained by swarm parameter measurements, and thermodynamic properties, which can be calculated. In this paper, we show for the well-known and electronegative gas octafluoropropane (C 3 F 8 ) that it is possible to transfer the model developed for SF 6 to this gas to describe the breakdown behaviour of C 3 F 8 . Thus the model can be beneficial in the screening process of new insulation gases. (paper)

Partial discharges and breakdown in C3F8

Science.gov (United States)

Koch, M.; Franck, C. M.

2014-10-01

Traditional search processes of gases or gas mixtures for replacing SF6 involve time consuming measurements of partial discharges and breakdown behaviour for several voltage waveforms and different field configurations. Recently a model for prediction of this behaviour for SF6 was described in literature. The model only requires basic properties of the gas such as the critical field strength and the effective ionization coefficient, which can be obtained by swarm parameter measurements, and thermodynamic properties, which can be calculated. In this paper, we show for the well-known and electronegative gas octafluoropropane (C3F8) that it is possible to transfer the model developed for SF6 to this gas to describe the breakdown behaviour of C3F8. Thus the model can be beneficial in the screening process of new insulation gases.

Mean-field models and superheavy elements

International Nuclear Information System (INIS)

Reinhard, P.G.; Bender, M.; Maruhn, J.A.; Frankfurt Univ.

2001-03-01

We discuss the performance of two widely used nuclear mean-field models, the relativistic mean-field theory (RMF) and the non-relativistic Skyrme-Hartree-Fock approach (SHF), with particular emphasis on the description of superheavy elements (SHE). We provide a short introduction to the SHF and RMF, the relations between these two approaches and the relations to other nuclear structure models, briefly review the basic properties with respect to normal nuclear observables, and finally present and discuss recent results on the binding properties of SHE computed with a broad selection of SHF and RMF parametrisations. (orig.)

Model predictions for atmospheric air breakdown by radio-frequency excitation in large gaps

Science.gov (United States)

Nguyen, H. K.; Mankowski, J.; Dickens, J. C.; Neuber, A. A.; Joshi, R. P.

2017-07-01

The behavior of the breakdown electric field versus frequency (DC to 100 MHz) for different gap lengths has been studied numerically at atmospheric pressure. Unlike previous reports, the focus here is on much larger gap lengths in the 1-5 cm range. A numerical analysis, with transport coefficients obtained from Monte Carlo calculations, is used to ascertain the electric field thresholds at which the growth and extinction of the electron population over time are balanced. Our analysis is indicative of a U-shaped frequency dependence, lower breakdown fields with increasing gap lengths, and trends qualitatively similar to the frequency-dependent field behavior for microgaps. The low frequency value of ˜34 kV/cm for a 1 cm gap approaches the reported DC Paschen limit.

Ohm's law for mean magnetic fields

International Nuclear Information System (INIS)

Boozer, A.H.

1986-05-01

The magnetic fields associated with plasmas frequently exhibit small amplitude MHD fluctuations. It is useful to have equations for the magnetic field averaged over these fluctuations, the so-called mean field equations. Under very general assumptions it is shown that the effect of MHD fluctuations on a force-free plasma can be represented by one parameter in Ohm's law, which is effectively the coefficient of electric current viscosity

Ohm's law for mean magnetic fields

International Nuclear Information System (INIS)

Boozer, A.H.

1986-01-01

The magnetic fields associated with plasmas frequently exhibit small-amplitude MHD fluctuations. It is useful to have equations for the magnetic field averaged over these fluctuations, the so-called mean field equations. Under very general assumptions, it is shown that the effect of MHD fluctuations on a force-free plasma can be represented by one parameter in Ohm's law, which is effectively the coefficient of electric current viscosity. (author)

Energetic high-voltage breakdowns in vacuum over a large gap for ITER neutral beam accelerator

Energy Technology Data Exchange (ETDEWEB)

Villecroze, F., E-mail: Frederic.villecroze@cea.fr [CEA, IRFM, F-13108 Saint-Paul-Lez-Durance (France); Christin, L.; Esch, H.P.L. de; Simonin, A. [CEA, IRFM, F-13108 Saint-Paul-Lez-Durance (France); Schunke, B.; Svensson, L.; Hemsworth, R.; Boilson, D. [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance (France)

2013-10-15

Highlights: ► We performed energetic high voltage breakdowns up to 370 kV with a stored energy of 1 kJ. ► No breakdowns at 200 kV could be produced over a gap of 85 mm using 100 cm{sup 2} copper electrodes. ► Electrodes damage was visible after the experiment. ► The number of arcs impacts is orders of magnitude above the number of breakdowns. -- Abstract: CEA has undertaken tests to study the resilience of copper electrodes in vacuum against energetic high-voltage breakdowns using external capacitors to provide the energy. Earlier tests succeeded in dissipating a maximum of 150 J in a 30 mm gap, limited by the equivalent series resistance (ESR) in the external capacitors. Using new ones with an ESR that is a factor of 10 lower it was unsuccessfully tried to produce breakdowns at 200 kV over the 85 mm gap, despite the use of a UV flash lamp and a “field enhancement ring” (FER) that locally increased the electric field on the cathode by 50%. Consequently, the breakdowns had to be produced by raising the voltage to 300–350 kV while maintaining the gap at 85 mm. During these tests, single breakdowns dissipated up to 1140 J in the 85 mm vacuum gap. Inspection of the electrodes revealed that substantial amounts of copper appear have been evaporated from the anode and deposited on to the cathode. Also electrode deconditioning occurred.

AC BREAKDOWN IN GASES

Science.gov (United States)

electron- emission (multipactor) region, and (3) the low-frequency region. The breakdown mechanism in each of these regions is explained. An extensive bibliography on AC breakdown in gases is included.

Numerical investigation of unsteady vortex breakdown past 80°/65° double-delta wing

Directory of Open Access Journals (Sweden)

Liu Jian

2014-06-01

Full Text Available An improved delayed detached eddy simulation (IDDES method based on the k-ω-SST (shear stress transport turbulence model was applied to predict the unsteady vortex breakdown past an 80°/65° double-delta wing (DDW, where the angles of attack (AOAs range from 30° to 40°. Firstly, the IDDES model and the relative numerical methods were validated by simulating the massively separated flow around an NACA0021 straight wing at the AOA of 60°. The fluctuation properties of the lift and pressure coefficients were analyzed and compared with the available measurements. For the DDW case, the computations were compared with such measurements as the mean lift, drag, pitching moment, pressure coefficients and breakdown locations. Furthermore, the unsteady properties were investigated in detail, such as the frequencies of force and moments, pressure fluctuation on the upper surface, typical vortex breakdown patterns at three moments, and the distributions of kinetic turbulence energy at a stream wise section. Two dominated modes are observed, in which their Strouhal numbers are 1.0 at the AOAs of 30°, 32° and 34° and 0.7 at the AOAs of 36°, 38° and 40°. The breakdown vortex always moves upstream and downstream and its types change alternatively. Furthermore, the vortex can be identified as breakdown or not through the mean pressure, root mean square of pressure, or even through correlation analysis.

Cave breakdown by vadose weathering.

Directory of Open Access Journals (Sweden)

Osborne R. Armstrong L.

2002-01-01

Full Text Available Vadose weathering is a significant mechanism for initiating breakdown in caves. Vadose weathering of ore bodies, mineral veins, palaeokarst deposits, non-carbonate keystones and impure, altered or fractured bedrock, which is intersected by caves, will frequently result in breakdown. Breakdown is an active, ongoing process. Breakdown occurs throughout the vadose zone, and is not restricted to large diameter passages, or to cave ceilings. The surfaces of disarticulated blocks are commonly coated, rather than having fresh broken faces, and blocks continue to disintegrate after separating from the bedrock. Not only gypsum, but also hydromagnesite and aragonite are responsible for crystal wedging. It is impossible to study or identify potential breakdown foci by surface surveys alone, in-cave observation and mapping are essential.

["Nervous breakdown": a diagnostic characterization study].

Science.gov (United States)

Salmán, E; Carrasco, J L; Liebowitz, M; Díaz Marsá, M; Prieto, R; Jusino, C; Cárdenas, D; Klein, D

1997-01-01

An evaluation was made of the influence of different psychiatric co-morbidities on the symptoms of the disorder popularly known as "ataque de nervios" (nervous breakdown) among the US Hispanic population. Using a self-completed instrument designed specially for both traditional nervous breakdown and for panic symptoms, and structured or semi-structured psychiatric interviews for Axis I disorders, and evaluation was made of Hispanic subjects who sought treatment for anxiety in a clinic (n = 156). This study centered on 102 subjects who presented symptoms of "nervous breakdown" and comorbidity with panic disorder, other anxiety disorders, or affective disorder. Variations in co-morbidity with "nervous breakdown" enabled the identification of different patterns of "nervous breakdown" presenting symptoms. Individuals with "nervous breakdown" and panic disorder characteristically expressed a greater sense of asphyxiation, fear of dying, and growing fear (panic-like) during their breakdowns. Subjects with "nervous breakdown" and affective disorder had a greater sensation of anger and more tendency toward screaming and aggressive behavior such as breaking things during the breakdown (emotional anger). Finally, subjects with "nervous breakdown" and co-morbidity with another anxiety disorder had fewer "paniclike" or "emotional anger" symptoms. These findings suggest that: a) the widely used term "nervous breakdown" is a popular label for different patterns of loss of emotional control; b) the type of loss of emotional control is influenced by the associated psychiatric disorder; and c) the symptoms characteristics of the "nervous breakdown" can be useful clinical markers for associated psychiatric disorders. Future research is needed to determine whether the known Hispanic entity "ataque de nervios" is simply a popular description for different aspects of well-known psychiatric disorders, or if it reflects specific demographic, environmental, personality and/or clinical

Vortex Breakdown Generated by off-axis Bifurcation in a cylinder with rotating covers

DEFF Research Database (Denmark)

Bisgaard, Anders; Brøns, Morten; Sørensen, Jens Nørkær

2006-01-01

Vortex breakdown of bubble type is studied for the flow in a cylinder with rotating top and bottom covers. For large ratios of the angular velocities of the covers, we observe numerically that the vortex breakdown bubble in the steady regime may occur through the creation of an off-axis vortex ring....... This scenario does not occur in existing bifurcation theory based on a simple degeneracy in the flow field. We extend the theory to cover a non-simple degeneracy, and derive the associated bifurcation diagrams. We show that the vortex breakdown scenario involving a vortex ring can be explained from this theory...

Mean-field Ensemble Kalman Filter

KAUST Repository

Law, Kody; Tembine, Hamidou; Tempone, Raul

2015-01-01

A proof of convergence of the standard EnKF generalized to non-Gaussian state space models is provided. A density-based deterministic approximation of the mean-field limiting EnKF (MFEnKF) is proposed, consisting of a PDE solver and a quadrature

Mean field games for cognitive radio networks

KAUST Repository

Tembine, Hamidou

2012-06-01

In this paper we study mobility effect and power saving in cognitive radio networks using mean field games. We consider two types of users: primary and secondary users. When active, each secondary transmitter-receiver uses carrier sensing and is subject to long-term energy constraint. We formulate the interaction between primary user and large number of secondary users as an hierarchical mean field game. In contrast to the classical large-scale approaches based on stochastic geometry, percolation theory and large random matrices, the proposed mean field framework allows one to describe the evolution of the density distribution and the associated performance metrics using coupled partial differential equations. We provide explicit formulas and algorithmic power management for both primary and secondary users. A complete characterization of the optimal distribution of energy and probability of success is given.

Exotic nuclei in self-consistent mean-field models

International Nuclear Information System (INIS)

Bender, M.; Rutz, K.; Buervenich, T.; Reinhard, P.-G.; Maruhn, J. A.; Greiner, W.

1999-01-01

We discuss two widely used nuclear mean-field models, the relativistic mean-field model and the (nonrelativistic) Skyrme-Hartree-Fock model, and their capability to describe exotic nuclei with emphasis on neutron-rich tin isotopes and superheavy nuclei. (c) 1999 American Institute of Physics

Effects of load voltage on voltage breakdown modes of electrical exploding aluminum wires in air

Energy Technology Data Exchange (ETDEWEB)

Wu, Jian; Li, Xingwen, E-mail: xwli@mail.xjtu.edu.cn; Yang, Zefeng; Wang, Kun; Chao, Youchuang; Shi, Zongqian; Jia, Shenli; Qiu, Aici [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Xi' an 710049 (China)

2015-06-15

The effects of the load voltage on the breakdown modes are investigated in exploding aluminum wires driven by a 1 kA, 0.1 kA/ns pulsed current in air. From laser probing images taken by laser shadowgraphy, schlieren imaging, and interferometry, the position of the shockwave front, the plasma channel, and the wire core edge of the exploding product can be determined. The breakdown mode makes a transition from the internal mode, which involves breakdown inside the wire core, to the shunting mode, which involves breakdown in the compressed air, with decreasing charging voltage. The breakdown electrical field for a gaseous aluminum wire core of nearly solid density is estimated to be more than 20 kV/cm, while the value for gaseous aluminum of approximately 0.2% solid density decreases to 15–20 kV/cm. The breakdown field in shunting mode is less than 20 kV/cm and is strongly affected by the vaporized aluminum, the desorbed gas, and the electrons emitted from the wire core during the current pause. Ohmic heating during voltage collapses will induce further energy deposition in the current channel and thus will result in different expansion speeds for both the wire core and the shockwave front in the different modes.

Missouri Work Zone Capacity : Results of Field Data Analysis

Science.gov (United States)

2011-06-01

This report presents the results of work zone field data analyzed on interstate highways in Missouri to determine : the mean breakdown and queue-discharge flow rates as measures of capacity. Several days of traffic data : collected at a work zone nea...

Preliminary Breakdown: Physical Mechanisms and Potential for Energetic Emissions

Science.gov (United States)

Petersen, D.; Beasley, W. H.

2014-12-01

Observations and analysis of the preliminary breakdown phase of virgin negative cloud-to-ground (-CG) lightning strokes will be presented. Of primary interest are the physical processes responsible for the fast electric field "characteristic" pulses that are often observed during this phase. The pulse widths of characteristic pulses are shown to occur as a superposed bimodal distribution, with the short and long modes having characteristic timescales on the order of 1 microsecond and 10 microseconds, respectively. Analysis of these pulses is based on comparison with laboratory observations of long spark discharge processes and with recently acquired high-speed video observations of a single -CG event. It will be argued that the fast electric field bimodal distribution is the result of conventional discharge processes operating in an extensive strong ambient electric field environment. An important related topic will also be discussed, where it will be argued that preliminary breakdown discharges are capable of generating energetic electrons and may therefore seed relativistic electron avalanches that go on to produce pulsed energetic photon emissions.

Breakdown assisted by a novel electron drift injection in the J-TEXT tokamak

International Nuclear Information System (INIS)

Wang, Nengchao; Jin, Hai; Zhuang, Ge; Ding, Yonghua; Pan, Yuan; Cen, Yishun; Chen, Zhipeng; Huang, Hai; Liu, Dequan; Rao, Bo; Zhang, Ming; Zou, Bichen

2014-01-01

A novel electron drift injection (EDI) system aiming to improve breakdown behavior has been designed and constructed on the Joint Texas EXperiment Tokamak Tokamak. Electrons emitted by the system undergo the E×B drift, ∇B drift and curvature drift in sequence in order to traverse the confining magnetic field. A local electrostatic well, generated by a concave-shaped plate biased more negative than the cathode, is introduced to interrupt the emitted electrons moving along the magnetic field line (in the parallel direction) in an attempt to bring an enhancement of the injection efficiency and depth. A series of experiments have demonstrated the feasibility of this method, and a penetration distance deeper than 9.5 cm is achieved. Notable breakdown improvements, including the reduction of breakdown delay and average loop voltage, are observed for discharges assisted by EDI. The lower limit of successfully ionized pressure is expanded

The structure and dynamics of bubble-type vortex breakdown

Science.gov (United States)

Spall, R. E.; Ash, R. L.; Gatski, T. B.

1990-01-01

A unique discrete form of the Navier-Stokes equations for unsteady, three-dimensional, incompressible flow has been used to study vortex breakdown numerically. A Burgers-type vortex was introduced along the central axis of the computational domain, and allowed to evolve in space and time. By varying the strength of the vortex and the free stream axial velocity distribution, using a previously developed Rossby number criterion as a guide, the location and size of the vortex breakdown region was controlled. While the boundaries of the vortex breakdown bubble appear to be nominally symmetric, the internal flow field is not. Consequently, the mechanisms for mixing and entrainment required to sustain the bubble region are different from those suggested by earlier axisymmetric models. Results presented in this study, for a Reynolds number of 200, are in good qualitative agreement with higher Reynolds number experimental observations, and a variety of plots have been presented to help illuminate the fluid physics.

Uncertainty quantification for mean field games in social interactions

KAUST Repository

Dia, Ben Mansour

2016-01-09

We present an overview of mean field games formulation. A comparative analysis of the optimality for a stochastic McKean-Vlasov process with time-dependent probability is presented. Then we examine mean-field games for social interactions and we show that optimizing the long-term well-being through effort and social feeling state distribution (mean-field) will help to stabilize couple (marriage). However , if the cost of effort is very high, the couple fluctuates in a bad feeling state or the marriage breaks down. We then examine the influence of society on a couple using mean field sentimental games. We show that, in mean-field equilibrium, the optimal effort is always higher than the one-shot optimal effort. Finally we introduce the Wiener chaos expansion for the construction of solution of stochastic differential equations of Mckean-Vlasov type. The method is based on the Cameron-Martin version of the Wiener Chaos expansion and allow to quantify the uncertainty in the optimality system.

Uncertainty quantification for mean field games in social interactions

KAUST Repository

Dia, Ben Mansour

2016-01-01

We present an overview of mean field games formulation. A comparative analysis of the optimality for a stochastic McKean-Vlasov process with time-dependent probability is presented. Then we examine mean-field games for social interactions and we show that optimizing the long-term well-being through effort and social feeling state distribution (mean-field) will help to stabilize couple (marriage). However , if the cost of effort is very high, the couple fluctuates in a bad feeling state or the marriage breaks down. We then examine the influence of society on a couple using mean field sentimental games. We show that, in mean-field equilibrium, the optimal effort is always higher than the one-shot optimal effort. Finally we introduce the Wiener chaos expansion for the construction of solution of stochastic differential equations of Mckean-Vlasov type. The method is based on the Cameron-Martin version of the Wiener Chaos expansion and allow to quantify the uncertainty in the optimality system.

Many-Body Mean-Field Equations: Parallel implementation

International Nuclear Information System (INIS)

Vallieres, M.; Umar, S.; Chinn, C.; Strayer, M.

1993-01-01

We describe the implementation of Hartree-Fock Many-Body Mean-Field Equations on a Parallel Intel iPSC/860 hypercube. We first discuss the Nuclear Mean-Field approach in physical terms. Then we describe our parallel implementation of this approach on the Intel iPSC/860 hypercube. We discuss and compare the advantages and disadvantages of the domain partition versus the Hilbert space partition for this problem. We conclude by discussing some timing experiments on various computing platforms

Linear–Quadratic Mean-Field-Type Games: A Direct Method

Directory of Open Access Journals (Sweden)

Tyrone E. Duncan

2018-02-01

Full Text Available In this work, a multi-person mean-field-type game is formulated and solved that is described by a linear jump-diffusion system of mean-field type and a quadratic cost functional involving the second moments, the square of the expected value of the state, and the control actions of all decision-makers. We propose a direct method to solve the game, team, and bargaining problems. This solution approach does not require solving the Bellman–Kolmogorov equations or backward–forward stochastic differential equations of Pontryagin’s type. The proposed method can be easily implemented by beginners and engineers who are new to the emerging field of mean-field-type game theory. The optimal strategies for decision-makers are shown to be in a state-and-mean-field feedback form. The optimal strategies are given explicitly as a sum of the well-known linear state-feedback strategy for the associated deterministic linear–quadratic game problem and a mean-field feedback term. The equilibrium cost of the decision-makers are explicitly derived using a simple direct method. Moreover, the equilibrium cost is a weighted sum of the initial variance and an integral of a weighted variance of the diffusion and the jump process. Finally, the method is used to compute global optimum strategies as well as saddle point strategies and Nash bargaining solution in state-and-mean-field feedback form.

Studying the Dynamics of Breakdown of Thin Horizontal Liquid Layers with Local Heating

Directory of Open Access Journals (Sweden)

Spesivtsev Serafim

2016-01-01

Full Text Available Experimental study of liquid layers breakdown when heated locally from the substrate side was made. Water and ethanol were used as working liquids with a layer thickness of 300 μm. Basic steps of the breakdown process were found and mean velocities of the dry spot formation were determined; the values are 0.06 mm/sec for ethanol and 5.15 mm/sec for water. The formation of residual layer over the hot-spot before the breakdown has been found for both liquids. The creation of a droplet cluster near the heating region is observed when using water as a working fluid. It was shown that evaporation is one of the general factors influencing the process of layer breakdown and dry spot formation as well as thermocapillary effect.

Mask characterization for CDU budget breakdown in advanced EUV lithography

Science.gov (United States)

Nikolsky, Peter; Strolenberg, Chris; Nielsen, Rasmus; Nooitgedacht, Tjitte; Davydova, Natalia; Yang, Greg; Lee, Shawn; Park, Chang-Min; Kim, Insung; Yeo, Jeong-Ho

2012-11-01

As the ITRS Critical Dimension Uniformity (CDU) specification shrinks, semiconductor companies need to maintain a high yield of good wafers per day and a high performance (and hence market value) of finished products. This cannot be achieved without continuous analysis and improvement of on-product CDU as one of the main drivers for process control and optimization with better understanding of main contributors from the litho cluster: mask, process, metrology and scanner. In this paper we will demonstrate a study of mask CDU characterization and its impact on CDU Budget Breakdown (CDU BB) performed for an advanced EUV lithography with 1D and 2D feature cases. We will show that this CDU contributor is one of the main differentiators between well-known ArFi and new EUV CDU budgeting principles. We found that reticle contribution to intrafield CDU should be characterized in a specific way: mask absorber thickness fingerprints play a role comparable with reticle CDU in the total reticle part of the CDU budget. Wafer CD fingerprints, introduced by this contributor, may or may not compensate variations of mask CD's and hence influence on total mask impact on intrafield CDU at the wafer level. This will be shown on 1D and 2D feature examples in this paper. Also mask stack reflectivity variations should be taken into account: these fingerprints have visible impact on intrafield CDs at the wafer level and should be considered as another contributor to the reticle part of EUV CDU budget. We observed also MEEF-through-field fingerprints in the studied EUV cases. Variations of MEEF may also play a role for the total intrafield CDU and may be taken into account for EUV Lithography. We characterized MEEF-through-field for the reviewed features, the results to be discussed in our paper, but further analysis of this phenomenon is required. This comprehensive approach to characterization of the mask part of EUV CDU characterization delivers an accurate and integral CDU Budget

Tattoo and Symbolic Meaning: A Descriptive Study of Tattoo Phenomenon Among Tattoo Users In The City of Medan, Indonesia

OpenAIRE

Zulkarnain, Iskandar; Bilardo, Topan

2016-01-01

Iskandar Zulkarnain The tattoo phenomenon is not something that just emerged from modernity or something that popped out in the cities. Historically, tattoo originated from the culture in the hinterland, which is traditional and ancient. The presence of tattoo in the modern city society has experienced a change in meaning. Tattoo has developed and has become a popular or competitive culture, which the young generation perceives as a symbol of freedom and diversity. However, the elder gener...

Nanosecond air breakdown parameters for electron and microwave beam propagation

International Nuclear Information System (INIS)

Ali, A.W.

1988-01-01

Air breakdown by avalanche ionization plays an important role in the electron beam and microwave propagations. For high electric fields and short pulse applications one needs avalanche ionization parameters for modeling and scaling of experimental devices. However, the breakdown parameters, i.e., the ionization frequency vs E/p (volt. cm -1 . Torr -1 ) in air is uncertain for very high values of E/P. A review is given of the experimental data for the electron drift velocity, the Townsend ionization coefficient in N 2 and O 2 and the ionization frequency and the collision frequency for momentum transfer in air are developed. (author)

Electric Conductivity and Dielectric-Breakdown Behavior for Polyurethane Magnetic Elastomers.

Science.gov (United States)

Sasaki, Shuhei; Tsujiei, Yuri; Kawai, Mika; Mitsumata, Tetsu

2017-02-23

The electric-voltage dependence of the electric conductivity for cross-linked and un-cross-linked magnetic elastomers was measured at various magnetic fields, and the effect of cross-linking on the electric conductivity and the dielectric-breakdown behavior was investigated. The electric conductivity for un-cross-linked elastomers at low voltages was independent of magnetic fields and the volume fraction of magnetic particles, indicating the electric conduction in the polyurethane matrix. At high voltages, the electric conductivity increased with the magnetic field, showing the electric conduction via chains of magnetic particles. On the other hand, the electric conductivity at low voltages for cross-linked elastomers with volume fractions below 0.06 was independent of the magnetic field, suggesting the electric conduction in the polyurethane matrix. At volume fractions above 0.14, the electric conductivity increased with the magnetic field, suggesting the electric conduction via chains of magnetic particles. At high voltages, the electric conductivity for cross-linked elastomers with a volume fraction of 0.02 was independent of the magnetic field, indicating the electric conduction through the polyurethane matrix. At volume fractions above 0.06, the electric conductivity suddenly increased at a critical voltage, exhibiting the dielectric breakdown at the bound layer of magnetic particles and/or the discontinuous part between chains.

Derivation of mean-field dynamics for fermions

International Nuclear Information System (INIS)

Petrat, Soeren

2014-01-01

In this work, we derive the time-dependent Hartree(-Fock) equations as an effective dynamics for fermionic many-particle systems. Our main results are the first for a quantum mechanical mean-field dynamics for fermions; in previous works, the mean-field limit is usually either coupled to a semiclassical limit, or the interaction is scaled down so much, that the system behaves freely for large particle number N. We mainly consider systems with total kinetic energy bounded by const.N and long-range interaction potentials, e.g., Coulomb interaction. Examples for such systems are large molecules or certain solid states. Our analysis also applies to attractive interactions, as, e.g., in fermionic stars. The fermionic Hartree(-Fock) equations are a standard tool to describe, e.g., excited states or chemical reactions of large molecules (like proteins). A deeper understanding of these equations as an approximation to the time evolution of a many body quantum system is thus highly relevant. We consider the fermionic Hartree equations (i.e., the Hartree-Fock equations without exchange term) in this work, since the exchange term is subleading in our setting. The main result is that the fermionic Hartree dynamics approximates the Schroedinger dynamics well for large N. This statement becomes exact in the thermodynamic limit N→∞. We give explicit values for the rates of convergence. We prove two types of results. The first type is very general and concerns arbitrary free Hamiltonians (e.g., relativistic, non-relativistic, with external fields) and arbitrary interactions. The theorems give explicit conditions on the solutions to the fermionic Hartree equations under which a derivation of the mean-field dynamics succeeds. The second type of results scrutinizes situations where the conditions are fulfilled. These results are about non-relativistic free Hamiltonians with external fields, systems with total kinetic energy bounded by const.N and with long-range interactions of

Substrate-bias effect on the breakdown characteristic in a new silicon high-voltage device structure

International Nuclear Information System (INIS)

Li Qi; Wang Weidong; Zhao Qiuming; Wei Xueming

2012-01-01

A novel silicon double-RESURF LDMOS structure with an improved breakdown characteristic by substrate bias technology (SB) is reported. The P-type epitaxial layer is embedded between an N-type drift region and an N-type substrate to block the conduction path in the off-state and change the distributions of the bulk electric field. The substrate bias strengthens the charge share effect of the drift region near the source, and the vertical electric field peak under the drain is decreased, which is especially helpful in improving the vertical breakdown voltage in a lateral power device with a thin drift region. The numerical results by MEDICI indicate that the breakdown voltage of the proposed device is increased by 97% compared with a conventional LDMOS, while maintaining a lowon-resistance. (semiconductor devices)

Breakdown study of dc silicon micro-discharge devices

International Nuclear Information System (INIS)

Schwaederlé, L; Kulsreshath, M K; Lefaucheux, P; Tillocher, T; Dussart, R; Overzet, L J

2012-01-01

The influence of geometrical and operating parameters on the electrical characteristics of dc microcavity discharges provides insight into their controlling physics. We present here results of such a study on silicon-based microcavity discharge devices carried out in helium at pressure ranging from 100 to 1000 Torr. Different micro-reactor configurations were measured. The differences include isolated single cavities versus arrays of closely spaced cavities, various cavity geometries (un-etched as well as isotropically and anisotropically etched), various dimensions (100 or 150 µm cavity diameter and 0-150 µm depth). The electrode gap was kept constant in all cases at approximately 6 µm. The applied electric field reaches 5 × 10 7 V m -1 which results in current and power densities up to 2 A cm -2 and 200 kW cm -3 , respectively. The number of microcavities and the microcavity depth are shown to be the most important geometrical parameters for predicting breakdown and operation of microcavity devices. The probability of initiatory electron generation which is volume dependent and the electric field strength which is depth dependent are, respectively, considered to be responsible. The cavity shape (isotropic/anisotropic) and diameter had no significant influence. The number of micro-discharges that could be ignited depends on the rate of voltage rise and pressure. Larger numbers ignite at lower frequency and pressure. In addition, the voltage polarity has the largest influence on the electrical characteristics of the micro-discharge of all parameters, which is due to both the asymmetric role of electrodes as electron emitter and the non-uniformity of the electric field resulting in different ionization efficiencies. The qualitative shape of all breakdown voltage versus pressure curves can be explained in terms of the distance over which the discharge breakdown effectively occurs as long as one understand that this distance can depend on pressure. (paper)

The Causes and Prevention Measures of Stuck Pump Phenomenon of Rod-pumped Well in CBM Field

Science.gov (United States)

Yonggui, Mei

2018-02-01

In the process of CBM field exploitation, in order to realize the drainage equipment to work continuous stably, the article pays attention to study and solve the stuck pump problem, and aim of reducing reservoir damage and lowing production costs. Through coal particles stuck pump experiment and sediment composition analysis, we find out five primary cause of stuck pump phenomenon: sand from coal seam, sediment from ground, iron corrosion, iron scrap caused by eccentric wear, coal cake. According to stuck pump mechanism, the article puts forward 8 measures to prevent stuck pump phenomenon, and the measures are focused on technology optimization, operation management and drainage process control. After 7 years production practice, the yearly stuck pump rate has dropped from 8.9% to 1.2%, and the pump inspection period has prolonged 2 times. The experiment result shows that pure coal particles cannot cause stuck pump, but sand, scrap iron, and iron corrosion are the primary cause of stuck pump. The article study and design the new pipe string structure that the bottom of the pipe string is open. This kind of pipe string applied the sedimentation terminal velocity theory to solve the stuck pump phenomenon, and it can be widely used in CBM drainage development.

On dielectric breakdown statistics

International Nuclear Information System (INIS)

Tuncer, Enis; James, D Randy; Sauers, Isidor; Ellis, Alvin R; Pace, Marshall O

2006-01-01

In this paper, we investigate the dielectric breakdown data of some insulating materials and focus on the applicability of the two- and three-parameter Weibull distributions. A new distribution function is also proposed. In order to assess the model distribution's trustworthiness, we employ the Monte Carlo technique and, randomly selecting data-subsets from the whole dielectric breakdown data, determine whether the selected probability functions accurately describe the breakdown data. The utility and strength of the proposed expression are illustrated distinctly by the numerical procedure. The proposed expression is shown to be a valuable alternative to the Weibull ones

Three-dimensional supersonic vortex breakdown

Science.gov (United States)

Kandil, Osama A.; Kandil, Hamdy A.; Liu, C. H.

1993-01-01

Three-dimensional supersonic vortex-breakdown problems in bound and unbound domains are solved. The solutions are obtained using the time-accurate integration of the unsteady, compressible, full Navier-Stokes (NS) equations. The computational scheme is an implicit, upwind, flux-difference splitting, finite-volume scheme. Two vortex-breakdown applications are considered in the present paper. The first is for a supersonic swirling jet which is issued from a nozzle into a supersonic uniform flow at a lower Mach number than that of the swirling jet. The second is for a supersonic swirling flow in a configured circular duct. In the first application, an extensive study of the effects of grid fineness, shape and grid-point distribution on the vortex breakdown is presented. Four grids are used in this study and they show a substantial dependence of the breakdown bubble and shock wave on the grid used. In the second application, the bubble-type and helix-type vortex breakdown have been captured.

Optimal Lot Sizing with Scrap and Random Breakdown Occurring in Backorder Replenishing Period

OpenAIRE

Ting, Chia-Kuan; Chiu, Yuan-Shyi; Chan, Chu-Chai

2011-01-01

This paper is concerned with determination of optimal lot size for an economic production quantity model with scrap and random breakdown occurring in backorder replenishing period. In most real-life manufacturing systems, generation of defective items and random breakdown of production equipment are inevitable. To deal with the stochastic machine failures, production planners practically calculate the mean time between failures (MTBF) and establish the robust plan accordingly, in terms of opt...

Shock/vortex interaction and vortex-breakdown modes

Science.gov (United States)

Kandil, Osama A.; Kandil, H. A.; Liu, C. H.

1992-01-01

Computational simulation and study of shock/vortex interaction and vortex-breakdown modes are considered for bound (internal) and unbound (external) flow domains. The problem is formulated using the unsteady, compressible, full Navier-Stokes (NS) equations which are solved using an implicit, flux-difference splitting, finite-volume scheme. For the bound flow domain, a supersonic swirling flow is considered in a configured circular duct and the problem is solved for quasi-axisymmetric and three-dimensional flows. For the unbound domain, a supersonic swirling flow issued from a nozzle into a uniform supersonic flow of lower Mach number is considered for quasi-axisymmetric and three-dimensional flows. The results show several modes of breakdown; e.g., no-breakdown, transient single-bubble breakdown, transient multi-bubble breakdown, periodic multi-bubble multi-frequency breakdown and helical breakdown.

Mean field approach to nuclear structure

International Nuclear Information System (INIS)

Nazarewicz, W.; Tennessee Univ., Knoxville, TN

1993-01-01

Several examples of mean-field calculations, relevant to the recent and planned low-spin experimental works, are presented. The perspectives for future studies (mainly related to spectroscopy of exotic nuclei) are reviewd

Self-consistent mean-field models for nuclear structure

International Nuclear Information System (INIS)

Bender, Michael; Heenen, Paul-Henri; Reinhard, Paul-Gerhard

2003-01-01

The authors review the present status of self-consistent mean-field (SCMF) models for describing nuclear structure and low-energy dynamics. These models are presented as effective energy-density functionals. The three most widely used variants of SCMF's based on a Skyrme energy functional, a Gogny force, and a relativistic mean-field Lagrangian are considered side by side. The crucial role of the treatment of pairing correlations is pointed out in each case. The authors discuss other related nuclear structure models and present several extensions beyond the mean-field model which are currently used. Phenomenological adjustment of the model parameters is discussed in detail. The performance quality of the SCMF model is demonstrated for a broad range of typical applications

Intertextuality as A Cultural Interaction Mechanism and Socio-Cultural Phenomenon

Directory of Open Access Journals (Sweden)

E P Shiniev

2010-03-01

Full Text Available The article focuses on intertextuality as a concept associated with the tradition of postmodernism textology and a phenomenon of text interaction with the semiotic cultural environment. The concept of intertextuality emerges as an essential condition for the construction of meaning which includes the dialogical characteristics of the polylogue culture field. The author examines the evolution of intertextuality since M.M. Bakhtin up to contemporary theoreticians of postmodernism. The concept of intertextuality is the prominent characteristics of the contemporary «post» culture and the major channel of inter-cultural diffusion.

Transient chaos - a resolution of breakdown of quantum-classical correspondence in optomechanics.

Science.gov (United States)

Wang, Guanglei; Lai, Ying-Cheng; Grebogi, Celso

2016-10-17

Recently, the phenomenon of quantum-classical correspondence breakdown was uncovered in optomechanics, where in the classical regime the system exhibits chaos but in the corresponding quantum regime the motion is regular - there appears to be no signature of classical chaos whatsoever in the corresponding quantum system, generating a paradox. We find that transient chaos, besides being a physically meaningful phenomenon by itself, provides a resolution. Using the method of quantum state diffusion to simulate the system dynamics subject to continuous homodyne detection, we uncover transient chaos associated with quantum trajectories. The transient behavior is consistent with chaos in the classical limit, while the long term evolution of the quantum system is regular. Transient chaos thus serves as a bridge for the quantum-classical transition (QCT). Strikingly, as the system transitions from the quantum to the classical regime, the average chaotic transient lifetime increases dramatically (faster than the Ehrenfest time characterizing the QCT for isolated quantum systems). We develop a physical theory to explain the scaling law.

Classification of networks of automata by dynamical mean field theory

International Nuclear Information System (INIS)

Burda, Z.; Jurkiewicz, J.; Flyvbjerg, H.

1990-01-01

Dynamical mean field theory is used to classify the 2 24 =65,536 different networks of binary automata on a square lattice with nearest neighbour interactions. Application of mean field theory gives 700 different mean field classes, which fall in seven classes of different asymptotic dynamics characterized by fixed points and two-cycles. (orig.)

Symplectic manifolds, coadjoint orbits, and Mean Field Theory

International Nuclear Information System (INIS)

Rosensteel, G.

1986-01-01

Mean field theory is given a geometrical interpretation as a Hamiltonian dynamical system. The Hartree-Fock phase space is the Grassmann manifold, a symplectic submanifold of the projective space of the full many-fermion Hilbert space. The integral curves of the Hartree-Fock vector field are the time-dependent Hartree-Fock solutions, while the critical points of the energy function are the time-independent states. The mean field theory is generalized beyond determinants to coadjoint orbit spaces of the unitary group; the Grassmann variety is the minimal coadjoint orbit

Optical breakdown of helium in Bessel laser radiation beams

International Nuclear Information System (INIS)

Andreev, N E; Pleshanov, I V; Margolin, L Ya; Pyatnitskii, Lev N

1998-01-01

Numerical simulation is used to investigate the dynamics of formation of a helium plasma in Bessel beams, shaped by an axicon and a phase converter from a laser radiation pulse with Gaussian temporal and radial intensity profiles. The beam intensities at the breakdown threshold are determined as a function of the pulse duration for various radial field distributions in a beam characterised by Bessel functions of order m (m = 0 - 5). It is shown that in the investigated range of parameters the threshold intensity is independent of m. The temporal and spatial evolution of the resultant plasma, and the dependence of the plasma characteristics on the pulse parameters are considered. Conditions are found for the formation of tubular plasma channels in beams of orders m≥1. The adopted model of the optical breakdown of helium is shown to be satisfactory because of a good agreement between the results of calculations of the moment of breakdown in a zeroth-order Bessel beam and experimental results. (interaction of laser radiation with matter. laser plasma)

Evaluation of methods for increasing vacuum breakdown strength

International Nuclear Information System (INIS)

Evans, R.D.; Cooke, C.M.; Berman, E.R.

1977-01-01

Research to determine the effectiveness of coated and gas shielded cathodes as a means of increasing vacuum breakdown strength under short pulse conditions is reported. A technique for rapidly evaluating large numbers of coatings on small electrodes at relatively low pulse voltage (120 kV or less) and methods for testing larger electrodes and fewer coatings at higher total voltage were developed. Experiments with gas shielded cathodes were also conducted. Results suggest that it may be possible to eliminate prebreakdown current and to double breakdown strength by applying a suitable coating to the cathode. Breakdown stresses in excess of 2 MV/cm were obtained in a 0.5 mm gap with sputtered coatings of alumina, Cr 2 O 3 , and several readily available epoxies. Electrodes two orders of magnitude greater in area were tested, and stresses approaching 1 MV/cm were measured in 5 mm gaps for several epoxies and for alumina. It has further been shown that, because similar trends occurred in the data from large and small experiments, it should be possible to screen potential coatings rapidly and effectively with minimum expenditure using a method similar to that employed for small electrodes at low pulse voltage

Diffusion phenomenon at the interface of Cu-brass under a strong gravitational field

Energy Technology Data Exchange (ETDEWEB)

Ogata, Yudai; Tokuda, Makoto; Januszko, Kamila; Khandaker, Jahirul Islam; Mashimo, Tsutomu, E-mail: mashimo@gpo.kumamoto-u.ac.jp [Institute of Pulsed Power Science, Kumamoto University, Kumamoto 860-8555 (Japan); Iguchi, Yusuke [Department of Solid State Physics, Debrecen University, 4032 Debrecen (Hungary); Ono, Masao [Advanced Science Research Center, Japan Atomic Energy Agency (JAEA), Ibaraki 319-1195 (Japan)

2015-03-28

To investigate diffusion phenomenon at the interface between Cu and brass under a strong gravitational field generated by ultracentrifuge apparatus, we performed gravity experiments on samples prepared by electroplating with interfaces normal and parallel to the direction of gravity. For the parallel-mode sample, for which sedimentation cannot occur thorough the interface, the concentration change was significant within the lower gravity region; many pores were observed in this region. Many vacancies arising from crystal strain due to the strong gravitational field moved into the lower gravity region, and enhanced the atoms mobilities. For the two normal-mode samples, which have interface normal to the direction of gravity, the composition gradient of the brass-on-Cu sample was steeper than that for Cu-on-brass. This showed that the atoms of denser Cu diffuse in the direction of gravity, whereas Zn atoms diffuse in the opposite direction by sedimentation. The interdiffusion coefficients became higher in the Cu-on-brass sample, and became lower in the brass-on-Cu sample. This rise may be related to the behavior of the vacancies.

An interpretive phenomenological method for illuminating the meaning of caring relationship.

Science.gov (United States)

Berg, Linda; Skott, Carola; Danielson, Ella

2006-03-01

This study is a part of a larger project in which the aim is to illuminate the meaning of the caring relationship between patients and nurses in daily nursing practice. Empirical studies in this area inspired from the interpretive phenomenological method are not commonly used. The aim of this paper is to describe how an interpretive phenomenological method was used to illuminate the meaning of the phenomenon caring relationship in daily nursing practice. Data were collected during 16 nursing care proceedings using participant observation with field notes, and in addition to that two interviews, one patient and one nurse. The interpretation moved back and forth between the whole and the parts in a dialectic process. Initial interpretive understanding of interviews and field notes, meaning units and comprehensive understanding were presented. Themes from the patient's interviews were competence, lack of continuity, strain and vulnerability. Themes from the nurse's interviews were competence and striving. Themes from the field notes were interactions towards a goal. The use of interpretive phenomenology offered an opportunity for learning to understand the meaning of the phenomenon caring relationship in daily nursing practice with both strengths and limitations. This study gave an understanding of the phenomenon through the illumination of the patient's and the nurse's thoughts, feelings and actions in the nursing care proceedings that led to a more profound knowledge about how they together create an encounter through their unique competence.

Cyclotron resonant gas breakdown with a 1.22-nm 13CH3F laser

International Nuclear Information System (INIS)

Hacker, M.P.; Lax, B.; Metz, R.N.; Temkin, R.J.

1979-01-01

Cyclotron-resonant laser-induced gas breakdown has been studied for the first time in the transverse geometry, using 1.222-nm 13 CH 3 F laser radiation propagating perpendicular to the magnetic field axis. The line shape of absorbed laser radiation versus magnetic field near electron cyclotron resonance (87.75 kG) indicates a strong dependence of the line shape on the focused laser intensity. This dependence is not predicted by the standard equilibrium theory of high-frequency gas breakdown in a magnetic field. We have developed an analytic theory to explain the observed line shapes. The theory takes into account the laser propagation characteristics, in particular that there is nonuniform ionization due to strong resonant absorption of the laser radiation in a length comparable to or shorter than that of the laser focal volume. The transverse geometry simplifies the theoretical analysis because the observed line shapes are not significantly affected by Doppler broadening. Extensive data have been obtained on the fraction of laser pulse energy absorbed in the gas breakdown volume as a function of magnetic field, helium gas pressure, and incident laser pulse energy. Good quantitative agreement is obtained between the observed laser pulse absorption line shapes and the nonuniform ionization theory

A three-dimensional breakdown model of SOI lateral power transistors with a circular layout

International Nuclear Information System (INIS)

Guo Yufeng; Wang Zhigong; Sheu Gene

2009-01-01

This paper presents an analytical three-dimensional breakdown model of SOI lateral power devices with a circular layout. The Poisson equation is solved in cylindrical coordinates to obtain the radial surface potential and electric field distributions for both fully- and partially-depleted drift regions. The breakdown voltages for N + N and P + N junctions are derived and employed to investigate the impact of cathode region curvature. A modified RESURF criterion is proposed to provide a design guideline for optimizing the breakdown voltage and doping concentration in the drift region in three dimensional space. The analytical results agree well with MEDICI simulation results and experimental data from earlier publications. (semiconductor devices)

Weakly coupled mean-field game systems

KAUST Repository

Gomes, Diogo A.; Patrizi, Stefania

2016-01-01

Here, we prove the existence of solutions to first-order mean-field games (MFGs) arising in optimal switching. First, we use the penalization method to construct approximate solutions. Then, we prove uniform estimates for the penalized problem

Breakdown conditioning of copper, CuZr and GlidCop® : effect of mechanical surface treatments

CERN Document Server

Ramsvik, T; Calatroni, S; Taborelli, M; CERN. Geneva. TS Department

2007-01-01

Motivated by the need of novel materials for the CLIC accelerating structures to resist mechanical fatigue, the copper based metals Copper Zirconium C15000 (CuZr) and GlidCop® Al-15 C15715 have been investigated by DC breakdown measurements, and compared with commercially pure Oxygen-free Copper C10100 (Cu-OFE). In all three cases the saturated breakdown fields (Esat) are similar, despite significant differences in their tensile strengths. In addition, the choice of mechanical surface preparation techniques influences the final breakdown characteristics. For both CuZr and GlidCop® immediate conditioning takes place when the surfaces are prepared by milling. For electro discharge machined (EDM) surfaces, however, several breakdown events are needed to obtain saturation. Specifically, for EDM treated CuZr and GlidCop®, ~50 and ~200 breakdown events are required to reach Esat.

General Relativistic Mean Field Theory for rotating nuclei

Energy Technology Data Exchange (ETDEWEB)

Madokoro, Hideki [Kyushu Univ., Fukuoka (Japan). Dept. of Physics; Matsuzaki, Masayuki

1998-03-01

The {sigma}-{omega} model Lagrangian is generalized to an accelerated frame by using the technique of general relativity which is known as tetrad formalism. We apply this model to the description of rotating nuclei within the mean field approximation, which we call General Relativistic Mean Field Theory (GRMFT) for rotating nuclei. The resulting equations of motion coincide with those of Munich group whose formulation was not based on the general relativistic transformation property of the spinor fields. Some numerical results are shown for the yrast states of the Mg isotopes and the superdeformed rotational bands in the A {approx} 60 mass region. (author)

Mean Field Games for Stochastic Growth with Relative Utility

Energy Technology Data Exchange (ETDEWEB)

Huang, Minyi, E-mail: mhuang@math.carleton.ca [Carleton University, School of Mathematics and Statistics (Canada); Nguyen, Son Luu, E-mail: sonluu.nguyen@upr.edu [University of Puerto Rico, Department of Mathematics (United States)

2016-12-15

This paper considers continuous time stochastic growth-consumption optimization in a mean field game setting. The individual capital stock evolution is determined by a Cobb–Douglas production function, consumption and stochastic depreciation. The individual utility functional combines an own utility and a relative utility with respect to the population. The use of the relative utility reflects human psychology, leading to a natural pattern of mean field interaction. The fixed point equation of the mean field game is derived with the aid of some ordinary differential equations. Due to the relative utility interaction, our performance analysis depends on some ratio based approximation error estimate.

Mean Field Games for Stochastic Growth with Relative Utility

International Nuclear Information System (INIS)

Huang, Minyi; Nguyen, Son Luu

2016-01-01

This paper considers continuous time stochastic growth-consumption optimization in a mean field game setting. The individual capital stock evolution is determined by a Cobb–Douglas production function, consumption and stochastic depreciation. The individual utility functional combines an own utility and a relative utility with respect to the population. The use of the relative utility reflects human psychology, leading to a natural pattern of mean field interaction. The fixed point equation of the mean field game is derived with the aid of some ordinary differential equations. Due to the relative utility interaction, our performance analysis depends on some ratio based approximation error estimate.

Skin breakdown in acute care pediatrics.

Science.gov (United States)

Suddaby, Elizabeth C; Barnett, Scott D; Facteau, Lorna

2006-04-01

The purpose of this study was to develop a simple, single-page measurement tool that evaluates risk of skin breakdown in the peadiatric population and apply it to the acutely hospitalized child. Data were collected over a 15-month period from 347 patients on four in-patient units (PICU, medical-surgical, oncology, and adolescents) on skin breakdown using the AHCPR staging guidelines and compared to the total score on the Starkid SkinScale in order to determine its ability to predict skin breakdown. The inter-rater reliability of the Starkid Skin Scale was r2 = 0.85 with an internal reliablity of 0.71. The sensitivity of the total score was low (17.5%) but highly specific (98.5%). The prevalence of skin breakdown in the acutely hospitalized child was 23%, the majority (77.5%) occurring as erythema of the skin. Buttocks, perineum, and occiput were the most common locations of breakdown. Occiput breakdown was more common in critically ill (PICU) patients while diaper dermatitis was more common in the general medical-surgical population.

Mean-field learning for satisfactory solutions

KAUST Repository

Tembine, Hamidou

2013-12-01

One of the fundamental challenges in distributed interactive systems is to design efficient, accurate, and fair solutions. In such systems, a satisfactory solution is an innovative approach that aims to provide all players with a satisfactory payoff anytime and anywhere. In this paper we study fully distributed learning schemes for satisfactory solutions in games with continuous action space. Considering games where the payoff function depends only on own-action and an aggregate term, we show that the complexity of learning systems can be significantly reduced, leading to the so-called mean-field learning. We provide sufficient conditions for convergence to a satisfactory solution and we give explicit convergence time bounds. Then, several acceleration techniques are used in order to improve the convergence rate. We illustrate numerically the proposed mean-field learning schemes for quality-of-service management in communication networks. © 2013 IEEE.

Virtual-site correlation mean field approach to criticality in spin systems

International Nuclear Information System (INIS)

Sen, Aditi; Sen, Ujjwal

2013-01-01

We propose a virtual-site correlation mean field theory for dealing with interacting many-body systems. It involves a coarse-graining technique that terminates a step before the mean field theory: While mean field theory deals with only single-body physical parameters, the virtual-site correlation mean field theory deals with single- as well as two-body ones, and involves a virtual site for every interaction term in the Hamiltonian. We generalize the theory to a cluster virtual-site correlation mean field, that works with a fundamental unit of the lattice of the many-body system. We apply these methods to interacting Ising spin systems in several lattice geometries and dimensions, and show that the predictions of the onset of criticality of these models are generally much better in the proposed theories as compared to the corresponding ones in mean field theories

Modification of linear response theory for mean-field approximations

NARCIS (Netherlands)

Hütter, M.; Öttinger, H.C.

1996-01-01

In the framework of statistical descriptions of many particle systems, the influence of mean-field approximations on the linear response theory is studied. A procedure, analogous to one where no mean-field approximation is involved, is used in order to determine the first order response of the

Prediction of breakdown voltages in novel gases for high voltage insulation

International Nuclear Information System (INIS)

Koch, M.

2015-01-01

This thesis submitted to the Swiss Federal Institute of Technology ETH in Zurich examines the use of sulphur hexafluoride (SF_6) and similar gases as important insulation media for high voltage equipment. Due to its superior insulation properties, SF_6 is widely used in gas-insulated switchgear. However, the gas also has a very high global warming potential and the content of SF_6 in the atmosphere is constantly increasing. The search for new insulation gases using classical breakdown experiments is discussed. A model for SF_6 based on the stepped leader model is described. This calculates the breakdown voltages in arbitrary electrode configurations and under standard voltage waveforms. Thus, the thesis provides a method for the prediction of breakdown voltages of arbitrary field configurations under standard voltage waveforms for gases with electron-attaching properties. With this, further gases can be characterized for usage as high voltage insulation media

Mean-field approximation for spacing distribution functions in classical systems

Science.gov (United States)

González, Diego Luis; Pimpinelli, Alberto; Einstein, T. L.

2012-01-01

We propose a mean-field method to calculate approximately the spacing distribution functions p(n)(s) in one-dimensional classical many-particle systems. We compare our method with two other commonly used methods, the independent interval approximation and the extended Wigner surmise. In our mean-field approach, p(n)(s) is calculated from a set of Langevin equations, which are decoupled by using a mean-field approximation. We find that in spite of its simplicity, the mean-field approximation provides good results in several systems. We offer many examples illustrating that the three previously mentioned methods give a reasonable description of the statistical behavior of the system. The physical interpretation of each method is also discussed.

The effect of a HfO2 insulator on the improvement of breakdown voltage in field-plated GaN-based HEMT

International Nuclear Information System (INIS)

Mao Wei; Hao Yue; Ma Xiao-Hua; Wang Chong; Zhang Jin-Cheng; Liu Hong-Xia; Bi Zhi-Wei; Xu Sheng-Rui; Yang Lin-An; Yang Ling; Zhang Kai; Zhang Nai-Qian; Pei Yi; Yang Cui

2011-01-01

A GaN/Al 0.3 Ga 0.7 N/AlN/GaN high-electron mobility transistor utilizing a field plate (with a 0.3 μm overhang towards the drain and a 0.2 μm overhang towards the source) over a 165-nm sputtered HfO 2 insulator (HfO 2 -FP-HEMT) is fabricated on a sapphire substrate. Compared with the conventional field-plated HEMT, which has the same geometric structure but uses a 60-nm SiN insulator beneath the field plate (SiN-FP-HEMT), the HfO 2 -FP-HEMT exhibits a significant improvement of the breakdown voltage (up to 181 V) as well as a record field-plate efficiency (up to 276 V/μm). This is because the HfO 2 insulator can further improve the modulation of the field plate on the electric field distribution in the device channel, which is proved by the numerical simulation results. Based on the simulation results, a novel approach named the proportional design is proposed to predict the optimal dielectric thickness beneath the field plate. It can simplify the field-plated HEMT design significantly. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Experimental dependence of ECR plasma breakdown on wave polarization in the TJ-II stellarator

International Nuclear Information System (INIS)

Cappa, A.; Castejon, F.; Tabares, F.; Fernandez, A.; Tafalla, D.; Cal, E. de la; Estrada, T.; Nagasaki, K.

2005-01-01

Recently, second harmonic ECRH plasma breakdown and its dependence on the initial conditions such as neutral gas pressure, injected power or beam polarization has been the subject of theoretical as well as experimental work. Although those studies have been carried out in the context of stellarators, they are particularly relevant in the case of large tokamaks, such as ITER, where conventional inductive breakdown is expected to be strongly improved if ECRH is used. A matter of interest is the dependence of breakdown time on wave polarization. In the existing theoretical models, wave polarization is not taken into account because it is assumed that the injected ECRH power is initially scrambled by the vessel walls and that the energy source for breakdown is only due to the non-linear wave-particle interaction between deeply trapped electrons and the averaged electric field. However, while this seems reasonable for the very beginning of the discharge, it may not be so as we progress towards breakdown. Actually, as experiments in Heliotron J have demonstrated, wave polarization must be taken into account in the description of the energy source. Breakdown experiments in TJ-II were performed in order to get a deep insight into this matter and part of the results of breakdown dependence on wave polarization were already discussed. In particular, it was demonstrated that the hypothesis about the energy source used in the models is failing long before full ionization is completed. But more information in relation with our understanding of the second harmonic ECRH breakdown, such as the toroidal and radial breakdown propagation, which is seen to be non-diffusive, can be extracted. Thus, the experiment results provide valuable data that can be used not only to improve the energy source but also to include spatial dimensions in the breakdown models. (author)

Fluorescent lamp with static magnetic field generating means

Science.gov (United States)

Moskowitz, P.E.; Maya, J.

1987-09-08

A fluorescent lamp wherein magnetic field generating means (e.g., permanent magnets) are utilized to generate a static magnetic field across the respective electrode structures of the lamp such that maximum field strength is located at the electrode's filament. An increase in efficacy during operation has been observed. 2 figs.

Neutron fraction and neutrino mean free path predictions in relativistic mean field models

International Nuclear Information System (INIS)

Hutauruk, P.T.P.; Williams, C.K.; Sulaksono, A.; Mart, T.

2004-01-01

The equation of state (EOS) of dense matter and neutrino mean free path (NMFP) in a neutron star have been studied by using relativistic mean field models motivated by effective field theory. It is found that the models predict too large proton fractions, although one of the models (G2) predicts an acceptable EOS. This is caused by the isovector terms. Except G2, the other two models predict anomalous NMFP's. In order to minimize the anomaly, besides an acceptable EOS, a large M* is favorable. A model with large M* retains the regularity in the NMFP even for a small neutron fraction

The effect of polymer type on electric breakdown strength on a nanosecond time scale

Institute of Scientific and Technical Information of China (English)

Zhao Liang; Su Jian-Cang; Pan Ya-Feng; Zhang Xi-Bo

2012-01-01

Based on the concepts of fast polarization,effective electric field and electron impact ionization criterion,the effect of polymer type on electric breakdown strength (EBD) on a nanosecond time scale is investigated,and a formula that qualitatively characterizes the relation between the electric breakdown strength and the polymer type is derived.According to this formula,it is found that the electric breakdown strength decreases with an increase in the effective relative dielectric constants of the polymers.By calculating the effective relative dielectric constants for different types of polymers,the theoretical relation for the electric breakdown strengths of common polymers is predicted.To verify the prediction,the polymers of PE (polyethylene),PTFE (polytetrafluoroethelene),PMMA (organic glass) and Nylon are tested with a nanosecond-pulse generator.The experimental result shows EBD (PTFE) ＞ EBD (PMMA) ＞ EBD (Nylon) ＞ EBD (PE).This result is consistent with the theoretical prediction.

On locally uniformly linearizable high breakdown location and scale functionals

NARCIS (Netherlands)

Davies, P.L.

1998-01-01

This article gives two constructions of a weighted mean which has a large domain, is affinely equivariant, has a locally high breakdown point and is locally uniformly linearizable. One construction is based on $M$-functionals with smooth defining $\\psi$- and $\\chi$ -functions which are used to

Breakdown, fractoemission, diffusion: role of defects in dielectrics

International Nuclear Information System (INIS)

Vigouroux, J.P.; Serruys, Y.

1987-01-01

During the surface analysis of dielectric materials, the impinging ionising particles induce point defects localised in the band gap and build an electrical charge. The electric field created by the charged defects modifies the physico-chemical properties of surface and bulk. We show that the fundamental study of defects allows a better understanding of technological phenomena such as dielectric breakdown, fracture and diffusion [fr

Dynamical breakdown of chiral symmetry and abnormal perturbation expansion

International Nuclear Information System (INIS)

Ebert, D.; Pervushin, V.N.

1976-01-01

Dynamical breakdown of γ 5 -symmetry is studied in the Abelian gauge theory of massless ''quarks'' interacting with massless vector ''gluons''. For this purpose the path-integral approach with bilocal fields as dynamical variables is used. The classical field equation defined by the stationary point of the generating functional turns out to be identical with the Schwinger-Dyson equation for the quark propagator. After a short discussion of the possible solutions of this equation an abnormal perturbation theory has been worked out

Relativistic mean-field mass models

Energy Technology Data Exchange (ETDEWEB)

Pena-Arteaga, D.; Goriely, S.; Chamel, N. [Universite Libre de Bruxelles, Institut d' Astronomie et d' Astrophysique, CP-226, Brussels (Belgium)

2016-10-15

We present a new effort to develop viable mass models within the relativistic mean-field approach with density-dependent meson couplings, separable pairing and microscopic estimations for the translational and rotational correction energies. Two interactions, DD-MEB1 and DD-MEB2, are fitted to essentially all experimental masses, and also to charge radii and infinite nuclear matter properties as determined by microscopic models using realistic interactions. While DD-MEB1 includes the σ, ω and ρ meson fields, DD-MEB2 also considers the δ meson. Both mass models describe the 2353 experimental masses with a root mean square deviation of about 1.1 MeV and the 882 measured charge radii with a root mean square deviation of 0.029 fm. In addition, we show that the Pb isotopic shifts and moments of inertia are rather well reproduced, and the equation of state in pure neutron matter as well as symmetric nuclear matter are in relatively good agreement with existing realistic calculations. Both models predict a maximum neutron-star mass of more than 2.6 solar masses, and thus are able to accommodate the heaviest neutron stars observed so far. However, the new Lagrangians, like all previously determined RMF models, present the drawback of being characterized by a low effective mass, which leads to strong shell effects due to the strong coupling between the spin-orbit splitting and the effective mass. Complete mass tables have been generated and a comparison with other mass models is presented. (orig.)

Mean-field theory of active electrolytes: Dynamic adsorption and overscreening

Science.gov (United States)

Frydel, Derek; Podgornik, Rudolf

2018-05-01

We investigate active electrolytes within the mean-field level of description. The focus is on how the double-layer structure of passive, thermalized charges is affected by active dynamics of constituting ions. One feature of active dynamics is that particles adhere to hard surfaces, regardless of chemical properties of a surface and specifically in complete absence of any chemisorption or physisorption. To carry out the mean-field analysis of the system that is out of equilibrium, we develop the "mean-field simulation" technique, where the simulated system consists of charged parallel sheets moving on a line and obeying active dynamics, with the interaction strength rescaled by the number of sheets. The mean-field limit becomes exact in the limit of an infinite number of movable sheets.

Direct relationship between breakdown strength and tracking index of composites

DEFF Research Database (Denmark)

Madsen, Søren Find; Henriksen, Mogens; Holbøll, Joachim

2006-01-01

. The breakdown field strength of specimens cut from similar samples is determined by a new method capable of estimating the stressed volume. The results from the two tests are finally compared and incorporated in a single analytical formula. All test specimens are supplied by Danish manufacturers of wind turbine...

Influence of Low Speed Rolling Movement on High Electrical Breakdown for Water Dielectric with Microsecond Charging

International Nuclear Information System (INIS)

Zhang Zicheng; Zhang Jiande; Yang Jianhua

2006-01-01

By means of a coaxial apparatus, high electrical breakdown experiments are carried out in the rest state and the low speed rolling state with microsecond charging and the experimental results are analyzed. The conclusions are: (1) the breakdown stress of water dielectric in the rolling state is in good agreement with that in Martin formula, and so is that in the rest state; (2) the breakdown stress of water dielectric in the rolling state is about 5% higher than that in the rest state; (3) the results simulated with ANSYS demonstrate that the breakdown stress of water dielectric decreases when the bubbles appear near the surface of electrodes; (4) the primary mechanism to increase the breakdown stress of water dielectric in the rolling state is that the bubbles are driven away and the number of bubbles near the surface of electrodes is decreased by rolling movement

A Maximum Principle for SDEs of Mean-Field Type

Energy Technology Data Exchange (ETDEWEB)

Andersson, Daniel, E-mail: danieand@math.kth.se; Djehiche, Boualem, E-mail: boualem@math.kth.se [Royal Institute of Technology, Department of Mathematics (Sweden)

2011-06-15

We study the optimal control of a stochastic differential equation (SDE) of mean-field type, where the coefficients are allowed to depend on some functional of the law as well as the state of the process. Moreover the cost functional is also of mean-field type, which makes the control problem time inconsistent in the sense that the Bellman optimality principle does not hold. Under the assumption of a convex action space a maximum principle of local form is derived, specifying the necessary conditions for optimality. These are also shown to be sufficient under additional assumptions. This maximum principle differs from the classical one, where the adjoint equation is a linear backward SDE, since here the adjoint equation turns out to be a linear mean-field backward SDE. As an illustration, we apply the result to the mean-variance portfolio selection problem.

A Maximum Principle for SDEs of Mean-Field Type

International Nuclear Information System (INIS)

Andersson, Daniel; Djehiche, Boualem

2011-01-01

We study the optimal control of a stochastic differential equation (SDE) of mean-field type, where the coefficients are allowed to depend on some functional of the law as well as the state of the process. Moreover the cost functional is also of mean-field type, which makes the control problem time inconsistent in the sense that the Bellman optimality principle does not hold. Under the assumption of a convex action space a maximum principle of local form is derived, specifying the necessary conditions for optimality. These are also shown to be sufficient under additional assumptions. This maximum principle differs from the classical one, where the adjoint equation is a linear backward SDE, since here the adjoint equation turns out to be a linear mean-field backward SDE. As an illustration, we apply the result to the mean-variance portfolio selection problem.

Dark-Bright Soliton Dynamics Beyond the Mean-Field Approximation

Science.gov (United States)

Katsimiga, Garyfallia; Koutentakis, Georgios; Mistakidis, Simeon; Kevrekidis, Panagiotis; Schmelcher, Peter; Theory Group of Fundamental Processes in Quantum Physics Team

2017-04-01

The dynamics of dark bright solitons beyond the mean-field approximation is investigated. We first examine the case of a single dark-bright soliton and its oscillations within a parabolic trap. Subsequently, we move to the setting of collisions, comparing the mean-field approximation to that involving multiple orbitals in both the dark and the bright component. Fragmentation is present and significantly affects the dynamics, especially in the case of slower solitons and in that of lower atom numbers. It is shown that the presence of fragmentation allows for bipartite entanglement between the distinguishable species. Most importantly the interplay between fragmentation and entanglement leads to the decay of each of the initial mean-field dark-bright solitons into fast and slow fragmented dark-bright structures. A variety of excitations including dark-bright solitons in multiple (concurrently populated) orbitals is observed. Dark-antidark states and domain-wall-bright soliton complexes can also be observed to arise spontaneously in the beyond mean-field dynamics. Deutsche Forschungsgemeinschaft (DFG) in the framework of the SFB 925 ``Light induced dynamics and control of correlated quantum systems''.

ENERGETIC PARTICLE TRANSPORT ACROSS THE MEAN MAGNETIC FIELD: BEFORE DIFFUSION

International Nuclear Information System (INIS)

Laitinen, T.; Dalla, S.

2017-01-01

Current particle transport models describe the propagation of charged particles across the mean field direction in turbulent plasmas as diffusion. However, recent studies suggest that at short timescales, such as soon after solar energetic particle (SEP) injection, particles remain on turbulently meandering field lines, which results in nondiffusive initial propagation across the mean magnetic field. In this work, we use a new technique to investigate how the particles are displaced from their original field lines, and we quantify the parameters of the transition from field-aligned particle propagation along meandering field lines to particle diffusion across the mean magnetic field. We show that the initial decoupling of the particles from the field lines is slow, and particles remain within a Larmor radius from their initial meandering field lines for tens to hundreds of Larmor periods, for 0.1–10 MeV protons in turbulence conditions typical of the solar wind at 1 au. Subsequently, particles decouple from their initial field lines and after hundreds to thousands of Larmor periods reach time-asymptotic diffusive behavior consistent with particle diffusion across the mean field caused by the meandering of the field lines. We show that the typical duration of the prediffusive phase, hours to tens of hours for 10 MeV protons in 1 au solar wind turbulence conditions, is significant for SEP propagation to 1 au and must be taken into account when modeling SEP propagation in the interplanetary space.

ENERGETIC PARTICLE TRANSPORT ACROSS THE MEAN MAGNETIC FIELD: BEFORE DIFFUSION

Energy Technology Data Exchange (ETDEWEB)

Laitinen, T.; Dalla, S., E-mail: tlmlaitinen@uclan.ac.uk [Jeremiah Horrocks Institute, University of Central Lancashire, Preston (United Kingdom)

2017-01-10

Current particle transport models describe the propagation of charged particles across the mean field direction in turbulent plasmas as diffusion. However, recent studies suggest that at short timescales, such as soon after solar energetic particle (SEP) injection, particles remain on turbulently meandering field lines, which results in nondiffusive initial propagation across the mean magnetic field. In this work, we use a new technique to investigate how the particles are displaced from their original field lines, and we quantify the parameters of the transition from field-aligned particle propagation along meandering field lines to particle diffusion across the mean magnetic field. We show that the initial decoupling of the particles from the field lines is slow, and particles remain within a Larmor radius from their initial meandering field lines for tens to hundreds of Larmor periods, for 0.1–10 MeV protons in turbulence conditions typical of the solar wind at 1 au. Subsequently, particles decouple from their initial field lines and after hundreds to thousands of Larmor periods reach time-asymptotic diffusive behavior consistent with particle diffusion across the mean field caused by the meandering of the field lines. We show that the typical duration of the prediffusive phase, hours to tens of hours for 10 MeV protons in 1 au solar wind turbulence conditions, is significant for SEP propagation to 1 au and must be taken into account when modeling SEP propagation in the interplanetary space.

One-dimensional breakdown voltage model of SOI RESURF lateral power device based on lateral linearly graded approximation

International Nuclear Information System (INIS)

Zhang Jun; Guo Yu-Feng; Xu Yue; Lin Hong; Yang Hui; Hong Yang; Yao Jia-Fei

2015-01-01

A novel one-dimensional (1D) analytical model is proposed for quantifying the breakdown voltage of a reduced surface field (RESURF) lateral power device fabricated on silicon on an insulator (SOI) substrate. We assume that the charges in the depletion region contribute to the lateral PN junctions along the diagonal of the area shared by the lateral and vertical depletion regions. Based on the assumption, the lateral PN junction behaves as a linearly graded junction, thus resulting in a reduced surface electric field and high breakdown voltage. Using the proposed model, the breakdown voltage as a function of device parameters is investigated and compared with the numerical simulation by the TCAD tools. The analytical results are shown to be in fair agreement with the numerical results. Finally, a new RESURF criterion is derived which offers a useful scheme to optimize the structure parameters. This simple 1D model provides a clear physical insight into the RESURF effect and a new explanation on the improvement in breakdown voltage in an SOI RESURF device. (paper)

Probabilistic theory of mean field games with applications

CERN Document Server

Carmona, René

2018-01-01

This two-volume book offers a comprehensive treatment of the probabilistic approach to mean field game models and their applications. The book is self-contained in nature and includes original material and applications with explicit examples throughout, including numerical solutions. Volume I of the book is entirely devoted to the theory of mean field games without a common noise. The first half of the volume provides a self-contained introduction to mean field games, starting from concrete illustrations of games with a finite number of players, and ending with ready-for-use solvability results. Readers are provided with the tools necessary for the solution of forward-backward stochastic differential equations of the McKean-Vlasov type at the core of the probabilistic approach. The second half of this volume focuses on the main principles of analysis on the Wasserstein space. It includes Lions' approach to the Wasserstein differential calculus, and the applications of its results to the analysis of stochastic...

Prediction of breakdown voltages in novel gases for high voltage insulation

Energy Technology Data Exchange (ETDEWEB)

Koch, M.

2015-07-01

This thesis submitted to the Swiss Federal Institute of Technology ETH in Zurich examines the use of sulphur hexafluoride (SF{sub 6}) and similar gases as important insulation media for high voltage equipment. Due to its superior insulation properties, SF{sub 6} is widely used in gas-insulated switchgear. However, the gas also has a very high global warming potential and the content of SF{sub 6} in the atmosphere is constantly increasing. The search for new insulation gases using classical breakdown experiments is discussed. A model for SF{sub 6} based on the stepped leader model is described. This calculates the breakdown voltages in arbitrary electrode configurations and under standard voltage waveforms. Thus, the thesis provides a method for the prediction of breakdown voltages of arbitrary field configurations under standard voltage waveforms for gases with electron-attaching properties. With this, further gases can be characterized for usage as high voltage insulation media.

Studies of Plasma Instabilities Excited by Ground-Based High Power HF (Heating) Facilities and of X and Gamma Ray Emission in Runaway Breakdown Processes

National Research Council Canada - National Science Library

Gurevich, Aleksander V

2006-01-01

.... The runaway breakdown process in inhomogeneous thunderstorm electric field; 5. X-ray emission in different gases due to runaway breakdown phenomena in a laboratory cyclotron installation; 6. An influence of combined effects of runaway breakdown and cosmic rays on lightning processes in thunderstorm atmosphere.

A measurement technique of time-dependent dielectric breakdown in MOS capacitors

Science.gov (United States)

Li, S. P.

1974-01-01

The statistical nature of time-dependent dielectric breakdown characteristics in MOS capacitors was evidenced by testing large numbers of capacitors fabricated on single wafers. A multipoint probe and automatic electronic visual display technique are introduced that will yield statistical results which are necessary for the investigation of temperature, electric field, thermal annealing, and radiation effects in the breakdown characteristics, and an interpretation of the physical mechanisms involved. It is shown that capacitors of area greater than 0.002 sq cm may yield worst-case results, and that a multipoint probe of capacitors of smaller sizes can be used to obtain a profile of nonuniformities in the SiO2 films.

A Stochastic Maximum Principle for Risk-Sensitive Mean-Field Type Control

KAUST Repository

Djehiche, Boualem; Tembine, Hamidou; Tempone, Raul

2015-01-01

In this paper we study mean-field type control problems with risk-sensitive performance functionals. We establish a stochastic maximum principle (SMP) for optimal control of stochastic differential equations (SDEs) of mean-field type, in which the drift and the diffusion coefficients as well as the performance functional depend not only on the state and the control but also on the mean of the distribution of the state. Our result extends the risk-sensitive SMP (without mean-field coupling) of Lim and Zhou (2005), derived for feedback (or Markov) type optimal controls, to optimal control problems for non-Markovian dynamics which may be time-inconsistent in the sense that the Bellman optimality principle does not hold. In our approach to the risk-sensitive SMP, the smoothness assumption on the value-function imposed in Lim and Zhou (2005) needs not be satisfied. For a general action space a Peng's type SMP is derived, specifying the necessary conditions for optimality. Two examples are carried out to illustrate the proposed risk-sensitive mean-field type SMP under linear stochastic dynamics with exponential quadratic cost function. Explicit solutions are given for both mean-field free and mean-field models.

A Stochastic Maximum Principle for Risk-Sensitive Mean-Field Type Control

KAUST Repository

Djehiche, Boualem

2015-02-24

In this paper we study mean-field type control problems with risk-sensitive performance functionals. We establish a stochastic maximum principle (SMP) for optimal control of stochastic differential equations (SDEs) of mean-field type, in which the drift and the diffusion coefficients as well as the performance functional depend not only on the state and the control but also on the mean of the distribution of the state. Our result extends the risk-sensitive SMP (without mean-field coupling) of Lim and Zhou (2005), derived for feedback (or Markov) type optimal controls, to optimal control problems for non-Markovian dynamics which may be time-inconsistent in the sense that the Bellman optimality principle does not hold. In our approach to the risk-sensitive SMP, the smoothness assumption on the value-function imposed in Lim and Zhou (2005) needs not be satisfied. For a general action space a Peng\\'s type SMP is derived, specifying the necessary conditions for optimality. Two examples are carried out to illustrate the proposed risk-sensitive mean-field type SMP under linear stochastic dynamics with exponential quadratic cost function. Explicit solutions are given for both mean-field free and mean-field models.

Humidity effects on wire insulation breakdown strength.

Energy Technology Data Exchange (ETDEWEB)

Appelhans, Leah

2013-08-01

Methods for the testing of the dielectric breakdown strength of insulation on metal wires under variable humidity conditions were developed. Two methods, an ASTM method and the twisted pair method, were compared to determine if the twisted pair method could be used for determination of breakdown strength under variable humidity conditions. It was concluded that, although there were small differences in outcomes between the two testing methods, the non-standard method (twisted pair) would be appropriate to use for further testing of the effects of humidity on breakdown performance. The dielectric breakdown strength of 34G copper wire insulated with double layer Poly-Thermaleze/Polyamide-imide insulation was measured using the twisted pair method under a variety of relative humidity (RH) conditions and exposure times. Humidity at 50% RH and below was not found to affect the dielectric breakdown strength. At 80% RH the dielectric breakdown strength was significantly diminished. No effect for exposure time up to 140 hours was observed at 50 or 80%RH.

Breakdown in traffic networks fundamentals of transportation science

CERN Document Server

Kerner, Boris S

2017-01-01

This book offers a detailed investigation of breakdowns in traffic and transportation networks. It shows empirically that transitions from free flow to so-called synchronized flow, initiated by local disturbances at network bottlenecks, display a nucleation-type behavior: while small disturbances in free flow decay, larger ones grow further and lead to breakdowns at the bottlenecks. Further, it discusses in detail the significance of this nucleation effect for traffic and transportation theories, and the consequences this has for future automatic driving, traffic control, dynamic traffic assignment, and optimization in traffic and transportation networks. Starting from a large volume of field traffic data collected from various sources obtained solely through measurements in real world traffic, the author develops his insights, with an emphasis less on reviewing existing methodologies, models and theories, and more on providing a detailed analysis of empirical traffic data and drawing consequences regarding t...

DC-driven plasma gun: self-oscillatory operation mode of atmospheric-pressure helium plasma jet comprised of repetitive streamer breakdowns

Science.gov (United States)

Wang, Xingxing; Shashurin, Alexey

2017-02-01

This paper presents and studies helium atmospheric pressure plasma jet comprised of a series of repetitive streamer breakdowns, which is driven by pure DC high voltage (self-oscillatory behavior). The repetition frequency of the breakdowns is governed by the geometry of discharge electrodes/surroundings and gas flow rate. Each next streamer is initiated when the electric field on the anode tip recovers after the previous breakdown and reaches the breakdown threshold value of about 2.5 kV cm-1. One type of the helium plasma gun designed using this operational principle is demonstrated. The gun operates on about 3 kV DC high voltage and is comprised of the series of the repetitive streamer breakdowns at a frequency of about 13 kHz.

Multiple helical modes of vortex breakdown

DEFF Research Database (Denmark)

Sørensen, Jens Nørkær; Naumov, I. V.; Okulov, Valery

2011-01-01

Experimental observations of vortex breakdown in a rotating lid-driven cavity are presented. The results show that vortex breakdown for cavities with high aspect ratios is associated with the appearance of stable helical vortex multiplets. By using results from stability theory generalizing Kelvi......’s problem on vortex polygon stability, and systematically exploring the cavity flow, we succeeded in identifying two new stable vortex breakdown states consisting of triple and quadruple helical multiplets....

Mean field theory of dynamic phase transitions in ferromagnets

International Nuclear Information System (INIS)

Idigoras, O.; Vavassori, P.; Berger, A.

2012-01-01

We have studied the second order dynamic phase transition (DPT) of the two-dimensional kinetic Ising model by means of numerical calculations. While it is well established that the order parameter Q of the DPT is the average magnetization per external field oscillation cycle, the possible identity of the conjugate field has been addressed only recently. In this work, we demonstrate that our entire set of numerical data is fully consistent with the applied bias field H b being the conjugate field of order parameter Q. For this purpose, we have analyzed the Q(H b )-dependence and we have found that it follows the expected power law behavior with the same critical exponent as the mean field equilibrium case.

Transient chaos - a resolution of breakdown of quantum-classical correspondence in optomechanics

Science.gov (United States)

Wang, Guanglei; Lai, Ying-Cheng; Grebogi, Celso

2016-01-01

Recently, the phenomenon of quantum-classical correspondence breakdown was uncovered in optomechanics, where in the classical regime the system exhibits chaos but in the corresponding quantum regime the motion is regular - there appears to be no signature of classical chaos whatsoever in the corresponding quantum system, generating a paradox. We find that transient chaos, besides being a physically meaningful phenomenon by itself, provides a resolution. Using the method of quantum state diffusion to simulate the system dynamics subject to continuous homodyne detection, we uncover transient chaos associated with quantum trajectories. The transient behavior is consistent with chaos in the classical limit, while the long term evolution of the quantum system is regular. Transient chaos thus serves as a bridge for the quantum-classical transition (QCT). Strikingly, as the system transitions from the quantum to the classical regime, the average chaotic transient lifetime increases dramatically (faster than the Ehrenfest time characterizing the QCT for isolated quantum systems). We develop a physical theory to explain the scaling law. PMID:27748418

Momentum and density dependence of the nuclear mean field

International Nuclear Information System (INIS)

Behera, B.; Routray, T.R.

1999-01-01

The purpose of this is to analyse the momentum, density and temperature dependence of the mean field in nuclear matter derived from finite range effective interactions and to examine the influence of the functional form of the interaction on the high momentum behaviour of the mean field. Emphasis will be given to use very simple parametrizations of the effective interaction with a minimum number of adjustable parameters and yet capable of giving a good description of the mean field in nuclear matter over a wide range of momentum, density and temperature. As an application of the calculated equation of state of nuclear matter, phase transitions to quark-gluon plasma is studied where the quark phase is described by a zeroth order bag model equation of state

Identification of Polymers by Means of LIBS

Science.gov (United States)

Anzano, Jesús M.; Bello-Gálvez, Cristina; Lasheras, Roberto J.

Laser-induced breakdown spectroscopy (LIBS) is mainly an elemental analysis technique which is applied several fields. However, molecular materials are almost entirely atomized when exposed to intense laser radiation sufficient for breakdown. This limitation has been solved by researchers using statistical tools as chemometric techniques. In this chapter, the authors expose one review about the identification of polymeric materials using LIBS; and particularly, the different chemometric techniques.

The evaluation of mean platelet volume levels in patients with primary and secondary Raynaud’s Phenomenon

Directory of Open Access Journals (Sweden)

Mehmet Erdem Memetoğlu

2014-03-01

Full Text Available Background — Mean platelet volume (MPV is an indicator of platelet activation. The pathophysiology of the primary and secondary Raynaud’s Phenomenon (RP have not been completely established. The aim of this study was to investigate the relationship between MPV and RP. Materials and Methods — Our study was a prospective randomized study carried out from January 2011 to March 2012. The study group consisted of 39 patients: 27 (70% patients having primary, 12 (30% patients having secondary RP. An age-, gender-, and body mass index-matched control group consisted of 40 healthy participants. We compared the MPV in patients with RP and control participants statistically. Results — MPV of RP group was 8.79±1.37 femtoliter (fL while MPV of control group was 8.39±1.36 fL. Comparison of MPV of RP group and control group showed no difference (p=0.274. The mean of MPV was significantly higher among patients with secondary RP (9.76±1.68 fl when compared with patients with primary RP (8.37±0.96 fl (p=0.018. Conclusion — The results of our study suggest that MPV may be used as a marker in secondary RP.

Mean field with corrections in lattice gauge theory

International Nuclear Information System (INIS)

Flyvbjerg, H.; Zuber, J.B.; Lautrup, B.

1981-12-01

A systematic expansion of the path integral for lattice gauge theory is performed around the mean field solution. In this letter the authors present the results for the pure gauge groups Z(2), SU(2) and SO(3). The agreement with Monte Carlo calculations is excellent. For the discrete group the calculation is performed with and without gauge fixing, whereas for the continuous groups gauge fixing is mandatory. In the case of SU(2) the absence of a phase transition is correctly signalled by mean field theory. (Auth.)

Configuration mixing of mean-field states

International Nuclear Information System (INIS)

Bender, M; Heenen, P-H

2005-01-01

Starting from self-consistent mean-field models, we discuss how to include correlations from fluctuations in collective degrees of freedom through symmetry restoration and configuration mixing, which give access to ground-state correlations and collective excitations. As an example for the method, we discuss the spectroscopy of neutron-deficient Pb isotopes

Mean Field Type Control with Congestion

Energy Technology Data Exchange (ETDEWEB)

Achdou, Yves, E-mail: achdou@ljll.univ-paris-diderot.fr; Laurière, Mathieu [Univ. Paris Diderot, Sorbonne Paris Cité, Laboratoire Jacques-Louis Lions, UMR 7598, UPMC, CNRS (France)

2016-06-15

We analyze some systems of partial differential equations arising in the theory of mean field type control with congestion effects. We look for weak solutions. Our main result is the existence and uniqueness of suitably defined weak solutions, which are characterized as the optima of two optimal control problems in duality.

AC electrical breakdown phenomena of epoxy/layered silicate nanocomposite in needle-plate electrodes.

Science.gov (United States)

Park, Jae-Jun; Lee, Jae-Young

2013-05-01

Epoxy/layered silicate nanocomposite for the insulation of heavy electric equipments were prepared by dispersing 1 wt% of a layered silicate into an epoxy matrix with a homogenizing mixer and then AC electrical treeing and breakdown tests were carried out. Wide-angle X-ray diffraction (WAXD) analysis and transmission electron microscopy (TEM) observation showed that nano-sized monolayers were exfoliated from a multilayered silicate in the epoxy matrix. When the nano-sized silicate layers were incorporated into the epoxy matrix, the breakdown rate in needle-plate electrode geometry was 10.6 times lowered than that of the neat epoxy resin under the applied electrical field of 520.9 kV/mm at 30 degrees C, and electrical tree propagated with much more branches in the epoxy/layered silicate nanocomposite. These results showed that well-dispersed nano-sized silicate layers retarded the electrical tree growth rate. The effects of applied voltage and ambient temperature on the tree initiation, growth, and breakdown rate were also studied, and it was found that the breakdown rate was largely increased, as the applied voltage and ambient temperature increased.

A computational study of the topology of vortex breakdown

Science.gov (United States)

Spall, Robert E.; Gatski, Thomas B.

1991-01-01

A fully three-dimensional numerical simulation of vortex breakdown using the unsteady, incompressible Navier-Stokes equations has been performed. Solutions to four distinct types of breakdown are identified and compared with experimental results. The computed solutions include weak helical, double helix, spiral, and bubble-type breakdowns. The topological structure of the various breakdowns as well as their interrelationship are studied. The data reveal that the asymmetric modes of breakdown may be subject to additional breakdowns as the vortex core evolves in the streamwise direction. The solutions also show that the freestream axial velocity distribution has a significant effect on the position and type of vortex breakdown.

The humidity effect on the breakdown voltage characteristics and the transport parameters of air

International Nuclear Information System (INIS)

Radmilović-Radjenović, M.; Radjenović, B.; Nikitović, Ž.; Matejčik, Š.; Klas, M.

2012-01-01

This paper contains experimental results for the direct current (DC) breakdown voltages and calculated transport parameters for dry, synthetic and ambient air. The breakdown voltage curves for dry, ambient and synthetic air at the gap size of 100μm are very similar. The differences between them are much more pronounced at the interelectrode separation of 20μm, especially at the right hand branch of the breakdown voltage curves. On the other hand, the effective yields γ for dry and synthetic air are in disagreement at lower values of the E/p. Results of calculations based on the Two Term Approximation indicate that the humidity has no a great influence on the transport parameters at all range of the reduce field E/N.

Mason’s equation application for prediction of voltage of oil shale treeing breakdown

Science.gov (United States)

Martemyanov, S. M.

2017-05-01

The application of the formula, which is used to calculate the maximum field at the tip of the pin-plane electrode system was proposed to describe the process of electrical treeing and treeing breakdown in an oil shale. An analytical expression for the calculation of the treeing breakdown voltage in the oil shale, as a function of the inter-electrode distance, was taken. A high accuracy of the correspondence of the model to the experimental data in the range of inter-electrode distances from 0.03 to 0.5 m was taken.

Critical study of the dispersive n- 90Zr mean field by means of a new variational method

Science.gov (United States)

Mahaux, C.; Sartor, R.

1994-02-01

A new variational method is developed for the construction of the dispersive nucleon-nucleus mean field at negative and positive energies. Like the variational moment approach that we had previously proposed, the new method only uses phenomenological optical-model potentials as input. It is simpler and more flexible than the previous approach. It is applied to a critical investigation of the n- 90Zr mean field between -25 and +25 MeV. This system is of particular interest because conflicting results had recently been obtained by two different groups. While the imaginary parts of the phenomenological optical-model potentials provided by these two groups are similar, their real parts are quite different. Nevertheless, we demonstrate that these two sets of phenomenological optical-model potentials are both compatible with the dispersion relation which connects the real and imaginary parts of the mean field. Previous hints to the contrary, by one of the two other groups, are shown to be due to unjustified approximations. A striking outcome of the present study is that it is important to explicitly introduce volume absorption in the dispersion relation, although volume absorption is negligible in the energy domain investigated here. Because of the existence of two sets of phenomenological optical-model potentials, our variational method yields two dispersive mean fields whose real parts are quite different at small or negative energies. No preference for one of the two dispersive mean fields can be expressed on purely empirical grounds since they both yield fair agreement with the experimental cross sections as well as with the observed energies of the bound single-particle states. However, we argue that one of these two mean fields is physically more meaningful, because the radial shape of its Hartree-Fock type component is independent of energy, as expected on theoretical grounds. This preferred mean field is very close to the one which had been obtained by the Ohio

The mean magnetic field of the sun - Method of observation and relation to the interplanetary magnetic field

Science.gov (United States)

Scherrer, P. H.; Wilcox, J. M.; Kotov, V.; Severnyi, A. B.; Howard, R.

1977-01-01

The mean solar magnetic field as measured in integrated light has been observed since 1968. Since 1970 it has been observed both at Hale Observatories and at the Crimean Astrophysical Observatory. The observing procedures at both observatories and their implications for mean field measurements are discussed. A comparison of the two sets of daily observations shows that similar results are obtained at both observatories. A comparison of the mean field with the interplanetary magnetic polarity shows that the IMF sector structure has the same pattern as the mean field polarity.

Mean field approximation versus exact treatment of collisions in few-body systems

International Nuclear Information System (INIS)

Lemm, J.; Weiguny, A.; Giraud, B.G.

1990-01-01

A variational principle for calculating matrix elements of the full resolvent operator for a many-body system is studied. Its mean field approximation results in non-linear equations of Hartree (-Fock) type, with initial and final channel wave functions as driving terms. The mean field equations will in general have many solutions whereas the exact problem being linear, has a unique solution. In a schematic model with separable forces the mean field equations are analytically soluble, and for the exact problem the resulting integral equations are solved numerically. Comparing exact and mean field results over a wide range of system parameters, the mean field approach proves to be a very reliable approximation, which is not plagued by the notorious problem of defining asymptotic channels in the time-dependent mean field method. (orig.)

Electrode breakdown potentials in MHD plasmas

International Nuclear Information System (INIS)

Sodha, M.S.; Raju, G.V.R.; Kumar, A.S.; Gupta, Bhumesh

1988-01-01

Electrode breakdown potentials and current densities have been calculated for both the thermionically electron emitting and non-emitting cathodes. Calculated values have been compared with the available experimental results. It is found that the cathode potential drop for the breakdown is almost unaffected by the emission. However, both the total potential difference between the anode and the cathode and the current density at the breakdown are higher for electron-emitting cathodes than for non-emitting cathodes. (author)

Orbital effect of the magnetic field in dynamical mean-field theory

Science.gov (United States)

Acheche, S.; Arsenault, L.-F.; Tremblay, A.-M. S.

2017-12-01

The availability of large magnetic fields at international facilities and of simulated magnetic fields that can reach the flux-quantum-per-unit-area level in cold atoms calls for systematic studies of orbital effects of the magnetic field on the self-energy of interacting systems. Here we demonstrate theoretically that orbital effects of magnetic fields can be treated within single-site dynamical mean-field theory with a translationally invariant quantum impurity problem. As an example, we study the one-band Hubbard model on the square lattice using iterated perturbation theory as an impurity solver. We recover the expected quantum oscillations in the scattering rate, and we show that the magnetic fields allow the interaction-induced effective mass to be measured through the single-particle density of states accessible in tunneling experiments. The orbital effect of magnetic fields on scattering becomes particularly important in the Hofstadter butterfly regime.

Weakly coupled mean-field game systems

KAUST Repository

Gomes, Diogo A.

2016-07-14

Here, we prove the existence of solutions to first-order mean-field games (MFGs) arising in optimal switching. First, we use the penalization method to construct approximate solutions. Then, we prove uniform estimates for the penalized problem. Finally, by a limiting procedure, we obtain solutions to the MFG problem. © 2016 Elsevier Ltd

Breakdown transient study of plasma distributions in a 2.45 GHz hydrogen discharge

Energy Technology Data Exchange (ETDEWEB)

Cortázar, O.D., E-mail: daniel.cortazar@uclm.es [Universidad de Castilla-La Mancha, ETSII-INEI, Applied Mechanics and Projects Department, C.J. Cela s/n, 13170 Ciudad Real (Spain); Megía-Macías, A. [ESS Bilbao Consortium, Polígono Ugaldeguren-III Pol. A 7B, 48170-Zamudio, Vizcaya (Spain); Tarvainen, O.; Koivisto, H. [University of Jyväskylä, Department of Physics, PO Box 35 (YFL), 40500 Jyväskylä (Finland)

2015-05-01

Plasma distribution transients associated with the breakdown of a 2.45 GHz hydrogen discharge similar to high current microwave ion sources are studied by means of an ultra-fast frame image acquisition system in visible light range. Eight different plasma distributions have been studied by photographing the 2D projections of the discharge through a transparent plasma electrode. The temporal evolution of images in Balmer-alpha and Fulcher band wavelengths have been recorded associated to atomic and molecular excitation and ionization processes. Some unexpected plasma distributions transient behaviors during breakdown are reported.

Mean-field theory and self-consistent dynamo modeling

International Nuclear Information System (INIS)

Yoshizawa, Akira; Yokoi, Nobumitsu

2001-12-01

Mean-field theory of dynamo is discussed with emphasis on the statistical formulation of turbulence effects on the magnetohydrodynamic equations and the construction of a self-consistent dynamo model. The dynamo mechanism is sought in the combination of the turbulent residual-helicity and cross-helicity effects. On the basis of this mechanism, discussions are made on the generation of planetary magnetic fields such as geomagnetic field and sunspots and on the occurrence of flow by magnetic fields in planetary and fusion phenomena. (author)

Précis of Breakdown of Will.

Science.gov (United States)

Ainslie, George

2005-10-01

Behavioral science has long been puzzled by the experience of temptation, the resulting impulsiveness, and the variably successful control of this impulsiveness. In conventional theories, a governing faculty like the ego evaluates future choices consistently over time, discounting their value for delay exponentially, that is, by a constant rate; impulses arise when this ego is confronted by a conditioned appetite. Breakdown of Will (Ainslie 2001) presents evidence that contradicts this model. Both people and nonhuman animals spontaneously discount the value of expected events in a curve where value is divided approximately by expected delay, a hyperbolic form that is more bowed than the rational, exponential curve. With hyperbolic discounting, options that pay off quickly will be temporarily preferred to richer but slower-paying alternatives, a phenomenon that, over periods from minutes to days, can account for impulsive behaviors, and over periods of fractional seconds can account for involuntary behaviors. Contradictory reward-getting processes can in effect bargain with each other, and stable preferences can be established by the perception of recurrent choices as test cases (precedents) in recurrent intertemporal prisoner's dilemmas. The resulting motivational pattern resembles traditional descriptions of the will, as well as of compulsive phenomena that can now be seen as side-effects of will: over-concern with precedent, intractable but circumscribed failures of self-control, a motivated ("dynamic") unconscious, and an inability to exploit emotional rewards. Hyperbolic curves also suggest a means of reducing classical conditioning to motivated choice, the last necessary step for modeling many involuntary processes like emotion and appetite as reward-seeking behaviors; such modeling, in turn, provides a rationale for empathic reward and the "construction" of reality.

Interaction Of CO2 Laser Nanosecond Pulse Train With The Metallic Targets In Optical Breakdown Regime

Science.gov (United States)

Apollonov, V. V.; Firsov, K. N.; Konov, V. I.; Nikitin, P. I.; Prokhorov, A. M.; Silenok, A. S.; Sorochenko, V. R.

1986-11-01

In the present paper the electric field and currents in the air-breakdown plasma, produced by the train of nanosecond pulses of TEA-002 - regenerative amplifier near the un-charged targets are studied. The breakdown thresholds and the efficiency of plasma-target heat transmission are also measured. The results of numerical calculations made for increasing of the pulse train contrast with respect to the background in a regenerative amplifier are advanced.

A mean field theory of coded CDMA systems

International Nuclear Information System (INIS)

Yano, Toru; Tanaka, Toshiyuki; Saad, David

2008-01-01

We present a mean field theory of code-division multiple-access (CDMA) systems with error-control coding. On the basis of the relation between the free energy and mutual information, we obtain an analytical expression of the maximum spectral efficiency of the coded CDMA system, from which a mean-field description of the coded CDMA system is provided in terms of a bank of scalar Gaussian channels whose variances in general vary at different code symbol positions. Regular low-density parity-check (LDPC)-coded CDMA systems are also discussed as an example of the coded CDMA systems

A mean field theory of coded CDMA systems

Energy Technology Data Exchange (ETDEWEB)

Yano, Toru [Graduate School of Science and Technology, Keio University, Hiyoshi, Kohoku-ku, Yokohama-shi, Kanagawa 223-8522 (Japan); Tanaka, Toshiyuki [Graduate School of Informatics, Kyoto University, Yoshida Hon-machi, Sakyo-ku, Kyoto-shi, Kyoto 606-8501 (Japan); Saad, David [Neural Computing Research Group, Aston University, Birmingham B4 7ET (United Kingdom)], E-mail: yano@thx.appi.keio.ac.jp

2008-08-15

We present a mean field theory of code-division multiple-access (CDMA) systems with error-control coding. On the basis of the relation between the free energy and mutual information, we obtain an analytical expression of the maximum spectral efficiency of the coded CDMA system, from which a mean-field description of the coded CDMA system is provided in terms of a bank of scalar Gaussian channels whose variances in general vary at different code symbol positions. Regular low-density parity-check (LDPC)-coded CDMA systems are also discussed as an example of the coded CDMA systems.

Rock’n’Roll as a Local Musical Phenomenon

Directory of Open Access Journals (Sweden)

Marija Ristivojević

2016-02-01

Full Text Available The paper considers the process of localization of a pop cultural and musical phenomenon – rock ’n’ roll. My basic premise is that rock ’n’ roll as a global music genre can be perceived as local, and hence represents a recognizable identification element for the local population. In this case the label r ’n’ r pertain to the phenomenon of Belgrade "new wave" music, which was popular during the 1980’s. Based on the analysis of narratives from relevant documentary films, it is my intention to find out whether "new wave" was initially perceived as a local phenomenon, and what the means of constructing this image are, as well as what it is that gives this phenomenon local legitimacy and credibility.

Breakdown of the Frozen-in Condition and Plasma Acceleration: Dynamical Theory

Science.gov (United States)

Song, Y.; Lysak, R. L.

2007-12-01

The magnetic reconnection hypothesis emphasizes the importance of the breakdown of the frozen-in condition, explains the strong dependence of the geomagnetic activity on the IMF, and approximates an average qualitative description for many IMF controlled effects in magnetospheric physics. However, some important theoretical aspects of reconnection, including its definition, have not been carefully examined. The crucial components of such models, such as the largely-accepted X-line reconnection picture and the broadly-used explanations of the breakdown of the frozen-in condition, lack complete theoretical support. The important irreversible reactive interaction is intrinsically excluded and overlooked in most reconnection models. The generation of parallel electric fields must be the result of a reactive plasma interaction, which is associated with the temporal changes and spatial gradients of magnetic and velocity shears (Song and Lysak, 2006). Unlike previous descriptions of the magnetic reconnection process, which depend on dissipative-type coefficients or some passive terms in the generalized Ohm's law, the reactive interaction is a dynamical process, which favors localized high magnetic and/or mechanical stresses and a low plasma density. The reactive interaction is often closely associated with the radiation of shear Alfvén waves and is independent of any assumed dissipation coefficients. The generated parallel electric field makes an irreversible conversion between magnetic energy and the kinetic energy of the accelerated plasma and the bulk flow. We demonstrate how the reactive interaction, e.g., the nonlinear interaction of MHD mesoscale wave packets at current sheets and in the auroral acceleration region, can create and support parallel electric fields, causing the breakdown of the frozen-in condition and plasma acceleration.

Magnetic breakdown in an array of overlapping Fermi surfaces

International Nuclear Information System (INIS)

Kadigrobov, A.M.; Radić, D.; Bjeliš, A.

2015-01-01

We develop a theoretical framework for a magnetic breakdown in an array of circular two-dimensional bands with a finite overlap of neighboring Fermi surfaces due to the presence of a presumably weak periodic potential, and apply the obtained results to the electron bands in carbon honeycomb structures of doped graphene and intercalated graphite compounds. In contrast to the standard treatment, inaugurated more than fifty years ago by Slutskin and Kadigrobov, with electron semiclassical trajectories encircling significantly overlapping Fermi surfaces, we examine a configuration in which bands are related in a way that the Fermi surfaces only slightly overlap, forming internal band pockets with areas of the size comparable to the area of the quantum magnetic flux for a given external magnetic field. Such band configuration has to be treated quantum mechanically. The calculation leads to the results for magnetic breakdown coefficients comprising an additional large factor with respect to the standard results, proportional to the ratio of the Fermi energy and the cyclotron energy. Also, these coefficients show oscillating dependence on energy, as well as on the wave number of periodic potential. Both mentioned elements enable the adjustment of the preferred wave vector of possible magnetic breakdown induced density wave instability at the highest possible critical temperature

Mean field games for cognitive radio networks

KAUST Repository

Tembine, Hamidou; Tempone, Raul; Vilanova, Pedro

2012-01-01

In this paper we study mobility effect and power saving in cognitive radio networks using mean field games. We consider two types of users: primary and secondary users. When active, each secondary transmitter-receiver uses carrier sensing

Co-non-solvency: Mean-field polymer theory does not describe polymer collapse transition in a mixture of two competing good solvents

Energy Technology Data Exchange (ETDEWEB)

Mukherji, Debashish; Stuehn, Torsten; Kremer, Kurt [Max-Planck Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz (Germany); Marques, Carlos M. [Max-Planck Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz (Germany); Institut Charles Sadron, Université de Strasbourg, CNRS, Strasbourg (France)

2015-03-21

Smart polymers are a modern class of polymeric materials that often exhibit unpredictable behavior in mixtures of solvents. One such phenomenon is co-non-solvency. Co-non-solvency occurs when two (perfectly) miscible and competing good solvents, for a given polymer, are mixed together. As a result, the same polymer collapses into a compact globule within intermediate mixing ratios. More interestingly, polymer collapses when the solvent quality remains good and even gets increasingly better by the addition of the better cosolvent. This is a puzzling phenomenon that is driven by strong local concentration fluctuations. Because of the discrete particle based nature of the interactions, Flory-Huggins type mean field arguments become unsuitable. In this work, we extend the analysis of the co-non-solvency effect presented earlier [D. Mukherji et al., Nat. Commun. 5, 4882 (2014)]. We explain why co-non-solvency is a generic phenomenon, which can only be understood by the thermodynamic treatment of the competitive displacement of (co)solvent components. This competition can result in a polymer collapse upon improvement of the solvent quality. Specific chemical details are not required to understand these complex conformational transitions. Therefore, a broad range of polymers are expected to exhibit similar reentrant coil-globule-coil transitions in competing good solvents.

Co-non-solvency: Mean-field polymer theory does not describe polymer collapse transition in a mixture of two competing good solvents

International Nuclear Information System (INIS)

Mukherji, Debashish; Stuehn, Torsten; Kremer, Kurt; Marques, Carlos M.

2015-01-01

Smart polymers are a modern class of polymeric materials that often exhibit unpredictable behavior in mixtures of solvents. One such phenomenon is co-non-solvency. Co-non-solvency occurs when two (perfectly) miscible and competing good solvents, for a given polymer, are mixed together. As a result, the same polymer collapses into a compact globule within intermediate mixing ratios. More interestingly, polymer collapses when the solvent quality remains good and even gets increasingly better by the addition of the better cosolvent. This is a puzzling phenomenon that is driven by strong local concentration fluctuations. Because of the discrete particle based nature of the interactions, Flory-Huggins type mean field arguments become unsuitable. In this work, we extend the analysis of the co-non-solvency effect presented earlier [D. Mukherji et al., Nat. Commun. 5, 4882 (2014)]. We explain why co-non-solvency is a generic phenomenon, which can only be understood by the thermodynamic treatment of the competitive displacement of (co)solvent components. This competition can result in a polymer collapse upon improvement of the solvent quality. Specific chemical details are not required to understand these complex conformational transitions. Therefore, a broad range of polymers are expected to exhibit similar reentrant coil-globule-coil transitions in competing good solvents

Spin-isospin mixing without spontaneous symmetry breakdown

International Nuclear Information System (INIS)

Mukherjee, A.; Roy, P.

1983-01-01

The phenomenon advertised in the title is demonstrated in an exactly symmetric SU(2) classical gauge theory with a scalar isodoublet of matter fields. Possible implications for chromodynamics are discussed briefly. (orig.)

Breakdown simulations in a focused microwave beam within the simplified model

International Nuclear Information System (INIS)

Semenov, V. E.; Rakova, E. I.; Glyavin, M. Yu.; Nusinovich, G. S.

2016-01-01

The simplified model is proposed to simulate numerically air breakdown in a focused microwave beam. The model is 1D from the mathematical point of view, but it takes into account the spatial non-uniformity of microwave field amplitude along the beam axis. The simulations are completed for different frequencies and different focal lengths of microwave beams. The results demonstrate complicated regimes of the breakdown evolution which represents a series of repeated ionization waves. These waves start at the focal point and propagate towards incident microwave radiation. The ionization wave parameters vary during propagation. At relatively low frequencies, the propagation regime of subsequent waves can also change qualitatively. Each next ionization wave is less pronounced than the previous one, and the breakdown evolution approaches the steady state with relatively small plasma density. The ionization wave parameters are sensitive to the weak source of external ionization, but the steady state is independent on such a source. As the beam focal length decreases, the stationary plasma density increases and the onset of the steady state occurs faster.

Experiments concerning the theories of vortex breakdown

Science.gov (United States)

Panton, Ronald L.; Stifle, Kirk E.

1991-01-01

An experimental project was undertaken to investigate the character of vortex breakdown with particular regard to the stagnation and wave guide theories of vortex breakdown. Three different wings were used to produce a trailing vortex which convected downstream without undergoing breakdown. Disturbances were then introduced onto the vortex using a moving wire to 'cut' the vortex. The development of upstream and downstream propagating disturbance waves was observed and the propagation velocities measured. A downstream traveling wave was observed to produce a structure similar in appearance to a vortex breakdown. An upstream traveling wave produced a moving turbulent region. The upstream disturbance moved into an axial velocity profile that had a wake-like defect while the downstream moving vortex breakdown moved against a jet-like overshoot. The longitudinal and swirl velocity profiles were documented by LDV measurement. Wave velocities, swirl angles, and swirl parameters are reported.

The Meaning of Out-of-Field Teaching for Educational Leadership

Science.gov (United States)

du Plessis, Anna E.; Carroll, Annemaree; Gillies, Robyn M.

2017-01-01

Assigning teachers to a position for which they are not suitably qualified influences effective educational leadership. The paper reveals assumptions and misconceptions about the lived experiences of teachers in out-of-field positions and what it means for effective educational leadership. The multilayered meaning of out-of-field teaching for…

Navier-Stokes prediction of a delta wing in roll with vortex breakdown

Science.gov (United States)

Chaderjian, Neal M.; Schiff, Lewis B.

1993-01-01

The three-dimensional, Reynolds-averaged, Navier-Stokes (RANS) equations are used to numerically simulate vortical flow about a 65 degree sweep delta wing. Subsonic turbulent flow computations are presented for this delta wing at 30 degrees angle of attack and static roll angles up to 42 degrees. This work is part of an on going effort to validate the RANS approach for predicting high-incidence vortical flows, with the eventual application to wing rock. The flow is unsteady and includes spiral-type vortex breakdown. The breakdown positions, mean surface pressures, rolling moments, normal forces, and streamwise center-of-pressure locations compare reasonably well with experiment. In some cases, the primary vortex suction peaks are significantly underpredicted due to grid coarseness. Nevertheless, the computations are able to predict the same nonlinear variation of rolling moment with roll angle that appeared in the experiment. This nonlinearity includes regions of local static roll instability, which is attributed to vortex breakdown.

The Development of Breakdown in Transformer Oil

Directory of Open Access Journals (Sweden)

Jozef Kudelcik

2007-01-01

Full Text Available The conditions under which breakdown of composite liquid - solid insulation can be occurred, e.g. in transformer, play an important role in designing of such insulation. The initial state of breakdown development is explained based on development of streamers in cavitations. The whole breakdown development in transformer oil is represented by RLC circuit and it depends on the parameters of outer circuit.

A regularized stationary mean-field game

KAUST Repository

Yang, Xianjin

2016-01-01

In the thesis, we discuss the existence and numerical approximations of solutions of a regularized mean-field game with a low-order regularization. In the first part, we prove a priori estimates and use the continuation method to obtain the existence of a solution with a positive density. Finally, we introduce the monotone flow method and solve the system numerically.

A regularized stationary mean-field game

KAUST Repository

Yang, Xianjin

2016-04-19

In the thesis, we discuss the existence and numerical approximations of solutions of a regularized mean-field game with a low-order regularization. In the first part, we prove a priori estimates and use the continuation method to obtain the existence of a solution with a positive density. Finally, we introduce the monotone flow method and solve the system numerically.

The nuclear N-body problem and the effective interaction in self-consistent mean-field methods

International Nuclear Information System (INIS)

Duguet, Thomas

2002-01-01

This work deals with two aspects of mean-field type methods extensively used in low-energy nuclear structure. The first study is at the mean-field level. The link between the wave-function describing an even-even nucleus and the odd-even neighbor is revisited. To get a coherent description as a function of the pairing intensity in the system, the utility of the formalization of this link through a two steps process is demonstrated. This two-steps process allows to identify the role played by different channels of the force when a nucleon is added in the system. In particular, perturbative formula evaluating the contribution of time-odd components of the functional to the nucleon separation energy are derived for zero and realistic pairing intensities. Self-consistent calculations validate the developed scheme as well as the derived perturbative formula. This first study ends up with an extended analysis of the odd-even mass staggering in nuclei. The new scheme allows to identify the contribution to this observable coming from different channels of the force. The necessity of a better understanding of time-odd terms in order to decide which odd-even mass formulae extracts the pairing gap the most properly is identified. These terms being nowadays more or less out of control, extended studies are needed to make precise the fit of a pairing force through the comparison of theoretical and experimental odd-even mass differences. The second study deals with beyond mean-field methods taking care of the correlations associated with large amplitude oscillations in nuclei. Their effects are usually incorporated through the GCM or the projected mean-field method. We derive a perturbation theory motivating such variational calculations from a diagrammatic point of view for the first time. Resuming two-body correlations in the energy expansion, we obtain an effective interaction removing the hard-core problem in the context of configuration mixing calculations. Proceeding to a

CONSIDERATIONS ON THE PHENOMENON OF DOUBLE TAXATION IN THE EUROPEAN UNION

Directory of Open Access Journals (Sweden)

ALICE CRISTINA MARIA ZDANOVSCHI

2012-05-01

Full Text Available In the general context of economic globalization, international economic cooperation, the liberalization movement of goods, services, capital and persons, and the effect of the exercise of fiscal sovereignty, appears the phenomenon of double or multiple international taxation of income and assets, following the vocation of several legal systems, which contain legislative differences and can generate tax obstacles, such as, the laws of the country of origin of the revenue and the legislation of the country of destination of income. Thus, more interesting becomes the study of the phenomenon of double taxation at EU level given the distinct presence of 27 sovereignties in full process of European integration So, this paper aims to identify how the European Union handles the phenomenon of double taxation, making a shift from defining this phenomenon to identifying the legislation designed to avoid or eliminate the phenomenon of double taxation in the field of EU direct taxation.Also, this paper deems necessary to stop a moment upon the fiscal harmonization and integration in the indirect taxation field of the European Union.

Mean field strategies induce unrealistic nonlinearities in calcium puffs

Directory of Open Access Journals (Sweden)

Guillermo eSolovey

2011-08-01

Full Text Available Mean field models are often useful approximations to biological systems, but sometimes, they can yield misleading results. In this work, we compare mean field approaches with stochastic models of intracellular calcium release. In particular, we concentrate on calcium signals generated by the concerted opening of several clustered channels (calcium puffs. To this end we simulate calcium puffs numerically and then try to reproduce features of the resulting calcium distribution using mean field models were all the channels open and close simultaneously. We show that an unrealistic nonlinear relationship between the current and the number of open channels is needed to reproduce the simulated puffs. Furthermore, a single channel current which is five times smaller than the one of the stochastic simulations is also needed. Our study sheds light on the importance of the stochastic kinetics of the calcium release channel activity to estimate the release fluxes.

A mean-field game economic growth model

KAUST Repository

Gomes, Diogo A.; Lafleche, Laurent; Nurbekyan, Levon

2016-01-01

Here, we examine a mean-field game (MFG) that models the economic growth of a population of non-cooperative, rational agents. In this MFG, agents are described by two state variables - the capital and consumer goods they own. Each agent seeks

Generation of strong pulsed magnetic fields using a compact, short pulse generator

Science.gov (United States)

Yanuka, D.; Efimov, S.; Nitishinskiy, M.; Rososhek, A.; Krasik, Ya. E.

2016-04-01

The generation of strong magnetic fields (˜50 T) using single- or multi-turn coils immersed in water was studied. A pulse generator with stored energy of ˜3.6 kJ, discharge current amplitude of ˜220 kA, and rise time of ˜1.5 μs was used in these experiments. Using the advantage of water that it has a large Verdet constant, the magnetic field was measured using the non-disturbing method of Faraday rotation of a polarized collimated laser beam. This approach does not require the use of magnetic probes, which are sensitive to electromagnetic noise and damaged in each shot. It also avoids the possible formation of plasma by either a flashover along the conductor or gas breakdown inside the coil caused by an induced electric field. In addition, it was shown that this approach can be used successfully to investigate the interesting phenomenon of magnetic field enhanced diffusion into a conductor.

Frequency and Temperature Dependence of Electrical Breakdown at 21, 30, and 39GHz

Science.gov (United States)

Braun, H. H.; Döbert, S.; Wilson, I.; Wuensch, W.

2003-06-01

A TeV-range e+e- linear collider has emerged as one of the most promising candidates to extend the high energy frontier of experimental elementary particle physics. A high accelerating gradient for such a collider is desirable to limit its overall length. Accelerating gradient is mainly limited by electrical breakdown, and it has been generally assumed that this limit increases with increasing frequency for normal-conducting accelerating structures. Since the choice of frequency has a profound influence on the design of a linear collider, the frequency dependence of breakdown has been measured using six exactly scaled single-cell cavities at 21, 30, and 39GHz. The influence of temperature on breakdown behavior was also investigated. The maximum obtainable surface fields were found to be in the range of 300 to 400 MV/m for copper, with no significant dependence on either frequency or temperature.

Frequency and Temperature Dependence of Electrical Breakdown at 21, 30 and 39 GHz

CERN Document Server

Braun, Hans Heinrich; Wilson, Ian H; Wuensch, Walter

2003-01-01

A TeV-range e+e- linear collider has emerged as one of the most promising candidates to extend the high energy frontier of experimental elementary particle physics. A high accelerating gradient for such a collider is desirable to limit its overall length. Accelerating gradient is mainly limited by electrical breakdown, and it has been generally assumed that this limit increases with increasing frequency for normal-conducting accelerating structures. Since the choice of frequency has a profound influence on the design of a linear collider, the frequency dependence of breakdown has been measured using six exactly scaled single-cell cavities at 21, 30, and 39 GHz. The influence of temperature on breakdown behavior was also investigated. The maximum obtainable surface fields were found to be in the range of 300 to 400 MV/m for copper, with no significant dependence on either frequency or temperature.

Modeling the Pineapple Express phenomenon via Multivariate Extreme Value Theory

Science.gov (United States)

Weller, G.; Cooley, D. S.

2011-12-01

The pineapple express (PE) phenomenon is responsible for producing extreme winter precipitation events in the coastal and mountainous regions of the western United States. Because the PE phenomenon is also associated with warm temperatures, the heavy precipitation and associated snowmelt can cause destructive flooding. In order to study impacts, it is important that regional climate models from NARCCAP are able to reproduce extreme precipitation events produced by PE. We define a daily precipitation quantity which captures the spatial extent and intensity of precipitation events produced by the PE phenomenon. We then use statistical extreme value theory to model the tail dependence of this quantity as seen in an observational data set and each of the six NARCCAP regional models driven by NCEP reanalysis. We find that most NCEP-driven NARCCAP models do exhibit tail dependence between daily model output and observations. Furthermore, we find that not all extreme precipitation events are pineapple express events, as identified by Dettinger et al. (2011). The synoptic-scale atmospheric processes that drive extreme precipitation events produced by PE have only recently begun to be examined. Much of the current work has focused on pattern recognition, rather than quantitative analysis. We use daily mean sea-level pressure (MSLP) fields from NCEP to develop a "pineapple express index" for extreme precipitation, which exhibits tail dependence with our observed precipitation quantity for pineapple express events. We build a statistical model that connects daily precipitation output from the WRFG model, daily MSLP fields from NCEP, and daily observed precipitation in the western US. Finally, we use this model to simulate future observed precipitation based on WRFG output driven by the CCSM model, and our pineapple express index derived from future CCSM output. Our aim is to use this model to develop a better understanding of the frequency and intensity of extreme

The Studies of a Vacuum Gap Breakdown after High-Current Arc Interruption with Increasing the Voltage

Science.gov (United States)

Schneider, A. V.; Popov, S. A.; Batrakov, A. V.; Dubrovskaya, E. L.; Lavrinovich, V. A.

2017-12-01

Vacuum-gap breakdown has been studied after high-current arc interruption with a subsequent increase in the transient recovery voltage across a gap. The effects of factors, such as the rate of the rise in the transient voltage, the potential of the shield that surrounds a discharge gap, and the arc burning time, have been determined. It has been revealed that opening the contacts earlier leads to the formation of an anode spot, which is the source of electrode material vapors into the discharge gap after current zero moment. Under the conditions of increasing voltage, this fact results in the breakdown. Too late opening leads to the breakdown of a short gap due to the high electric fields.

High-Voltage Breakdown Penalties for the Beam-Breakup Instability

International Nuclear Information System (INIS)

Ekdahl, Carl August

2016-01-01

The strength of the dangerous beam breakup (BBU) instability in linear induction accelerators (LIAs) is determined by the transverse coupling impedance Z_⊥ of the induction cell cavity. For accelerating gap width w less than the beam pipe radius b, the transverse impedance is theoretically proportional to w/b, favoring narrow gaps to suppress BBU. On the other hand, cells with narrow gaps cannot support high accelerating gradients, because of electrical breakdown and shorting of the gap. Thus, there is an engineering trade-off between BBU growth and accelerating gradient, which must be considered for next generation LIAs now being designed. In this article this tradeoff is explored, using a simple pillbox cavity as an illustrative example. For this model, widening the gap to reduce the probability of breakdown increases BBU growth, unless higher magnetic focusing fields are used to further suppress the instability.

The relativistic mean-field description of nuclei and nuclear dynamics

International Nuclear Information System (INIS)

Reinhard, P.G.

1989-01-01

The relativistic mean-field model of the nucleus is reviewed. It describes the nucleus as a system of Dirac-Nucleons which interact in a relativistic covariant manner via meson fields. The meson fields are treated as mean fields, i.e. as non quantal c-number fields. The effects of the Dirac sea of the nucleons is neglected. The model is interpreted as a phenomenological ansatz providing a selfconsistent relativistic description of nuclei and nuclear dynamics. It is viewed, so to say, as the relativistic generalisation of the Skyrme-Hartree-Fock ansatz. The capability and the limitations of the model to describe nuclear properties are discussed. Recent applications to spherical and deformed nuclei and to nuclear dynamics are presented. (orig.)

Performance limiting effects in X-band accelerators

Directory of Open Access Journals (Sweden)

Faya Wang

2011-01-01

Full Text Available Acceleration gradient is a critical parameter for the design of future TeV-scale linear colliders. The major obstacle to higher gradient in room-temperature accelerators is rf breakdown, which is still a very mysterious phenomenon that depends on the geometry and material of the accelerator as well as the input power and operating frequency. Pulsed heating has been associated with breakdown for many years; however, there have been no experiments that clearly separate field and heating effects on the breakdown rate. Recently, such experiments have been performed at SLAC with both standing-wave and traveling-wave structures. These experiments have demonstrated that pulsed heating is limiting the gradient. Nevertheless the X-band structures breakdown studies show damage to the iris surfaces in locations of high electric field rather than of high magnetic field after thousands of breakdowns. It is not yet clear how the relative roles of electric field, magnetic field, and heating factor into the damage caused by rf breakdown. Thus, a dual-moded cavity has been designed to better study the electric field, magnetic field, and pulsed heating effects on breakdown damage.

Microbunching instability in a chicane: Two-dimensional mean field treatment

Directory of Open Access Journals (Sweden)

Gabriele Bassi

2009-08-01

Full Text Available We study the microbunching instability in a bunch compressor by a parallel code with some improved numerical algorithms. The two-dimensional charge/current distribution is represented by a Fourier series, with coefficients determined through Monte Carlo sampling over an ensemble of tracked points. This gives a globally smooth distribution with low noise. The field equations are solved accurately in the lab frame using retarded potentials and a novel choice of integration variables that eliminates singularities. We apply the scheme with parameters for the first bunch compressor system of FERMI@Elettra, with emphasis on the amplification of a perturbation at a particular wavelength and the associated longitudinal bunch spectrum. Gain curves are in rough agreement with those of the linearized Vlasov system at intermediate wavelengths, but show some deviation at the smallest wavelengths treated and show the breakdown of a coasting beam assumption at long wavelengths. The linearized Vlasov system is discussed in some detail. A new 2D integral equation is derived which reduces to a well-known 1D integral equation in the coasting beam case.

Stochastic quantization and mean field approximation

International Nuclear Information System (INIS)

Jengo, R.; Parga, N.

1983-09-01

In the context of the stochastic quantization we propose factorized approximate solutions for the Fokker-Planck equation for the XY and Zsub(N) spin systems in D dimensions. The resulting differential equation for a factor can be solved and it is found to give in the limit of t→infinity the mean field or, in the more general case, the Bethe-Peierls approximation. (author)

Analyzing randomly occurring voltage breakdowns

International Nuclear Information System (INIS)

Wiltshire, C.W.

1977-01-01

During acceptance testing of high-vacuum neutron tubes, 40% of the tubes failed after experiencing high-voltage breakdowns during the aging process. Use of a digitizer in place of an oscilloscope revealed two types of breakdowns, only one of which affected acceptance testing. This information allowed redesign of the aging sequence to prevent tube damage and improve yield and quality of the final product

Impulse breakdown of liquids

CERN Document Server

Ushakov, Vasily Y

2007-01-01

The book describes the main physical processes and phenomena in pulsed electric breakdown. The knowledge and the control of the electric breakdown of liquids is important not only for the insulation inside power systems but it is also used for the creation and information of high voltage and high current pulses. Such high-voltage micro- and nanosecond pulses find wide application in experimental physics, electro discharge technology, physics of dielectrics, radar detection and ranging, high-speed photography. The nature of charge carriers, mechanism of formation and evolution of the gas phase,

Merging Belief Propagation and the Mean Field Approximation

DEFF Research Database (Denmark)

Riegler, Erwin; Kirkelund, Gunvor Elisabeth; Manchón, Carles Navarro

2010-01-01

We present a joint message passing approach that combines belief propagation and the mean field approximation. Our analysis is based on the region-based free energy approximation method proposed by Yedidia et al., which allows to use the same objective function (Kullback-Leibler divergence......) as a starting point. In this method message passing fixed point equations (which correspond to the update rules in a message passing algorithm) are then obtained by imposing different region-based approximations and constraints on the mean field and belief propagation parts of the corresponding factor graph....... Our results can be applied, for example, to algorithms that perform joint channel estimation and decoding in iterative receivers. This is demonstrated in a simple example....

Nuclear collective vibrations in extended mean-field theory

Energy Technology Data Exchange (ETDEWEB)

Lacroix, D. [Lab. de Physique Corpusculaire/ ENSICAEN, 14 - Caen (France); Ayik, S. [Tennessee Technological Univ., Cookeville, TN (United States); Chomaz, Ph. [Grand Accelerateur National d' Ions Lourds (GANIL), 14 - Caen (France)

2003-07-01

The extended mean-field theory, which includes both the incoherent dissipation mechanism due to nucleon-nucleon collisions and the coherent dissipation mechanism due to coupling to low-lying surface vibrations, is briefly reviewed. Expressions of the strength functions for the collective excitations are presented in the small amplitude limit of this approach. This fully microscopic theory is applied by employing effective Skyrme forces to various giant resonance excitations at zero and finite temperature. The theory is able to describe the gross properties of giant resonance excitations, the fragmentation of the strength distributions as well as their fine structure. At finite temperature, the success and limitations of this extended mean-field description are discussed. (authors)

Constrained deterministic leader-follower mean field control

NARCIS (Netherlands)

Möller, L.; Gentile, B.; Parise, F.; Grammatico, S.; Lygeros, J.

2016-01-01

We consider a mean field game among a large population of noncooperative agents divided into two categories: leaders and followers. Each agent is subject to heterogeneous convex constraints and minimizes a quadratic cost function; the cost of each leader is affected by the leaders' aggregate

Measuring protein breakdown rate in individual proteins in vivo

DEFF Research Database (Denmark)

Holm, Lars; Kjaer, Michael

2010-01-01

To outline different approaches of how protein breakdown can be quantified and to present a new approach to determine the fractional breakdown rate of individual slow turnover proteins in vivo.......To outline different approaches of how protein breakdown can be quantified and to present a new approach to determine the fractional breakdown rate of individual slow turnover proteins in vivo....

Mean-field theory of anyons near Bose statistics

International Nuclear Information System (INIS)

McCabe, J.; MacKenzie, R.

1992-01-01

The validity of a mean-field approximation for a boson-based free anyon gas near Bose statistics is shown. The magnetic properties of the system is discussed in the approximation that the statistical magnetic field is uniform. It is proved that the anyon gas does not exhibit a Meissner effect in the domain of validity the approximation. (K.A.) 7 refs

Time-Dependent Mean-Field Games in the Subquadratic Case

KAUST Repository

Gomes, Diogo A.; Pimentel, Edgard A.; Sá nchez-Morgado, Hé ector

2014-01-01

In this paper we consider time-dependent mean-field games with subquadratic Hamiltonians and power-like local dependence on the measure. We establish existence of classical solutions under a certain set of conditions depending on both the growth of the Hamiltonian and the dimension. This is done by combining regularity estimates for the Hamilton-Jacobi equation based on the Gagliardo-Nirenberg interpolation inequality with polynomial estimates for the Fokker-Planck equation. This technique improves substantially the previous results on the regularity of time-dependent mean-field games.

Time-Dependent Mean-Field Games in the Subquadratic Case

KAUST Repository

Gomes, Diogo A.

2014-10-14

In this paper we consider time-dependent mean-field games with subquadratic Hamiltonians and power-like local dependence on the measure. We establish existence of classical solutions under a certain set of conditions depending on both the growth of the Hamiltonian and the dimension. This is done by combining regularity estimates for the Hamilton-Jacobi equation based on the Gagliardo-Nirenberg interpolation inequality with polynomial estimates for the Fokker-Planck equation. This technique improves substantially the previous results on the regularity of time-dependent mean-field games.

Non-equilibrium mean-field theories on scale-free networks

International Nuclear Information System (INIS)

Caccioli, Fabio; Dall'Asta, Luca

2009-01-01

Many non-equilibrium processes on scale-free networks present anomalous critical behavior that is not explained by standard mean-field theories. We propose a systematic method to derive stochastic equations for mean-field order parameters that implicitly account for the degree heterogeneity. The method is used to correctly predict the dynamical critical behavior of some binary spin models and reaction–diffusion processes. The validity of our non-equilibrium theory is further supported by showing its relation with the generalized Landau theory of equilibrium critical phenomena on networks

Comparative study on preliminary breakdown pulse trains observed in Johor, Malaysia and Florida, USA

Science.gov (United States)

Baharudin, Z. A.; Ahmad, Noor Azlinda; Fernando, M.; Cooray, V.; Mäkelä, J. S.

2012-11-01

In this paper, the preliminary breakdown (PB) pulse train preceding the negative first return stroke (RS) is recorded using a broad band antenna system. These analyses were carried out in Johor Bahru, Malaysia and Florida, United States. This is a novel initiative at examining and identifying the characteristics of the PB pulse trains in the negative cloud-to-ground flashes observed in Malaysia. The arithmetic mean of the total pulse train duration is 12.3 ms and the weighted arithmetic mean of the pulse durations and interpulse intervals are 11 μs and 152 μs, respectively. The arithmetic mean ratio between the maximum peak amplitude of the PB pulse and the peak RS electric field was 27.8%, and the corresponding value in Florida was 29.4%. The arithmetic mean of the time duration between the most active part of the pulse train, and the RS was 57.6 ms in Malaysia and 22 ms in Florida. A qualitative comparison of our results with those obtained earlier in Sri Lanka, Sweden and Finland supports the hypothesis that the PBP/RS ratio is higher in the northern regions compared to the tropical regions.

Standoff Laser-Induced Breakdown Spectroscopy (LIBS) Using a Miniature Wide Field of View Spatial Heterodyne Spectrometer with Sub-Microsteradian Collection Optics.

Science.gov (United States)

Barnett, Patrick D; Lamsal, Nirmal; Angel, S Michael

2017-04-01

A spatial heterodyne spectrometer (SHS) is described for standoff laser-induced breakdown spectroscopy (LIBS) measurements. The spatial heterodyne LIBS spectrometer (SHLS) is a diffraction grating based interferometer with no moving parts that offers a very large field of view, high light throughput, and high spectral resolution in a small package. The field of view of the SHLS spectrometer is shown to be ∼1° in standoff LIBS measurements. In the SHLS system described here, the collection aperture was defined by the 10 mm diffraction gratings in the SHS and standoff LIBS measurements were made up to 20 m with no additional collection optics, corresponding to a collection solid angle of 0.2 μsr, or f/2000, and also using a small telescope to increase the collection efficiency. The use of a microphone was demonstrated to rapidly optimize laser focus for 20 m standoff LIBS measurements.

Stochastic mean-field dynamics for fermions in the weak coupling limit

International Nuclear Information System (INIS)

Lacroix, D.

2005-09-01

Assuming that the effect of the residual interaction beyond mean-field is weak and can be treated as a statistical ensemble of two-body interactions, a Markovian quantum jump theory is developed for fermionic systems. In this theory, jumps occur between many-body densities formed of pairs of states D |Φ a > b | / b | |Φ a > where |Φ a > and |Φ b > are anti-symmetrized products of single-particle states. The underlying Stochastic Mean-Field (SMF) theory is discussed and applied to the monopole vibration of a spherical 40 Ca nucleus under the influence of a statistical ensemble of two-body contact interactions. In this example, the mean-field evolution of one-body observables is recovered by averaging over different stochastic trajectories while fluctuations beyond mean-field are observed. Finally, the nature of the fluctuations is discussed. (author)

Numerical Borehole Breakdown Investigations using XFEM

Science.gov (United States)

Beckhuis, Sven; Leonhart, Dirk; Meschke, Günther

2016-04-01

During pressurization of a wellbore a typical downhole pressure record shows the following regimes: first the applied wellbore pressure balances the reservoir pressure, then after the compressive circumferential hole stresses are overcome, tensile stresses are induced on the inside surface of the hole. When the magnitude of these stresses reach the tensile failure stress of the surrounding rock medium, a fracture is initiated and propagates into the reservoir. [1] In standard theories this pressure, the so called breakdown pressure, is the peak pressure in the down-hole pressure record. However experimental investigations [2] show that the breakdown did not occur even if a fracture was initiated at the borehole wall. Drilling muds had the tendency to seal and stabilize fractures and prevent fracture propagation. Also fracture mechanics analysis of breakdown process in mini-frac or leak off tests [3] show that the breakdown pressure could be either equal or larger than the fracture initiation pressure. In order to gain a deeper understanding of the breakdown process in reservoir rock, numerical investigations using the extended finite element method (XFEM) for hydraulic fracturing of porous materials [4] are discussed. The reservoir rock is assumed to be pre-fractured. During pressurization of the borehole, the injection pressure, the pressure distribution and the position of the highest flux along the fracture for different fracturing fluid viscosities are recorded and the influence of the aforementioned values on the stability of fracture propagation is discussed. [1] YEW, C. H. (1997), "Mechanics of Hydraulic Fracturing", Gulf Publishing Company [2] MORITA, N.; BLACK, A. D.; FUH, G.-F. (1996), "Borehole Breakdown Pressure with Drilling Fluids". International Journal of Rock Mechanics and Mining Sciences 33, pp. 39-51 [3] DETOURNAY, E.; CARBONELL, R. (1996), "Fracture Mechanics Analysis of the Breakdown Process in Minifrac or Leakoff Test", Society of Petroleum

Electric field induced instabilities in free emulsion films

Energy Technology Data Exchange (ETDEWEB)

Tchoukov, P.; Dabros, T. [Natural Resources Canada, Devon, AB (Canada); Mostowfi, F. [Schlumberger DBR Technology Center, Edmonton, AB (Canada); Panchev, N. [Champion Technologies Inc., Houston, TX (United States); Czarnecki, J. [Alberta Univ., Edmonton, AB (Canada). Dept. of Chemical and Materials Engineering

2009-07-01

This presentation reported on a study that investigated the mechanism of electric field-induced breakdown of free emulsion films. Instability patterns were observed on the plane of a water-oil-water film following electric polarization. The length-scales of the instabilities were measured by analyzing images immediately after applying the electric field. Linear stability analysis was used to calculate the theoretical dominant wavelengths. The calculated values were found to be in good agreement with measured values. The films were formed in a thin film apparatus modified so that the oil film separated 2 aqueous phase compartments, each in contact with a platinum electrode. This enabled the measurement of disjoining pressure while applying the electric field to the film. It was concluded that breakdown of thin films induced by electric field has many applications, including electrostatic de-emulsification/desalination of crude oil and emulsion stability measurements. It was concluded that electroporation and dielectric breakdown may be responsible for electric field-induced breakdown. This study also presented evidence of an increase in electric field-induced instabilities in emulsion films resulting in rupture. tabs., figs.

Pedestrian Flow in the Mean Field Limit

KAUST Repository

Haji Ali, Abdul Lateef

2012-11-01

We study the mean-field limit of a particle-based system modeling the behavior of many indistinguishable pedestrians as their number increases. The base model is a modified version of Helbing\\'s social force model. In the mean-field limit, the time-dependent density of two-dimensional pedestrians satisfies a four-dimensional integro-differential Fokker-Planck equation. To approximate the solution of the Fokker-Planck equation we use a time-splitting approach and solve the diffusion part using a Crank-Nicholson method. The advection part is solved using a Lax-Wendroff-Leveque method or an upwind Backward Euler method depending on the advection speed. Moreover, we use multilevel Monte Carlo to estimate observables from the particle-based system. We discuss these numerical methods, and present numerical results showing the convergence of observables that were calculated using the particle-based model as the number of pedestrians increases to those calculated using the probability density function satisfying the Fokker-Planck equation.

Prospective nailfold capillaroscopy evaluation of Raynaud's phenomenon in children and adolescents.

Science.gov (United States)

Piotto, Daniela G P; Hilário, Maria O E; Carvalho, Natalia S; Len, Cláudio A; Andrade, Luis E C; Terreri, Maria T R A

2013-01-01

To evaluate prospectively the clinical features and nailfold capillaroscopy findings of a cohort of children and adolescents who presented Raynaud's phenomenon (RP) without criteria for autoimmune rheumatic diseases. 40 children and adolescents with isolated RP were included. Evidence of systemic autoimmune rheumatic diseases (SARD) was ruled out by thorough clinical and laboratory examination. Concomitantly we also performed wide-field nailfold capillaroscopy evaluation using an optical microscope with magnifications of 10 and 16X. All patients were prospectively re-evaluated within a mean interval time between evaluations of 1.6 years. Thirty (75%) out of 40 patients were female with a mean age of 14.6 years and mean follow-up time of 4.2 years. The mean age of disease onset was 10.4 years and the mean time until diagnosis was 1.4 years. Fourteen out of 40 patients (35%) presented antinuclear antibodies (ANA). Five (12.5%) patients had altered nailfold capillaroscopy at first examination: four presented non-specific microangiopathy and one presented scleroderma pattern. At the re-evaluation three patients (7.5%) presented nailfold capillaroscopy alterations (two SD pattern and one non-specific microangiopathy). The two patients who showed scleroderma pattern at the nailfold capillaroscopy presented along the follow-up a diagnosis of mixed connective tissue disease and hypothyroidism, respectively. One 10 year-old girl with normal nailfold capillaroscopy and presence of autoantibodies (ANA 1/640, nuclear homogeneous pattern, anti-native DNA 1/80) was diagnosed with systemic lupus erythematosus after 1 year of initial evaluation. None of the other children presented diagnosis of SARD along the follow-up. Primary Raynaud´s phenomenon remained the diagnosis in most cases in this series of children and adolescents presenting with initial RP complaint. Nailfold capillaroscopy and determination of autoantibodies were useful ancillary tools in the investigation of

Applicability of self-consistent mean-field theory

International Nuclear Information System (INIS)

Guo Lu; Sakata, Fumihiko; Zhao Enguang

2005-01-01

Within the constrained Hartree-Fock (CHF) theory, an analytic condition is derived to estimate whether a concept of the self-consistent mean field is realized in the level repulsive region. The derived condition states that an iterative calculation of the CHF equation does not converge when the quantum fluctuations coming from two-body residual interaction and quadrupole deformation become larger than a single-particle energy difference between two avoided crossing orbits. By means of numerical calculation, it is shown that the analytic condition works well for a realistic case

Socio-economic applications of finite state mean field games

KAUST Repository

Gomes, Diogo A.

2014-10-06

In this paper, we present different applications of finite state mean field games to socio-economic sciences. Examples include paradigm shifts in the scientific community or consumer choice behaviour in the free market. The corresponding finite state mean field game models are hyperbolic systems of partial differential equations, for which we present and validate different numerical methods. We illustrate the behaviour of solutions with various numerical experiments,which show interesting phenomena such as shock formation. Hence, we conclude with an investigation of the shock structure in the case of two-state problems.

Fundamental properties of field emission-driven direct current microdischarges

International Nuclear Information System (INIS)

Rumbach, Paul; Go, David B.

2012-01-01

For half a century, it has been known that the onset of field emission in direct current microdischarges with gap sizes less than 10 μm can lead to breakdown at applied voltages far less than predicted by Paschen's law. It is still unclear how field emission affects other fundamental plasma properties at this scale. In this work, a one-dimensional fluid model is used to predict basic scaling laws for fundamental properties including ion density, electric field due to space charge, and current-voltage relations in the pre-breakdown regime. Computational results are compared with approximate analytic solutions. It is shown that field emission provides an abundance of cathode electrons, which in turn create large ion concentrations through ionizing collisions well before Paschen's criterion for breakdown is met. Breakdown due to ion-enhanced field emission occurs when the electric field due to space charge becomes comparable to the applied electric field. Simple scaling analysis of the 1D Poisson equation demonstrates that an ion density of n + ≈ 0.1V A ε 0 /qd 2 is necessary to significantly distort the electric field. Defining breakdown in terms of this critical ion density leads analytically to a simple, effective secondary emission coefficient γ ′ of the same mathematical form initially suggested by Boyle and Kisliuk [Phys. Rev. 97, 255 (1955)].

Effects of rf breakdown on the beam in the Compact Linear Collider prototype accelerator structure

Directory of Open Access Journals (Sweden)

A. Palaia

2013-08-01

Full Text Available Understanding the effects of rf breakdown in high-gradient accelerator structures on the accelerated beam is an extremely relevant aspect in the development of the Compact Linear Collider (CLIC and is one of the main issues addressed at the Two-beam Test Stand at the CLIC Test Facility 3 at CERN. During a rf breakdown high currents are generated causing parasitic magnetic fields that interact with the accelerated beam affecting its orbit. The beam energy is also affected because the power is partly reflected and partly absorbed thus reducing the available energy to accelerate the beam. We discuss here measurements of such effects observed on an electron beam accelerated in a CLIC prototype structure. Measurements of the trajectory of bunch trains on a nanosecond time scale showed fast changes in correspondence of breakdown that we compare with measurements of the relative beam spots on a scintillating screen. We identify different breakdown scenarios for which we offer an explanation based also on measurements of the power at the input and output ports of the accelerator structure. Finally we present the distribution of the magnitude of the observed changes in the beam position and we discuss its correlation with rf power and breakdown location in the accelerator structure.

Stochastic mean-field dynamics for fermions in the weak coupling limit

Energy Technology Data Exchange (ETDEWEB)

Lacroix, D

2005-09-15

Assuming that the effect of the residual interaction beyond mean-field is weak and can be treated as a statistical ensemble of two-body interactions, a Markovian quantum jump theory is developed for fermionic systems. In this theory, jumps occur between many-body densities formed of pairs of states D |{phi}{sub a}> <|{phi}{sub b}| / <|{phi}{sub b} | |{phi} {sub a}> where |{phi}{sub a}> and |{phi}{sub b}> are anti-symmetrized products of single-particle states. The underlying Stochastic Mean-Field (SMF) theory is discussed and applied to the monopole vibration of a spherical {sup 40}Ca nucleus under the influence of a statistical ensemble of two-body contact interactions. In this example, the mean-field evolution of one-body observables is recovered by averaging over different stochastic trajectories while fluctuations beyond mean-field are observed. Finally, the nature of the fluctuations is discussed. (author)

Materials and Breakdown Phenomena: Heterogeneous Molybdenum Metallic Films

Directory of Open Access Journals (Sweden)

Augusto Marcelli

2017-05-01

Full Text Available Technological activities to design, manufacture, and test new accelerating devices using different materials and methods is under way all over the world. The main goal of these studies is to increase the accelerating gradients and reduce the probability of radio-frequency (RF breakdown. Indeed, it is still not clear why, by increasing the intensity of the applied field, intense surface damage is observed in copper structures, limiting the lifetime and, therefore, the practical applications. A possible solution is represented by a coating of a relatively thick layer of molybdenum in order to improve the breakdown rate. molybdenum can be reliably grown on different substrates with a negligible strain and, for thicknesses up to 600 nm, with a resistivity < 100–150·μΩ cm. Moreover, Mo coatings with controlled composition, internal stress, and roughness may allow improving thermo-mechanical properties reaching values not attainable by uncoated copper. Although the Mo conductivity remains lower compared to Cu, a Mo coating represents a very interesting option for high gradient accelerator components manufactured in copper.

Noisy mean field game model for malware propagation in opportunistic networks

KAUST Repository

Tembine, Hamidou

2012-01-01

In this paper we present analytical mean field techniques that can be used to better understand the behavior of malware propagation in opportunistic large networks. We develop a modeling methodology based on stochastic mean field optimal control that is able to capture many aspects of the problem, especially the impact of the control and heterogeneity of the system on the spreading characteristics of malware. The stochastic large process characterizing the evolution of the total number of infected nodes is examined with a noisy mean field limit and compared to a deterministic one. The stochastic nature of the wireless environment make stochastic approaches more realistic for such types of networks. By introducing control strategies, we show that the fraction of infected nodes can be maintained below some threshold. In contrast to most of the existing results on mean field propagation models which focus on deterministic equations, we show that the mean field limit is stochastic if the second moment of the number of object transitions per time slot is unbounded with the size of the system. This allows us to compare one path of the fraction of infected nodes with the stochastic trajectory of its mean field limit. In order to take into account the heterogeneity of opportunistic networks, the analysis is extended to multiple types of nodes. Our numerical results show that the heterogeneity can help to stabilize the system. We verify the results through simulation showing how to obtain useful approximations in the case of very large systems. © 2012 ICST Institute for Computer Science, Social Informatics and Telecommunications Engineering.

Dielectric breakdown of ultrathin aluminum oxide films induced by scanning tunneling microscopy

International Nuclear Information System (INIS)

Magtoto, N. P.; Niu, C.; Ekstrom, B. M.; Addepalli, S.; Kelber, J. A.

2000-01-01

Dielectric breakdown of 7-Aa-thick Al 2 O 3 (111) films grown on Ni 3 Al(111) under ultrahigh vacuum conditions is induced by increasing the bias voltage on the scanning tunneling microscopy tip under constant current feedback. Breakdown is marked by the precipitous retreat of the tip from the surface, and the formation of an elevated feature in the scanning tunneling microscopy image, typically greater than 5 nm high and ∼100 nm in diameter. Constant height measurements performed at tip/sample distances of 1 nm or less yield no tip/substrate physical interaction, indicating that such features do not result from mass transport. Consistent with this, current/voltage measurements within the affected regions indicate linear behavior, in contrast to a band gap of 1.5 eV observed at unaffected regions of the oxide surface. A threshold electric field value of 11±1 MV cm -1 is required to induce breakdown, in good agreement with extrapolated values from capacitance measurements on thicker oxides. (c) 2000 American Institute of Physics

On the existence of classical solutions for stationary extended mean field games

KAUST Repository

Gomes, Diogo A.; Patrizi, Stefania; Voskanyan, Vardan

2014-01-01

In this paper we consider extended stationary mean-field games, that is mean-field games which depend on the velocity field of the players. We prove various a-priori estimates which generalize the results for quasi-variational mean-field games in Gomes et al. (2012). In addition we use adjoint method techniques to obtain higher regularity bounds. Then we establish the existence of smooth solutions under fairly general conditions by applying the continuity method. When applied to standard stationary mean-field games as in Lasry and Lions (2006), Gomes and Sanchez-Morgado (2011) or Gomes et al. (2012) this paper yields various new estimates and regularity properties not available previously. We discuss additionally several examples where the existence of classical solutions can be proved. © 2013 Elsevier Ltd. All rights reserved.

On the existence of classical solutions for stationary extended mean field games

KAUST Repository

Gomes, Diogo A.

2014-04-01

In this paper we consider extended stationary mean-field games, that is mean-field games which depend on the velocity field of the players. We prove various a-priori estimates which generalize the results for quasi-variational mean-field games in Gomes et al. (2012). In addition we use adjoint method techniques to obtain higher regularity bounds. Then we establish the existence of smooth solutions under fairly general conditions by applying the continuity method. When applied to standard stationary mean-field games as in Lasry and Lions (2006), Gomes and Sanchez-Morgado (2011) or Gomes et al. (2012) this paper yields various new estimates and regularity properties not available previously. We discuss additionally several examples where the existence of classical solutions can be proved. © 2013 Elsevier Ltd. All rights reserved.

Mean-field Ohm's law and coaxial helicity injection in force-free plasmas

International Nuclear Information System (INIS)

Weening, R. H.

2011-01-01

A theoretical analysis of steady-state coaxial helicity injection (CHI) in force-free plasmas is presented using a parallel mean-field Ohm's law that includes resistivity η and hyper-resistivity Λ terms. Using Boozer coordinates, a partial differential equation is derived for the time evolution of the mean-field poloidal magnetic flux, or magnetic Hamiltonian function, from the parallel mean-field Ohm's law. A general expression is obtained from the mean-field theory for the efficiency of CHI current drive in force-free plasmas. Inductances of internal energy, magnetic helicity, and poloidal magnetic flux are used to characterize axisymmetric plasma equilibria that have a model current profile. Using the model current profile, a method is suggested to determine the level of magnetohydrodynamic activity at the magnetic axis and the consequent deviation from the completely relaxed Taylor state. The mean-field Ohm's law model suggests that steady-state CHI can be viewed most simply as a boundary layer problem.

Gap junctions mediate large-scale Turing structures in a mean-field cortex driven by subcortical noise

Science.gov (United States)

Steyn-Ross, Moira L.; Steyn-Ross, D. A.; Wilson, M. T.; Sleigh, J. W.

2007-07-01

One of the grand puzzles in neuroscience is establishing the link between cognition and the disparate patterns of spontaneous and task-induced brain activity that can be measured clinically using a wide range of detection modalities such as scalp electrodes and imaging tomography. High-level brain function is not a single-neuron property, yet emerges as a cooperative phenomenon of multiply-interacting populations of neurons. Therefore a fruitful modeling approach is to picture the cerebral cortex as a continuum characterized by parameters that have been averaged over a small volume of cortical tissue. Such mean-field cortical models have been used to investigate gross patterns of brain behavior such as anesthesia, the cycles of natural sleep, memory and erasure in slow-wave sleep, and epilepsy. There is persuasive and accumulating evidence that direct gap-junction connections between inhibitory neurons promote synchronous oscillatory behavior both locally and across distances of some centimeters, but, to date, continuum models have ignored gap-junction connectivity. In this paper we employ simple mean-field arguments to derive an expression for D2 , the diffusive coupling strength arising from gap-junction connections between inhibitory neurons. Using recent neurophysiological measurements reported by Fukuda [J. Neurosci. 26, 3434 (2006)], we estimate an upper limit of D2≈0.6cm2 . We apply a linear stability analysis to a standard mean-field cortical model, augmented with gap-junction diffusion, and find this value for the diffusive coupling strength to be close to the critical value required to destabilize the homogeneous steady state. Computer simulations demonstrate that larger values of D2 cause the noise-driven model cortex to spontaneously crystalize into random mazelike Turing structures: centimeter-scale spatial patterns in which regions of high-firing activity are intermixed with regions of low-firing activity. These structures are consistent with the

A computational study of the taxonomy of vortex breakdown

Science.gov (United States)

Spall, Robert E.; Gatski, Thomas B.

1990-01-01

The results of a fully three-dimensional numerical simulation of vortex breakdown using the unsteady, incompressible Navier-Stokes equations are presented. The solutions show that the freestream axial velocity distribution has a significant effect on the position and type of vortex breakdown. Common features between bubble-type and spiral-type breakdown are identified and the role of flow stagnation and the critical state are discussed as complimentary ideas describing the initiation of breakdown.

Experimental Study of the Effect of Beam Loading on RF Breakdown Rate in CLIC High-Gradient Accelerating Structures

CERN Document Server

Tecker, F; Kelisani, M; Doebert, S; Grudiev, A; Quirante, J; Riddone, G; Syratchev, I; Wuensch, W; Kononenko, O; Solodko, A; Lebet, S

2013-01-01

RF breakdown is a key issue for the multi-TeV highluminosity e+e- Compact Linear Collider (CLIC). Breakdowns in the high-gradient accelerator structures can deflect the beam and decrease the desired luminosity. The limitations of the accelerating structures due to breakdowns have been studied so far without a beam present in the structure. The presence of the beam modifies the distribution of the electrical and magnetic field distributions, which determine the breakdown rate. Therefore an experiment has been designed for high power testing a CLIC prototype accelerating structure with a beam present in the CLIC Test Facility (CTF3). A special beam line allows extracting a beam with nominal CLIC beam current and duration from the CTF3 linac. The paper describes the beam optics design for this experimental beam line and the commissioning of the experiment with beam.

Development of mean field theories in nuclear physics and in desordered media

International Nuclear Information System (INIS)

Orland, Henri.

1981-04-01

This work, in two parts, deals with the development of mean field theories in nuclear physics (nuclei in balance and collisions of heavy ions) as well as in disordered media. In the first part, two different ways of tackling the problem of developments around mean field theories are explained. Possessing an approach wave function for the system, the natural idea for including the correlations is to develop the exact wave function of the system around the mean field wave function. The first two chapters show two different ways of dealing with this problem: the perturbative approach - Hartree-Fock equations with two body collisions and functional methods. In the second part: mean field theory for spin glasses. The problem for spin glasses is to construct a physically acceptable mean field theory. The importance of this problem in statistical mechanics is linked to the fact that the mean field theory provides a qualitative description of the low temperature phase and is the starting point needed for using more sophisticated methods (renormalization group). Two approaches to this problem are presented, one based on the Sherrington-Kirkpatrick model and the other based on a model of spins with purely local disorder and competitive interaction between the spins [fr

A Combined Electro-Thermal Breakdown Model for Oil-Impregnated Paper

Directory of Open Access Journals (Sweden)

Meng Huang

2017-12-01

Full Text Available The breakdown property of oil-impregnated paper is a key factor for converter transformer design and operation, but it is not well understood. In this paper, breakdown voltages of oil-impregnated paper were measured at different temperatures. The results showed that with the increase of temperature, electrical, electro-thermal and thermal breakdown occurred successively. An electro-thermal breakdown model was proposed based on the heat equilibrium and space charge transport, and negative differential mobility was introduced to the model. It was shown that carrier mobility determined whether it was electrical or thermal breakdown, and the model can effectively explain the temperature-dependent breakdown.

Mean field dynamics of networks of delay-coupled noisy excitable units

Energy Technology Data Exchange (ETDEWEB)

Franović, Igor, E-mail: franovic@ipb.ac.rs [Scientific Computing Laboratory, Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Todorović, Kristina; Burić, Nikola [Department of Physics and Mathematics, Faculty of Pharmacy, University of Belgrade, Vojvode Stepe 450, Belgrade (Serbia); Vasović, Nebojša [Department of Applied Mathematics, Faculty of Mining and Geology, University of Belgrade, PO Box 162, Belgrade (Serbia)

2016-06-08

We use the mean-field approach to analyze the collective dynamics in macroscopic networks of stochastic Fitzhugh-Nagumo units with delayed couplings. The conditions for validity of the two main approximations behind the model, called the Gaussian approximation and the Quasi-independence approximation, are examined. It is shown that the dynamics of the mean-field model may indicate in a self-consistent fashion the parameter domains where the Quasi-independence approximation fails. Apart from a network of globally coupled units, we also consider the paradigmatic setup of two interacting assemblies to demonstrate how our framework may be extended to hierarchical and modular networks. In both cases, the mean-field model can be used to qualitatively analyze the stability of the system, as well as the scenarios for the onset and the suppression of the collective mode. In quantitative terms, the mean-field model is capable of predicting the average oscillation frequency corresponding to the global variables of the exact system.

Nonequilibrium dynamical mean-field theory

Energy Technology Data Exchange (ETDEWEB)

Eckstein, Martin

2009-12-21

The aim of this thesis is the investigation of strongly interacting quantum many-particle systems in nonequilibrium by means of the dynamical mean-field theory (DMFT). An efficient numerical implementation of the nonequilibrium DMFT equations within the Keldysh formalism is provided, as well a discussion of several approaches to solve effective single-site problem to which lattice models such as the Hubbard-model are mapped within DMFT. DMFT is then used to study the relaxation of the thermodynamic state after a sudden increase of the interaction parameter in two different models: the Hubbard model and the Falicov-Kimball model. In the latter case an exact solution can be given, which shows that the state does not even thermalize after infinite waiting times. For a slow change of the interaction, a transition to adiabatic behavior is found. The Hubbard model, on the other hand, shows a very sensitive dependence of the relaxation on the interaction, which may be called a dynamical phase transition. Rapid thermalization only occurs at the interaction parameter which corresponds to this transition. (orig.)

Nonequilibrium dynamical mean-field theory

International Nuclear Information System (INIS)

Eckstein, Martin

2009-01-01

The aim of this thesis is the investigation of strongly interacting quantum many-particle systems in nonequilibrium by means of the dynamical mean-field theory (DMFT). An efficient numerical implementation of the nonequilibrium DMFT equations within the Keldysh formalism is provided, as well a discussion of several approaches to solve effective single-site problem to which lattice models such as the Hubbard-model are mapped within DMFT. DMFT is then used to study the relaxation of the thermodynamic state after a sudden increase of the interaction parameter in two different models: the Hubbard model and the Falicov-Kimball model. In the latter case an exact solution can be given, which shows that the state does not even thermalize after infinite waiting times. For a slow change of the interaction, a transition to adiabatic behavior is found. The Hubbard model, on the other hand, shows a very sensitive dependence of the relaxation on the interaction, which may be called a dynamical phase transition. Rapid thermalization only occurs at the interaction parameter which corresponds to this transition. (orig.)

The influence of applied internal and external rotation on the pivot shift phenomenon.

Science.gov (United States)

Kopf, Sebastian; Musahl, Volker; Perka, Carsten; Kauert, Ralf; Hoburg, Arnd; Becker, Roland

2017-04-01

The pivot shift test is performed in different techniques and the rotation of the tibia seems to have a significant impact on the amount of the pivot shift phenomenon. It has been hypothesised that external rotation will increase the phenomenon due to less tension at the iliotibial band in knee extension. Twenty-four patients with unilateral anterior cruciate ligament insufficiency were included prospectively. The pivot shift test was performed bilaterally in internal and external tibial rotation under general anaesthesia. Knee motion was captured using a femoral and a tibial inertial sensor. The difference between positive and negative peak values in Euclidean norm of acceleration was calculated to evaluate the amount of the pivot shift phenomenon. The pivot shift phenomenon was significantly increased in patients with ACL insufficiency when the test was performed in external [mean 5.2 ms - 2 (95% CI 4.3-6.0)] compared to internal tibial rotation [mean 4.4 ms - 2 (95% CI 3.5-5.4)] (p = 0.002). In healthy, contralateral knees did not show any difference between external [mean 4.0 ms - 2 (95% CI 3.3-4.7)] and internal tibial rotation [mean 4.0 ms - 2 (95% CI 3.4-4.6)] (ns). The pivot shift phenomenon was increased with external rotation in ACL-insufficient knees, and therefore, one should perform the pivot shift test, rather, in external rotation to easily evoke the, sometimes difficult to detect, pivot shift phenomenon. I (diagnostic study).

Stress-induced breakdown during galvanostatic anodising of zirconium

International Nuclear Information System (INIS)

Van Overmeere, Q.; Proost, J.

2010-01-01

Although internal stress is frequently being suggested as a plausible reason for oxide breakdown during valve metal anodising, no direct quantitative evidence has been made available yet. In this work, we anodized sputtered zirconium thin films galvanostatically at room temperature in sulphuric acid until breakdown was observed, and simultaneously measured the internal stress evolution in the oxide in situ, using a high-resolution curvature setup. It was found that the higher the magnitude of the observed internal compressive stress in the oxide, the smaller the oxide thickness at which breakdown occurred. The moment of breakdown was identified from a slope change in the cell voltage evolution, indicative for a decrease in anodising efficiency. The latter presumably occurs as a result of oxygen evolution, initiated by the relative increase of the cubic or tetragonal zirconia phase content relative to the monoclinic one. This was evidenced in turn by comparing electron diffractograms, taken in a transmission electron microscope, before and after breakdown. The critical role of internal stress on oxide breakdown during zirconium anodising can therefore be associated with its promoting effect on the densifying phase transformation of monoclinic oxide.

Obstacle-induced spiral vortex breakdown

OpenAIRE

Pasche, Simon; Gallaire, François; Dreyer, Matthieu; Farhat, Mohamed

2014-01-01

An experimental investigation on vortex breakdown dynamics is performed. An adverse pressure gradient is created along the axis of a wing-tip vortex by introducing a sphere downstream of an elliptical hydrofoil. The instrumentation involves high-speed visualizations with air bubbles used as tracers and 2D Laser Doppler Velocimeter (LDV). Two key parameters are identified and varied to control the onset of vortex breakdown: the swirl number, defined as the maximum azimuthal velocity divided by...

Bubble behavior and breakdown characteristics in LHe under simulating quench condition of S.C. magnet

Energy Technology Data Exchange (ETDEWEB)

Wang, Z.; Yoshizuka, H.; Takano, K.; Hara, M. [Kyushu University, Fukuoka (Japan)

1996-09-20

In large superconducting magneto, liquid helium is usually used both as coolant and electrical insulator. An abnormal high voltage and thermal bubbles often appear simultaneously during the quenching period. Such an incident is thought serious from a point of view of electrical insulation. In this work, thermal bubble behavior affected by the electrostatic forces in liquid helium and electrical breakdown mechanism of liquid helium are studied under the simulating quench condition of S.C magnet. The results show that (1) the electrostatic forces produced by nonuniform electric field are useful for reducing the effect of thermal bubbles on electrical breakdown in almost all cases, although the bubble aggregation occurs in the region where the gradient force is counterbalancing with the buoyancy and (2) the fins on the surface of superconducting wires are helpful to prevent the bubbles from being released into strong field region if the groove between fins is formed along the field decreasing direction on the wire surface. 11 refs., 14 figs., 1 tab.

A New Phenomenon in Saudi Females' Code-Switching: A Morphemic Analysis

Science.gov (United States)

Turjoman, Mona O.

2016-01-01

This sociolinguistics study investigates a new phenomenon that has recently surfaced in the field of code-switching among Saudi females residing in the Western region of Saudi Arabia. This phenomenon basically combines bound Arabic pronouns, tense markers or definite article to English free morphemes or the combination of bound English affixes to…

Vortex breakdown incipience: Theoretical considerations

Science.gov (United States)

Berger, Stanley A.; Erlebacher, Gordon

1992-01-01

The sensitivity of the onset and the location of vortex breakdowns in concentrated vortex cores, and the pronounced tendency of the breakdowns to migrate upstream have been characteristic observations of experimental investigations; they have also been features of numerical simulations and led to questions about the validity of these simulations. This behavior seems to be inconsistent with the strong time-like axial evolution of the flow, as expressed explicitly, for example, by the quasi-cylindrical approximate equations for this flow. An order-of-magnitude analysis of the equations of motion near breakdown leads to a modified set of governing equations, analysis of which demonstrates that the interplay between radial inertial, pressure, and viscous forces gives an elliptic character to these concentrated swirling flows. Analytical, asymptotic, and numerical solutions of a simplified non-linear equation are presented; these qualitatively exhibit the features of vortex onset and location noted above.

Effects of Nanoparticle Materials on Prebreakdown and Breakdown Properties of Transformer Oil

Directory of Open Access Journals (Sweden)

Yuzhen Lv

2018-04-01

Full Text Available In order to reveal the effects of nanoparticle materials on prebreakdown and breakdown properties of transformer oil, three types of nanoparticle materials, including conductive Fe3O4, semiconductive TiO2 and insulating Al2O3 nanoparticles, were prepared with the same size and surface modification. An experimental study on the breakdown strength and prebreakdown streamer propagation characteristics were investigated for transformer oil and three types of nanofluids under positive lightning impulse voltage. The results indicate that the type of nanoparticle materials has a notable impact on breakdown strength and streamer propagation characteristics of transformer oil. Breakdown voltages of nanofluids are markedly increased by 41.3% and 29.8% respectively by the presence of Fe3O4 and TiO2 nanoparticles. Whereas a slight increase of only 7.4% is observed for Al2O3 nanofluid. Moreover, main discharge channels with thicker and denser branches are formed and the streamer propagation velocities are greatly lowered both in Fe3O4 and TiO2 nanofluids, while no obvious change appears in the propagation process of streamers in Al2O3 nanofluid in comparison with that in pure oil. The test results of trap characteristics reveal that the densities of shallow traps both in Fe3O4 and TiO2 nanofluids are much higher than that in Al2O3 nanofluid and pure oil, greatly reducing the distortion of the electric field. Thus, the propagations of positive streamers in the nanofluids are significantly suppressed by Fe3O4 and TiO2 nanoparticles, leading to the improvements of breakdown strength.

Electrical strength of vacuum gap at repetitive breakdown

International Nuclear Information System (INIS)

Dubinin, N.P.; Chistyakov, N.P.

1983-01-01

The investigation of repetitive pulse breakdown of vacuum space, which electrodes have been subjected to various treatment in vacuum and inert gas, is carried out. In case of electrode warm-up in vacuum up to 400 deg C as well as electronic heating up to 900 deg C the voltage in case of repetitive breakdown hasncreased approximately twice and in case of a through treatment, which is accomplished by a high-current glow discharge in inert gas, the maximum high voltage in case of the first breakdown at repetitive breakdown has decreased by 30...40%, remaining 2-3 times higher than in the first case

Quantum mean-field approximations for nuclear bound states and tunneling

International Nuclear Information System (INIS)

Negele, J.W.; Levit, S.; Paltiel, Z.; Massachusetts Inst. of Tech., Cambridge

1979-01-01

A conceptual framework has been presented in which observables are approximated in terms of a self-consistent quantum mean-field theory. Since the SPA (Stationary Phase Approximation) determines the optimal mean field to approximate a given observable, it is natural that when one changes the observable, the best mean field to describe it changes as well. Although the theory superficially appears applicable to any observable expressible in terms of an evolution operator, for example an S-matrix element, one would have to go far beyond the SPA to adequately approximate the overlap of two many-body wave functions. The most salient open problems thus concern quantitative assessment of the accuracy of the SPA, reformulation of the theory to accomodate hard cores, and selection of sensible expectation values of few-body operators to address in scattering problems

Condition monitoring with Mean field independent components analysis

DEFF Research Database (Denmark)

Pontoppidan, Niels Henrik; Sigurdsson, Sigurdur; Larsen, Jan

2005-01-01

We discuss condition monitoring based on mean field independent components analysis of acoustic emission energy signals. Within this framework it is possible to formulate a generative model that explains the sources, their mixing and also the noise statistics of the observed signals. By using...... a novelty approach we may detect unseen faulty signals as indeed faulty with high precision, even though the model learns only from normal signals. This is done by evaluating the likelihood that the model generated the signals and adapting a simple threshold for decision. Acoustic emission energy signals...... from a large diesel engine is used to demonstrate this approach. The results show that mean field independent components analysis gives a better detection of fault compared to principal components analysis, while at the same time selecting a more compact model...

Particle Production and Effective Thermalization in Inhomogeneous Mean Field Theory

NARCIS (Netherlands)

Aarts, G.; Smit, J.

2000-01-01

As a toy model for dynamics in nonequilibrium quantum field theory we consider the abelian Higgs model in 1+1 dimensions with fermions. In the approximate dynamical equations, inhomogeneous classical (mean) Bose fields are coupled to quantized fermion fields, which are treated with a mode function

Measurement of skeletal muscle collagen breakdown by microdialysis

DEFF Research Database (Denmark)

Miller, B F; Ellis, D; Robinson, M M

2011-01-01

Exercise increases the synthesis of collagen in the extracellular matrix of skeletal muscle. Breakdown of skeletal muscle collagen has not yet been determined because of technical limitations. The purpose of the present study was to use local sampling to determine skeletal muscle collagen breakdown...... collagen breakdown 17–21 h post-exercise, and our measurement of OHP using GC–MS was in agreement with traditional assays....

Improving Breakdown Behavior by Substrate Bias in a Novel Double Epi-layer Lateral Double Diffused MOS Transistor

International Nuclear Information System (INIS)

Li Qi; Wang Wei-Dong; Liu Yun; Wei Xue-Ming

2012-01-01

A new lateral double diffused MOS (LDMOS) transistor with a double epitaxial layer formed by an n-type substrate and a p-type epitaxial layer is reported (DEL LDMOS). The mechanism of the improved breakdown characteristic is that the high electric field around the drain is reduced by substrate reverse bias, which causes the redistribution of the bulk electric field in the drift region, and the vertical blocking voltage is shared by the drain side and the source side. The numerical results indicate that the trade-off between breakdown voltage and on-resistance of the proposed device is improved greatly in comparison to that of the conventional LDMOS. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

48 CFR 252.236-7000 - Modification proposals-price breakdown.

Science.gov (United States)

2010-10-01

...-price breakdown. 252.236-7000 Section 252.236-7000 Federal Acquisition Regulations System DEFENSE... CLAUSES Text of Provisions And Clauses 252.236-7000 Modification proposals—price breakdown. As prescribed in 236.570(a), use the following clause: Modification Proposals—Price Breakdown (DEC 1991) (a) The...

Fundamental studies of passivity and passivity breakdown

International Nuclear Information System (INIS)

Macdonald, D.D.; Urquidi-Macdonald, M.; Song, H.; Biaggio-Rocha, S.; Searson, P.

1991-11-01

This report summarizes the findings of our fundamental research program on passivity and passivity breakdown. During the past three and one half years in this program (including the three year incrementally-funded grant prior to the present grant), we developed and experimentally tested various physical models for the growth and breakdown of passive films on metal surfaces. These models belong to a general class termed ''point defects models'' (PDMs), in which the growth and breakdown of passive films are described in terms of the movement of anion and cation vacancies

Electrical insulation characteristics of liquid helium under high speed rotating field

International Nuclear Information System (INIS)

Ishii, I.; Fuchino, S.; Okano, M.; Tamada, N.

1996-01-01

Electrical breakdown behavior of liquid helium was investigated under high speed rotating field. In the development of superconducting turbine generator it is essential to get the knowledge of electrical insulation characteristics of liquid helium under high speed rotating field. When the current of the field magnet of a superconducting generator is changed, changing magnetic field generates heat in the conductor and it causes bubbles in the liquid helium around the conductor. The behavior of the bubbles is affected largely by the buoyancy which is generated by the centrifugal force. Electrical breakdown behavior of the liquid helium is strongly dependent on the gas bubbles in the liquid. Electrical breakdown voltage between electrodes was measured in a rotating cryostat with and without heater input for bubble formation. Decrease of the breakdown voltage by the heater power was smaller in the rotating field than that in the non rotating field

Low pressure arc discharge lamp apparatus with magnetic field generating means

Science.gov (United States)

Grossman, Mark W.; George, William A.; Maya, Jakob

1987-01-01

A low-pressure arc discharge apparatus having a magnetic field generating means for increasing the output of a discharge lamp is disclosed. The magnetic field generating means, which in one embodiment includes a plurality of permanent magnets, is disposed along the lamp for applying a constant transverse magnetic field over at least a portion of the positive discharge column produced in the arc discharge lamp operating at an ambient temperature greater than about 25.degree. C.

Low pressure arc discharge lamp apparatus with magnetic field generating means

Science.gov (United States)

Grossman, M.W.; George, W.A.; Maya, J.

1987-10-06

A low-pressure arc discharge apparatus having a magnetic field generating means for increasing the output of a discharge lamp is disclosed. The magnetic field generating means, which in one embodiment includes a plurality of permanent magnets, is disposed along the lamp for applying a constant transverse magnetic field over at least a portion of the positive discharge column produced in the arc discharge lamp operating at an ambient temperature greater than about 25 C. 3 figs.

Explicit Solutions for One-Dimensional Mean-Field Games

KAUST Repository

Prazeres, Mariana

2017-01-01

In this thesis, we consider stationary one-dimensional mean-field games (MFGs) with or without congestion. Our aim is to understand the qualitative features of these games through the analysis of explicit solutions. We are particularly interested

Two numerical methods for mean-field games

KAUST Repository

Gomes, Diogo A.

2016-01-01

Here, we consider numerical methods for stationary mean-field games (MFG) and investigate two classes of algorithms. The first one is a gradient flow method based on the variational characterization of certain MFG. The second one uses monotonicity properties of MFG. We illustrate our methods with various examples, including one-dimensional periodic MFG, congestion problems, and higher-dimensional models.

Two numerical methods for mean-field games

KAUST Repository

Gomes, Diogo A.

2016-01-09

Here, we consider numerical methods for stationary mean-field games (MFG) and investigate two classes of algorithms. The first one is a gradient flow method based on the variational characterization of certain MFG. The second one uses monotonicity properties of MFG. We illustrate our methods with various examples, including one-dimensional periodic MFG, congestion problems, and higher-dimensional models.

Mean-field dynamos: The old concept and some recent developments. Karl Schwarzschild Award Lecture 2013

Science.gov (United States)

Rädler, K.-H.

This article elucidates the basic ideas of electrodynamics and magnetohydrodynamics of mean fields in turbulently moving conducting fluids. It is stressed that the connection of the mean electromotive force with the mean magnetic field and its first spatial derivatives is in general neither local nor instantaneous and that quite a few claims concerning pretended failures of the mean-field concept result from ignoring this aspect. In addition to the mean-field dynamo mechanisms of α2 and α Ω type several others are considered. Much progress in mean-field electrodynamics and magnetohydrodynamics results from the test-field method for calculating the coefficients that determine the connection of the mean electromotive force with the mean magnetic field. As an important example the memory effect in homogeneous isotropic turbulence is explained. In magnetohydrodynamic turbulence there is the possibility of a mean electromotive force that is primarily independent of the mean magnetic field and labeled as Yoshizawa effect. Despite of many efforts there is so far no convincing comprehensive theory of α quenching, that is, the reduction of the α effect with growing mean magnetic field, and of the saturation of mean-field dynamos. Steps toward such a theory are explained. Finally, some remarks on laboratory experiments with dynamos are made.

Isospin-dependent properties of asymmetric nuclear matter in relativistic mean-field models

OpenAIRE

Chen, Lie-Wen; Ko, Che Ming; Li, Bao-An

2007-01-01

Using various relativistic mean-field models, including the nonlinear ones with meson field self-interactions, those with density-dependent meson-nucleon couplings, and the point-coupling models without meson fields, we have studied the isospin-dependent bulk and single-particle properties of asymmetric nuclear matter. In particular, we have determined the density dependence of nuclear symmetry energy from these different relativistic mean-field models and compare the results with the constra...

Experimental Investigation of the Relationship between Breakdown Strength and Tracking Characteristics of Composites

DEFF Research Database (Denmark)

Madsen, Søren Find; Holbøll, Joachim; Henriksen, Mogens

2005-01-01

]. The breakdown field strength of specimens cut from similar samples is then determined by a new method capable of estimating the stressed volume [8]. The two values are finally compared and sought incorporated in an analytical formula. All test specimens are supplied by Danish manufacturers of wind turbine...

Competitors' Cluster - A Phenomenon in the Field of Retail Locating

OpenAIRE

Wang, Libo (Michael); Zhu, Bo (Pritt)

2005-01-01

Cluster is a common phenomenon in developed countries. Horizontal clusters and vertical clusters are often seen in these countries. In the domestic retailing, a particular type of cluster—competitors’ cluster plays an important role in the past, nowadays and in the future. Though many researchers have investigated into clusters and talked a lot about the benefits firms could share by clustering together, few of them explained directly why the competitors of the same trade cluster together for...

Shapes and dynamics from the time-dependent mean field

International Nuclear Information System (INIS)

Stevenson, P.D.; Goddard, P.M.; Rios, A.

2015-01-01

Explaining observed properties in terms of underlying shape degrees of freedom is a well-established prism with which to understand atomic nuclei. Self-consistent mean-field models provide one tool to understand nuclear shapes, and their link to other nuclear properties and observables. We present examples of how the time-dependent extension of the mean-field approach can be used in particular to shed light on nuclear shape properties, particularly looking at the giant resonances built on deformed nuclear ground states, and at dynamics in highly-deformed fission isomers. Example calculations are shown of 28 Si in the first case, and 240 Pu in the latter case

Socio-economic applications of finite state mean field games.

Science.gov (United States)

Gomes, Diogo; Velho, Roberto M; Wolfram, Marie-Therese

2014-11-13

In this paper, we present different applications of finite state mean field games to socio-economic sciences. Examples include paradigm shifts in the scientific community or consumer choice behaviour in the free market. The corresponding finite state mean field game models are hyperbolic systems of partial differential equations, for which we present and validate different numerical methods. We illustrate the behaviour of solutions with various numerical experiments, which show interesting phenomena such as shock formation. Hence, we conclude with an investigation of the shock structure in the case of two-state problems. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

AVLIS Production Plant work breakdown structure and Dictionary

International Nuclear Information System (INIS)

1984-01-01

The work breakdown structure has been prepared for the AVLIS Production Plant to define, organize, and identify the work efforts and is summarized in Fig. 1-1 for the top three project levels. The work breakdown structure itself is intended to be the primary organizational tool of the AVLIS Production Plant and is consistent with the overall AVLIS Program Work Breakdown Structure. It is designed to provide a framework for definition and accounting of all of the elements that are required for the eventual design, procurement, and construction of the AVLIS Production Plant. During the present phase of the AVLIS Project, the conceptual engineering phase, the work breakdown structure is intended to be the master structure and project organizer of documents, designs, and cost estimates. As the master project organizer, the key role of the work breakdown structure is to provide the mechanism for developing completeness in AVLIS cost estimates and design development of all hardware and systems. The work breakdown structure provides the framework for tracking, on a one-to-one basis, the component design criteria, systems requirements, design concepts, design drawings, performance projections, and conceptual cost estimates. It also serves as a vehicle for contract reporting. 12 figures, 2 tables

Laser-induced breakdown spectroscopy - An emerging chemical sensor technology for real-time field-portable, geochemical, mineralogical, and environmental applications

International Nuclear Information System (INIS)

Harmon, Russell S.; DeLucia, Frank C.; McManus, Catherine E.; McMillan, Nancy J.; Jenkins, Thomas F.; Walsh, Marianne E.; Miziolek, Andrzej

2006-01-01

Laser induced breakdown spectroscopy (LIBS) is a simple spark spectrochemical sensor technology in which a laser beam is directed at a sample surface to create a high-temperature microplasma and a detector used to collect the spectrum of light emission and record its intensity at specific wavelengths. LIBS is an emerging chemical sensor technology undergoing rapid advancement in instrumentation capability and in areas of application. Attributes of a LIBS sensor system include: (i) small size and weight; (ii) technologically mature, inherently rugged, and affordable components; (iii) real-time response; (iv) in situ analysis with no sample preparation required; (v) a high sensitivity to low atomic weight elements which are difficult to determine by other field-portable sensor techniques, and (vi) point sensing or standoff detection. Recent developments in broadband LIBS provide the capability for detection at very high resolution (0.1 nm) of all elements in any unknown target material because all chemical elements emit in the 200-980 nm spectral region. This progress portends a unique potential for the development of a rugged and reliable field-portable chemical sensor that has the potential to be utilized in variety of geochemical, mineralogical, and environmental applications

Self-consistent mean field forces in turbulent plasmas: Current and momentum relaxation

International Nuclear Information System (INIS)

Hegna, C.C.

1997-08-01

The properties of turbulent plasmas are described using the two-fluid equations. Under some modest assumptions, global constraints for the turbulent mean field forces that act on the ion and electron fluids are derived. These constraints imply a functional form for the parallel mean field forces in the Ohm's law and the momentum balance equation. These forms suggest that the fluctuations attempt to relax the plasma to a state where both the current and the bulk plasma momentum are aligned along the mean magnetic field with proportionality constants that are global constants. Observations of flow profile evolution during discrete dynamo activity in reversed field pinch experiments are interpreted

Analysis on X-band structure breakdown at GLCTA

International Nuclear Information System (INIS)

Suehara, T.; Sanuki, T.; Komamiya, S.; Higo, T.; Hayano, H.; Terunuma, N.; Saeki, T.; Watanabe, K.; Hayakawa, A.; Tsukada, Y.

2004-01-01

We have built a new monitoring system for accelerator structure breakdown in the X-band high-gradient test facility at KEK (GLCTA: Global Linear Collider Test Accelerator). An X-band test structure KX01 (made by KEK) has been processed at GLCTA and we have been collecting data for about 3 months using this breakdown monitoring system. We describe overview of the monitoring system and preliminary result of breakdown analysis of the structure. (author)

Breakdown Cause and Effect Analysis. Case Study

Science.gov (United States)

Biały, Witold; Ružbarský, Juraj

2018-06-01

Every company must ensure that the production process proceeds without interferences. Within this article, the author uses the term "interferences" in reference to unplanned stoppages caused by breakdowns. Unfortunately, usually due to machine operators' mistakes, machines break, which causes stoppages thus generating additional costs for the company. This article shows a cause and effect analysis of a breakdown in a production process. The FMEA as well as quality management tools: the Ishikawa diagram and Pareto chart were used for the analysis. Correction measures were presented which allowed for a significant reduction in the number of stoppages caused by breakdowns.

Charge-Dipole Acceleration of Polar Gas Molecules towards Charged Nanoparticles: Involvement in Powerful Charge-Induced Catalysis of Heterophase Chemical Reactions and Ball Lightning Phenomenon

Directory of Open Access Journals (Sweden)

Oleg Meshcheryakov

2010-01-01

Full Text Available In humid air, the substantial charge-dipole attraction and electrostatic acceleration of surrounding water vapour molecules towards charged combustible nanoparticles cause intense electrostatic hydration and preferential oxidation of these nanoparticles by electrostatically accelerated polar water vapour molecules rather than nonaccelerated nonpolar oxygen gas molecules. Intense electrostatic hydration of charged combustible nanoparticles converts the nanoparticle's oxide-based shells into the hydroxide-based electrolyte shells, transforming these nanoparticles into reductant/air core-shell nanobatteries, periodically short-circuited by intraparticle field and thermionic emission. Partially synchronized electron emission breakdowns within trillions of nanoparticles-nanobatteries turn a cloud of charged nanoparticles-nanobatteries into a powerful radiofrequency aerosol generator. Electrostatic oxidative hydration and charge-catalyzed oxidation of charged combustible nanoparticles also contribute to a self-oscillating thermocycling process of evolution and periodic autoignition of inflammable gases near to the nanoparticle's surface. The described effects might be of interest for the improvement of certain nanotechnological heterophase processes and to better understand ball lightning phenomenon.

Nuclear matter in relativistic mean field theory with isovector scalar meson.

Energy Technology Data Exchange (ETDEWEB)

Kubis, S.; Kutschera, M. [Institute of Nuclear Physics, Cracow (Poland)

1996-12-01

Relativistic mean field (RMF) theory of nuclear matter with the isovector scalar mean field corresponding to the {delta}-meson [a{sub 0}(980)] is studied. While the {delta}-meson field vanishes in symmetric nuclear matter, it can influence properties of asymmetric nuclear matter in neutron stars. The RMF contribution due to {delta}-field to the nuclear symmetry energy is negative. To fit the empirical value, E{sub s}{approx}30 MeV, a stronger {rho}-meson coupling is required than in absence of the {delta}-field. The energy per particle of neutron star matter is than larger at high densities than the one with no {delta}-field included. Also, the proton fraction of {beta}-stable matter increases. Splitting of proton and neutron effective masses due to the {delta}-field can affect transport properties of neutron star matter. (author). 4 refs, 6 figs.

Nuclear matter in relativistic mean field theory with isovector scalar meson

International Nuclear Information System (INIS)

Kubis, S.; Kutschera, M.

1996-12-01

Relativistic mean field (RMF) theory of nuclear matter with the isovector scalar mean field corresponding to the δ-meson [a 0 (980)] is studied. While the δ-meson field vanishes in symmetric nuclear matter, it can influence properties of asymmetric nuclear matter in neutron stars. The RMF contribution due to δ-field to the nuclear symmetry energy is negative. To fit the empirical value, E s ∼30 MeV, a stronger ρ-meson coupling is required than in absence of the δ-field. The energy per particle of neutron star matter is than larger at high densities than the one with no δ-field included. Also, the proton fraction of β-stable matter increases. Splitting of proton and neutron effective masses due to the δ-field can affect transport properties of neutron star matter. (author). 4 refs, 6 figs