Electron-positron pair production in inhomogeneous electromagnetic fields

International Nuclear Information System (INIS)

Kohlfürst, C.

2015-01-01

The process of electron-positron pair production is investigated within the phase-space Wigner formalism. The similarities between atomic ionization and pair production for homogeneous, but time-dependent linearly polarized electric fields are examined mainly in the regime of multiphoton absorption (field-dependent threshold, above-threshold pair production). Characteristic signatures in the particle spectra are identified (effective mass, channel closing). The non-monotonic dependence of the particle yield on the carrier frequency is discussed as well. The investigations are then extended to spatially inhomogeneous electric fields. New effects arising due to the spatial dependence of the effective mass are discussed in terms of a semi-classical interpretation. An increase in the normalized particle yield is found for various field configurations.Pair production in inhomogeneous electric and magnetic fields is also studied. The influence of a time-dependent spatially inhomogeneous magnetic field on the momentum spectrum and the particle yield is investigated. The Lorentz invariants are identified to be crucial in order to understand pair production by strong electric fields in the presence of strong magnetic fields. (author) [de

Regionally-varying and regionally-uniform electricity pricing policies compared across four usage categories

International Nuclear Information System (INIS)

Cho, Seong-Hoon; Kim, Taeyoung; Kim, Hyun Jae; Park, Kihyun; Roberts, Roland K.

2015-01-01

The objective of our research is to predict how electricity demand varies spatially between status quo regionally-uniform electricity pricing and hypothetical regionally-varying electricity pricing across usage categories. We summarize the empirical results of a case study of electricity demand in South Korea with three key findings and their related implications. First, the price elasticities of electricity demand differ across usage categories. Specifically, electricity demands for manufacturing and retail uses are price inelastic and close to unit elastic, respectively, while those for agricultural and residential uses are not statistically significant. This information is important in designing energy policy, because higher electricity prices could reduce electricity demands for manufacturing and retail uses, resulting in slower growth in those sectors. Second, spatial spillovers in electricity demand vary across uses. Understanding the spatial structure of electricity demand provides useful information to energy policy makers for anticipating changes in demand across regions via regionally-varying electricity pricing for different uses. Third, simulation results suggest that spatial variations among electricity demands by usage category under a regionally-varying electricity-pricing policy differ from those under a regionally-uniform electricity-pricing policy. Differences in spatial changes between the policies provide information for developing a realistic regionally-varying electricity-pricing policy according to usage category. - Highlights: • We compare regionally-varying and regionally-uniform electricity pricing policies. • We summarize empirical results of a case study of electricity demand in South Korea. • We confirm that spatial spillovers in electricity demands vary across different uses. • We find positive spatial spillovers in the manufacturing and residential sectors. • Our methods help policy makers evaluate regionally-varying pricing

Predicting electroporation of cells in an inhomogeneous electric field based on mathematical modeling and experimental CHO-cell permeabilization to propidium iodide determination.

Science.gov (United States)

Dermol, Janja; Miklavčič, Damijan

2014-12-01

High voltage electric pulses cause electroporation of the cell membrane. Consequently, flow of the molecules across the membrane increases. In our study we investigated possibility to predict the percentage of the electroporated cells in an inhomogeneous electric field on the basis of the experimental results obtained when cells were exposed to a homogeneous electric field. We compared and evaluated different mathematical models previously suggested by other authors for interpolation of the results (symmetric sigmoid, asymmetric sigmoid, hyperbolic tangent and Gompertz curve). We investigated the density of the cells and observed that it has the most significant effect on the electroporation of the cells while all four of the mathematical models yielded similar results. We were able to predict electroporation of cells exposed to an inhomogeneous electric field based on mathematical modeling and using mathematical formulations of electroporation probability obtained experimentally using exposure to the homogeneous field of the same density of cells. Models describing cell electroporation probability can be useful for development and presentation of treatment planning for electrochemotherapy and non-thermal irreversible electroporation. Copyright © 2014 Elsevier B.V. All rights reserved.

Modeling of Electricity Demand for Azerbaijan: Time-Varying Coefficient Cointegration Approach

Directory of Open Access Journals (Sweden)

Jeyhun I. Mikayilov

2017-11-01

Full Text Available Recent literature has shown that electricity demand elasticities may not be constant over time and this has investigated using time-varying estimation methods. As accurate modeling of electricity demand is very important in Azerbaijan, which is a transitional country facing significant change in its economic outlook, we analyze whether the response of electricity demand to income and price is varying over time in this economy. We employed the Time-Varying Coefficient cointegration approach, a cutting-edge time-varying estimation method. We find evidence that income elasticity demonstrates sizeable variation for the period of investigation ranging from 0.48% to 0.56%. The study has some useful policy implications related to the income and price aspects of the electricity consumption in Azerbaijan.

Electrical Programming of Soft Matter: Using Temporally Varying Electrical Inputs To Spatially Control Self Assembly.

Science.gov (United States)

Yan, Kun; Liu, Yi; Zhang, Jitao; Correa, Santiago O; Shang, Wu; Tsai, Cheng-Chieh; Bentley, William E; Shen, Jana; Scarcelli, Giuliano; Raub, Christopher B; Shi, Xiao-Wen; Payne, Gregory F

2018-02-12

The growing importance of hydrogels in translational medicine has stimulated the development of top-down fabrication methods, yet often these methods lack the capabilities to generate the complex matrix architectures observed in biology. Here we show that temporally varying electrical signals can cue a self-assembling polysaccharide to controllably form a hydrogel with complex internal patterns. Evidence from theory and experiment indicate that internal structure emerges through a subtle interplay between the electrical current that triggers self-assembly and the electrical potential (or electric field) that recruits and appears to orient the polysaccharide chains at the growing gel front. These studies demonstrate that short sequences (minutes) of low-power (∼1 V) electrical inputs can provide the program to guide self-assembly that yields hydrogels with stable, complex, and spatially varying structure and properties.

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.

On the penetration of solar wind inhomogeneities into the magnetosphere

International Nuclear Information System (INIS)

Maksimov, V.P.; Senatorov, V.N.

1980-01-01

Laboratory experiments were used as a basis to study the process of interaction between solar wind inhomogeneities and the Earth's magnetosphere. The given inhomogeneity represents a lump of plasma characterized by an increased concentration of particles (nsub(e) approximately 20-30 cm -3 ), a discrete form (characteristic dimensions of the lump are inferior to the magnetosphere diameter) and the velocity v approximately 350 km/s. It is shown that there is the possibility of penetration of solar wind inhomogeneities inside the Earth's magnetosphere because of the appearance in the inhomogeneity of an electric field of transverse polarization. The said process is a possible mechanism of the formation of the magnetopshere entrance layer

Inhomogeneous Markov Models for Describing Driving Patterns

DEFF Research Database (Denmark)

Iversen, Emil Banning; Møller, Jan K.; Morales, Juan Miguel

2017-01-01

. Specifically, an inhomogeneous Markov model that captures the diurnal variation in the use of a vehicle is presented. The model is defined by the time-varying probabilities of starting and ending a trip, and is justified due to the uncertainty associated with the use of the vehicle. The model is fitted to data...... collected from the actual utilization of a vehicle. Inhomogeneous Markov models imply a large number of parameters. The number of parameters in the proposed model is reduced using B-splines....

Inhomogeneous Markov Models for Describing Driving Patterns

DEFF Research Database (Denmark)

Iversen, Jan Emil Banning; Møller, Jan Kloppenborg; Morales González, Juan Miguel

. Specically, an inhomogeneous Markov model that captures the diurnal variation in the use of a vehicle is presented. The model is dened by the time-varying probabilities of starting and ending a trip and is justied due to the uncertainty associated with the use of the vehicle. The model is tted to data...... collected from the actual utilization of a vehicle. Inhomogeneous Markov models imply a large number of parameters. The number of parameters in the proposed model is reduced using B-splines....

Characterization technique for inhomogeneous 4H-SiC Schottky contacts: A practical model for high temperature behavior

Science.gov (United States)

Brezeanu, G.; Pristavu, G.; Draghici, F.; Badila, M.; Pascu, R.

2017-08-01

In this paper, a characterization technique for 4H-SiC Schottky diodes with varying levels of metal-semiconductor contact inhomogeneity is proposed. A macro-model, suitable for high-temperature evaluation of SiC Schottky contacts, with discrete barrier height non-uniformity, is introduced in order to determine the temperature interval and bias domain where electrical behavior of the devices can be described by the thermionic emission theory (has a quasi-ideal performance). A minimal set of parameters, the effective barrier height and peff, the non-uniformity factor, is associated. Model-extracted parameters are discussed in comparison with literature-reported results based on existing inhomogeneity approaches, in terms of complexity and physical relevance. Special consideration was given to models based on a Gaussian distribution of barrier heights on the contact surface. The proposed methodology is validated by electrical characterization of nickel silicide Schottky contacts on silicon carbide (4H-SiC), where a discrete barrier distribution can be considered. The same method is applied to inhomogeneous Pt/4H-SiC contacts. The forward characteristics measured at different temperatures are accurately reproduced using this inhomogeneous barrier model. A quasi-ideal behavior is identified for intervals spanning 200 °C for all measured Schottky samples, with Ni and Pt contact metals. A predictable exponential current-voltage variation over at least 2 orders of magnitude is also proven, with a stable barrier height and effective area for temperatures up to 400 °C. This application-oriented characterization technique is confirmed by using model parameters to fit a SiC-Schottky high temperature sensor's response.

Consumer responses to time varying prices for electricity

International Nuclear Information System (INIS)

Thorsnes, Paul; Williams, John; Lawson, Rob

2012-01-01

We report new experimental evidence of the household response to weekday differentials in peak and off-peak electricity prices. The data come from Auckland, New Zealand, where peak residential electricity consumption occurs in winter for heating. Peak/off-peak price differentials ranged over four randomly selected groups from 1.0 to 3.5. On average, there was no response except in winter. In winter, participant households reduced electricity consumption by at least 10%, took advantage of lower off-peak prices but did not respond to the peak price differentials. Response varied with house and household size, time spent away from home, and whether water was heated with electricity. - Highlights: ► Seasonal effects in winter. ► High conservation effect from information. ► Higher peak prices no effect on peak use. ► Low off-peak prices encourage less conservation off-peak.

Electricity Futures Prices : Time Varying Sensitivity to Fundamentals

NARCIS (Netherlands)

S-E. Fleten (Stein-Erik); R. Huisman (Ronald); M. Kilic (Mehtap); H.P.G. Pennings (Enrico); S. Westgaard (Sjur)

2014-01-01

textabstractThis paper provides insight in the time-varying relation between electricity futures prices and fundamentals in the form of prices of contracts for fossil fuels. As supply curves are not constant and different producers have different marginal costs of production, we argue that the

Reduced dielectric response in spatially varying electric fields

DEFF Research Database (Denmark)

Hansen, Jesper Schmidt

2015-01-01

relations between the flux and the gradient of the polarization. Comparison between the theory and molecular dynamics simulations confirms this effect. The effect is significant for small length scale electric field variations and the inclusion of the flux is thus important in nanoscale modeling......In this paper, the dynamical equation for polarization is derived. From this the dielectric response to a spatially varying electric field is analyzed showing a reduced response due to flux of polarization in the material. This flux is modeled as a diffusive process through linear constitutive...

Defect-driven inhomogeneities in Ni /4H-SiC Schottky barriers

Science.gov (United States)

Tumakha, S.; Ewing, D. J.; Porter, L. M.; Wahab, Q.; Ma, X.; Sudharshan, T. S.; Brillson, L. J.

2005-12-01

Nanoscale depth-resolved cathodoluminescence spectroscopy (DRCLS) of Ni diode arrays on 4H-SiC epitaxial wafers reveals a striking correspondence between deep level defects and electrical transport measurements on a diode-by-diode basis. Current-voltage measurements display both ideal and nonideal diode characteristics due to multiple barriers within individual contacts. Near-interface DRCLS demonstrates the presence of three discrete midgap defect levels with 2.2, 2.45, and 2.65eV emission energies whose concentrations vary on a submicron scale among and within individual diodes, correlating with barrier inhomogeneity. These results also suggest that SiC native defect levels can account for the maximum range of n-type barrier heights.

Dependence of inhomogeneous vibrational linewidth broadening on attractive forces from local liquid number densities

International Nuclear Information System (INIS)

George, S.M.; Harris, C.B.

1982-01-01

The dependence of inhomogeneous vibrational linewidth broadening on attractive forces form slowly varying local liquid number densities is examined. The recently developed Schweizer--Chandler theory of vibrational dephasing is used to compute absolute inhomogeneous broadening linewidths. The computed linewidths are compared to measured inhomogeneous broadening linewidths determined using picosecond vibrational dephasing experiments. There is a similarity between correlations of the Schweizer--Chandler and George--Auweter--Harris predicted inhomogeneous broadening linewidths and the measured inhomogeneous broadening linewidths. For the methyl stretches under investigation, this correspondence suggests that the width of the number density distribution in the liquid determines the relative inhomogeneous broadening magnitudes

Assessment of inhomogeneous ELF magnetic field exposures

International Nuclear Information System (INIS)

Leitgeb, N.; Cech, R.; Schroettner, J.

2008-01-01

In daily life as well as at workplaces, exposures to inhomogeneous magnetic fields become very frequent. This makes easily applicable compliance assessment methods increasingly important. Reference levels have been defined linking basic restrictions to levels of homogeneous fields at worst-case exposure conditions. If reference levels are met, compliance with basic restrictions can be assumed. If not, further investigations could still prove compliance. Because of the lower induction efficiency, inhomogeneous magnetic fields such as from electric appliances could be allowed exceeding reference levels. To easily assess inhomogeneous magnetic fields, a quick and flexible multi-step assessment procedure is proposed. On the basis of simulations with numerical, anatomical human models reference factors were calculated elevating reference levels to link hot-spot values measured at source surfaces to basic limits and allowing accounting for different source distance, size, orientation and position. Compliance rules are proposed minimising assessment efforts. (authors)

Traveltime approximations for inhomogeneous HTI media

KAUST Repository

Alkhalifah, Tariq Ali

2011-01-01

Traveltimes information is convenient for parameter estimation especially if the medium is described by an anisotropic set of parameters. This is especially true if we could relate traveltimes analytically to these medium parameters, which is generally hard to do in inhomogeneous media. As a result, I develop traveltimes approximations for horizontaly transversely isotropic (HTI) media as simplified and even linear functions of the anisotropic parameters. This is accomplished by perturbing the solution of the HTI eikonal equation with respect to η and the azimuthal symmetry direction (usually used to describe the fracture direction) from a generally inhomogeneous elliptically anisotropic background medium. The resulting approximations can provide accurate analytical description of the traveltime in a homogenous background compared to other published moveout equations out there. These equations will allow us to readily extend the inhomogenous background elliptical anisotropic model to an HTI with a variable, but smoothly varying, η and horizontal symmetry direction values. © 2011 Society of Exploration Geophysicists.

Microstructural inhomogeneity of electrical conductivity in subcutaneous fat tissue.

Directory of Open Access Journals (Sweden)

Ilja L Kruglikov

Full Text Available Microscopic peculiarities stemming from a temperature increase in subcutaneous adipose tissue (sWAT after applying a radio-frequency (RF current, must be strongly dependent on the type of sWAT. This effect is connected with different electrical conductivities of pathways inside (triglycerides in adipocytes and outside (extra-cellular matrix the cells and to the different weighting of these pathways in hypertrophic and hyperplastic types of sWAT. The application of the RF current to hypertrophic sWAT, which normally has a strongly developed extracellular matrix with high concentrations of hyaluronan and collagen in a peri-cellular space of adipocytes, can produce, micro-structurally, a highly inhomogeneous temperature distribution, characterized by strong temperature gradients between the peri-cellular sheath of the extra-cellular matrix around the hypertrophic adipocytes and their volumes. In addition to normal temperature effects, which are generally considered in body contouring, these temperature gradients can produce thermo-mechanical stresses on the cells' surfaces. Whereas these stresses are relatively small under normal conditions and cannot cause any direct fracturing or damage of the cell structure, these stresses can, under some supportive conditions, be theoretically increased by several orders of magnitude, causing the thermo-mechanical cell damage. This effect cannot be realized in sWAT of normal or hyperplastic types where the peri-cellular structures are under-developed. It is concluded that the results of RF application in body contouring procedures must be strongly dependent on the morphological structure of sWAT.

Multiscale response of ionic systems to a spatially varying electric field

DEFF Research Database (Denmark)

Hansen, Jesper Schmidt

2017-01-01

In this paper the response of ionic systems subjected to a spatially varying electric field is studied. Following the Nernst-Planck equation, two forces driving the mass flux are present, namely, the concentration gradient and the electric potential gradient. The mass flux due to the concentratio...

Attraction and repulsion of spiral waves by inhomogeneity of conduction anisotropy--a model of spiral wave interaction with electrical remodeling of heart tissue.

Science.gov (United States)

Kuklik, Pawel; Sanders, Prashanthan; Szumowski, Lukasz; Żebrowski, Jan J

2013-01-01

Various forms of heart disease are associated with remodeling of the heart muscle, which results in a perturbation of cell-to-cell electrical coupling. These perturbations may alter the trajectory of spiral wave drift in the heart muscle. We investigate the effect of spatially extended inhomogeneity of transverse cell coupling on the spiral wave trajectory using a simple active media model. The spiral wave was either attracted or repelled from the center of inhomogeneity as a function of cell excitability and gradient of the cell coupling. High levels of excitability resulted in an attraction of the wave to the center of inhomogeneity, whereas low levels resulted in an escape and termination of the spiral wave. The spiral wave drift velocity was related to the gradient of the coupling and the initial position of the wave. In a diseased heart, a region of altered transverse coupling corresponds with local gap junction remodeling that may be responsible for stabilization-destabilization of spiral waves and hence reflect potentially important targets in the treatment of heart arrhythmias.

Forces and energy dissipation in inhomogeneous non-equilibrium superconductors

International Nuclear Information System (INIS)

Poluehktov, Yu.M.; Slezov, V.V.

1987-01-01

The phenomenological theory of volume forces and dissipation processes in inhomogeneous non-equilibrium superconductors near temperature transition from the normal to superconducting state is constructed. The approach is based on application of dynamic equations of superconductivity formulated on the basis of the Lagrangian formalism. These equations are generalized the Ginzburg-Landau theory in the nonstationary non-equilibrium case for ''foul'' superconductors. The value estimations of volume forces arising in inhomogeneities during relaxation of an order parameter and when the electrical field is penetrated into the superconductor, are given

Critical-temperature inhomogeneities and resistivity rounding in copper oxide superconductors

International Nuclear Information System (INIS)

Maza, J.; Vidal, F.

1991-01-01

By using effective-medium approaches, we obtain the onset of the electrical-resistivity rounding, above the normal-superconducting transition, associated with inhomogeneities of the mean-field critical temperature T c0 at scales larger than the superconducting correlation length. These results are compared with available data in single-crystal and single-phase (to within 4%) polycrystalline YBa 2 Cu 3 O 7-δ samples. This comparison shows that the measured resistivity rounding cannot be explained by these types of local T c0 inhomogeneities. Complementarily, our calculations allow us to check some proposals on T c0 inhomogeneities associated with local sample strains or oxygen-content variations. The interplay between T c0 inhomogeneities and superconducting order-parameter fluctuations (SCOPF) leads to the conclusion that in the mean-field-like region (MFR) above the superconducting transition, the T c0 inhomogeneity contribution to the measured resistivity rounding in high-quality (single-phase) cuprate oxide superconductors is negligible. In contrast, our analysis confirms that in the MFR these effects may be explained quantitatively on the grounds of the Lawrence-Doniach theory for SCOPF

Diffusion MRI: Mitigation of Magnetic Field Inhomogeneities

Czech Academy of Sciences Publication Activity Database

Marcon, P.; Bartušek, Karel; Dokoupil, Zdeněk; Gescheidtová, E.

2012-01-01

Roč. 12, č. 5 (2012), s. 205-212 ISSN 1335-8871 R&D Projects: GA MŠk ED0017/01/01; GA ČR GAP102/11/0318; GA ČR GAP102/12/1104 Institutional support: RVO:68081731 Keywords : correction * diffusion * inhomogeneity * eddy currents * magnetic resonance Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.233, year: 2012

X-ray emission from a nanosecond-pulse discharge in an inhomogeneous electric field at atmospheric pressure

International Nuclear Information System (INIS)

Zhang Cheng; Shao Tao; Ren Chengyan; Zhang Dongdong; Tarasenko, Victor; Kostyrya, Igor D.; Ma Hao; Yan Ping

2012-01-01

This paper describes experimental studies of the dependence of the X-ray intensity on the anode material in nanosecond high-voltage discharges. The discharges were generated by two nanosecond-pulse generators in atmospheric air with a highly inhomogeneous electric field by a tube-plate gap. The output pulse of the first generator (repetitive pulse generator) has a rise time of about 15 ns and a full width at half maximum of 30–40 ns. The output of the second generator (single pulse generator) has a rise time of about 0.3 ns and a full width at half maximum of 1 ns. The electrical characteristics and the X-ray emission of nanosecond-pulse discharge in atmospheric air are studied by the measurement of voltage-current waveforms, discharge images, X-ray count and dose. Our experimental results showed that the anode material rarely affects electrical characteristics, but it can significantly affect the X-ray density. Comparing the density of X-rays, it was shown that the highest x-rays density occurred in the diffuse discharge in repetitive pulse mode, then the spark discharge with a small air gap, and then the corona discharge with a large air gap, in which the X-ray density was the lowest. Therefore, it could be confirmed that the bremsstrahlung at the anode contributes to the X-ray emission from nanosecond-pulse discharges.

Parametric trapping of electromagnetic waves in an inhomogeneous plasma

International Nuclear Information System (INIS)

Silin, V.P.; Starodub, A.N.

1977-01-01

Considered is parametric instability in an inhomogeneous plasma at which a pumping wave is transformed to an electromagnetic wave and aperiodically in-time-growing disturbances. It is shown that after achievement of some boundary pumping value by electric field intensity an absolute parametric instability evolution becomes possible. In-time growing plasma disturbances are localized near electric field extremums of a pumping wave. Such localization areas are small as compared to characteristic size of pumping inhomogeneity in a plasma. The secondary electromagnetic waves stay within the localization areas and, therefore, are not scattered by a plasma. As following from this it has been established, that due to parametric instability electromagnetic radiation trapping by a plasma occurs. Such a trapping is considerably connected with a spatial structure of a pumping field and it cannot arise within the field of a running wave in the theoretical model considered. However parametric trapping turns out to be possible even with very small reflection coefficients

Peeling stress analysis for an inhomogeneous high-Tc superconductor with a discontinuous interface at the substrate

International Nuclear Information System (INIS)

Gao Zhiwen; Lee, Kang Yong; Zhou Youhe

2011-01-01

Research highlights: → The thermal stress generated in the inhomogeneous HTS is larger on a SiTiO 3 substrate than on a MgO substrate. → The maximum thermal stresses, i.e., the peeling stresses, occur near the bottom corner of the inhomogeneous HTS and may induce fracture behavior at the bi-material interface. → The inhomogeneous HTS cools at a slower pace than the homogeneous HTS from the room temperature to the operating temperature. → The magnitude of the peeling stress for a homogeneous HTS is larger than that for an inhomogeneous HTS. - Abstract: This paper presents an analysis of a superconductor-substrate system to calculate the peeling stress of a high temperature superconductor (HTS) when the temperature decreases from ambient to operating conditions (cryogenic temperatures). Firstly, the values for the material properties of the inhomogeneous high temperature superconductor (HTS) were obtained by fitting a second order polynomial to the experimental data. It is assumed that the material properties of the inhomogeneous HTS vary with varying height coordinate and temperature. Then, through the proposed graded finite element method, the coupled thermo-mechanical equations were solved numerically. The numerical results show that the thermal stress generated in the inhomogeneous HTS is larger on a SiTiO 3 substrate than on a MgO substrate. The maximum thermal stresses, i.e., the peeling stresses, occur near the bottom corner of the inhomogeneous HTS and may induce fracture behavior at the bi-material interface. The inhomogeneous HTS cools at a slower pace than the homogeneous HTS from the room temperature to the operating temperature. It is also shown that the magnitude of the peeling stress for a homogeneous HTS is larger than that for an inhomogeneous HTS. It is intended that the model presented here be useful to researchers who are interested in the mechanical properties of an inhomogeneous HTS.

Barrier height inhomogeneity in electrical transport characteristics of InGaN/GaN heterostructure interfaces

Energy Technology Data Exchange (ETDEWEB)

Roul, Basanta [Materials Research Centre, Indian Institute of Science, Bangalore 560012 (India); Central Research Laboratory, Bharat Electronics, Bangalore 560013 (India); Mukundan, Shruti; Chandan, Greeshma; Mohan, Lokesh; Krupanidhi, S. B., E-mail: sbk@mrc.iisc.ernet.in [Materials Research Centre, Indian Institute of Science, Bangalore 560012 (India)

2015-03-15

We have grown InGaN/GaN heterostructures using plasma-assisted molecular beam epitaxy and studied the temperature dependent electrical transport characteristics. The barrier height (φ{sub b}) and the ideally factor (η) estimated using thermionic emission model were found to be temperature dependent. The conventional Richardson plot of ln(J{sub s}/T{sup 2}) versus 1/kT showed two temperature regions (region-I: 400–500 K and region-II: 200–350 K) and it provides Richardson constants (A{sup ∗}) which are much lower than the theoretical value of GaN. The observed variation in the barrier height and the presence of two temperature regions were attributed to spatial barrier inhomogeneities at the heterojunction interface and was explained by assuming a double Gaussian distribution of barrier heights with mean barrier height values 1.61 and 1.21 eV with standard deviation (σ{sub s}{sup 2}) of 0.044 and 0.022 V, respectively. The modified Richardson plot of ln(J{sub s}/T{sup 2}) − (q{sup 2}σ{sub s}{sup 2}/2k{sup 2}T{sup 2}) versus 1/kT for two temperature regions gave mean barrier height values as 1.61 eV and 1.22 eV with Richardson constants (A{sup ∗}) values 25.5 Acm{sup −2}K{sup −2} and 43.9 Acm{sup −2}K{sup −2}, respectively, which are very close to the theoretical value. The observed barrier height inhomogeneities were interpreted on the basis of the existence of a double Gaussian distribution of barrier heights at the interface.

Propagation of acoustic waves in a one-dimensional macroscopically inhomogeneous poroelastic material.

Science.gov (United States)

Gautier, G; Kelders, L; Groby, J P; Dazel, O; De Ryck, L; Leclaire, P

2011-09-01

Wave propagation in macroscopically inhomogeneous porous materials has received much attention in recent years. The wave equation, derived from the alternative formulation of Biot's theory of 1962, was reduced and solved recently in the case of rigid frame inhomogeneous porous materials. This paper focuses on the solution of the full wave equation in which the acoustic and the elastic properties of the poroelastic material vary in one-dimension. The reflection coefficient of a one-dimensional macroscopically inhomogeneous porous material on a rigid backing is obtained numerically using the state vector (or the so-called Stroh) formalism and Peano series. This coefficient can then be used to straightforwardly calculate the scattered field. To validate the method of resolution, results obtained by the present method are compared to those calculated by the classical transfer matrix method at both normal and oblique incidence and to experimental measurements at normal incidence for a known two-layers porous material, considered as a single inhomogeneous layer. Finally, discussion about the absorption coefficient for various inhomogeneity profiles gives further perspectives. © 2011 Acoustical Society of America

Utilizing pulsed laser deposition lateral inhomogeneity as a tool in combinatorial material science.

Science.gov (United States)

Keller, David A; Ginsburg, Adam; Barad, Hannah-Noa; Shimanovich, Klimentiy; Bouhadana, Yaniv; Rosh-Hodesh, Eli; Takeuchi, Ichiro; Aviv, Hagit; Tischler, Yaakov R; Anderson, Assaf Y; Zaban, Arie

2015-04-13

Pulsed laser deposition (PLD) is widely used in combinatorial material science, as it enables rapid fabrication of different composite materials. Nevertheless, this method was usually limited to small substrates, since PLD deposition on large substrate areas results in severe lateral inhomogeneity. A few technical solutions for this problem have been suggested, including the use of different designs of masks, which were meant to prevent inhomogeneity in the thickness, density, and oxidation state of a layer, while only the composition is allowed to be changed. In this study, a possible way to take advantage of the large scale deposition inhomogeneity is demonstrated, choosing an iron oxide PLD-deposited library with continuous compositional spread (CCS) as a model system. An Fe₂O₃-Nb₂O₅ library was fabricated using PLD, without any mask between the targets and the substrate. The library was measured using high-throughput scanners for electrical, structural, and optical properties. A decrease in electrical resistivity that is several orders of magnitude lower than pure α-Fe₂O₃ was achieved at ∼20% Nb-O (measured at 47 and 267 °C) but only at points that are distanced from the center of the PLD plasma plume. Using hierarchical clustering analysis, we show that the PLD inhomogeneity can be used as an additional degree of freedom, helping, in this case, to achieve iron oxide with much lower resistivity.

Ray tracing for inhomogeneous media applied to the human eye

Science.gov (United States)

Diaz-Gonzalez, G.; Iturbe-Castillo, M. D.; Juarez-Salazar, R.

2017-08-01

Inhomogeneous or gradient index media exhibit a refractive index varying with the position. This kind of media are very interesting because they can be found in both synthetic as well as real life optical devices such as the human lens. In this work we present the development of a computational tool for ray tracing in refractive optical systems. Particularly, the human eye is used as the optical system under study. An inhomogeneous medium with similar characteristics to the human lens is introduced and modeled by the so-called slices method. The useful of our proposal is illustrated by several graphical results.

Determination of critical exponents of inhomogeneous Gd films

Energy Technology Data Exchange (ETDEWEB)

Rosales-Rivera, A., E-mail: arosalesr@unal.edu.co [Laboratorio de Magnetismo y Materiales Avanzados, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia); Salazar, N.A. [Laboratorio de Magnetismo y Materiales Avanzados, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia); Hovorka, O.; Idigoras, O.; Berger, A. [CIC nanoGUNE Consolider, Tolosa Hiribidea 76, E-20018 Donostia-San Sebastian (Spain)

2012-08-15

The role of inhomogeneity on the critical behavior is studied for non-epitaxial Gd films. For this purpose, the film inhomogeneity was varied experimentally by annealing otherwise identical samples at different temperatures T{sub AN}=200, 400, and 500 Degree-Sign C. Vibrating sample magnetometry (VSM) was used for magnetization M vs. T measurements at different external fields H. A method based upon the linear superposition of different sample parts having different Curie temperatures T{sub C} was used to extract the critical exponents and the intrinsic distribution of Curie temperatures. We found that this method allows extracting reliable values of the critical exponents for all annealing temperatures, which enabled us to study the effects of disorder onto the universality class of Gd films.

Determination of critical exponents of inhomogeneous Gd films

International Nuclear Information System (INIS)

Rosales-Rivera, A.; Salazar, N.A.; Hovorka, O.; Idigoras, O.; Berger, A.

2012-01-01

The role of inhomogeneity on the critical behavior is studied for non-epitaxial Gd films. For this purpose, the film inhomogeneity was varied experimentally by annealing otherwise identical samples at different temperatures T AN =200, 400, and 500 °C. Vibrating sample magnetometry (VSM) was used for magnetization M vs. T measurements at different external fields H. A method based upon the linear superposition of different sample parts having different Curie temperatures T C was used to extract the critical exponents and the intrinsic distribution of Curie temperatures. We found that this method allows extracting reliable values of the critical exponents for all annealing temperatures, which enabled us to study the effects of disorder onto the universality class of Gd films.

Motoneuron membrane potentials follow a time inhomogeneous jump diffusion process

DEFF Research Database (Denmark)

Jahn, Patrick; Berg, Rune W; Hounsgaard, Jørn

2011-01-01

models can only be applied over short time windows. However, experimental data show varying time constants, state dependent noise, a graded firing threshold and time-inhomogeneous input. In the present study we build a jump diffusion model that incorporates these features, and introduce a firing...

Uncovering edge states and electrical inhomogeneity in MoS2 field-effect transistors.

Science.gov (United States)

Wu, Di; Li, Xiao; Luan, Lan; Wu, Xiaoyu; Li, Wei; Yogeesh, Maruthi N; Ghosh, Rudresh; Chu, Zhaodong; Akinwande, Deji; Niu, Qian; Lai, Keji

2016-08-02

The understanding of various types of disorders in atomically thin transition metal dichalcogenides (TMDs), including dangling bonds at the edges, chalcogen deficiencies in the bulk, and charges in the substrate, is of fundamental importance for TMD applications in electronics and photonics. Because of the imperfections, electrons moving on these 2D crystals experience a spatially nonuniform Coulomb environment, whose effect on the charge transport has not been microscopically studied. Here, we report the mesoscopic conductance mapping in monolayer and few-layer MoS2 field-effect transistors by microwave impedance microscopy (MIM). The spatial evolution of the insulator-to-metal transition is clearly resolved. Interestingly, as the transistors are gradually turned on, electrical conduction emerges initially at the edges before appearing in the bulk of MoS2 flakes, which can be explained by our first-principles calculations. The results unambiguously confirm that the contribution of edge states to the channel conductance is significant under the threshold voltage but negligible once the bulk of the TMD device becomes conductive. Strong conductance inhomogeneity, which is associated with the fluctuations of disorder potential in the 2D sheets, is also observed in the MIM images, providing a guideline for future improvement of the device performance.

Alfvén wave interaction with inhomogeneous plasmas: acceleration and energy cascade towards small-scales

Directory of Open Access Journals (Sweden)

V. Génot

2004-06-01

Full Text Available Investigating the process of electron acceleration in auroral regions, we present a study of the temporal evolution of the interaction of Alfvén waves (AW with a plasma inhomogeneous in a direction transverse to the static magnetic field. This type of inhomogeneity is typical of the density cavities extended along the magnetic field in auroral acceleration regions. We use self-consistent Particle In Cell (PIC simulations which are able to reproduce the full nonlinear evolution of the electromagnetic waves, as well as the trajectories of ions and electrons in phase space. Physical processes are studied down to the ion Larmor radius and electron skin depth scales. We show that the AW propagation on sharp density gradients leads to the formation of a significant parallel (to the magnetic field electric field (E-field. It results from an electric charge separation generated on the density gradients by the polarization drift associated with the time varying AW E-field. Its amplitude may reach a few percents of the AW E-field. This parallel component accelerates electrons up to keV energies over a distance of a few hundred Debye lengths, and induces the formation of electron beams. These beams trigger electrostatic plasma instabilities which evolve toward the formation of nonlinear electrostatic structures (identified as electron holes and double layers. When the electrostatic turbulence is fully developed we show that it reduces the further wave/particle exchange. This sequence of mechanisms is analyzed with the program WHAMP, to identify the instabilities at work and wavelet analysis techniques are used to characterize the regime of energy conversions (from electromagnetic to electrostatic structures, from large to small length scales. This study elucidates a possible scenario to account for the particle acceleration and the wave dissipation in inhomogeneous plasmas. It would consist of successive phases of acceleration along the magnetic field

Validation of Micro-Meso Electrical Relations for Laminates with Varying Anisotropy

KAUST Repository

Selvakumaran, Lakshmi

2015-08-01

For electrical impedance tomography (EIT) to be useful in monitoring transverse cracks in composites, it is imperative to establish the relation between conductivity and cracking density. Micro to meso scale homogenization has been developed for classical carbon fiber reinforced polymer (CFRP) laminate which provides such a relationship. However, we have shown in previous studies that the detectability of transverse cracks in such CFRP, which are characterized by very anisotropic electrical properties, is poor. Then, it is better to lower the electrical anisotropy, which can be achieved by various technologies including doping the polymeric resin by conductive nanoparticles. However, the validity of mesoscale homogenization for laminates with such low anisotropy has not been tested before. Here, we show that the mesoscale damage indicator is intrinsic for composites with varying anisotropy.

Electrical impedance spectroscopy (EIS)-based evaluation of biological tissue phantoms to study multifrequency electrical impedance tomography (Mf-EIT) systems

KAUST Repository

Bera, Tushar Kanti

2016-03-18

Abstract: Electrical impedance tomography (EIT) phantoms are essential for the calibration, comparison and evaluation of the EIT systems. In EIT, the practical phantoms are typically developed based on inhomogeneities surrounded by a homogeneous background to simulate a suitable conductivity contrast. In multifrequency EIT (Mf-EIT) evaluation, the phantoms must be developed with the materials which have recognizable or distinguishable impedance variations over a wide range of frequencies. In this direction the impedance responses of the saline solution (background) and a number vegetable and fruit tissues (inhomogeneities) are studied with electrical impedance spectroscopy (EIS) and the frequency responses of bioelectrical impedance and conductivity are analyzed. A number of practical phantoms with different tissue inhomogeneities and different inhomogeneity configurations are developed and the multifrequency impedance imaging is studied with the Mf-EIT system to evaluate the phantoms. The conductivity of the vegetable inhomogeneities reconstructed from the EIT imaging is compared with the conductivity values obtained from the EIS studies. Experimental results obtained from multifrequency EIT reconstruction demonstrate that the electrical impedance of all the biological tissues inhomogenity decreases with frequency. The potato tissue phantom produces better impedance image in high frequency ranges compared to the cucumber phantom, because the cucumber impedance at high frequency becomes lesser than that of the potato at the same frequency range. Graphical Abstract: [Figure not available: see fulltext.] © 2016 The Visualization Society of Japan

Pair creation in inhomogeneous fields from worldline instantons

International Nuclear Information System (INIS)

Dunne, Gerald V.; Schubert, Christian

2006-01-01

We show how to do semiclassical nonperturbative computations within the worldline approach to quantum field theory using ''worldline instantons''. These worldline instantons are classical solutions to the Euclidean worldline loop equations of motion, and are closed spacetime loops parametrized by the proper-time. Specifically, we compute the imaginary part of the one loop effective action in scalar and spinor QED using worldline instantons, for a wide class of inhomogeneous electric field backgrounds

Ion-optical properties of Wien's filters with inhomogeneous fields

International Nuclear Information System (INIS)

Golikov, Yu.K.; Matyshev, A.A.; Solov'ev, K.V.

1991-01-01

Common conditions of beam stigmatic focusing in the Wien filters with direct axial trajectory in arbitrary two-dimensional inhomogeneous crossed electrical magnetic fields are obtained. Coefficients for geometrical aberrations of the second order of the crossed field system, characterized by stigmatic focusing properties, are found. Possibility of synthesis on the basis of the developed field system theory with required ion-optical properties is shown

Studies of small-scale plasma inhomogeneities in the cusp ionosphere using sounding rocket data

Science.gov (United States)

Chernyshov, Alexander A.; Spicher, Andres; Ilyasov, Askar A.; Miloch, Wojciech J.; Clausen, Lasse B. N.; Saito, Yoshifumi; Jin, Yaqi; Moen, Jøran I.

2018-04-01

Microprocesses associated with plasma inhomogeneities are studied on the basis of data from the Investigation of Cusp Irregularities (ICI-3) sounding rocket. The ICI-3 rocket is devoted to investigating a reverse flow event in the cusp F region ionosphere. By numerical stability analysis, it is demonstrated that inhomogeneous-energy-density-driven (IEDD) instability can be a mechanism for the excitation of small-scale plasma inhomogeneities. The Local Intermittency Measure (LIM) method also applied the rocket data to analyze irregular structures of the electric field during rocket flight in the cusp. A qualitative agreement between high values of the growth rates of the IEDD instability and the regions with enhanced LIM is observed. This suggests that IEDD instability is connected to turbulent non-Gaussian processes.

Barrier inhomogeneities limited current and 1/f noise transport in GaN based nanoscale Schottky barrier diodes

Science.gov (United States)

Kumar, Ashutosh; Heilmann, M.; Latzel, Michael; Kapoor, Raman; Sharma, Intu; Göbelt, M.; Christiansen, Silke H.; Kumar, Vikram; Singh, Rajendra

2016-01-01

The electrical behaviour of Schottky barrier diodes realized on vertically standing individual GaN nanorods and array of nanorods is investigated. The Schottky diodes on individual nanorod show highest barrier height in comparison with large area diodes on nanorods array and epitaxial film which is in contrast with previously published work. The discrepancy between the electrical behaviour of nanoscale Schottky diodes and large area diodes is explained using cathodoluminescence measurements, surface potential analysis using Kelvin probe force microscopy and 1ow frequency noise measurements. The noise measurements on large area diodes on nanorods array and epitaxial film suggest the presence of barrier inhomogeneities at the metal/semiconductor interface which deviate the noise spectra from Lorentzian to 1/f type. These barrier inhomogeneities in large area diodes resulted in reduced barrier height whereas due to the limited role of barrier inhomogeneities in individual nanorod based Schottky diode, a higher barrier height is obtained. PMID:27282258

Comparison study of different head model structures with homogeneous/inhomogeneous conductivity

International Nuclear Information System (INIS)

Wen, P.; Li, Y.

2001-01-01

Most of the human head models used in dipole localisation research, which have been reported in the literature to date, assume a simplified cranial structure wherein the head is modelled as a set of distinct homogenous tissue compartments. The inherent inhomogeneity of the tissues has so far been ignored in these models due to the difficulties involved in obtaining the conductivity characteristics with sufficiently high enough spatial resolution throughout the head. A technique for developing an inhomogeneous head model based on the generation of pseudo-conductivity values from the existing but sparse conductivity values is proposed in this paper. Comparative studies are conducted on different model structures and different mechanisms for generating the pseudo conductivities. An evaluation of the results of these studies as reported in this paper, shows that contrary to current simplifying assumptions, tissue inhomogeneity has a major influence on the computation of electrical potential distributions in the head. Brain electrical activity is spatially distributed in three dimensions in the head and evolves with time. Electroencephalography (EEG) is a widely used noninvasive technique which measures the potential distribution on the scalp caused by the brain electrical activity. A number of interesting correlations between features of the recorded EEG waveforms and various aspects of attention memory and linguistic tAS/Ks have been discovered. These correlations are estimated by comparing, for a given brain function, the recorded EEGs against the scalp potentials obtained from the computation of an electric field model of the head. The accuracy of these estimates depends not only on such factors as EEG measured errors but also, more importantly, on how closely the head model approximates the physiological head. This has spurred interest in the use of a more realistic head geometry with more accurate conductivity values which would use the detailed anatomical

'Perfectly disordered' medium as a model for the description of micro-inhomogeneous mixtures

International Nuclear Information System (INIS)

Levin, V M; Markov, M G; Alvarez-Tostado, J M

2004-01-01

The correct description of the macroscopic (overall) physical properties of micro-inhomogeneous (composite) materials by micro-mechanics methods (the self-consistent schemes, for example) requires information about the microstructure and texture of such materials. Often, such information (of shapes inhomogeneities and peculiarities of their spatial distribution) is not available. In this paper, we suggest a method of calculation of the characteristics of micro-inhomogeneous materials that could be applied to a wide class of isotropic materials. This method assumes the absence of a closed order in the material microstructure (a 'perfectly disordered' (PD) medium). We used the PD approximation to predict the effective thermo- and poroelastic, electric and thermal properties of micro-inhomogeneous media. The expressions for the effective characteristics obtained by this method are always inside of the Hashin-Shtrikman universal bounds. For a two-phase material with fluid component, the effective bulk module satisfies Gassmann's relation for fluid-filled porous media and generalizes such a relation to inhomogeneous thermoelastic and poroelastic media. A comparison of the theoretical results with available experimental data shows a satisfactory coincidence even in the case of high contrast of the component properties. The simplicity of the numerical realization of the method makes it attractive for applications in the absence of detailed information about the material's microstructure

Waves in inhomogeneous plasma of cylindrical geometry

International Nuclear Information System (INIS)

Rebut, P.H.

1966-01-01

The conductivity tensor of a hot and inhomogeneous plasma has been calculated for a cylindrical geometry using Vlasov equations. The method used consists in a perturbation method involving the first integrals of the unperturbed movement. The conductivity tensor will be particularly useful for dealing with stability problems. In the case of a cold plasma the wave equation giving the electric fields as a function of the radius is obtained. This equation shows the existence of resonant layers which lead to an absorption analogous to the Landau absorption in a hot plasma. (author) [fr

Inhomogeneous microstructural growth by irradiation

DEFF Research Database (Denmark)

Krishan, K.; Singh, Bachu Narain; Leffers, Torben

1985-01-01

In the present paper we discuss the development of heterogeneous microstructure for uniform irradiation conditions. It is shown that microstructural inhomogeneities on a scale of 0.1 μm can develop purely from kinematic considerations because of the basic structure of the rate equations used...... to describe such evolution. Two aspects of the growth of such inhomogeneities are discussed. Firstly, it is shown that a local variation in the sink densities of the various microstructural defects will tend to enhance the inhomogeneity rather than remove it. Secondly, such inhomogeneities will lead to point...... defect fluxes that result in a spatial growth of the inhomogeneous region, which will be stopped only when the microstructural density around this region becomes large. The results have important implications in the formation of denuded zones and void formation in metals....

Electron cyclotron instabilities of finite pressure inhomogeneous plasma in crossed fields

International Nuclear Information System (INIS)

Kirochkin, Yu.A.; Pokroev, A.G.; Stepanov, K.N.

1979-01-01

The stability of inhomogeneous plasma sheet with β<=1 in crossed electric and magnetic fields is investigated. The differential equation describing potential oscillations is obtained. Using the local approximation the sheet is shown to be unstable against the excitation of short wavelength electron cyclotron oscillations. The validity criterion of this method for a given type of waves is derived

Density perturbations due to the inhomogeneous discrete spatial structure of space-time

International Nuclear Information System (INIS)

Wolf, C.

1998-01-01

For the case that space-time permits an inhomogeneous discrete spatial structure due to varying gravitational fields or a foam-like structure of space-time, it is demonstrated that thermodynamic reasoning implies that matter-density perturbations will arise in the early universe

Controlling Electricity Consumption by Forecasting its Response to Varying Prices

DEFF Research Database (Denmark)

Corradi, Olivier; Ochsenfeld, Henning Peter; Madsen, Henrik

2013-01-01

electricity consumption using a one-way price signal. Estimation of the price-response is based on data measurable at grid level, removing the need to install sensors and communication devices between each individual consumer and the price-generating entity. An application for price-responsive heating systems......In a real-time electricity pricing context where consumers are sensitive to varying prices, having the ability to anticipate their response to a price change is valuable. This paper proposes models for the dynamics of such price-response, and shows how these dynamics can be used to control...... is studied based on real data, before conducting a control by price experiment using a mixture of real and synthetic data. With the control objective of following a constant consumption reference, peak heating consumption is reduced by nearly 5%, and 11% of the mean daily heating consumption is shifted....

Instabilities in inhomogeneous plasma

International Nuclear Information System (INIS)

Mikhailovsky, A.B.

1983-01-01

The plasma inhomogeneity across the magnetic field causes a wide class of instabilities which are called instabilities of an inhomogeneous plasma or gradient instabilities. The instabilities that can be studied in the approximation of a magnetic field with parallel straight field lines are treated first, followed by a discussion of the influence of shear on these instabilities. The instabilities of a weakly inhomogeneous plasma with the Maxwellian velocity distribution of particles caused by the density and temperature gradients are often called drift instabilities, and the corresponding types of perturbations are the drift waves. An elementary theory of drift instabilities is presented, based on the simplest equations of motion of particles in the field of low-frequency and long-wavelength perturbations. Following that is a more complete theory of inhomogeneous collisionless plasma instabilities which uses the permittivity tensor and, in the case of electrostatic perturbations, the scalar of permittivity. The results are used to study the instabilities of a strongly inhomogeneous plasma. The instabilities of a plasma in crossed fields are discussed and the electromagnetic instabilities of plasma with finite and high pressure are described. (Auth.)

The effect of inhomogeneous initial stress on Love wave propagation in layered magneto-electro-elastic structures

International Nuclear Information System (INIS)

Zhang, J; Shen, Y P; Du, J K

2008-01-01

The effect of inhomogeneous initial stress on Love wave propagation in layered magneto-electro-elastic structures is investigated in this paper. The coupled magneto-electro-elastic field equations are solved by adopting the Wentzel–Kramers–Brillouin (WKB) approximate approach. Then the phase velocity can be calculated by applying boundary and continuity conditions. A specific example of a structure consisting of a CoFe 2 O 4 layer and a BaTiO 3 substrate is used to illustrate the influence of inhomogeneous initial stress on the phase velocity, corresponding coupled magneto-electric factor and stress fields. The different influence between constant initial stress and inhomogeneous initial stress is discussed and the results are expected to be helpful for the preparation and application of Love wave sensors

Electric emissions from electrical appliances

International Nuclear Information System (INIS)

Leitgeb, N.; Cech, R.; Schroettner, J.

2008-01-01

Electric emissions from electric appliances are frequently considered negligible, and standards consider electric appliances to comply without testing. By investigating 122 household devices of 63 different categories, it could be shown that emitted electric field levels do not justify general disregard. Electric reference values can be exceeded up to 11-fold. By numerical dosimetry with homogeneous human models, induced intra-corporal electric current densities were determined and factors calculated to elevate reference levels to accounting for reduced induction efficiency of inhomogeneous fields. These factors were found not high enough to allow generally concluding on compliance with basic restrictions without testing. Electric appliances usually simultaneously emit both electric and magnetic fields exposing almost the same body region. Since the sum of induced current densities is limited, one field component reduces the available margin for the other. Therefore, superposition of electric current densities induced by either field would merit consideration. (authors)

Nonlinear electrostatic ion cyclotron waves in an rf-plugged inhomogeneous plasma slab

International Nuclear Information System (INIS)

Ikemura, Tsutomu.

1977-01-01

A theory based on the fluid and perturbation theories is developed to analytically study a nonlinear electrostatic ion cyclotron wave excited in an rf-plugged inhomogeneous plasma slab by applying a pair of external potentials phi sub(ext)(x,z) = +-PHI 0 cos ω 0 t.exp(-z 2 /2h 2 ) at its boundaries x = +-L. Here, B 0 is applied along the z-axis. The potential forms of the fundamental and the nonlinear second harmonic are found as functions of x, z and t provided the field-free densities vary as exp(-x 2 /2d 2 )(d 2 /h 2 0 ) created by the fundamental potential can approximately be regarded as a dipole field, provided that /1-μ/ 0 2 -ω sub(cl)sup(2))m sub(i)d 2 /(γ sub(i)T sub(i)+Z γ sub(e)T sub(e)). Under the stricter condition μ asymptotically equals 1, a dipole-like electric field can also be excited in the entire region for the case of high density and weak nonlinearity. It is shown that the assumption ω 0 -1 √ γ sub(e)T sub(e)/m sub(e) can lead to the Boltzmann relation for the electron fluid even in inhomogeneous plasmas. Moreover, the density depletion delta N sub(i) obtained here contains a new considerable term proportional to /phi/ 2 , in addition to the usual term proportional to -/delta phi/delta x/ 2 which originates from the ponderomotive force. (auth.)

Casimir stress in an inhomogeneous medium

International Nuclear Information System (INIS)

Philbin, T.G.; Xiong, C.; Leonhardt, U.

2010-01-01

The Casimir effect in an inhomogeneous dielectric is investigated using Lifshitz's theory of electromagnetic vacuum energy. A permittivity function that depends continuously on one Cartesian coordinate is chosen, bounded on each side by homogeneous dielectrics. The result for the Casimir stress is infinite everywhere inside the inhomogeneous region, a divergence that does not occur for piece-wise homogeneous dielectrics with planar boundaries. A Casimir force per unit volume can be extracted from the infinite stress but it diverges on the boundaries between the inhomogeneous medium and the homogeneous dielectrics. An alternative regularization of the vacuum stress is considered that removes the contribution of the inhomogeneity over small distances, where macroscopic electromagnetism is invalid. The alternative regularization yields a finite Casimir stress inside the inhomogeneous region, but the stress and force per unit volume diverge on the boundaries with the homogeneous dielectrics. The case of inhomogeneous dielectrics with planar boundaries thus falls outside the current understanding of the Casimir effect.

High-order harmonic generation driven by inhomogeneous plasmonics fields spatially bounded: influence on the cut-off law

Science.gov (United States)

Neyra, E.; Videla, F.; Ciappina, M. F.; Pérez-Hernández, J. A.; Roso, L.; Lewenstein, M.; Torchia, G. A.

2018-03-01

We study high-order harmonic generation (HHG) in model atoms driven by plasmonic-enhanced fields. These fields result from the illumination of plasmonic nanostructures by few-cycle laser pulses. We demonstrate that the spatial inhomogeneous character of the laser electric field, in a form of Gaussian-shaped functions, leads to an unexpected relationship between the HHG cutoff and the laser wavelength. Precise description of the spatial form of the plasmonic-enhanced field allows us to predict this relationship. We combine the numerical solutions of the time-dependent Schrödinger equation (TDSE) with the plasmonic-enhanced electric fields obtained from 3D finite element simulations. We additionally employ classical simulations to supplement the TDSE outcomes and characterize the extended HHG spectra by means of their associated electron trajectories. A proper definition of the spatially inhomogeneous laser electric field is instrumental to accurately describe the underlying physics of HHG driven by plasmonic-enhanced fields. This characterization opens up new perspectives for HHG control with various experimental nano-setups.

Inhomogeneous dusty Universes and their deceleration

CERN Document Server

Giovannini, Massimo

2006-01-01

Exact results stemming directly from Einstein equations imply that inhomogeneous Universes endowed with vanishing pressure density can only decelerate, unless the energy density of the Universe becomes negative. Recent proposals seem to argue that inhomogeneous (but isotropic) space-times, filled only with incoherent matter,may turn into accelerated Universes for sufficiently late times. To scrutinize these scenarios, fully inhomogeneous Einstein equations are discussed in the synchronous system. In a dust-dominated Universe, the inhomogeneous generalization of the deceleration parameter is always positive semi-definite implying that no acceleration takes place.

Inhomogeneous Markov point processes by transformation

DEFF Research Database (Denmark)

Jensen, Eva B. Vedel; Nielsen, Linda Stougaard

2000-01-01

We construct parametrized models for point processes, allowing for both inhomogeneity and interaction. The inhomogeneity is obtained by applying parametrized transformations to homogeneous Markov point processes. An interesting model class, which can be constructed by this transformation approach......, is that of exponential inhomogeneous Markov point processes. Statistical inference For such processes is discussed in some detail....

Particle creation in inhomogeneous spacetimes

International Nuclear Information System (INIS)

Frieman, J.A.

1989-01-01

We study the creation of particles by inhomogeneous perturbations of spatially flat Friedmann-Robertson-Walker cosmologies. For massless scalar fields, the pair-creation probability can be expressed in terms of geometric quantities (curvature invariants). The results suggest that inhomogeneities on scales up to the particle horizon will be damped out near the Planck time. Perturbations on scales larger than the horizon are explicitly shown to yield no created pairs. The results generalize to inhomogeneous spacetimes several earlier studies of pair creation in homogeneous anisotropic cosmologies

Strict calculation of electron energy distribution functions in inhomogeneous plasmas

International Nuclear Information System (INIS)

Winkler, R.

1996-01-01

It is objective of the paper to report on strict calculations of the velocity or energy distribution function function and related macroscopic properties of the electrons from appropriate electron kinetic equations under various plasma conditions and to contribute to a better understanding of the electron behaviour in inhomogeneous plasma regions. In particular, the spatial relaxation of plasma electrons acted upon by uniform electric fields, the response of plasma electrons on spatial disturbances of the electric field, the electron kinetics under the impact of space charge field confinement in the dc column plasma and the electron velocity distribution is stronger field as occurring in the electrode regions of a dc glow discharge is considered. (author)

Discharge characteristics in inhomogeneous fields under air flow

DEFF Research Database (Denmark)

Vogel, Stephan; Holbøll, Joachim

2017-01-01

the frequency and magnitude of partial discharges in the vicinity of the electrode due to an increased rate of space charge removal around the tip of the needle and in the gap. The positive polarity shows higher dependency on air flow compared to the negative polarity. It is shown that positive breakdown......This research investigates the impact of high velocity air flow on Partial Discharge (PD) patterns generated in strongly inhomogeneous fields. In the laboratory, a needle plane electrode configuration was exposed to a high electrical DC-field and a laminar air flow up to 22 ms. The needle...

Bose-Einstein condensates with spatially inhomogeneous interaction and bright solitons

International Nuclear Information System (INIS)

Shin, H.J.; Radha, R.; Kumar, V. Ramesh

2011-01-01

In this Letter, we investigate the dynamics of Bose-Einstein Condensates (BECs) with spatially inhomogeneous interaction and generate bright solitons for the condensates by solving the associated mean field description governed by the Gross-Pitaevskii (GP) equation. We then investigate the properties of BECs in an optical lattice and periodic potential. We show that the GP equation in an optical lattice potential is integrable provided the interaction strength between the atoms varies periodically in space. The model discussed in the Letter offers the luxury of choosing the form of the lattice without destroying the integrability. Besides, we have also brought out the possible ramifications of the integrable model in the condensates of quasi-particles. -- Highlights: → We generate bright solitons for the collisionally inhomogeneous BECs. → We then study their properties in an optical lattice and periodic potential. → The model may have wider ramifications in the BECs of quasi-particles.

Perturbed soliton excitations in inhomogeneous DNA

International Nuclear Information System (INIS)

Daniel, M.; Vasumathi, V.

2005-05-01

We study nonlinear dynamics of inhomogeneous DNA double helical chain under dynamic plane-base rotator model by considering angular rotation of bases in a plane normal to the helical axis. The DNA dynamics in this case is found to be governed by a perturbed sine-Gordon equation when taking into account the interstrand hydrogen bonding energy and intrastrand inhomogeneous stacking energy and making an analogy with the Heisenberg model of the Hamiltonian for an inhomogeneous anisotropic spin ladder with ferromagnetic legs and antiferromagentic rung coupling. In the homogeneous limit the dynamics is governed by the kink-antikink soliton of the sine-Gordon equation which represents the formation of open state configuration in DNA double helix. The effect of inhomogeneity in stacking energy in the form of localized and periodic variations on the formation of open states in DNA is studied under perturbation. The perturbed soliton is obtained using a multiple scale soliton perturbation theory by solving the associated linear eigen value problem and constructing the complete set of eigen functions. The inhomogeneity in stacking energy is found to modulate the width and speed of the soliton depending on the nature of inhomogeneity. Also it introduces fluctuations in the form of train of pulses or periodic oscillation in the open state configuration (author)

Simple inhomogeneous cosmological (toy) models

International Nuclear Information System (INIS)

Isidro, Eddy G. Chirinos; Zimdahl, Winfried; Vargas, Cristofher Zuñiga

2016-01-01

Based on the Lemaître-Tolman-Bondi (LTB) metric we consider two flat inhomogeneous big-bang models. We aim at clarifying, as far as possible analytically, basic features of the dynamics of the simplest inhomogeneous models and to point out the potential usefulness of exact inhomogeneous solutions as generalizations of the homogeneous configurations of the cosmological standard model. We discuss explicitly partial successes but also potential pitfalls of these simplest models. Although primarily seen as toy models, the relevant free parameters are fixed by best-fit values using the Joint Light-curve Analysis (JLA)-sample data. On the basis of a likelihood analysis we find that a local hump with an extension of almost 2 Gpc provides a better description of the observations than a local void for which we obtain a best-fit scale of about 30 Mpc. Future redshift-drift measurements are discussed as a promising tool to discriminate between inhomogeneous configurations and the ΛCDM model.

Propagation of flexural waves in inhomogeneous plates exhibiting hysteretic nonlinearity: Nonlinear acoustic black holes.

Science.gov (United States)

Gusev, Vitalyi E; Ni, Chenyin; Lomonosov, Alexey; Shen, Zhonghua

2015-08-01

Theory accounting for the influence of hysteretic nonlinearity of micro-inhomogeneous material on flexural wave in the plates of continuously varying thickness is developed. For the wedges with thickness increasing as a power law of distance from its edge strong modifications of the wave dynamics with propagation distance are predicted. It is found that nonlinear absorption progressively disappearing with diminishing wave amplitude leads to complete attenuation of acoustic waves in most of the wedges exhibiting black hole phenomenon. It is also demonstrated that black holes exist beyond the geometrical acoustic approximation. Applications include nondestructive evaluation of micro-inhomogeneous materials and vibrations damping. Copyright © 2015 Elsevier B.V. All rights reserved.

Multicolour Observations, Inhomogeneity & Evolution

OpenAIRE

Hellaby, Charles

2000-01-01

We propose a method of testing source evolution theories that is independent of the effects of inhomogeneity, and thus complementary to other studies of evolution. It is suitable for large scale sky surveys, and the new generation of large telescopes. In an earlier paper it was shown that basic cosmological observations - luminosity versus redshift, area distance versus redshift and number counts versus redshift - cannot separate the effects of cosmic inhomogeneity, cosmic evolution and sourc...

Estimation of geometrically undistorted B0 inhomogeneity maps

International Nuclear Information System (INIS)

Matakos, A; Balter, J; Cao, Y

2014-01-01

Geometric accuracy of MRI is one of the main concerns for its use as a sole image modality in precision radiation therapy (RT) planning. In a state-of-the-art scanner, system level geometric distortions are within acceptable levels for precision RT. However, subject-induced B 0 inhomogeneity may vary substantially, especially in air-tissue interfaces. Recent studies have shown distortion levels of more than 2 mm near the sinus and ear canal are possible due to subject-induced field inhomogeneity. These distortions can be corrected with the use of accurate B 0 inhomogeneity field maps. Most existing methods estimate these field maps from dual gradient-echo (GRE) images acquired at two different echo-times under the assumption that the GRE images are practically undistorted. However distortion that may exist in the GRE images can result in estimated field maps that are distorted in both geometry and intensity, leading to inaccurate correction of clinical images. This work proposes a method for estimating undistorted field maps from GRE acquisitions using an iterative joint estimation technique. The proposed method yields geometrically corrected GRE images and undistorted field maps that can also be used for the correction of images acquired by other sequences. The proposed method is validated through simulation, phantom experiments and applied to patient data. Our simulation results show that our method reduces the root-mean-squared error of the estimated field map from the ground truth by ten-fold compared to the distorted field map. Both the geometric distortion and the intensity corruption (artifact) in the images caused by the B 0 field inhomogeneity are corrected almost completely. Our phantom experiment showed improvement in the geometric correction of approximately 1 mm at an air-water interface using the undistorted field map compared to using a distorted field map. The proposed method for undistorted field map estimation can lead to improved geometric

Estimation of geometrically undistorted B0 inhomogeneity maps

Science.gov (United States)

Matakos, A.; Balter, J.; Cao, Y.

2014-09-01

Geometric accuracy of MRI is one of the main concerns for its use as a sole image modality in precision radiation therapy (RT) planning. In a state-of-the-art scanner, system level geometric distortions are within acceptable levels for precision RT. However, subject-induced B0 inhomogeneity may vary substantially, especially in air-tissue interfaces. Recent studies have shown distortion levels of more than 2 mm near the sinus and ear canal are possible due to subject-induced field inhomogeneity. These distortions can be corrected with the use of accurate B0 inhomogeneity field maps. Most existing methods estimate these field maps from dual gradient-echo (GRE) images acquired at two different echo-times under the assumption that the GRE images are practically undistorted. However distortion that may exist in the GRE images can result in estimated field maps that are distorted in both geometry and intensity, leading to inaccurate correction of clinical images. This work proposes a method for estimating undistorted field maps from GRE acquisitions using an iterative joint estimation technique. The proposed method yields geometrically corrected GRE images and undistorted field maps that can also be used for the correction of images acquired by other sequences. The proposed method is validated through simulation, phantom experiments and applied to patient data. Our simulation results show that our method reduces the root-mean-squared error of the estimated field map from the ground truth by ten-fold compared to the distorted field map. Both the geometric distortion and the intensity corruption (artifact) in the images caused by the B0 field inhomogeneity are corrected almost completely. Our phantom experiment showed improvement in the geometric correction of approximately 1 mm at an air-water interface using the undistorted field map compared to using a distorted field map. The proposed method for undistorted field map estimation can lead to improved geometric

OBSERVABLE DEVIATIONS FROM HOMOGENEITY IN AN INHOMOGENEOUS UNIVERSE

Energy Technology Data Exchange (ETDEWEB)

Giblin, John T. Jr. [Department of Physics, Kenyon College, 201 N College Road Gambier, OH 43022 (United States); Mertens, James B.; Starkman, Glenn D. [CERCA/ISO, Department of Physics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106 (United States)

2016-12-20

How does inhomogeneity affect our interpretation of cosmological observations? It has long been wondered to what extent the observable properties of an inhomogeneous universe differ from those of a corresponding Friedmann–Lemaître–Robertson–Walker (FLRW) model, and how the inhomogeneities affect that correspondence. Here, we use numerical relativity to study the behavior of light beams traversing an inhomogeneous universe, and construct the resulting Hubble diagrams. The universe that emerges exhibits an average FLRW behavior, but inhomogeneous structures contribute to deviations in observables across the observer’s sky. We also investigate the relationship between angular diameter distance and the angular extent of a source, finding deviations that grow with source redshift. These departures from FLRW are important path-dependent effects, with implications for using real observables in an inhomogeneous universe such as our own.

OBSERVABLE DEVIATIONS FROM HOMOGENEITY IN AN INHOMOGENEOUS UNIVERSE

International Nuclear Information System (INIS)

Giblin, John T. Jr.; Mertens, James B.; Starkman, Glenn D.

2016-01-01

How does inhomogeneity affect our interpretation of cosmological observations? It has long been wondered to what extent the observable properties of an inhomogeneous universe differ from those of a corresponding Friedmann–Lemaître–Robertson–Walker (FLRW) model, and how the inhomogeneities affect that correspondence. Here, we use numerical relativity to study the behavior of light beams traversing an inhomogeneous universe, and construct the resulting Hubble diagrams. The universe that emerges exhibits an average FLRW behavior, but inhomogeneous structures contribute to deviations in observables across the observer’s sky. We also investigate the relationship between angular diameter distance and the angular extent of a source, finding deviations that grow with source redshift. These departures from FLRW are important path-dependent effects, with implications for using real observables in an inhomogeneous universe such as our own.

Two and Three-Dimensional Nonlocal DFT for Inhomogeneous Fluids I: Algorithms and Parallelization

Energy Technology Data Exchange (ETDEWEB)

Frink, Laura J. Douglas; Salinger, Andrew

1999-08-09

Fluids adsorbed near surfaces, macromolecules, and in porous materials are inhomogeneous, inhibiting spatially varying density distributions. This inhomogeneity in the fluid plays an important role in controlling a wide variety of complex physical phenomena including wetting, self-assembly, corrosion, and molecular recognition. One of the key methods for studying the properties of inhomogeneous fluids in simple geometries has been density functional theory (DFT). However, there has been a conspicuous lack of calculations in complex 2D and 3D geometries. The computational difficulty arises from the need to perform nested integrals that are due to nonlocal terms in the free energy functional These integral equations are expensive both in evaluation time and in memory requirements; however, the expense can be mitigated by intelligent algorithms and the use of parallel computers. This paper details our efforts to develop efficient numerical algorithms so that no local DFT calculations in complex geometries that require two or three dimensions can be performed. The success of this implementation will enable the study of solvation effects at heterogeneous surfaces, in zeolites, in solvated (bio)polymers, and in colloidal suspensions.

Joint Probability Distribution Function for the Electric Microfield and its Ion-Octupole Inhomogeneity Tensor

International Nuclear Information System (INIS)

Halenka, J.; Olchawa, W.

2005-01-01

From experiments, see e.g. [W. Wiese, D. Kelleher, and D. Paquette, Phys. Rev. A 6, 1132 (1972); V. Helbig and K. Nich, J. Phys. B 14, 3573 (1981).; J. Halenka, Z. Phys. D 16, 1 (1990); . Djurovic, D. Nikolic, I. Savic, S. Sorge, and A.V. Demura, Phys. Rev. E 71, 036407 (2005)], results that the hydrogen lines formed in plasma with N e φ 10 16 cm -3 are asymmetrical. The inhomogeneity of ionic micro field and the higher order corrections (quadratic and next ones) in perturbation theory are the reason for such asymmetry. So far, the ion-emitter quadrupole interaction and the quadratic Stark effect have been included in calculations. The recent work shows that a significant discrepancy between calculations and measurements occurs in the wings of H-beta line in plasmas with cm -3 . It should be stressed here that e.g. for the energy operator the correction raised by the quadratic Stark effect is proportional to (where is the emitter-perturber distance) similarly as the correction caused by the emitter-perturber octupole interaction and the quadratic correction from emitter-perturber quadrupole interaction. Thus, it is obvious that a model of the profile calculation is consistent one if all the aforementioned corrections are simultaneously included. Such calculations are planned in the future paper. A statistics of the octupole inhomogeneity tensor in a plasma is necessarily needed in the first step of such calculations. For the first time the distribution functions of the octupole inhomogeneity have been calculated in this paper using the Mayer-Mayer cluster expansion method similarly as for the quadrupole function in the paper [J. Halenka, Z. Phys. D 16, 1 (1990)]. The quantity is the reduced scale of the micro field strength, where is the Holtsmark normal field and is the mean distance defined by the relationship, that is approximately equal to the mean ion-ion distance; whereas is the screening parameter, where is the electronic Debye radius. (author)

Scroll-wave dynamics in human cardiac tissue: lessons from a mathematical model with inhomogeneities and fiber architecture.

Directory of Open Access Journals (Sweden)

Rupamanjari Majumder

2011-04-01

Full Text Available Cardiac arrhythmias, such as ventricular tachycardia (VT and ventricular fibrillation (VF, are among the leading causes of death in the industrialized world. These are associated with the formation of spiral and scroll waves of electrical activation in cardiac tissue; single spiral and scroll waves are believed to be associated with VT whereas their turbulent analogs are associated with VF. Thus, the study of these waves is an important biophysical problem. We present a systematic study of the combined effects of muscle-fiber rotation and inhomogeneities on scroll-wave dynamics in the TNNP (ten Tusscher Noble Noble Panfilov model for human cardiac tissue. In particular, we use the three-dimensional TNNP model with fiber rotation and consider both conduction and ionic inhomogeneities. We find that, in addition to displaying a sensitive dependence on the positions, sizes, and types of inhomogeneities, scroll-wave dynamics also depends delicately upon the degree of fiber rotation. We find that the tendency of scroll waves to anchor to cylindrical conduction inhomogeneities increases with the radius of the inhomogeneity. Furthermore, the filament of the scroll wave can exhibit drift or meandering, transmural bending, twisting, and break-up. If the scroll-wave filament exhibits weak meandering, then there is a fine balance between the anchoring of this wave at the inhomogeneity and a disruption of wave-pinning by fiber rotation. If this filament displays strong meandering, then again the anchoring is suppressed by fiber rotation; also, the scroll wave can be eliminated from most of the layers only to be regenerated by a seed wave. Ionic inhomogeneities can also lead to an anchoring of the scroll wave; scroll waves can now enter the region inside an ionic inhomogeneity and can display a coexistence of spatiotemporal chaos and quasi-periodic behavior in different parts of the simulation domain. We discuss the experimental implications of our study.

Inhomogeneous wire explosion in water

International Nuclear Information System (INIS)

Hwangbo, C.K.; Kong, H.J.; Lee, S.S.

1980-01-01

Inhomogeneous processes are observed in underwater copper wire explosion induced by a condensed capacitor discharge. The wire used is 0.1 mm in diameter and 10 mm long, and the capacitor of 2 μF is charged to 5 KV. A N 2 laser is used for the diagnostic of spatial extension of exploding copper vapour. The photographs obtained in this experiment show unambiguously the inhomogeneous explosion along the exploding wire. The quenching of plasma by the surrounding water inhibits the expansion of the vapour. It is believed the observed inhomogeneous explosion along the wire is located and localized around Goronkin's striae, which was first reported by Goronkin and discussed by Froengel as a pre-breakdown phenomenon. (author)

Dynamics of inhomogeneous chiral condensates

Science.gov (United States)

Carlomagno, Juan Pablo; Krein, Gastão; Kroff, Daniel; Peixoto, Thiago

2018-01-01

We study the dynamics of the formation of inhomogeneous chirally broken phases in the final stages of a heavy-ion collision, with particular interest on the time scales involved in the formation process. The study is conducted within the framework of a Ginzburg-Landau time evolution, driven by a free energy functional motivated by the Nambu-Jona-Lasinio model. Expansion of the medium is modeled by one-dimensional Bjorken flow and its effect on the formation of inhomogeneous condensates is investigated. We also use a free energy functional from a nonlocal Nambu-Jona-Lasinio model which predicts metastable phases that lead to long-lived inhomogeneous condensates before reaching an equilibrium phase with homogeneous condensates.

Robustness of inflation to inhomogeneous initial conditions

Energy Technology Data Exchange (ETDEWEB)

Clough, Katy; Lim, Eugene A. [Theoretical Particle Physics and Cosmology Group, Physics Department, Kings College London, Strand, London WC2R 2LS (United Kingdom); DiNunno, Brandon S.; Fischler, Willy; Flauger, Raphael; Paban, Sonia, E-mail: katy.clough@kcl.ac.uk, E-mail: eugene.a.lim@gmail.com, E-mail: bsd86@physics.utexas.edu, E-mail: fischler@physics.utexas.edu, E-mail: flauger@physics.utexas.edu, E-mail: paban@physics.utexas.edu [Department of Physics, The University of Texas at Austin, Austin, TX, 78712 (United States)

2017-09-01

We consider the effects of inhomogeneous initial conditions in both the scalar field profile and the extrinsic curvature on different inflationary models. In particular, we compare the robustness of small field inflation to that of large field inflation, using numerical simulations with Einstein gravity in 3+1 dimensions. We find that small field inflation can fail in the presence of subdominant gradient energies, suggesting that it is much less robust to inhomogeneities than large field inflation, which withstands dominant gradient energies. However, we also show that small field inflation can be successful even if some regions of spacetime start out in the region of the potential that does not support inflation. In the large field case, we confirm previous results that inflation is robust if the inflaton occupies the inflationary part of the potential. Furthermore, we show that increasing initial scalar gradients will not form sufficiently massive inflation-ending black holes if the initial hypersurface is approximately flat. Finally, we consider the large field case with a varying extrinsic curvature K , such that some regions are initially collapsing. We find that this may again lead to local black holes, but overall the spacetime remains inflationary if the spacetime is open, which confirms previous theoretical studies.

A new simulation model for inhomogeneous Au/n-GaN structure

Energy Technology Data Exchange (ETDEWEB)

Kavasoglu, Nese, E-mail: knesese@gmail.com; Kavasoglu, Abdulkadir Sertap; Metin, Bengul [Mugla Sitki Kocman University, Faculty of Sciences, Department of Physics, Photovoltaic Material and Device Laboratory (Turkey)

2016-05-15

The larger the device area, the more difficult to carry on homogeneity during the fabrication and following treatments. Structural inhomogeneity may indicate themselves in variations in local electronic device parameters. Electrical current through the potential barriers is exponentially sensitive to the local device parameters and its fluctuations in the Schottky devices. A new simulation program is developed to describe a relation between multiple, random barrier heights and current-voltage characteristics of the Schottky device. We model the barrier height inhomogeneity in terms of random microcells connected in parallel, which have different barrier height values. Analyzing the integral of the simulated light current-voltage curves show that fluctuations of the local barrier height result in a degradation of the open circuit voltage, fill factor and in consequence, of the over all power conversation efficiency. The implementation described here is quite general and can be used to simulate any device parameter fluctuations in the Schottky devices.

Fuel effects on the stability of turbulent flames with compositionally inhomogeneous inlets

KAUST Repository

Guiberti, T. F.

2016-10-11

This paper reports an analysis of the influence of fuels on the stabilization of turbulent piloted jet flames with inhomogeneous inlets. The burner is identical to that used earlier by the Sydney Group and employs two concentric tubes within the pilot stream. The inner tube, carrying fuel, can be recessed, leading to a varying degree of inhomogeneity in mixing with the outer air stream. Three fuels are tested: dimethyl ether (DME), liquefied petroleum gas (LPG), and compressed natural gas (CNG). It is found that improvement in flame stability at the optimal compositional inhomogeneity is highest for CNG and lowest for DME. Three possible reasons for this different enhancement in stability are investigated: mixing patterns, pilot effects, and fuel chemistry. Numerical simulations realized in the injection tube highlight similarities and differences in the mixing patterns for all three fuels and demonstrate that mixing cannot explain the different stability gains. Changing the heat release rates from the pilot affects the three fuels in similar ways and this also implies that the pilot stream is unlikely to be responsible for the observed differences. Fuel reactivity is identified as a key factor in enhancing stability at some optimal compositional inhomogeneity. This is confirmed by inference from joint images of PLIF-OH and PLIF-CHO, collected at a repetition rate of 10kHz in turbulent flames of DME, and from one-dimensional calculations of laminar flames using detailed chemistry for DME, CNG, and LPG.

Big Bounce and inhomogeneities

International Nuclear Information System (INIS)

Brizuela, David; Mena Marugan, Guillermo A; Pawlowski, Tomasz

2010-01-01

The dynamics of an inhomogeneous universe is studied with the methods of loop quantum cosmology, via a so-called hybrid quantization, as an example of the quantization of vacuum cosmological spacetimes containing gravitational waves (Gowdy spacetimes). The analysis of this model with an infinite number of degrees of freedom, performed at the effective level, shows that (i) the initial Big Bang singularity is replaced (as in the case of homogeneous cosmological models) by a Big Bounce, joining deterministically two large universes, (ii) the universe size at the bounce is at least of the same order of magnitude as that of the background homogeneous universe and (iii) for each gravitational wave mode, the difference in amplitude at very early and very late times has a vanishing statistical average when the bounce dynamics is strongly dominated by the inhomogeneities, whereas this average is positive when the dynamics is in a near-vacuum regime, so that statistically the inhomogeneities are amplified. (fast track communication)

Nearly incompressible fluids: Hydrodynamics and large scale inhomogeneity

International Nuclear Information System (INIS)

Hunana, P.; Zank, G. P.; Shaikh, D.

2006-01-01

incompressible equations for higher order fluctuation components are derived and it is shown that they converge to the usual homogeneous nearly incompressible equations in the limit of no large-scale background. We use a time and length scale separation procedure to obtain wave equations for the acoustic pressure and velocity perturbations propagating on fast-time-short-wavelength scales. On these scales, the pseudosound relation, used to relate density and pressure fluctuations, is also obtained. In both cases, the speed of propagation (sound speed) depends on background variables and therefore varies spatially. For slow-time scales, a simple pseudosound relation cannot be obtained and density and pressure fluctuations are implicitly related through a relation which can be solved only numerically. Subject to some simplifications, a generalized inhomogeneous pseudosound relation is derived. With this paper, we extend the theory of nearly incompressible hydrodynamics to flows, including the solar wind, which include large-scale inhomogeneities (in this case radially symmetric and in equilibrium)

Large scale inhomogeneities and the cosmological principle

International Nuclear Information System (INIS)

Lukacs, B.; Meszaros, A.

1984-12-01

The compatibility of cosmologic principles and possible large scale inhomogeneities of the Universe is discussed. It seems that the strongest symmetry principle which is still compatible with reasonable inhomogeneities, is a full conformal symmetry in the 3-space defined by the cosmological velocity field, but even in such a case, the standard model is isolated from the inhomogeneous ones when the whole evolution is considered. (author)

Moessbauer spectroscopy of locally inhomogeneous systems

International Nuclear Information System (INIS)

Rusakov, V. S.; Kadyrzhanov, K. K.

2004-01-01

Substances with characteristic local inhomogeneities - with different from position to position neighborhood and properties of like atoms - gain recently increased scientific attention and wide practical application. We would call a system locally inhomogeneous if atoms in the system are in non-equivalent atomic locations and reveal different properties. Such systems are, first of all, variable composition phases, amorphous, multi-phase, admixture, defect and other systems. LIS are most convenient model objects for studies of structure, charge, and spin atomic states, interatomic interactions, relations between matter properties and its local characteristics as well as for studies of diffusion kinetics, phase formation, crystallization and atomic ordering; all that explains considerable scientific interest in such LIS. Such systems find their practical application due to wide spectrum of useful, and sometimes unique, properties that can be controlled varying character and degree of local inhomogeneity. Moessbauer spectroscopy is one of the most effective methods for investigation of LIS. Local character of obtained information combined with information on cooperative phenomena makes it possible to run investigations impossible for other methods. Moessbauer spectroscopy may provide with abundant information on peculiarities of macro- and microscopic state of matter including that for materials without regular structure. At the same time, analysis, processing and interpretation of Moessbauer spectra for LIS (that are sets of a large amount of partial spectra) face considerable difficulties. Development of computer technique is accompanied with development of mathematical methods used for obtaining physical information from experimental data. The methods make it possible to improve considerably, with some available a priori information, effectiveness of the research. Utilization of up-to-date mathematical methods in Moessbauer spectroscopy requires not only adaptation

Parametric instabilities in inhomogeneous plasma

International Nuclear Information System (INIS)

Nicholson, D.R.

1975-01-01

The nonlinear coupling of three waves in a plasma is considered. One of the waves is assumed large and constant; its amplitude is the parameter of the parametric instability. The spatial-temporal evolution of the other two waves is treated theoretically, in one dimension, by analytic methods and by direct numerical integration of the basic equations. Various monotonic forms of inhomogeneity are considered; agreement with previous work is found and new results are established. Nonmonotonic inhomogeneities are considered, in the form of turbulence and, as a model problem, in the form of a simple sinusoidal modulation. Relatively small amounts of nonmonotonic inhomogeneity, in the presence of a linear density gradient, are found to destabilize the well-known convective saturation, absolute growth occurring instead. (U.S.)

Consideration of inhomogeneities in irradiation planning. Pt. 1

International Nuclear Information System (INIS)

Zwicker, H.; Felix, R.

1976-01-01

In radiation therapy, the focal doses during irradiation of a tumor are based on the values for water, since water has almost the same absorption coefficient as muscular tissue, even for different kinds and energies of radiation. But calculation of the tumor dose will become inaccurate if inhomogeneities in the ray path are not considered such as fat, bones, plaster, metal plates, Kuentscher nails, endoprotheses. These materials, having a density sigma different from water, represent inhomogeneities relative to water with regard to the absorption of high-energy radiation. The experiments yielded the following results: All measurements revealed that the change in the course of the depth dose curve caused by inhomogeneities in water depends essentially on the density sigma and on the thickness d of the inhomogeneity. If the density sigma of the inhomogeneity exceeds one, a shift of the depth dose curve in water results in the direction of the surface; if the density sigma is smaller than one, the depth dose curve will move towards greater depth because of the inhomogeneity. With Co-60 gamma radiation, the shift of the depth dose curve in water due to an inhomogeneity occurs almost parallel. A correlation obtained empirically allows a calculation of th extent of the shift the depth dose is subject to for different inhomogeneities. (orig./ORU) [de

Antennas in inhomogeneous media

CERN Document Server

Galejs, Janis; Fock, V A; Wait, J R

2013-01-01

Antennas in Inhomogeneous Media details the methods of analyzing antennas in such inhomogeneous media. The title covers the complex geometrical configurations along with its variational formulations. The coverage of the text includes various conditions the antennas are subjected to, such as antennas in the interface between two media; antennas in compressible isotropic plasma; and linear antennas in a magnetoionic medium. The selection also covers insulated loops in lossy media; slot antennas with a stratified dielectric or isotropic plasma layers; and cavity-backed slot antennas. The book wil

Quantum entanglement in inhomogeneous 1D systems

Science.gov (United States)

Ramírez, Giovanni

2018-04-01

The entanglement entropy of the ground state of a quantum lattice model with local interactions usually satisfies an area law. However, in 1D systems some violations may appear in inhomogeneous systems or in random systems. In our inhomogeneous system, the inhomogeneity parameter, h, allows us to tune different regimes where a volumetric violation of the area law appears. We apply the strong disorder renormalization group to describe the maximally entangled state of the system in a strong inhomogeneity regime. Moreover, in a weak inhomogeneity regime, we use a continuum approximation to describe the state as a thermo-field double in a conformal field theory with an effective temperature which is proportional to the inhomogeneity parameter of the system. The latter description also shows that the universal scaling features of this model are captured by a massless Dirac fermion in a curved space-time with constant negative curvature R = h2, providing another example of the relation between quantum entanglement and space-time geometry. The results we discuss here were already published before, but here we present a more didactic exposure of basic concepts of the rainbow system for the students attending the Latin American School of Physics "Marcos Moshinsky" 2017.

Inhomogeneous initial data and small-field inflation

Science.gov (United States)

Marsh, M. C. David; Barrow, John D.; Ganguly, Chandrima

2018-05-01

We consider the robustness of small-field inflation in the presence of scalar field inhomogeneities. Previous numerical work has shown that if the scalar potential is flat only over a narrow interval, such as in commonly considered inflection-point models, even small-amplitude inhomogeneities present at the would-be onset of inflation at τ = τi can disrupt the accelerated expansion. In this paper, we parametrise and evolve the inhomogeneities from an earlier time τIC at which the initial data were imprinted, and show that for a broad range of inflationary and pre-inflationary models, inflection-point inflation withstands initial inhomogeneities. We consider three classes of perturbative pre-inflationary solutions (corresponding to energetic domination by the scalar field kinetic term, a relativistic fluid, and isotropic negative curvature), and two classes of exact solutions to Einstein's equations with large inhomogeneities (corresponding to a stiff fluid with cylindrical symmetry, and anisotropic negative curvature). We derive a stability condition that depends on the Hubble scales H(τi) and H(τIC), and a few properties of the pre-inflationary cosmology. For initial data imprinted at the Planck scale, the absence of an inhomogeneous initial data problem for inflection-point inflation leads to a novel, lower limit on the tensor-to-scalar ratio.

The effect of inhomogeneity of microstructure on ducility in superplasticity

International Nuclear Information System (INIS)

Manonukul, A.; Dunne, F.P.E.

1996-01-01

Finite element cell models have been developed to represent inhomogeneous grain size fields that occur in commercial Ti-6Al-4V. The models are used to investigate the influence of microstructure on superplastic stress-strain behaviour, inhomogeneity of deformation, and on ductility in superplastic deformation. It is shown that increasing the level of initial microstructural inhomogeneity leads to increasing flow stress for given strain, and that the microstructural inhomogeneity leads to inhomogeneous deformation. As superplasticity proceeds, the level of microstructural inhomogeneity diminishes, but the inhomogeneity itself is preserved during the deformation. It is shown that the inhomogeneity of microstructure leads to strain localisation which increases in severity with deformation until material necking and failure occur. Increasing the initial microstructural inhomogeneity is shown to lead to a decrease in ductility, but the effect diminishes for grain size ranges in excess of 30 μm. An empirical relationship is presented that relates the ductility to the initial grain size range through a power law. (orig.)

Electrical stress and strain in lunar regolith simulants

Science.gov (United States)

Marshall, J.; Richard, D.; Davis, S.

2011-11-01

Experiments to entrain dust with electrostatic and fluid-dynamic forces result in particulate clouds of aggregates rather than individual dust grains. This is explained within the framework of Griffith-flaw theory regarding the comminution/breakage of weak solids. Physical and electrical inhomogeneities in powders are equivalent to microcracks in solids insofar as they facilitate failure at stress risers. Electrical charging of powders induces bulk sample stresses similar to mechanical stresses experienced by strong solids, depending on the nature of the charging. A powder mass therefore "breaks" into clumps rather than separating into individual dust particles. This contrasts with the expectation that electrical forces on the Moon will eject a submicron population of dust from the regolith into the exosphere. A lunar regolith will contain physical and electrostatic inhomogeneities similar to those in most charged powders.

Acoustic Streaming and Its Suppression in Inhomogeneous Fluids.

Science.gov (United States)

Karlsen, Jonas T; Qiu, Wei; Augustsson, Per; Bruus, Henrik

2018-02-02

We present a theoretical and experimental study of boundary-driven acoustic streaming in an inhomogeneous fluid with variations in density and compressibility. In a homogeneous fluid this streaming results from dissipation in the boundary layers (Rayleigh streaming). We show that in an inhomogeneous fluid, an additional nondissipative force density acts on the fluid to stabilize particular inhomogeneity configurations, which markedly alters and even suppresses the streaming flows. Our theoretical and numerical analysis of the phenomenon is supported by ultrasound experiments performed with inhomogeneous aqueous iodixanol solutions in a glass-silicon microchip.

Inhomogeneity at the LaAlO3/SrTiO3 interface

Science.gov (United States)

Claeson, T.; Kalabukhov, A.; Gunnarsson, R.; Winkler, D.; Borjesson, J.; Ljustina, N.; Olsson, E.; Popok, V.; Boikov, Yu.; Serenkov, I.; Sakharov, V.

2010-03-01

High electrical conductivity has been reported for the interface between two wide-band gap insulators, LaAlO3 (LAO) and SrTiO3 (STO). It occurs above a critical thickness of LAO and can be tuned by an electric field. The conduction has been attributed to i) ``polar catastrophe'' , where the electrostatic charge at the interface is compensated by the transfer of half an electron per unit cell to the interface, ii) oxygen vacancies in the STO, and iii) cation intermixing, which may result in the formation of metallic La1-xSrxTiO3 layer. The relation between microstructure and electrical properties is crucial for understanding the origin of electrical conductivity. We have investigated the interface composition using medium-energy ion spectroscopy, high resolution electron microscopy, and Kelvin probe force microscopy. We find a correlation between cationic intermixing at the interface and electrical properties and inhomogeneities of the interface conductivity that may support a percolation model. Work supported by Swedish VR & KAW, Russian ISTC 3743, EC NANOXIDE

Metrical theorems on systems of small inhomogeneous linear forms

DEFF Research Database (Denmark)

Hussain, Mumtaz; Kristensen, Simon

In this paper we establish complete Khintchine-Groshev and Schmidt type theorems for inhomogeneous small linear forms in the so-called doubly metric case, in which the inhomogeneous parameter is not fixed.......In this paper we establish complete Khintchine-Groshev and Schmidt type theorems for inhomogeneous small linear forms in the so-called doubly metric case, in which the inhomogeneous parameter is not fixed....

Effects of nanoscale density inhomogeneities on shearing fluids

DEFF Research Database (Denmark)

Ben, Dalton,; Peter, Daivis,; Hansen, Jesper Schmidt

2013-01-01

It is well known that density inhomogeneities at the solid-liquid interface can have a strong effect on the velocity profile of a nanoconfined fluid in planar Poiseuille flow. However, it is difficult to control the density inhomogeneities induced by solid walls, making this type of system...... systems. Using the sinusoidal transverse force method to produce shearing velocity profiles and the sinusoidal longitudinal force method to produce inhomogeneous density profiles, we are able to observe the interactions between the two property inhomogeneities at the level of individual Fourier components....... This gives us a method for direct measurement of the coupling between the density and velocity fields and allows us to introduce various feedback control mechanisms which customize fluid behavior in individual Fourier components. We briefly discuss the role of temperature inhomogeneity and consider whether...

Inhomogenous loop quantum cosmology with matter

International Nuclear Information System (INIS)

Martín-de Bias, D; Mena Marugán, G A; Martín-Benito, M

2012-01-01

The linearly polarized Gowdy T 3 model with a massless scalar field with the same symmetries as the metric is quantized by applying a hybrid approach. The homogeneous geometry degrees of freedom are loop quantized, fact which leads to the resolution of the cosmological singularity, while a Fock quantization is employed for both matter and gravitational inhomogeneities. Owing to the inclusion of the massless scalar field this system allows us to modelize flat Friedmann-Robertson-Walker cosmologies filled with inhomogeneities propagating in one direction. It provides a perfect scenario to study the quantum back-reaction between the inhomogeneities and the polymeric homogeneous and isotropic background.

Estimating functions for inhomogeneous Cox processes

DEFF Research Database (Denmark)

Waagepetersen, Rasmus

2006-01-01

Estimation methods are reviewed for inhomogeneous Cox processes with tractable first and second order properties. We illustrate the various suggestions by means of data examples.......Estimation methods are reviewed for inhomogeneous Cox processes with tractable first and second order properties. We illustrate the various suggestions by means of data examples....

Multiscale response of ionic systems to a spatially varying electric field

Directory of Open Access Journals (Sweden)

Jesper Schmidt Hansen

2017-05-01

Full Text Available In this paper the response of ionic systems subjected to a spatially varying electric field is studied. Following the Nernst-Planck equation, two forces driving the mass flux are present, namely, the concentration gradient and the electric potential gradient. The mass flux due to the concentration gradient is modelled through Fick's law, and a new constitutive relation for the mass flux due to the potential gradient is proposed. In the regime of low screening the response function due to the potential gradient is closely related to the ionic conductivity. In the large screening regime, on the other hand, the response function is governed by the charge-charge structure. Molecular dynamics simulations are conducted and the two wave vector dependent response functions are evaluated for models of a molten salt and an ionic liquid. In the low screening regime the response functions show same wave vector dependency, indicating that it is the same underlying physical processes that govern the response. In the screening regime the wave vector dependency is very different and, thus, the overall response is determined by different processes. This is in agreement with the observed failure of the Nernst-Einstein relation.

Propagation of strong electromagnetic beams in inhomogeneous plasmas

Energy Technology Data Exchange (ETDEWEB)

Ferrari, A; Massaglia, S [Consiglio Nazionale delle Ricerche, Turin (Italy). Lab. di Cosmo-Geofisica; Turin Univ. (Italy). Ist. di Fisica Generale)

1980-09-01

We study some simple aspects of nonlinear propagation of relativistically strong electromagnetic beams in inhomogeneous plasmas, especially in connection with effects of beam self-trapping in extended extragalactic radio sources. The two effects of (i) long scale longitudinal and radial inhomogeneities inherent to the plasma and (ii) radial inhomogeneities produced by the ponderomotive force of the beam itself are investigated.

Dynamics of an inhomogeneous anisotropic antiferromagnetic spin chain

International Nuclear Information System (INIS)

Daniel, M.; Amuda, R.

1994-11-01

We investigate the nonlinear spin excitations in the two sublattice model of a one dimensional classical continuum Heisenberg inhomogeneous antiferromagnetic spin chain. The dynamics of the inhomogeneous chain reduces to that of its homogeneous counterpart when the inhomogeneity assumes a particular form. Apart from the usual twists and pulses, we obtain some planar configurations representing the nonlinear dynamics of spins. (author). 12 refs

Full-wave solution of short impulses in inhomogeneous plasma

International Nuclear Information System (INIS)

Ferencz, Orsolya E.

2005-01-01

In this paper the problem of real impulse propagation in arbitrarily inhomogeneous media will be presented on a fundamentally new, general, theoretical way. The general problem of wave propagation of monochromatic signals in inhomogeneous media was enlightened. The earlier theoretical models for spatial inhomogeneities have some errors regarding the structure of the resultant signal originated from backward and forward propagating parts. The application of the method of inhomogeneous basic modes (MIBM) and the complete full-wave solution of arbitrarily shaped non-monochromatic plane waves in plasmas made it possible to obtain a better description of the problem, on a fully analytical way, directly from Maxwell's equations. The model investigated in this paper is inhomogeneous of arbitrary order (while the wave pattern can exist), anisotropic (magnetized), linear, cold plasma, in which the gradient of the one-dimensional spatial inhomogeneity is parallel to the direction of propagation. (author)

Two- and three-dimensional nonlocal density functional theory for inhomogeneous fluids. 1. Algorithms and parallelization

International Nuclear Information System (INIS)

Frink, L.J.D.; Salinger, A.G.

2000-01-01

Fluids adsorbed near surfaces, near macromolecules, and in porous materials are inhomogeneous, exhibiting spatially varying density distributions. This inhomogeneity in the fluid plays an important role in controlling a wide variety of complex physical phenomena including wetting, self-assembly, corrosion, and molecular recognition. One of the key methods for studying the properties of inhomogeneous fluids in simple geometries has been density functional theory (DFT). However, there has been a conspicuous lack of calculations in complex two- and three-dimensional geometries. The computational difficulty arises from the need to perform nested integrals that are due to nonlocal terms in the free energy functional. These integral equations are expensive both in evaluation time and in memory requirements; however, the expense can be mitigated by intelligent algorithms and the use of parallel computers. This paper details the efforts to develop efficient numerical algorithms so that nonlocal DFT calculations in complex geometries that require two or three dimensions can be performed. The success of this implementation will enable the study of solvation effects at heterogeneous surfaces, in zeolites, in solvated (bio)polymers, and in colloidal suspensions

Large sample neutron activation analysis of a reference inhomogeneous sample

International Nuclear Information System (INIS)

Vasilopoulou, T.; Athens National Technical University, Athens; Tzika, F.; Stamatelatos, I.E.; Koster-Ammerlaan, M.J.J.

2011-01-01

A benchmark experiment was performed for Neutron Activation Analysis (NAA) of a large inhomogeneous sample. The reference sample was developed in-house and consisted of SiO 2 matrix and an Al-Zn alloy 'inhomogeneity' body. Monte Carlo simulations were employed to derive appropriate correction factors for neutron self-shielding during irradiation as well as self-attenuation of gamma rays and sample geometry during counting. The large sample neutron activation analysis (LSNAA) results were compared against reference values and the trueness of the technique was evaluated. An agreement within ±10% was observed between LSNAA and reference elemental mass values, for all matrix and inhomogeneity elements except Samarium, provided that the inhomogeneity body was fully simulated. However, in cases that the inhomogeneity was treated as not known, the results showed a reasonable agreement for most matrix elements, while large discrepancies were observed for the inhomogeneity elements. This study provided a quantification of the uncertainties associated with inhomogeneity in large sample analysis and contributed to the identification of the needs for future development of LSNAA facilities for analysis of inhomogeneous samples. (author)

Effect of inhomogeneities on streamer propagation: II. Streamer dynamics in high pressure humid air with bubbles

International Nuclear Information System (INIS)

Babaeva, Natalia Yu; Kushner, Mark J

2009-01-01

The branching of electric discharge streamers in atmospheric pressure air, dense gases and liquids is a common occurrence whose origins are likely found with many causes, both deterministic and stochastic. One mechanism for streamer branching may be inhomogeneities in the path of a streamer which either divert the streamer (typically a region of lower ionization) or produce a new branch (a region of higher ionization). The propagation and branching of streamers in liquids is likely aided by low density inhomogeneities, bubbles; however, modeling of streamers in liquids is made difficult by the lack of transport coefficients. As a first step towards understanding the propagation and branching of streamers in liquids, we investigated the consequences of random inhomogeneities in the form of low pressure bubbles on the propagation of streamers in high pressure humid air. By virtue of their lower density, bubbles have larger E/N (electric field/gas number density) than the ambient gas with larger rates of ionization. The intersection of a streamer with a bubble will focus the plasma into the bubble by virtue of that higher rate of ionization but the details of the interaction depend on the relative sizes of the bubble and streamer. When a streamer intersects a field of bubbles, the large E/N in the bubble avalanches seed electrons produced by photoionization from the streamer. Each bubble then launches both a negative and positive going streamer that may link with those from adjacent bubbles or the original streamer. The total process then appears as streamer branching.

Influence of tidal volume on ventilation inhomogeneity assessed by electrical impedance tomography during controlled mechanical ventilation

International Nuclear Information System (INIS)

Becher, T; Kott, M; Schädler, D; Vogt, B; Meinel, T; Weiler, N; Frerichs, I

2015-01-01

The global inhomogeneity (GI) index is a parameter of ventilation inhomogeneity that can be calculated from images of tidal ventilation distribution obtained by electrical impedance tomography (EIT). It has been suggested that the GI index may be useful for individual adjustment of positive end-expiratory pressure (PEEP) and for guidance of ventilator therapy. The aim of the present work was to assess the influence of tidal volume (V_T) on the GI index values. EIT data from 9 patients with acute respiratory distress syndrome ventilated with a low and a high V_T of 5   ±   1 (mean  ±  SD) and 9   ±   1 ml kg"−"1 predicted body weight at a high and a low level of PEEP (PEEP_h_i_g_h, PEEP_l_o_w) were analyzed. PEEP_h_i_g_h and PEEP_l_o_w were set 2 cmH_2O above and 5 cmH_2O below the lower inflection point of a quasi-static pressure volume loop, respectively. The lower inflection point was identified at 8.1   ±   1.4 (mean  ±  SD) cmH_2O, resulting in a PEEP_h_i_g_h of 10.1   ±   1.4 and a PEEP_l_o_w of 3.1   ±   1.4 cmH_2O. At PEEP_h_i_g_h, we found no significant trend in GI index with low V_T when compared to high V_T (0.49   ±   0.15 versus 0.44   ±   0.09, p = 0.13). At PEEP_l_o_w, we found a significantly higher GI index with low V_T compared to high V_T (0.66   ±   0.19 versus 0.59   ±   0.17, p = 0.01). When comparing the PEEP levels, we found a significantly lower GI index at PEEP_h_i_g_h both for high and low V_T. We conclude that high V_T may lead to a lower GI index, especially at low PEEP settings. This should be taken into account when using the GI index for individual adjustment of ventilator settings. (paper)

Analytical method for analysis of electromagnetic scattering from inhomogeneous spherical structures using duality principles

Science.gov (United States)

Kiani, M.; Abdolali, A.; Safari, M.

2018-03-01

In this article, an analytical approach is presented for the analysis of electromagnetic (EM) scattering from radially inhomogeneous spherical structures (RISSs) based on the duality principle. According to the spherical symmetry, similar angular dependencies in all the regions are considered using spherical harmonics. To extract the radial dependency, the system of differential equations of wave propagation toward the inhomogeneity direction is equated with the dual planar ones. A general duality between electromagnetic fields and parameters and scattering parameters of the two structures is introduced. The validity of the proposed approach is verified through a comprehensive example. The presented approach substitutes a complicated problem in spherical coordinate to an easy, well posed, and previously solved problem in planar geometry. This approach is valid for all continuously varying inhomogeneity profiles. One of the major advantages of the proposed method is the capability of studying two general and applicable types of RISSs. As an interesting application, a class of lens antenna based on the physical concept of the gradient refractive index material is introduced. The approach is used to analyze the EM scattering from the structure and validate strong performance of the lens.

Cyclotron spectra from inhomogeneous accretion columns. II. Polarization

International Nuclear Information System (INIS)

Wu, K.; Chanmugam, G.

1989-01-01

Circularly and linearly polarized radiation from inhomogeneous cyclotron emission regions with uniform magnetic field and temperature but different electron density profiles are studied. Calculations show that the inhomogeneous models generally produce larger polarization for low harmonics and smaller polarization for high harmonics compared to the homogeneous models. Polarization light curves for different inhomogeneous models with a wide variety of parameters are presented, providing handy theoretical results to compare with observations. The observed polarization light curves of ST LMi, EF Eri, and BL Hydri are fitted using an inhomogeneous model for the first time, and good fits are obtained, supporting the hypothesis that the cyclotron emission regions of AM Her systems have a complicated structure. 37 refs

Time-varying convergence in European electricity spot markets and their association with carbon and fuel prices

International Nuclear Information System (INIS)

Menezes, Lilian M. de; Houllier, Melanie A.; Tamvakis, Michael

2016-01-01

Long-run dynamics of electricity prices are expected to reflect fuel price developments, since fuels generally account for a large share in the cost of generation. As an integrated European market for electricity develops, wholesale electricity prices should be converging as a result of market coupling and increased interconnectivity. Electricity mixes are also changing, spurred by a drive to significantly increase the share of renewables. Consequently, the electricity wholesale price dynamics are evolving, and the fuel–electricity price nexus that has been described in the literature is likely to reflect this evolution. This study investigates associations between spot prices from the British, French and Nordpool markets with those in connected electricity markets and fuel input prices, from December 2005 to October 2013. In order to assess the time-varying dynamics of electricity spot price series, localized autocorrelation functions are used. Electricity spot prices in the three markets are found to have stationary and non-stationary periods. When a trend in spot prices is observed, it is likely to reflect the trend in fuel prices. Cointegration analysis is then used to assess co-movement between electricity spot prices and fuel inputs to generation. The results show that British electricity spot prices are associated with fuel prices and not with price developments in connected markets, while the opposite is observed in the French and Nordpool day-ahead markets. - Highlights: • Electricity market integration policies may have altered EU spot electricity prices. • LACF is used to assess the changing nature of electricity spot prices. • EU electricity spot prices show both stationary and non-stationary periods. • Carbon and fuel prices have greater impact on British spot prices. • In continental Europe, electricity prices have decoupled from fuel prices.

MRI intensity inhomogeneity correction by combining intensity and spatial information

International Nuclear Information System (INIS)

Vovk, Uros; Pernus, Franjo; Likar, Bostjan

2004-01-01

We propose a novel fully automated method for retrospective correction of intensity inhomogeneity, which is an undesired phenomenon in many automatic image analysis tasks, especially if quantitative analysis is the final goal. Besides most commonly used intensity features, additional spatial image features are incorporated to improve inhomogeneity correction and to make it more dynamic, so that local intensity variations can be corrected more efficiently. The proposed method is a four-step iterative procedure in which a non-parametric inhomogeneity correction is conducted. First, the probability distribution of image intensities and corresponding second derivatives is obtained. Second, intensity correction forces, condensing the probability distribution along the intensity feature, are computed for each voxel. Third, the inhomogeneity correction field is estimated by regularization of all voxel forces, and fourth, the corresponding partial inhomogeneity correction is performed. The degree of inhomogeneity correction dynamics is determined by the size of regularization kernel. The method was qualitatively and quantitatively evaluated on simulated and real MR brain images. The obtained results show that the proposed method does not corrupt inhomogeneity-free images and successfully corrects intensity inhomogeneity artefacts even if these are more dynamic

On the parallel momentum balance in low pressure plasmas with an inhomogeneous magnetic field

International Nuclear Information System (INIS)

Smolyakov, A.I.; Garbet, X.; Bourdelle, C.

2009-01-01

This paper describes the structure of the parallel momentum balance in low pressure plasmas with an inhomogeneous magnetic field. The parallel momentum balance equation is derived from magnetohydrodynamic equations by an expansion in the inverse magnetic field 1/B as a small parameter. Contributions of the gyroviscosity and inertia terms are clarified. It is shown that magnetic field curvature leads to important coupling of parallel flow with fluctuations of the electric field and plasma pressure.

A varying-α brane world cosmology

International Nuclear Information System (INIS)

Youm, Donam

2001-08-01

We study the brane world cosmology in the RS2 model where the electric charge varies with time in the manner described by the varying fine-structure constant theory of Bekenstein. We map such varying electric charge cosmology to the dual variable-speed-of-light cosmology by changing system of units. We comment on cosmological implications for such cosmological models. (author)

Electromagnetic wave propagation over an inhomogeneous flat earth (two-dimensional integral equation formulation)

International Nuclear Information System (INIS)

de Jong, G.

1975-01-01

With the aid of a two-dimensional integral equation formulation, the ground wave propagation of electromagnetic waves transmitted by a vertical electric dipole over an inhomogeneous flat earth is investigated. For the configuration in which a ground wave is propagating across an ''island'' on a flat earth, the modulus and argument of the attenuation function have been computed. The results for the two-dimensional treatment are significantly more accurate in detail than the calculations using a one-dimensional integral equation

Variation of Bragg curve characteristic induced by changing the position of inhomogeneous material: Geant4 simulation study

Energy Technology Data Exchange (ETDEWEB)

Park, So-Hyun; Jung, Won-Gyun; Suh, Tae-Suk [Catholic University, Seoul (Korea, Republic of); Jang, Hong-Seok; Choi, Byeong-Oak [Seoul St. Mary' s Hospital, Seoul (Korea, Republic of); Rah, Jeong-Eun; Park, Sun-Gyong; Lee, Se-Byeong [National Cancer Center, Ilsan (Korea, Republic of)

2011-02-15

When proton beam passes through the human body, the stopping power and the depth-dose distribution of the proton are influenced by the relative location among adjacent materials or the difference in material conditions. Our study demonstrates the effect of inhomogeneous materials placed in the Plateau and Bragg peak regions of the Bragg curve in water. We evaluated the Bragg peak position, range, penumbra and integrated doses by using the Geant4 simulation toolkit. The positions of inhomogeneities were selected as the proximal 36% and 50% points of the maximum dose, which indicates the location at entrance regions of the Plateau and the Bragg peak, respectively. Bone (density {rho} = 1.85 g/cm{sup 3}) and adipose tissue (density {rho} = 0.92 g/cm{sup 3}) were selected as inhomogeneous materials. The thickness of each material was varied by 0.1 cm between 0.1 cm and 1.0 cm. In addition, the initial energy of the proton beam was changed in 30 MeV steps between 108 MeV and 220 MeV. The effects of inhomogeneous conditions were performed for various parameters: Bragg peak position, range, penumbra width, full width at half maximum and dose of Bragg curve. A dose perturbation was observed in the region of the Bragg peak and inhomogeneous material, especially, When the bone equivalent material was inserted within the Bragg curve. However, there were no significant variations in the other parameters, except for the dose perturbation depending on the inserted location of each material. This study shows the characteristic changes in the Bragg curve due to inhomogeneous materials.

In situ study of electric field controlled ion transport in the Fe/BaTiO3 interface

Science.gov (United States)

Merkel, D. G.; Bessas, D.; Bazsó, G.; Jafari, A.; Rüffer, R.; Chumakov, A. I.; Khanh, N. Q.; Sajti, Sz; Celse, J.-P.; Nagy, D. L.

2018-01-01

Electric field controlled ion transport and interface formation of iron thin films on a BaTiO3 substrate have been investigated by in situ nuclear resonance scattering and x-ray reflectometry techniques. At early stage of deposition, an iron-II oxide interface layer was observed. The hyperfine parameters of the interface layer were found insensitive to the evaporated layer thickness. When an electric field was applied during growth, a 10 Å increase of the nonmagnetic/magnetic thickness threshold and an extended magnetic transition region was measured compared to the case where no field was applied. The interface layer was found stable under this threshold when further evaporation occurred, contrary to the magnetic layer where the magnitude and orientation of the hyperfine magnetic field vary continuously. The obtained results of the growth mechanism and of the electric field effect of the Fe/BTO system will allow the design of novel applications by creating custom oxide/metallic nanopatterns using laterally inhomogeneous electric fields during sample preparation.

Modeling of inhomogeneous mixing of plasma species in argon–steam arc discharge

Czech Academy of Sciences Publication Activity Database

Jeništa, Jiří; Takana, H.; Uehara, S.; Nishiyama, H.; Bartlová, M.; Aubrecht, V.; Murphy, A.B.

2018-01-01

Roč. 51, č. 4 (2018), č. článku 045202. ISSN 0022-3727 R&D Projects: GA ČR(CZ) GA15-19444S; GA ČR(CZ) GC17-10246J Institutional support: RVO:61389021 Keywords : arc * combined diffusion coefficients * (in)homogeneous mixing * mass (mole) fraction * hybrid-stabilized electric arc Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.588, year: 2016 http://iopscience.iop.org/article/10.1088/1361-6463/aa9f6f/meta

The influence of flow maldistribution on the performance of inhomogeneous parallel plate heat exhangers

DEFF Research Database (Denmark)

Nielsen, Kaspar Kirstein; Engelbrecht, Kurt; Bahl, Christian R.H.

2013-01-01

of 50 random stacks having equal average channel thicknesses with 20 channels each are used to provide a statistical base. The standard deviation of the stacks is varied as are the flow rate (Reynolds number) and the thermal conductivity of the solid heat exchanger material. It is found that the heat...... transfer performance of inhomogeneous stacks of parallel plates may be reduced significantly due to the maldistribution of the fluid flow compared to the ideal homogeneous case. The individual channels experience different flow velocities and this further induces an inter-channel thermal cross talk.......The heat transfer performance of inhomogeneous parallel plate heat exchangers in transient operation is investigated using an established model. A performance parameter, denoted the Nusselt-scaling factor, is used as benchmark and calculated using a well-established single blow technique. A sample...

Forced solitary Rossby waves under the influence of slowly varying topography with time

International Nuclear Information System (INIS)

Yang Hong-Wei; Yin Bao-Shu; Yang De-Zhou; Xu Zhen-Hua

2011-01-01

By using a weakly nonlinear and perturbation method, the generalized inhomogeneous Korteweg—de Vries (KdV)—Burgers equation is derived, which governs the evolution of the amplitude of Rossby waves under the influence of dissipation and slowly varying topography with time. The analysis indicates that dissipation and slowly varying topography with time are important factors in causing variation in the mass and energy of solitary waves. (general)

Distribution of electric field and charge collection in silicon strip detectors

International Nuclear Information System (INIS)

Anokhin, I.E.; Zinets, O.S.

1995-01-01

The distribution of electric field in silicon strip detectors is analyzed in the case of dull depletion as well as for partial depletion. Influence of inhomogeneous electric fields on the charge collection and performances of silicon strip detectors is discussed

Acoustic Streaming and Its Suppression in Inhomogeneous Fluids

DEFF Research Database (Denmark)

Karlsen, Jonas Tobias; Qiu, Wei; Augustsson, Per

2018-01-01

We present a theoretical and experimental study of boundary-driven acoustic streaming in an inhomogeneous fluid with variations in density and compressibility. In a homogeneous fluid this streaming results from dissipation in the boundary layers (Rayleigh streaming). We show...... that in an inhomogeneous fluid, an additional nondissipative force density acts on the fluid to stabilize particular inhomogeneity configurations, which markedly alters and even suppresses the streaming flows. Our theoretical and numerical analysis of the phenomenon is supported by ultrasound experiments performed...

Electrical impedance spectroscopy (EIS)-based evaluation of biological tissue phantoms to study multifrequency electrical impedance tomography (Mf-EIT) systems

KAUST Repository

Bera, Tushar Kanti; Nagaraju, J.; Lubineau, Gilles

2016-01-01

. In this direction the impedance responses of the saline solution (background) and a number vegetable and fruit tissues (inhomogeneities) are studied with electrical impedance spectroscopy (EIS) and the frequency responses of bioelectrical impedance and conductivity

Nonlocal Free Energy of a Spatially Inhomogeneous Superconductor

International Nuclear Information System (INIS)

Grigorishin, K.V.; Lev, B.I.

2012-01-01

The microscopic approach is developed for obtaining of the free energy of a superconductor based on direct calculation of the vacuum amplitude. The free energy functional of the spatially inhomogeneous superconductor in a magnetic field is obtained with help of the developed approach. The obtained functional is generalization of Ginzburg-Landau functionals for any temperature, for arbitrary spatial variations of the order parameter and for the nonlocality of a magnetic response and the order parameter. Moreover, the nonlocality of the magnetic response is the consequence of order parameter's nonlocality. The extremals of this functional are considered in the explicit form in the low- and high-temperature limit at the condition of slowness of spatial variations of the order parameter. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Inhomogeneous inflation: The initial-value problem

International Nuclear Information System (INIS)

Laguna, P.; Kurki-Suonio, H.; Matzner, R.A.

1991-01-01

We present a spatially three-dimensional study for solving the initial-value problem in general relativity for inhomogeneous cosmologies. We use York's conformal approach to solve the constraint equations of Einstein's field equations for scalar field sources and find the initial data which will be used in the evolution. This work constitutes the first stage in the development of a code to analyze the effects of matter and spacetime inhomogeneities on inflation

Ehrenfest force in inhomogeneous magnetic field

International Nuclear Information System (INIS)

Sisakyan, A.N.; Shevchenko, O.Yu.; Samojlov, V.N.

2000-01-01

The Ehrenfest force in an inhomogeneous magnetic field is calculated. It is shown that there exist such (very rare) topologically nontrivial physical situations when the Gauss theorem in its classic formulation fails and, as a consequence, apart from the usual Lorentz force an additional, purely imaginary force acts on the charged particle. This force arises only in inhomogeneous magnetic fields of special configurations, has a purely quantum origin, and disappears in the classical limit

On guided circumferential waves in soft electroactive tubes under radially inhomogeneous biasing fields

Science.gov (United States)

Wu, Bin; Su, Yipin; Chen, Weiqiu; Zhang, Chuanzeng

2017-02-01

Soft electroactive (EA) tube actuators and many other cylindrical devices have been proposed recently in literature, which show great advantages over those made from conventional hard solid materials. However, their practical applications may be limited because these soft EA devices are prone to various failure modes. In this paper, we present an analysis of the guided circumferential elastic waves in soft EA tube actuators, which has potential applications in the in-situ nondestructive evaluation (NDE) or online structural health monitoring (SHM) to detect structural defects or fatigue cracks in soft EA tube actuators and in the self-sensing of soft EA tube actuators based on the concept of guided circumferential elastic waves. Both circumferential SH and Lamb-type waves in an incompressible soft EA cylindrical tube under inhomogeneous biasing fields are considered. The biasing fields, induced by the application of an electric voltage difference to the electrodes on the inner and outer cylindrical surfaces of the EA tube in addition to an axial pre-stretch, are inhomogeneous in the radial direction. Dorfmann and Ogden's theory of nonlinear electroelasticity and the associated linear theory for small incremental motion constitute the basis of our analysis. By means of the state-space formalism for the incremental wave motion along with the approximate laminate technique, dispersion relations are derived in a particularly efficient way. For a neo-Hookean ideal dielectric model, the proposed approach is first validated numerically. Numerical examples are then given to show that the guided circumferential wave propagation characteristics are significantly affected by the inhomogeneous biasing fields and the geometrical parameters. Some particular phenomena such as the frequency veering and the nonlinear dependence of the phase velocity on the radial electric voltage are discussed. Our numerical findings demonstrate that it is feasible to use guided circumferential

Surge of plasma waves in an inhomogeneous plasma

International Nuclear Information System (INIS)

Benhassine, Mohammed

1985-01-01

The first part of this research thesis addresses the propagation of waves in a plasma. It presents the equation of propagation of an electromagnetic wave in a plasma without magnetic field, and analyses the propagation in an inhomogeneous medium. The second part addresses the wave-particle interaction: interaction between electrons and an electromagnetic wave, between electrons and an electrostatic wave (trapping), and between electrons and a localised electric field. The third chapter presents the analytic theory of oscillations of a cold plasma (macroscopic equations in Lagrangian coordinates, analytic solution before surge). The next chapter discusses physical interpretations before the wave surge, after the wave surge, and about energy exchange (within or outside of resonance). Numerical simulations and their results are then reported and discussed. The sixth chapter addresses the case of an electrostatic wave surge in a hot plasma. It notably addresses the following aspects: equivalence between the description of moments and the Waterbag model, interaction between non linearity and thermal effects, variation of electric field amplitude with temperature. Results of numerical simulations are presented, and the last part addresses experimental predictions for microwaves-plasma interaction and laser-matter interaction [fr

Evolution of vacuum bubbles embedded in inhomogeneous spacetimes

Energy Technology Data Exchange (ETDEWEB)

Pannia, Florencia Anabella Teppa [Grupo de Astrofísica, Relatividad y Cosmología, Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque s/n B1900FWA, La Plata (Argentina); Bergliaffa, Santiago Esteban Perez, E-mail: fteppa@fcaglp.unlp.edu.ar, E-mail: sepbergliaffa@gmail.com [Departamento de Física Teórica, Instituto de Física, Universidade do Estado de Rio de Janeiro, CEP 20550-013, Rio de Janeiro, Brazil. (Brazil)

2017-03-01

We study the propagation of bubbles of new vacuum in a radially inhomogeneous background filled with dust or radiation, and including a cosmological constant, as a first step in the analysis of the influence of inhomogeneities in the evolution of an inflating region. We also compare the cases with dust and radiation backgrounds and show that the evolution of the bubble in radiation environments is notably different from that in the corresponding dust cases, both for homogeneous and inhomogeneous ambients, leading to appreciable differences in the evolution of the proper radius of the bubble.

Inhomogeneity of the grain size of aircraft engine turbine polycrystalline blades

Directory of Open Access Journals (Sweden)

J. Chmiela

2011-10-01

Full Text Available The determination of the behaviour of inhomogeneous materials with a complex microstructure requires taking into account the inhomogeneity of the grain size, as it is the basis for the process of designing and modelling effective behaviours. Therefore, the functional description of the inhomogeneity is becoming an important issue. The paper presents an analytical approach to the grain size inhomogeneity, based on the derivative of a logarithmic-logistic function. The solution applied enabled an effective evaluation of the inhomogeneity of two macrostructures of aircraft engine turbine blades, characterized by a high degree of diversity in the grain size. For the investigated single-modal and bimodal grain size distributions on a perpendicular projection and for grains with a non-planar surface, we identified the parameters that describe the degree of inhomogeneity of the constituents of weight distributions and we also derived a formula describing the overall degree of inhomogeneity of bimodal distributions. The solution presented in the paper is of a general nature and it can be used to describe the degree of inhomogeneity of multi-modal distributions. All the calculations were performed using the Mathematica® package.

Modelling of coupled heat and electric field distribution during ohmic heating of solid foods with varying sizes

DEFF Research Database (Denmark)

Feyissa, Aberham Hailu; Bøknæs, Niels; Nielsen, P.L.

factors leading to variations and uncertainties in prediction of the right process parameters. The current work is focused on modelling of OH of solid food pieces of varying sizes cooked in one batch. A 3D mathematical model of coupled heat transfer and electric field during OH of shrimps has been...

The dynamics of spiral tip adjacent to inhomogeneity in cardiac tissue

Science.gov (United States)

Zhang, Juan; Tang, Jun; Ma, Jun; Luo, Jin Ming; Yang, Xian Qing

2018-02-01

Rotating spiral waves in cardiac tissue are implicated in life threatening cardiac arrhythmias. Experimental and theoretical evidences suggest the inhomogeneities in cardiac tissue play a significant role in the dynamics of spiral waves. Based on a modified 2D cardiac tissue model, the interaction of inhomogeneity on the nearby rigidly rotating spiral wave is numerically studied. The adjacent area of the inhomogeneity is divided to two areas, when the initial rotating center of the spiral tip is located in the two areas, the spiral tip will be attracted and anchor on the inhomogeneity finally, or be repulsed away. The width of the area is significantly dependent on the intensity and size of the inhomogeneity. Our numerical study sheds some light on the mechanism of the interaction of inhomogeneity on the spiral wave in cardiac tissue.

Dynamics of Peregrine combs and Peregrine walls in an inhomogeneous Hirota and Maxwell-Bloch system

Science.gov (United States)

Wang, Lei; Wang, Zi-Qi; Sun, Wen-Rong; Shi, Yu-Ying; Li, Min; Xu, Min

2017-06-01

Under investigation in this paper is an inhomogeneous Hirota-Maxwell-Bloch (IHMB) system which can describe the propagation of optical solitons in an erbium-doped optical fiber. The breather multiple births (BMBs) are derived with periodically varying group velocity dispersion (GVD) coefficients. Under large periodic modulations in the GVD coefficient of IHMB system, the Peregrine comb (PC) solution is produced, which can be viewed as the limiting case of the BMBs. When the amplitude of the modulation satisfies a special condition, the Peregrine wall (PW) that can be regarded as an intermediate state between rogue wave and PC is obtained. The effects of the third-order dispersion on the spatiotemporal characteristics of PCs and PWs are studied. Our results may be useful for the experimental control and manipulation of the formation of generalized Peregrine rogue waves in inhomogeneous erbium-doped optical fiber.

SECTIONING METHOD APPLICATION AT ELLIPSOMETRY OF INHOMOGENEOUS REFLECTION SYSTEMS

Directory of Open Access Journals (Sweden)

A. N. Gorlyak

2014-05-01

Full Text Available The paper deals with investigation of application peculiarities of ellipsometry methods and UF spectrophotometry at mechanical and chemical processing of optical engineering surface elements made of quartz glass. Ellipsometer LEF–3M–1, spectrophotometer SF–26 and interferometer MII–4 are used as experiment tools; they obtain widely known technical characteristics. Polarization characteristics of reflected light beam were measured by ellipsometry method; spectrophotometry method was used for measuring radiation transmission factor in UF spectrum area; by interference method surface layer thickness at quartz glass etching was measured. A method for HF–sectioning of inhomogeneous surface layer of polished quartz glass is developed based on ellipsometry equation for reflection system «inhomogeneous layer – inhomogeneous padding». The method makes it possible to carry out the measuring and analysis of optical characteristics for inhomogeneous layers system on inhomogeneous padding and to reconstruct optical profile of surface layers at quartz glass chemical processing. For definition of refractive index change along the layer depth, approximation of experimental values for polarization characteristics of homogeneous layers system is used. Inhomogeneous surface layer of polished quartz glass consists of an area (with thickness up to 20 nm and layer refractive index less than refractive index for quartz glass and an area (with thickness up to 0,1 μm and layer refractive index larger than refractive index for quartz glass. Ellipsometry and photometry methods are used for definition of technological conditions and optical characteristics of inhomogeneous layers at quartz glass chemical processing for optical elements with minimum radiation losses in UF spectrum area.

The "Forgotten" Pseudomomenta and Gauge Changes in Generalized Landau Level Problems: Spatially Nonuniform Magnetic and Temporally Varying Electric Fields

Science.gov (United States)

Konstantinou, Georgios; Moulopoulos, Konstantinos

2017-05-01

By perceiving gauge invariance as an analytical tool in order to get insight into the states of the "generalized Landau problem" (a charged quantum particle moving inside a magnetic, and possibly electric field), and motivated by an early article that correctly warns against a naive use of gauge transformation procedures in the usual Landau problem (i.e. with the magnetic field being static and uniform), we first show how to bypass the complications pointed out in that article by solving the problem in full generality through gauge transformation techniques in a more appropriate manner. Our solution provides in simple and closed analytical forms all Landau Level-wavefunctions without the need to specify a particular vector potential. This we do by proper handling of the so-called pseudomomentum ěc {{K}} (or of a quantity that we term pseudo-angular momentum L z ), a method that is crucially different from the old warning argument, but also from standard treatments in textbooks and in research literature (where the usual Landau-wavefunctions are employed - labeled with canonical momenta quantum numbers). Most importantly, we go further by showing that a similar procedure can be followed in the more difficult case of spatially-nonuniform magnetic fields: in such case we define ěc {{K}} and L z as plausible generalizations of the previous ordinary case, namely as appropriate line integrals of the inhomogeneous magnetic field - our method providing closed analytical expressions for all stationary state wavefunctions in an easy manner and in a broad set of geometries and gauges. It can thus be viewed as complementary to the few existing works on inhomogeneous magnetic fields, that have so far mostly focused on determining the energy eigenvalues rather than the corresponding eigenkets (on which they have claimed that, even in the simplest cases, it is not possible to obtain in closed form the associated wavefunctions). The analytical forms derived here for these

Method for measuring energy-input inhomogeneities in electroionization CO/sub 2/-lasers

Energy Technology Data Exchange (ETDEWEB)

Borovkov, V V; Kornilov, V G; Sukhanov, L V; Chelpanov, V I

1987-08-01

A Michelson interferometer at a wavelength of 0.63 micron was used to measure optical inhomogeneities due to variations of the polarizability of the molecular components in CO/sub 2/-laser mixtures under vibrational excitation in a nonself-sustained electric discharge. It is suggested that the observed effect can be used for the noninertial and noncontact diagnostics of energy-input distribution over the cross section of the active medium of an electroionization CO/sub 2/-laser. Results are presented for N/sub 2/-He, CO/sub 2/-He, CO/sub 2/-N/sub 2/-He, and CO/sub 2/-He mixtures. 10 references.

Rotational inhomogeneities from pre-big bang?

International Nuclear Information System (INIS)

Giovannini, Massimo

2005-01-01

The evolution of the rotational inhomogeneities is investigated in the specific framework of four-dimensional pre-big bang models. While minimal (dilaton-driven) scenarios do not lead to rotational fluctuations, in the case of non-minimal (string-driven) models, fluid sources are present in the pre-big bang phase. The rotational modes of the geometry, coupled to the divergenceless part of the velocity field, can then be amplified depending upon the value of the barotropic index of the perfect fluids. In the light of a possible production of rotational inhomogeneities, solutions describing the coupled evolution of the dilaton field and of the fluid sources are scrutinized in both the string and Einstein frames. In semi-realistic scenarios, where the curvature divergences are regularized by means of a non-local dilaton potential, the rotational inhomogeneities are amplified during the pre-big bang phase but they decay later on. Similar analyses can also be performed when a contraction occurs directly in the string frame metric

Rotational inhomogeneities from pre-big bang?

Energy Technology Data Exchange (ETDEWEB)

Giovannini, Massimo [Department of Physics, Theory Division, CERN, 1211 Geneva 23 (Switzerland)

2005-01-21

The evolution of the rotational inhomogeneities is investigated in the specific framework of four-dimensional pre-big bang models. While minimal (dilaton-driven) scenarios do not lead to rotational fluctuations, in the case of non-minimal (string-driven) models, fluid sources are present in the pre-big bang phase. The rotational modes of the geometry, coupled to the divergenceless part of the velocity field, can then be amplified depending upon the value of the barotropic index of the perfect fluids. In the light of a possible production of rotational inhomogeneities, solutions describing the coupled evolution of the dilaton field and of the fluid sources are scrutinized in both the string and Einstein frames. In semi-realistic scenarios, where the curvature divergences are regularized by means of a non-local dilaton potential, the rotational inhomogeneities are amplified during the pre-big bang phase but they decay later on. Similar analyses can also be performed when a contraction occurs directly in the string frame metric.

MICROWAVE INTERACTIONS WITH INHOMOGENEOUS PARTIALLY IONIZED PLASMA

Energy Technology Data Exchange (ETDEWEB)

Kritz, A. H.

1962-11-15

Microwave interactions with inhomogeneous plasmas are often studied by employing a simplified electromagnetic approach, i.e., by representing the effects of the plasma by an effective dielectric coefficient. The problems and approximations associated with this procedure are discussed. The equation describing the microwave field in an inhomogeneous partially ionized plasma is derived, and the method that is applied to obtain the reflected, transmitted, and absorbed intensities in inhomogeneous plasmas is presented. The interactions of microwaves with plasmas having Gaussian electron density profiles are considered. The variation of collision frequency with position is usually neglected. In general, the assumption of constant collision frequency is not justified; e.g., for a highly ionized plasma, the electron density profile determines, in part, the profile of the electron-ion collision frequency. The effect of the variation of the collision frequency profile on the interaction of microwaves with inhomogeneous plasmas is studied in order to obtain an estimate of the degree of error that may result when constant collision frequency is assumed instead of a more realistic collision frequency profile. It is shown that the degree of error is of particular importance when microwave analysis is used as a plasma diagnostic. (auth)

Investigation of local optical inhomogeneities in flashlamp photolysis lasers

Energy Technology Data Exchange (ETDEWEB)

Alekhin, B V; Borovkov, V V; Lazhintsev, B V; Nor-Arenian, V A; Sukhanov, L V; Ustinenko, V A

1979-09-01

Local changes in the refractive index which occur in the active medium under flashlamp-excited photolysis laser action are examined experimentally. Under conditions of the inverse population storage and suppression of the laser action by a strong quencher, local inhomogeneities have been absent. It is shown that the stimulated emission is inhomogeneous over the active medium and features regular character with the radiation density modulation within 20-30 percent and with typical size of inhomogeneities of not greater than 0.5 mm. On the basis of experimental results and estimation, a conclusion is drawn that the local optical inhomogeneities are caused by gasdynamic displacements of the gas due to different heat evolutions in the regions of the radiation density maximum and minimum.

Bistable soliton states and switching in doubly inhomogeneously ...

Indian Academy of Sciences (India)

Dec. 2001 physics pp. 969–979. Bistable soliton states and switching in doubly inhomogeneously doped fiber couplers. AJIT KUMAR. Department of Physics, Indian Institute of Technology, Hauz Khas, New Delhi 110 016, India. Abstract. Switching between the bistable soliton states in a doubly and inhomogeneously doped.

Plasma acceleration in a wave with varying frequency

International Nuclear Information System (INIS)

Petrzilka, V.A.

1978-01-01

The averaged velocity of a test particle and the averaged velocity of a plasma in an electromagnetic wave packet with varying frequency (e.g., a radiation pulse from pulsar) is derived. The total momentum left by the wave packet in regions of plasma inhomogeneity is found. In case the plasma concentration is changing due to ionization the plasma may be accelerated parallelly or antiparallelly to the direction of the wave packet propagation which is relevant for a laser induced breakdown in gas. (author)

Full-wave solution of short impulses in inhomogeneous plasma

Indian Academy of Sciences (India)

... in arbitrarily inhomogeneous media will be presented on a fundamentally new, ... The general problem of wave propagation of monochromatic signals in inhomogeneous media was enlightened in [1]. ... Pramana – Journal of Physics | News.

Acousto-electrical speckle pattern in Lorentz force electrical impedance tomography

International Nuclear Information System (INIS)

Grasland-Mongrain, Pol; Destrempes, François; Cloutier, Guy; Mari, Jean-Martial; Souchon, Rémi; Catheline, Stefan; Chapelon, Jean-Yves; Lafon, Cyril

2015-01-01

Ultrasound speckle is a granular texture pattern appearing in ultrasound imaging. It can be used to distinguish tissues and identify pathologies. Lorentz force electrical impedance tomography is an ultrasound-based medical imaging technique of the tissue electrical conductivity. It is based on the application of an ultrasound wave in a medium placed in a magnetic field and on the measurement of the induced electric current due to Lorentz force. Similarly to ultrasound imaging, we hypothesized that a speckle could be observed with Lorentz force electrical impedance tomography imaging. In this study, we first assessed the theoretical similarity between the measured signals in Lorentz force electrical impedance tomography and in ultrasound imaging modalities. We then compared experimentally the signal measured in both methods using an acoustic and electrical impedance interface. Finally, a bovine muscle sample was imaged using the two methods. Similar speckle patterns were observed. This indicates the existence of an ‘acousto-electrical speckle’ in the Lorentz force electrical impedance tomography with spatial characteristics driven by the acoustic parameters but due to electrical impedance inhomogeneities instead of acoustic ones as is the case of ultrasound imaging. (paper)

Acousto-electrical speckle pattern in Lorentz force electrical impedance tomography

Science.gov (United States)

Grasland-Mongrain, Pol; Destrempes, François; Mari, Jean-Martial; Souchon, Rémi; Catheline, Stefan; Chapelon, Jean-Yves; Lafon, Cyril; Cloutier, Guy

2015-05-01

Ultrasound speckle is a granular texture pattern appearing in ultrasound imaging. It can be used to distinguish tissues and identify pathologies. Lorentz force electrical impedance tomography is an ultrasound-based medical imaging technique of the tissue electrical conductivity. It is based on the application of an ultrasound wave in a medium placed in a magnetic field and on the measurement of the induced electric current due to Lorentz force. Similarly to ultrasound imaging, we hypothesized that a speckle could be observed with Lorentz force electrical impedance tomography imaging. In this study, we first assessed the theoretical similarity between the measured signals in Lorentz force electrical impedance tomography and in ultrasound imaging modalities. We then compared experimentally the signal measured in both methods using an acoustic and electrical impedance interface. Finally, a bovine muscle sample was imaged using the two methods. Similar speckle patterns were observed. This indicates the existence of an ‘acousto-electrical speckle’ in the Lorentz force electrical impedance tomography with spatial characteristics driven by the acoustic parameters but due to electrical impedance inhomogeneities instead of acoustic ones as is the case of ultrasound imaging.

Application of the thermal step method to space charge measurements in inhomogeneous solid insulating structures: A theoretical approach

International Nuclear Information System (INIS)

Cernomorcenco, Andrei; Notingher, Petru Jr.

2008-01-01

The thermal step method is a nondestructive technique for determining electric charge distribution across solid insulating structures. It consists in measuring and analyzing a transient capacitive current due to the redistribution of influence charges when the sample is crossed by a thermal wave. This work concerns the application of the technique to inhomogeneous insulating structures. A general equation of the thermal step current appearing in such a sample is established. It is shown that this expression is close to the one corresponding to a homogeneous sample and allows using similar techniques for calculating electric field and charge distribution

Influence of inhomogeneous surface heat capacity on the estimation of radiative response coefficients in a two-zone energy balance model

Science.gov (United States)

Park, Jungmin; Choi, Yong-Sang

2018-04-01

Observationally constrained values of the global radiative response coefficient are pivotal to assess the reliability of modeled climate feedbacks. A widely used approach is to measure transient global radiative imbalance related to surface temperature changes. However, in this approach, a potential error in the estimate of radiative response coefficients may arise from surface inhomogeneity in the climate system. We examined this issue theoretically using a simple two-zone energy balance model. Here, we dealt with the potential error by subtracting the prescribed radiative response coefficient from those calculated within the two-zone framework. Each zone was characterized by the different magnitude of the radiative response coefficient and the surface heat capacity, and the dynamical heat transport in the atmosphere between the zones was parameterized as a linear function of the temperature difference between the zones. Then, the model system was forced by randomly generated monthly varying forcing mimicking time-varying forcing like an observation. The repeated simulations showed that inhomogeneous surface heat capacity causes considerable miscalculation (down to -1.4 W m-2 K-1 equivalent to 31.3% of the prescribed value) in the global radiative response coefficient. Also, the dynamical heat transport reduced this miscalculation driven by inhomogeneity of surface heat capacity. Therefore, the estimation of radiative response coefficients using the surface temperature-radiation relation is appropriate for homogeneous surface areas least affected by the exterior.

Diffusion in inhomogeneous polymer membranes

Science.gov (United States)

Kasargod, Sameer S.; Adib, Farhad; Neogi, P.

1995-10-01

The dual mode sorption solubility isotherms assume, and in instances Zimm-Lundberg analysis of the solubilities show, that glassy polymers are heterogeneous and that the distribution of the solute in the polymer is also inhomogeneous. Under some conditions, the heterogeneities cannot be represented as holes. A mathematical model describing diffusion in inhomogeneous polymer membranes is presented using Cahn and Hilliard's gradient theory. The fractional mass uptake is found to be proportional to the fourth root of time rather than the square root, predicted by Fickian diffusion. This type of diffusion is classified as pseudo-Fickian. The model is compared with one experimental result available. A negative value of the persistence factor is obtained and the results are interpreted.

Electric control of emergent magnonic spin current and dynamic multiferroicity in magnetic insulators at finite temperatures

Science.gov (United States)

Wang, Xi-guang; Chotorlishvili, L.; Guo, Guang-hua; Berakdar, J.

2018-04-01

Conversion of thermal energy into magnonic spin currents and/or effective electric polarization promises new device functionalities. A versatile approach is presented here for generating and controlling open circuit magnonic spin currents and an effective multiferroicity at a uniform temperature with the aid of spatially inhomogeneous, external, static electric fields. This field applied to a ferromagnetic insulator with a Dzyaloshinskii-Moriya type coupling changes locally the magnon dispersion and modifies the density of thermally excited magnons in a region of the scale of the field inhomogeneity. The resulting gradient in the magnon density can be viewed as a gradient in the effective magnon temperature. This effective thermal gradient together with local magnon dispersion result in an open-circuit, electric field controlled magnonic spin current. In fact, for a moderate variation in the external electric field the predicted magnonic spin current is on the scale of the spin (Seebeck) current generated by a comparable external temperature gradient. Analytical methods supported by full-fledge numerics confirm that both, a finite temperature and an inhomogeneous electric field are necessary for this emergent non-equilibrium phenomena. The proposal can be integrated in magnonic and multiferroic circuits, for instance to convert heat into electrically controlled pure spin current using for example nanopatterning, without the need to generate large thermal gradients on the nanoscale.

Dispersion functions for weakly relativistic magnetized plasmas in inhomogeneous magnetic field

International Nuclear Information System (INIS)

Gaelzer, R.; Schneider, R.S.; Ziebell, L.F.

1995-01-01

The study of wave propagation and absorption inhomogeneous plasmas can be made by using a formulation in which the dielectric properties of the plasma are described by an effective dielectric tensor which incorporates inhomogeneity effects, inserted into a dispersion relation which is formally the same as that of an homogeneous plasma. We have recently utilized this formalism in the study of electron cyclotron absorption in inhomogeneous media, both in the case of homogeneous magnetic field and in the case of inhomogeneous magnetic field. In the present paper we resume the study of the case with inhomogeneous magnetic field, in order to introduce a generalized dispersion function useful for the case of a Maxwellian plasma, and discuss some of its properties. (author). 10 refs

Guidelines for limiting exposure to time-varying electric and magnetic fields (1 Hz to 100 kHz)

International Nuclear Information System (INIS)

Anon.

2011-01-01

This paper is the French translation of an article from the International Commission on Non-Ionizing Radiation Protection (ICNIRP) Guidelines, entitled 'Guidelines for Limiting Exposure to Time-Varying Electric and Magnetic Fields (1 Hz To 100 kHz)'. In This document, guidelines are established for the protection of humans exposed to electric and magnetic fields in the low-frequency range of the electromagnetic spectrum. The general principles for the development of ICNIRP guidelines are published elsewhere (ICNIRP 2002). For the purpose of this document, the low-frequency range extends from 1 Hz to 100 kHz. Above 100 kHz, effects such as heating need to be considered, which are covered by other ICNIRP guidelines. However, in the frequency range from 100 kHz up to approximately 10 MHz protection from both, low frequency effects on the nervous system as well as high frequency effects need to be considered depending on exposure conditions. Therefore, some guidance in this document is extended to 10 MHz to cover the nervous system effects in this frequency range. Guidelines for static magnetic fields have been issued in a separate document (ICNIRP 2009). Guidelines applicable to movement-induced electric fields or time-varying magnetic fields up to 1 Hz will be published separately. This publication replaces the low-frequency part of the 1998 guidelines (ICNIRP 1998). ICNIRP is currently revising the guidelines for the high-frequency portion of the spectrum (above 100 kHz). (authors)

Axi-symmetric analysis of vertically inhomogeneous elastic multilayered systems

CSIR Research Space (South Africa)

Maina, JW

2009-06-01

Full Text Available primary resilient responses are investigated by way of worked examples of hypothetical three-layer system, which was analyzed by considering homogenous and inhomogeneous material properties in each of the three layers. Effect of a inhomogeneity parameter...

A study of low-dimensional inhomogeneous systems

International Nuclear Information System (INIS)

Arredondo Leon, Yesenia

2009-01-01

While the properties of homogeneous one-dimensional systems, even with disorder, are relatively well-understood, very little is known about the properties of strongly interacting inhomogeneous systems. Their high-energy physics is determined by the underlying chemistry which, in the atomic scale, introduces Coulomb correlations and local potentials. On the other hand, at large length scales, the physics has to be described by the Tomonaga-Luttinger liquid (TLL) model. In order to establish a connection between the low-energy TLL and the quasi-one-dimensional systems synthesized in the laboratory, we investigate the density-density correlation function in inhomogeneous one-dimensional systems in the asymptotic region. To investigate homogeneous as well as inhomogeneous systems, we use the density-matrix renormalization group (DMRG) method. We present results for ground state properties, such as the density-density correlation function and the parameter K c , which characterizes its decay at large distances. (orig.)

A study of low-dimensional inhomogeneous systems

Energy Technology Data Exchange (ETDEWEB)

Arredondo Leon, Yesenia

2009-01-15

While the properties of homogeneous one-dimensional systems, even with disorder, are relatively well-understood, very little is known about the properties of strongly interacting inhomogeneous systems. Their high-energy physics is determined by the underlying chemistry which, in the atomic scale, introduces Coulomb correlations and local potentials. On the other hand, at large length scales, the physics has to be described by the Tomonaga-Luttinger liquid (TLL) model. In order to establish a connection between the low-energy TLL and the quasi-one-dimensional systems synthesized in the laboratory, we investigate the density-density correlation function in inhomogeneous one-dimensional systems in the asymptotic region. To investigate homogeneous as well as inhomogeneous systems, we use the density-matrix renormalization group (DMRG) method. We present results for ground state properties, such as the density-density correlation function and the parameter K{sub c}, which characterizes its decay at large distances. (orig.)

Spectrum of harmonic emission by inhomogeneous plasma in intense electromagnetic wave

International Nuclear Information System (INIS)

Kovalev, V.F.; Pustovalov, V.V.

1989-01-01

The spectrum and angular distribution of the harmonics of arbitrary index emitted by a cold, inhomogeneous electron plasma subjected to a p-polarized electromagnetic wave have been studied analytically. The results are shown in graphical form. The intensity of the wave was varied over a wide range. At energy flux densities of the electromagnetic wave at which the inverse effect of the higher harmonics on the lower harmonics becomes appreciable, it becomes possible to observe a decay of the absolute value of the complex amplitude of a harmonic with increasing harmonic index in vacuum which is substantially slower than that predicted by the theory for a weak nonlinearity

Disordered electrical potential observed on the surface of SiO2 by electric field microscopy

International Nuclear Information System (INIS)

GarcIa, N; Yan Zang; Ballestar, A; Barzola-Quiquia, J; Bern, F; Esquinazi, P

2010-01-01

The electrical potential on the surface of ∼300 nm thick SiO 2 grown on single-crystalline Si substrates has been characterized at ambient conditions using electric field microscopy. Our results show an inhomogeneous potential distribution with fluctuations up to ∼0.4 V within regions of 1 μm. The potential fluctuations observed at the surface of these usual dielectric holders of graphene sheets should induce strong variations in the graphene charge densities and provide a simple explanation for some of the anomalous behaviors of the transport properties of graphene.

Electric polarization of magnetic textures: New horizons of micromagnetism

International Nuclear Information System (INIS)

Pyatakov, A.P.; Meshkov, G.A.; Zvezdin, A.K.

2012-01-01

A common scenario of magnetoelectric coupling in multiferroics is the electric polarization induced by spatially modulated spin structures. It is shown in this paper that the same mechanism works in magnetic dielectrics with inhomogeneous magnetization distribution: the domain walls and magnetic vortexes can be the sources of electric polarization. The electric field driven magnetic domain wall motion is observed in iron garnet films. The electric field induced nucleation of vortex state of magnetic nanodots is theoretically predicted and numerically simulated. From the practical point of view the electric field control of micromagnetic structures suggests a low-power approach for spintronics and magnonics.

Scattering of a spherical pulse from a small inhomogeneity ...

Indian Academy of Sciences (India)

R. Narasimhan (Krishtel eMaging Solutions)

Perturbations in elastic constants and density distinguish a volume inhomogeneity from its homoge- neous surroundings. The equation of motion for the first order scattering is studied in the perturbed medium. The scattered waves are generated by the interaction between the primary waves and the inhomogeneity.

Collapse arresting in an inhomogeneous quintic nonlinear Schrodinger model

DEFF Research Database (Denmark)

Gaididei, Yuri Borisovich; Schjødt-Eriksen, Jens; Christiansen, Peter Leth

1999-01-01

Collapse of (1 + 1)-dimensional beams in the inhomogeneous one-dimensional quintic nonlinear Schrodinger equation is analyzed both numerically and analytically. It is shown that in the vicinity of a narrow attractive inhomogeneity, the collapse of beams in which the homogeneous medium would blow up...

Thermal quantum discord of spins in an inhomogeneous magnetic field

International Nuclear Information System (INIS)

Guo Jinliang; Mi Yingjuan; Zhang Jian; Song Heshan

2011-01-01

In contrast with the thermal entanglement, we study the quantum discord and classical correlation in a two-qubit Heisenberg XXZ model with an inhomogeneous magnetic field. It is shown that the effects of the external magnetic fields, including the uniform and inhomogeneous magnetic fields, on the thermal entanglement, quantum discord and classical correlation behave differently in various aspects, which depend on system temperature and model type. We can tune the inhomogeneous magnetic field to enhance the entanglement or classical correlation and meanwhile decrease the quantum discord. In addition, taking into account the inhomogeneous magnetic field, the sudden change in the behaviour of quantum discord still survives, which can detect the critical points of quantum phase transitions at finite temperature, but not for a uniform magnetic field.

Inhomogeneous superconductors

International Nuclear Information System (INIS)

Tinkham, M.

1978-01-01

The coherence length xi and penetration depth lambda set the characteristic length scales in superconductors, typically 100 to 5,000 A. A lattice of flux lines, each carrying a single quantum, can penetrate type II superconductors, i.e., those for which kappa identical with lambda/xi > 1/√2. Inhomogeneities on the scale of the flux lattice spacing are required to pin the lattice to prevent dissipative flux motion. Recent work using voids as pinning centers has demonstrated this principle, but practical materials rely on cold-work, inclusions of second phases, etc., to provide the inhomogeneity. For stability against thermal fluctuations, the superconductor should have the form of many filaments of diameter 10 to 100 μm imbedded in a highly conductive normal metal matrix. Such wire is made by drawing down billets of copper containing rods of the superconductor. An alternative approach is the metallurgical one of Tsuei, which leads to thousands of superconducting filamentary segments in a copper matrix. The superconducting proximity effect causes the whole material to superconduct at low current densities. At high current densities, the range of the proximity effect is reduced so that the effective superconducting volume fraction falls below the percolation threshold, and a finite resistance arises from the copper matrix. But, because of the extremely elongated filaments, this resistance is orders of magnitude lower than that of the normal wire, and low enough to permit the possibility of technical applications

Inhomogeneities and superconductivity in poly-phase Fe-Se-Te systems

Science.gov (United States)

Hartwig, S.; Schäfer, N.; Schulze, M.; Landsgesell, S.; Abou-Ras, D.; Blum, Ch. G. F.; Wurmehl, S.; Sokolowski, A.; Büchner, B.; Prokeš, K.

2018-02-01

The impact of synthesis conditions, post-preparation heating procedure, aging and influence of pressure on the superconducting properties of FeSe0.4Te0.6 crystals is reported. Two FeSe0.4Te0.6 single crystals were used in the study, prepared from stoichiometric melt but cooled down with very different cooling rates, and investigated using magnetic bulk and electrical-resistivity methods. The fast-cooled crystal contains large inclusions of Fe3Se2.1Te1.8 and exhibits bulk superconductivity in its as-prepared state, while the other is homogeneous and shows only traces of superconductivity. AC susceptibility measurements under hydrostatic pressure show that the superconducting transition temperature of the inhomogeneous crystal increases from 12.3 K at ambient pressure to Tsc = 17.9 K at 9 kbar. On the other hand, neither pressure nor mechanically-induced stress is sufficient to induce superconductivity in the homogeneous crystal. However, an additional heat treatment at 673 K followed by fast cooling down and/or long-term aging at ambient conditions leads to the appearance of bulk superconductivity also in the latter sample. This sample remains homogeneous on a scale down to few μm but shows an additional magnetic phase transition around 130 K suggesting that it must be inhomogeneous. For comparison also Fe3Se2.1Te1.8 polycrystals have been prepared and their magnetic properties have been studied. It appears that this phase is not superconducting by itself. It is concluded that nano-scale inhomogeneities that appear in the FeSexTe1-x system due to a spinodal decomposition in the solid state are necessary for bulk superconductivity, possibly due to minor changes in the crystal structure and microstructure. Macroscopic inclusions quenched by fast cooling from high temperatures lead obviously to strain and hence variations in the lattice constants, an effect that is further supported by application of pressure/stress.

Effect of Inhomogeneity correction for lung volume model in TPS

International Nuclear Information System (INIS)

Chung, Se Young; Lee, Sang Rok; Kim, Young Bum; Kwon, Young Ho

2004-01-01

The phantom that includes high density materials such as steel was custom-made to fix lung and bone in order to evaluation inhomogeneity correction at the time of conducting radiation therapy to treat lung cancer. Using this, values resulting from the inhomogeneous correction algorithm are compared on the 2 and 3 dimensional radiation therapy planning systems. Moreover, change in dose calculation was evaluated according to inhomogeneous by comparing with the actual measurement. As for the image acquisition, inhomogeneous correction phantom(Pig's vertebra, steel(8.21 g/cm 3 ), cork(0.23 g/cm 3 )) that was custom-made and the CT(Volume zoom, Siemens, Germany) were used. As for the radiation therapy planning system, Marks Plan(2D) and XiO(CMS, USA, 3D) were used. To compare with the measurement value, linear accelerator(CL/1800, Varian, USA) and ion chamber were used. Image, obtained from the CT was used to obtain point dose and dose distribution from the region of interest (ROI) while on the radiation therapy planning device. After measurement was conducted under the same conditions, value on the treatment planning device and measured value were subjected to comparison and analysis. And difference between the resulting for the evaluation on the use (or non-use) of inhomogeneity correction algorithm, and diverse inhomogeneity correction algorithm that is included in the radiation therapy planning device was compared as well. As result of comparing the results of measurement value on the region of interest within the inhomogeneity correction phantom and the value that resulted from the homogeneous and inhomogeneous correction, gained from the therapy planning device, margin of error of the measurement value and inhomogeneous correction value at the location 1 of the lung showed 0.8% on 2D and 0.5% on 3D. Margin of error of the measurement value and inhomogeneous correction value at the location 1 of the steel showed 12% on 2D and 5% on 3D, however, it is possible to

Impact of cosmic inhomogeneities on SNe observations

Science.gov (United States)

Kainulainen, Kimmo; Marra, Valerio

2010-06-01

We study the impact of cosmic inhomogeneities on the interpretation of SNe observations. We build an inhomogeneous universe model that can confront supernova data and yet is reasonably well compatible with the Copernican Principle. Our model combines a relatively small local void, that gives apparent acceleration at low redshifts, with a meatball model that gives sizeable lensing (dimming) at high redshifts. Together these two elements, which focus on different effects of voids on the data, allow the model to mimic the concordance model.

Distributions of electric and elastic fields at domain boundaries

International Nuclear Information System (INIS)

Novak, Josef; Fousek, Jan; Maryska, Jiri; Marvan, Milan

2005-01-01

In this paper we describe the application of the finite element method (FEM) in modelling spatial distributions of electric and elastic fields in a ferroelectric crystals with two domains separated by a 90 deg. domain wall. The domain boundary is idealized as a two-dimensional defect in an electro-elastic continuum. It represents the source of inhomogenity and internal distortion in both elastic and electric fields. The main results are distributions of electric field, strain and mechanical force along the domain boundary

Bright and dark solitons in the normal dispersion regime of inhomogeneous optical fibers: Soliton interaction and soliton control

International Nuclear Information System (INIS)

Liu Wenjun; Tian Bo; Xu Tao; Sun Kun; Jiang Yan

2010-01-01

Symbolically investigated in this paper is a nonlinear Schroedinger equation with the varying dispersion and nonlinearity for the propagation of optical pulses in the normal dispersion regime of inhomogeneous optical fibers. With the aid of the Hirota method, analytic one- and two-soliton solutions are obtained. Relevant properties of physical and optical interest are illustrated. Different from the previous results, both the bright and dark solitons are hereby derived in the normal dispersion regime of the inhomogeneous optical fibers. Moreover, different dispersion profiles of the dispersion-decreasing fibers can be used to realize the soliton control. Finally, soliton interaction is discussed with the soliton control confirmed to have no influence on the interaction. The results might be of certain value for the study of the signal generator and soliton control.

Nonlinear interaction of waves in an inhomogeneous plasma

International Nuclear Information System (INIS)

Istomin, Ya.N.

1988-01-01

Nonlinear wave processes in a weakly inhomogeneous plasma are considered. A quasilinear equation is derived which takes into account the effect of the waves on resonance particles, provided that the inhomogeneity appreciably affects the nature of the resonance interaction. Three-wave interaction is investigated under the same conditions. As an example, the nonlinear interaction in a relativistic plasma moving along a strong curvilinear magnetic field is considered

Influence of interface inhomogeneities in thin-film Schottky diodes

Science.gov (United States)

Wilson, Joshua; Zhang, Jiawei; Li, Yunpeng; Wang, Yiming; Xin, Qian; Song, Aimin

2017-11-01

The scalability of thin-film transistors has been well documented, but there have been very few investigations into the effects of device scalability in Schottky diodes. Indium-gallium-zinc-oxide (IGZO) Schottky diodes were fabricated with IGZO thicknesses of 50, 150, and 250 nm. Despite the same IGZO-Pt interface and Schottky barrier being formed in all devices, reducing the IGZO thickness caused a dramatic deterioration of the current-voltage characteristics, most notably increasing the reverse current by nearly five orders of magnitude. Furthermore, the forward characteristics display an increase in the ideality factor and a reduction in the barrier height. The origins of this phenomenon have been elucidated using device simulations. First, when the semiconductor layer is fully depleted, the electric field increases with the reducing thickness, leading to an increased diffusion current. However, the effects of diffusion only offer a small contribution to the huge variations in reverse current seen in the experiments. To fully explain this effect, the role of inhomogeneities in the Schottky barrier height has been considered. Contributions from lower barrier regions (LBRs) are found to dominate the reverse current. The conduction band minimum below these LBRs is strongly dependent upon thickness and bias, leading to reverse current variations as large as several orders of magnitude. Finally, it is demonstrated that the thickness dependence of the reverse current is exacerbated as the magnitude of the inhomogeneities is increased and alleviated in the limit where the LBRs are large enough not to be influenced by the adjacent higher barrier regions.

Nonlinear acoustic waves in micro-inhomogeneous solids

CERN Document Server

Nazarov, Veniamin

2014-01-01

Nonlinear Acoustic Waves in Micro-inhomogeneous Solids covers the broad and dynamic branch of nonlinear acoustics, presenting a wide variety of different phenomena from both experimental and theoretical perspectives. The introductory chapters, written in the style of graduate-level textbook, present a review of the main achievements of classic nonlinear acoustics of homogeneous media. This enables readers to gain insight into nonlinear wave processes in homogeneous and micro-inhomogeneous solids and compare it within the framework of the book. The subsequent eight chapters covering: Physical m

TU-H-206-04: An Effective Homomorphic Unsharp Mask Filtering Method to Correct Intensity Inhomogeneity in Daily Treatment MR Images

International Nuclear Information System (INIS)

Yang, D; Gach, H; Li, H; Mutic, S

2016-01-01

Purpose: The daily treatment MRIs acquired on MR-IGRT systems, like diagnostic MRIs, suffer from intensity inhomogeneity issue, associated with B1 and B0 inhomogeneities. An improved homomorphic unsharp mask (HUM) filtering method, automatic and robust body segmentation, and imaging field-of-view (FOV) detection methods were developed to compute the multiplicative slow-varying correction field and correct the intensity inhomogeneity. The goal is to improve and normalize the voxel intensity so that the images could be processed more accurately by quantitative methods (e.g., segmentation and registration) that require consistent image voxel intensity values. Methods: HUM methods have been widely used for years. A body mask is required, otherwise the body surface in the corrected image would be incorrectly bright due to the sudden intensity transition at the body surface. In this study, we developed an improved HUM-based correction method that includes three main components: 1) Robust body segmentation on the normalized image gradient map, 2) Robust FOV detection (needed for body segmentation) using region growing and morphologic filters, and 3) An effective implementation of HUM using repeated Gaussian convolution. Results: The proposed method was successfully tested on patient images of common anatomical sites (H/N, lung, abdomen and pelvis). Initial qualitative comparisons showed that this improved HUM method outperformed three recently published algorithms (FCM, LEMS, MICO) in both computation speed (by 50+ times) and robustness (in intermediate to severe inhomogeneity situations). Currently implemented in MATLAB, it takes 20 to 25 seconds to process a 3D MRI volume. Conclusion: Compared to more sophisticated MRI inhomogeneity correction algorithms, the improved HUM method is simple and effective. The inhomogeneity correction, body mask, and FOV detection methods developed in this study would be useful as preprocessing tools for many MRI-related research and

Inhomogeneity of epidemic spreading with entropy-based infected clusters.

Science.gov (United States)

Wen-Jie, Zhou; Xing-Yuan, Wang

2013-12-01

Considering the difference in the sizes of the infected clusters in the dynamic complex networks, the normalized entropy based on infected clusters (δ*) is proposed to characterize the inhomogeneity of epidemic spreading. δ* gives information on the variability of the infected clusters in the system. We investigate the variation in the inhomogeneity of the distribution of the epidemic with the absolute velocity v of moving agent, the infection density ρ, and the interaction radius r. By comparing δ* in the dynamic networks with δH* in homogeneous mode, the simulation experiments show that the inhomogeneity of epidemic spreading becomes smaller with the increase of v, ρ, r.

Microinstabilities in a moderately inhomogeneous plasma

International Nuclear Information System (INIS)

Singer, C.E.

1977-01-01

We describe the onset of plasma instability due to heat conduction in a fully ionized hydrogen plasma with small temperature, pressure, and electric potential gradients. The effect of these gradients on plasma stability depends on a single inhomogeneity parameter B/sub t/, which is a measure of the ratio of the electron mean free path to the scale height of the plasma. A large value of vertical-barB/sub t/vertical-bar indicates that the plasma is collisionless. We find the least value of vertical-barB/sub t/vertical-bar needed to produce instability for the range of electron to hydrogen ion temperature ratios T and ion to magnetic pressure ratios β/sub i/, relevant to the solar wind and other plasmas. The wave parameters of the first unstable modes (the modes which become unstable for the least value of vertical-barB/sub t/vertical-bar) are described. The fast mode is the first unstable mode at high β/sub i/, the intermediate mode is the first unstable mode at low β/sub i/, and low temperature ratios, and the slow mode is the first unstable mode at low β/sub i/ and higher temperature ratios

Random field assessment of nanoscopic inhomogeneity of bone

OpenAIRE

Dong, X. Neil; Luo, Qing; Sparkman, Daniel M.; Millwater, Harry R.; Wang, Xiaodu

2010-01-01

Bone quality is significantly correlated with the inhomogeneous distribution of material and ultrastructural properties (e.g., modulus and mineralization) of the tissue. Current techniques for quantifying inhomogeneity consist of descriptive statistics such as mean, standard deviation and coefficient of variation. However, these parameters do not describe the spatial variations of bone properties. The objective of this study was to develop a novel statistical method to characterize and quanti...

Phase-space analysis of the Schwinger effect in inhomogeneous electromagnetic fields

Science.gov (United States)

Kohlfürst, Christian

2018-05-01

Schwinger pair production in spatially and temporally inhomogeneous electric and magnetic fields is studied. The focus is on the particle phase-space distribution within a high-intensity few-cycle pulse. Accurate numerical solutions of a quantum kinetic theory (DHW formalism) are presented in momentum space and, with the aid of coarse-graining techniques, in a mixed spatial-momentum representation. Additionally, signatures of the carrier-envelope phase as well as spin-field interactions are discussed on the basis of a trajectory-based model taking into account instantaneous pair production and relativistic single-particle dynamics. Although our simple semi-classical single-particle model cannot describe every aspect of the particle production process (quantum interferences), essential features such as spin-field interactions are captured.

Observable relations in an inhomogeneous self-similar cosmology

International Nuclear Information System (INIS)

Wesson, P.S.

1979-01-01

An exact self-similar solution is taken in general relativity as a model for an inhomogeneous cosmology. The self-similarity property means (conceptually) that the model is scale-free and (mathematically) that its essential parameters are functions of only one dimensionless variable zeta (equivalentct/R, where R and t are distance and time coordinates and c is the velocity of light). It begins inhomogeneous (zeta=0 or t=0), and tends to a homogeneous Einstein--de Sitter type state as zeta (or t) →infinity. Such a model can be used (a) for evaluating the observational effects of a clumpy universe; (b) for studying astrophysical processes such as galaxy formation and the growth and decay of inhomogeneities in initially clumpy cosmologies; and (c) as a relativistic basis for cosmological models with extended clustering of the de Vaucouleurs and Peebles types. The model has two adjustable parameters, namely, the observer's coordinate zeta 0 and a constant α/sub s/ that fixes the effect of the inhomogeneity. Expressions are obtained for the redshift, Hubble parameter, deceleration parameter, magnitude-redshift relation, and (number density of objects) --redshift relation. Expected anisotropies in the 3 K microwave background are also examined. There is no conflict with observation if zeta 0 /α/sub s/> or approx. =10, and four tests of the model are suggested that can be used to further determine the acceptability of inhomogeneous cosmologies of this type. The ratio α/sub s//zeta 0 on presently available data is α/sub s//zeta 0 < or approx. =10% and this, loosely speaking, means that the universe at the present epoch is globally homogeneous to within about 10%

QCD under extreme conditions. Inhomogeneous condensation

Energy Technology Data Exchange (ETDEWEB)

Heinz, Achim

2014-10-15

Almost 40 years after the first publication on the phase diagram of quantum chromodynamics (QCD) big progress has been made but many questions are still open. This work covers several aspects of low-energy QCD and introduces advanced methods to calculate selected parts of the QCD phase diagram. Spontaneous chiral symmetry breaking as well as its restoration is a major aspect of QCD. Two effective models, the Nambu-Jona-Lasinio (NJL) model and the linear σ-model, are widely used to describe the QCD chiral phase transition. We study the large-N{sub c} behavior of the critical temperature T{sub c} for chiral symmetry restoration in the framework of both models. While in the NJL model T{sub c} is independent of N{sub c} (and in agreement with the expected QCD scaling), the scaling behavior in the linear σ-model reads T{sub c} ∝ N{sup 1/2}{sub c}. However, this mismatch can be corrected: phenomenologically motivated temperature-dependent parameters or the extension with the Polyakov-loop renders the scaling in the linear σ-model compatible with the QCD scaling. The requirement that the chiral condensate which is the order parameter of the chiral symmetry is constant in space is too restrictive. Recent studies on inhomogeneous chiral condensation in cold, dense quark matter suggest a rich crystalline structure. These studies feature models with quark degrees of freedom. In this thesis we investigate the formation of the chiral density wave (CDW) in the framework of the so-called extended linear sigma model (eLSM) at high densities and zero temperature. The eLSM is a modern development of the linear σ-model which contains scalar, pseudoscalar, vector, as well as axial-vector mesons, and in addition, a light tetraquark state. The nucleon and its chiral partner are introduced as parity doublets in the mirror assignment. The model describes successfully the vacuum phenomenology and nuclear matter ground-state properties. As a result we find that an inhomogeneous phase

Electrical resistance imaging of a time-varying interface in stratified flows using an unscented Kalman filter

International Nuclear Information System (INIS)

Ijaz, Umer Zeeshan; Khambampati, Anil Kumar; Kim, Kyung Youn; Chung, Soon Il; Kim, Sin

2008-01-01

In this paper, we estimate a time-varying interfacial boundary in stratified flows of two immiscible liquids using electrical resistance tomography. The interfacial boundary is approximated with front points spaced discretely along the interface. The design variables to be estimated are the locations of the front points, which are varying with the moving interface. The inverse problem is treated as a stochastic nonlinear state estimation problem with the nonstationary phase boundary (state) being estimated with the aid of an unscented Kalman filter. Numerical experiments are performed to evaluate the performance of an unscented Kalman filter. Specifically, a detailed analysis has been done on the effect of the number of front points and contrast ratio on the reconstruction performance. The reconstruction results show that an unscented Kalman filter is better suited for estimation in comparison to the conventional extended Kalman filter

Inclusions and inhomogeneities under stress

CSIR Research Space (South Africa)

Nabarro, FRN

1996-02-01

Full Text Available Some general theorems, new and old, concerning the behaviour of elastic inclusions and inhomogeneities in bodies without or with external stress, are assembled. The principal new result is that arbitrary external tractions cannot influence the shape...

Finite element modelling of moisture related and visco-elastic deformations in inhomogeneous timber beams

DEFF Research Database (Denmark)

Ormarsson, Sigurdur; Dahlblom, Ola

2013-01-01

Wood is a hygro-mechanical, non-isotropic and inhomogeneous material concerning both modulus of elasticity (MOE) and shrinkage properties. In stress calculations associated with ordinary timber design, these matters are often not dealt with properly. The main reason for this is that stress...... and the longitudinal shrinkage coefficient vary considerably from pith to bark. The question is how much these variations affect the stress distribution in wooden structures exposed to variable moisture climate. The paper presents a finite element implementation of a beam element with the aim of studying how wooden...

The inhomogeneous Suslov problem

Energy Technology Data Exchange (ETDEWEB)

García-Naranjo, Luis C., E-mail: luis@mym.iimas.unam.mx [Departamento de Matemáticas y Mecánica, IIMAS-UNAM, Apdo Postal 20-726, Mexico City 01000 (Mexico); Maciejewski, Andrzej J., E-mail: andrzej.j.maciejewski@gmail.com [J. Kepler Institute of Astronomy, University of Zielona Góra, Licealna 9, 65-417 Zielona Góra (Poland); Marrero, Juan C., E-mail: jcmarrero@ull.edu.es [ULL-CSIC, Geometría Diferencial y Mecánica Geométrica, Departamento de Matemática Fundamental, Facultad de Matemáticas, Universidad de la Laguna, La Laguna, Tenerife, Canary Islands (Spain); Przybylska, Maria, E-mail: M.Przybylska@if.uz.zgora.pl [Institute of Physics, University of Zielona Góra, Licealna 9, 65-417 Zielona Góra (Poland)

2014-06-27

We consider the Suslov problem of nonholonomic rigid body motion with inhomogeneous constraints. We show that if the direction along which the Suslov constraint is enforced is perpendicular to a principal axis of inertia of the body, then the reduced equations are integrable and, in the generic case, possess a smooth invariant measure. Interestingly, in this generic case, the first integral that permits integration is transcendental and the density of the invariant measure depends on the angular velocities. We also study the Painlevé property of the solutions. - Highlights: • We consider the Suslov problem of nonholonomic rigid body motion with inhomogeneous constraints. • We study the problem in detail for a particular choice of the parameters that has a clear physical interpretation. • We show that the equations of motion possess an invariant measure whose density depends on the velocity variables. • We show that the reduced system is integrable due to the existence of a transcendental first integral. • We study the Painlevé property of the solutions.

Two-step estimation procedures for inhomogeneous shot-noise Cox processes

DEFF Research Database (Denmark)

Prokesová, Michaela; Dvorák, Jirí; Jensen, Eva B. Vedel

In the present paper we develop several two-step estimation procedures for inhomogeneous shot-noise Cox processes. The intensity function is parametrized by the inhomogeneity parameters while the pair-correlation function is parametrized by the interaction parameters. The suggested procedures...

A nonquasiclassical description of inhomogeneous superconductors

International Nuclear Information System (INIS)

Zaikin, A.D.; Panyukov, S.V.

1988-01-01

Exact microscopic equations are derived that make it possible to describe inhomogeneous superconductors when the quasi-classical approach is not suitable. These equations are simpler than the Gorkov equations. The authors generalize the derived equations for describing the nonequilibrium states of inhomogeneous superconductors. It is demonstrated that the derived equations (including the case of a nonequilibrium quasi particle distribution function) may be written in the form of linear differential equations for the simultaneous wave function μ, ν. The quasi-classical limit of such equations is examined. Effective boundary conditions are derived for the μ, ν functions that allow description of superconductors with a sharp change in parameters within the scope of the quasi-classical approach

Line shapes and time dynamics of the Förster resonances between two Rydberg atoms in a time-varying electric field

KAUST Repository

Yakshina, E. A.

2016-10-21

The observation of the Stark-tuned Förster resonances between Rydberg atoms excited by narrowband cw laser radiation requires usage of a Stark-switching technique in order to excite the atoms first in a fixed electric field and then to induce the interactions in a varied electric field, which is scanned across the Förster resonance. In our experiments with a few cold Rb Rydberg atoms, we have found that the transients at the edges of the electric pulses strongly affect the line shapes of the Förster resonances, since the population transfer at the resonances occurs on a time scale of ∼100 ns, which is comparable with the duration of the transients. For example, a short-term ringing at a certain frequency causes additional radio-frequency-assisted Förster resonances, while nonsharp edges lead to asymmetry. The intentional application of the radio-frequency field induces transitions between collective states, whose line shape depends on the interaction strengths and time. Spatial averaging over the atom positions in a single interaction volume yields a cusped line shape of the Förster resonance. We present a detailed experimental and theoretical analysis of the line shape and time dynamics of the Stark-tuned Förster resonances Rb(nP3/2)+Rb(nP3/2)→Rb(nS1/2)+Rb([n+1]S1/2) for two Rb Rydberg atoms interacting in a time-varying electric field.

Line shapes and time dynamics of the Förster resonances between two Rydberg atoms in a time-varying electric field

KAUST Repository

Yakshina, E. A.; Tretyakov, D. B.; Beterov, I. I.; Entin, V. M.; Andreeva, C.; Cinins, A.; Markovski, A.; Iftikhar, Z.; Ekers, Aigars; Ryabtsev, I. I.

2016-01-01

The observation of the Stark-tuned Förster resonances between Rydberg atoms excited by narrowband cw laser radiation requires usage of a Stark-switching technique in order to excite the atoms first in a fixed electric field and then to induce the interactions in a varied electric field, which is scanned across the Förster resonance. In our experiments with a few cold Rb Rydberg atoms, we have found that the transients at the edges of the electric pulses strongly affect the line shapes of the Förster resonances, since the population transfer at the resonances occurs on a time scale of ∼100 ns, which is comparable with the duration of the transients. For example, a short-term ringing at a certain frequency causes additional radio-frequency-assisted Förster resonances, while nonsharp edges lead to asymmetry. The intentional application of the radio-frequency field induces transitions between collective states, whose line shape depends on the interaction strengths and time. Spatial averaging over the atom positions in a single interaction volume yields a cusped line shape of the Förster resonance. We present a detailed experimental and theoretical analysis of the line shape and time dynamics of the Stark-tuned Förster resonances Rb(nP3/2)+Rb(nP3/2)→Rb(nS1/2)+Rb([n+1]S1/2) for two Rb Rydberg atoms interacting in a time-varying electric field.

Anistropically varying conductivity in irreversible electroporation simulations.

Science.gov (United States)

Labarbera, Nicholas; Drapaca, Corina

2017-11-01

One recent area of cancer research is irreversible electroporation (IRE). Irreversible electroporation is a minimally invasive procedure where needle electrodes are inserted into the body to ablate tumor cells with electricity. The aim of this paper is to propose a mathematical model that incorporates a tissue's conductivity increasing more in the direction of the electrical field as this has been shown to occur in experiments. It was necessary to mathematically derive a valid form of the conductivity tensor such that it is dependent on the electrical field direction and can be easily implemented into numerical software. The derivation of a conductivity tensor that can take arbitrary functions for the conductivity in the directions tangent and normal to the electrical field is the main contribution of this paper. Numerical simulations were performed for isotropic-varying and anisotropic-varying conductivities to evaluate the importance of including the electrical field's direction in the formulation for conductivity. By starting from previously published experimental results, this paper derived a general formulation for an anistropic-varying tensor for implementation into irreversible electroporation modeling software. The anistropic-varying tensor formulation allows the conductivity to take into consideration both electrical field direction and magnitude, as opposed to previous published works that only took into account electrical field magnitude. The anisotropic formulation predicts roughly a five percent decrease in ablation size for the monopolar simulation and approximately a ten percent decrease in ablation size for the bipolar simulations. This is a positive result as previously reported results found the isotropic formulation to overpredict ablation size for both monopolar and bipolar simulations. Furthermore, it was also reported that the isotropic formulation overpredicts the ablation size more for the bipolar case than the monopolar case. Thus, our

Spatial inhomogeneous barrier heights at graphene/semiconductor Schottky junctions

Science.gov (United States)

Tomer, Dushyant

Graphene, a semimetal with linear energy dispersion, forms Schottky junction when interfaced with a semiconductor. This dissertation presents temperature dependent current-voltage and scanning tunneling microscopy/spectroscopy (STM/S) measurements performed on graphene Schottky junctions formed with both three and two dimensional semiconductors. To fabricate Schottky junctions, we transfer chemical vapor deposited monolayer graphene onto Si- and C-face SiC, Si, GaAs and MoS2 semiconducting substrates using polymer assisted chemical method. We observe three main type of intrinsic spatial inhomogeneities, graphene ripples, ridges and semiconductor steps in STM imaging that can exist at graphene/semiconductor junctions. Tunneling spectroscopy measurements reveal fluctuations in graphene Dirac point position, which is directly related to the Schottky barrier height. We find a direct correlation of Dirac point variation with the topographic undulations of graphene ripples at the graphene/SiC junction. However, no such correlation is established at graphene/Si and Graphene/GaAs junctions and Dirac point variations are attributed to surface states and trapped charges at the interface. In addition to graphene ripples and ridges, we also observe atomic scale moire patterns at graphene/MoS2 junction due to van der Waals interaction at the interface. Periodic topographic modulations due to moire pattern do not lead to local variation in graphene Dirac point, indicating that moire pattern does not contribute to fluctuations in electronic properties of the heterojunction. We perform temperature dependent current-voltage measurements to investigate the impact of topographic inhomogeneities on electrical properties of the Schottky junctions. We observe temperature dependence in junction parameters, such as Schottky barrier height and ideality factor, for all types of Schottky junctions in forward bias measurements. Standard thermionic emission theory which assumes a perfect

Microinstabilities in a radially contracting inhomogeneous cylindrical plasma slab

International Nuclear Information System (INIS)

Deutsch, R.; Kaeppeler, H.J.

1980-07-01

In order to study the development of microinstabilities in a collapsing cylindrical plasma sheath, corresponding to the situations in a z-pinch or a plasma focus, the dispersion relation for electromagnetic perturbations is derived with the aid of a newly established slab-model for an inhomogeneous, radially contracting plasma. In contrast to previously used slab-models, the orientation of the electric field is in direction of the cylinder axis and the azimuthal magnetic field is induced by the current flowing through the cylindrical plasma slab. The Vlasov equation is used together with the Krook collision term in order to include the influence of collisions. The results of this theory presented in this report will be used to calculate the growth of drift instabilities in the compression phase of a plasma focus, and shall serve as a basis for further development of a more general dispersion relation including runaway-effects. (orig.)

Inhomogeneities and the Modeling of Radio Supernovae

Energy Technology Data Exchange (ETDEWEB)

Björnsson, C.-I.; Keshavarzi, S. T., E-mail: bjornsson@astro.su.se [Department of Astronomy, AlbaNova University Center, Stockholm University, SE–106 91 Stockholm (Sweden)

2017-05-20

Observations of radio supernovae (SNe) often exhibit characteristics not readily accounted for by a homogeneous, spherically symmetric synchrotron model; e.g., flat-topped spectra/light curves. It is shown that many of these deviations from the standard model can be attributed to an inhomogeneous source structure. When inhomogeneities are present, the deduced radius of the source and, hence, the shock velocity, is sensitive to the details of the modeling. As the inhomogeneities are likely to result from the same mechanism that amplify the magnetic field, a comparison between observations and the detailed numerical simulations now under way may prove mutually beneficial. It is argued that the radio emission in Type Ib/c SNe has a small volume filling factor and comes from a narrow region associated with the forward shock, while the radio emission region in SN 1993J (Type IIb) is determined by the extent of the Rayleigh–Taylor instability emanating from the contact discontinuity. Attention is also drawn to the similarities between radio SNe and the structural properties of SN remnants.

Magnetophoretic potential at the movement of cluster products of electrochemical reactions in an inhomogeneous magnetic field

International Nuclear Information System (INIS)

Gorobets, O. Yu.; Gorobets, Yu. I.; Rospotniuk, V. P.

2015-01-01

An electric field arises from the influence of a nonuniform static magnetic field on charged colloid particles with magnetic susceptibility different from that of the surrounding liquid. It arises, for example, under the influence of a nonuniform static magnetic field in clusters of electrochemical reaction products created during metal etching, deposition, and corrosion processes without an external electric current passing through an electrolyte near a magnetized electrode surface. The corresponding potential consists of a Nernst potential of inhomogeneous distribution of concentration of colloid particles and a magnetophoretic potential (MPP). This potential has been calculated using a thermodynamic approach based on the equations of thermodynamics of nonequilibrium systems and the Onsager relations for a mass flow of correlated magnetic clusters under a gradient magnetic force in the electrolyte. The conditions under which the MPP contribution to the total electric potential may be significant are discussed with a reference to the example of a corroding spherical ferromagnetic steel electrode

Magnetophoretic potential at the movement of cluster products of electrochemical reactions in an inhomogeneous magnetic field

Energy Technology Data Exchange (ETDEWEB)

Gorobets, O. Yu., E-mail: pitbm@ukr.net; Gorobets, Yu. I., E-mail: Gorobets@imag.kiev.ua [National Technical University of Ukraine “KPI”, Peremogy Avenue 37, Kyiv 03056 (Ukraine); Institute of Magnetism NAS of Ukraine and National Academy of Sciences of Ukraine, Vernadsky Avenue, 36-b, Kyiv 03142 (Ukraine); Rospotniuk, V. P. [National Technical University of Ukraine “KPI”, Peremogy Avenue 37, Kyiv 03056 (Ukraine)

2015-08-21

An electric field arises from the influence of a nonuniform static magnetic field on charged colloid particles with magnetic susceptibility different from that of the surrounding liquid. It arises, for example, under the influence of a nonuniform static magnetic field in clusters of electrochemical reaction products created during metal etching, deposition, and corrosion processes without an external electric current passing through an electrolyte near a magnetized electrode surface. The corresponding potential consists of a Nernst potential of inhomogeneous distribution of concentration of colloid particles and a magnetophoretic potential (MPP). This potential has been calculated using a thermodynamic approach based on the equations of thermodynamics of nonequilibrium systems and the Onsager relations for a mass flow of correlated magnetic clusters under a gradient magnetic force in the electrolyte. The conditions under which the MPP contribution to the total electric potential may be significant are discussed with a reference to the example of a corroding spherical ferromagnetic steel electrode.

Distinguishing different types of inhomogeneity in Neyman-Scott point processes

Czech Academy of Sciences Publication Activity Database

Mrkvička, Tomáš

2014-01-01

Roč. 16, č. 2 (2014), s. 385-395 ISSN 1387-5841 Institutional support: RVO:60077344 Keywords : clustering * growing clusters * inhomogeneous cluster centers * inhomogeneous point process * location dependent scaling * Neyman-Scott point process Subject RIV: BA - General Mathematics Impact factor: 0.913, year: 2014

Collapse arresting in an inhomogeneous two-dimensional nonlinear Schrodinger model

DEFF Research Database (Denmark)

Schjødt-Eriksen, Jens; Gaididei, Yuri Borisovich; Christiansen, Peter Leth

2001-01-01

Collapse of (2 + 1)-dimensional beams in the inhomogeneous two-dimensional cubic nonlinear Schrodinger equation is analyzed numerically and analytically. It is shown that in the vicinity of a narrow attractive inhomogeneity, the collapse of beams that in a homogeneous medium would collapse may...

Quasiadiabatic modes from viscous inhomogeneities

CERN Document Server

Giovannini, Massimo

2016-04-20

The viscous inhomogeneities of a relativistic plasma determine a further class of entropic modes whose amplitude must be sufficiently small since curvature perturbations are observed to be predominantly adiabatic and Gaussian over large scales. When the viscous coefficients only depend on the energy density of the fluid the corresponding curvature fluctuations are shown to be almost adiabatic. After addressing the problem in a gauge-invariant perturbative expansion, the same analysis is repeated at a non-perturbative level by investigating the nonlinear curvature inhomogeneities induced by the spatial variation of the viscous coefficients. It is demonstrated that the quasiadiabatic modes are suppressed in comparison with a bona fide adiabatic solution. Because of its anomalously large tensor to scalar ratio the quasiadiabatic mode cannot be a substitute for the conventional adiabatic paradigm so that, ultimately, the present findings seems to exclude the possibility of a successful accelerated dynamics solely...

From clusters to biomolecules: electric dipole, structure and dynamics

International Nuclear Information System (INIS)

Broyer, M; Antoine, R; Compagnon, I; Rayane, D; Dugourd, P

2007-01-01

In this paper, it is demonstrated that the electric dipole of complex molecules or clusters can be measured by beam deviation in an inhomogeneous electric field. This measurement, associated to appropriate theoretical calculations and simulations, allows us to determine the geometry of these systems and their dynamical behaviour as a function of temperature. Selected examples for mixed clusters (metal-fullerene, metal-benzene, salt) and biomolecules (hydrogen bound amino acids and glycine based polypeptides) are discussed

Effect of corneal inhomogeneity on the mechanical behavior of the eye

Science.gov (United States)

Stein, A. A.; Moiseeva, I. N.

2018-05-01

The effect of spatial inhomogeneity of the effective cornea stiffness distribution on the mechanical properties of the eye is investigated on the basis of the two-component model of the eyeball, in which the cornea is represented by a momentless deformable, linearly elastic surface and the scleral region by an elastic element that responds to changes in intraocular pressure by changes in volume. The approach used makes it possible to consider within the same model both the natural corneal inhomogeneity and mechanical consequences of local cornea weakening owing to surgical procedures. The dependences on changes in intraocular pressure of parameters that characterize deformation properties of both the cornea (apex displacement) and the eyeball as a whole (change in intraocular volume) are obtained. For moderate inhomogeneity they differ from the same dependences for the homogenous cornea with effective stiffness equal to the average value for the corresponding inhomogeneous distribution only slightly. However, if the effective stiffness amplitude is very high, corneal inhomogeneity discernibly affects the integral response of the cornea and the eyeball as a whole to changes in pressure. The effect of inhomogeneity on the data of tonometry also mainly depends on the average effective corneal stiffness. The difference between the tonometric and true pressures increases with surgical cornea weakening in the apical region for both Schiøtz and Maklakoff tonometers.

Inflation and inhomogeneities: a hybrid quantization

International Nuclear Information System (INIS)

Olmedo, J; Fernández-Méndez, M; Mena Marugán, G A

2012-01-01

We provide a complete quantization of a homogeneous and isotropic spacetime with positive spatial curvature coupled to a massive scalar field in the framework of Loop Quantum Cosmology. The physical Hilbert space is constructed out of the space of initial data on the minimum volume section. By means of a perturbative treatment we introduce inhomogeneities and thereafter we adopt a hybrid quantum approach, in which these inhomogeneous degrees of freedom are described by a standard Fock quantization. For the considered case of compact spatial topology, the requirements of: i) invariance of the vacuum state under the spatial isometries, and ii) unitary implementation of the quantum dynamics, pick up a privileged set of canonical fields and a unique Fock representation (up to unitary equivalence).

Influence of magnetic-field inhomogeneity on nonlinear magneto-optical resonances

International Nuclear Information System (INIS)

Pustelny, S.; Jackson Kimball, D. F.; Rochester, S. M.; Yashchuk, V. V.; Budker, D.

2006-01-01

In this work, a sensitivity of the rate of relaxation of ground-state atomic coherences to magnetic-field inhomogeneities is studied. Such coherences give rise to many interesting phenomena in light-atom interactions, and their lifetimes are a limiting factor for achieving better sensitivity, resolution, or contrast in many applications. For atoms contained in a vapor cell, some of the coherence-relaxation mechanisms are related to magnetic-field inhomogeneities. We present a simple model describing relaxation due to such inhomogeneities in a buffer-gas-free antirelaxation-coated cell. A relation is given between relaxation rate and magnetic-field inhomogeneities including the dependence on cell size and atomic species. Experimental results, which confirm predictions of the model, are presented. Different regimes, in which the relaxation rate is equally sensitive to the gradients in any direction and in which it is insensitive to gradients transverse to the bias magnetic field, are predicted and demonstrated experimentally

Large linear magnetoresistivity in strongly inhomogeneous planar and layered systems

International Nuclear Information System (INIS)

Bulgadaev, S.A.; Kusmartsev, F.V.

2005-01-01

Explicit expressions for magnetoresistance R of planar and layered strongly inhomogeneous two-phase systems are obtained, using exact dual transformation, connecting effective conductivities of in-plane isotropic two-phase systems with and without magnetic field. These expressions allow to describe the magnetoresistance of various inhomogeneous media at arbitrary concentrations x and magnetic fields H. All expressions show large linear magnetoresistance effect with different dependencies on the phase concentrations. The corresponding plots of the x- and H-dependencies of R(x,H) are represented for various values, respectively, of magnetic field and concentrations at some values of inhomogeneity parameter. The obtained results show a remarkable similarity with the existing experimental data on linear magnetoresistance in silver chalcogenides Ag 2+δ Se. A possible physical explanation of this similarity is proposed. It is shown that the random, stripe type, structures of inhomogeneities are the most suitable for a fabrication of magnetic sensors and a storage of information at room temperatures

Emergence of ultrafast sparsely synchronized rhythms and their responses to external stimuli in an inhomogeneous small-world complex neuronal network.

Science.gov (United States)

Kim, Sang-Yoon; Lim, Woochang

2017-09-01

We consider an inhomogeneous small-world network (SWN) composed of inhibitory short-range (SR) and long-range (LR) interneurons, and investigate the effect of network architecture on emergence of synchronized brain rhythms by varying the fraction of LR interneurons p long . The betweenness centralities of the LR and SR interneurons (characterizing the potentiality in controlling communication between other interneurons) are distinctly different. Hence, in view of the betweenness, SWNs we consider are inhomogeneous, unlike the "canonical" Watts-Strogatz SWN with nearly the same betweenness centralities. For small p long , the load of communication traffic is much concentrated on a few LR interneurons. However, as p long is increased, the number of LR connections (coming from LR interneurons) increases, and then the load of communication traffic is less concentrated on LR interneurons, which leads to better efficiency of global communication between interneurons. Sparsely synchronized rhythms are thus found to emerge when passing a small critical value p long (c) (≃0.16). The population frequency of the sparsely synchronized rhythm is ultrafast (higher than 100 Hz), while the mean firing rate of individual interneurons is much lower (∼30 Hz) due to stochastic and intermittent neural discharges. These dynamical behaviors in the inhomogeneous SWN are also compared with those in the homogeneous Watts-Strogatz SWN, in connection with their network topologies. Particularly, we note that the main difference between the two types of SWNs lies in the distribution of betweenness centralities. Unlike the case of the Watts-Strogatz SWN, dynamical responses to external stimuli vary depending on the type of stimulated interneurons in the inhomogeneous SWN. We consider two cases of external time-periodic stimuli applied to sub-populations of the LR and SR interneurons, respectively. Dynamical responses (such as synchronization suppression and enhancement) to these two cases of

Solitons of an envelope in an inhomogeneous medium

International Nuclear Information System (INIS)

Churilov, S.M.

1982-01-01

Solutions of the Schroedinger nonlinear equation (SNE) used for the description of evolution of a wave packet envelope has been investigated in inhomogeneous and nonstationary media. It is shown that the SNE solution possessing two important properties exists. Firstly, the wave packet remains localized when propagating in an inhomogeneous medium. Secondly, the soliton width and amplitude are determined only with local characteristics of medium and don't depend on the prehistory. Problem of limits of obtained result applicability has been considered

Radio frequency conductivity of plasma in inhomogeneous magnetic field

International Nuclear Information System (INIS)

Itoh, Sanae; Nishikawa, Kyoji; Fukuyama, Atsushi; Itoh, Kimitaka.

1985-01-01

Nonlocal conductivity tensor is obtained to study the kinetic effects on propagation and absorption of radio frequency (rf) waves in dispersive plasmas. Generalized linear propagator in the presence of the inhomogeneity of magnetic field strength along the field line is calculated. The influence of the inhomogeneity to the rf wave-energy deposition is found to be appreciable. Application to toroidal plasmas is shown. (author)

Density gradient instabilities in a neutron inhomogeneous guiding-centre plasma

International Nuclear Information System (INIS)

Shoucri, M.M.; Gagne, R.R.J.

1977-01-01

The guiding-centre equations for a plasma of cold ions and thermal electrons admit neutral and non-neutral inhomogeneous equilibrium solutions, and the linear stability of these solutions has been recently investigated numerically by Shoucri and Knorr (1975). With arbitrary density profiles, numerical techniques appear to be the only practical way to study the linear stability of the inhomogeneous equilibrium solutions for the guiding centre plasma. However, analytical methods can be applied to some simple types of density profiles. The purpose of the present note is to present some analytical results on the linear instabilities of an inhomogeneous neutral guiding centre plasma. (U.K.)

On Electron Hole Evolution in Inhomogeneous Plasmas

Science.gov (United States)

Kuzichev, I.; Vasko, I.; Agapitov, O. V.; Mozer, F.; Artemyev, A.

2017-12-01

Electron holes (EHs) are the stationary localized non-linear structures in phase space existing due to an electron population trapped within EH electrostatic potential. EHs were found to be a common phenomenon in the Earth's magnetosphere. Such structures were observed in reconnecting current sheets, injection fronts in the outer radiation belt, and in many other situations. EHs usually propagate along magnetic field lines with velocities about electron thermal velocity, are localized on the scale of about 4-10 Debye lengths, and have the field amplitude up to hundreds of mV/m. Generation of these structures, evolution, and their role in relaxation of instabilities and energy dissipation, particle energization, supporting large-scale potential drops is under active investigation. In this report, we present the results of 1.5D gyrokinetic Vlasov-Maxwell simulations of the EH evolution in plasmas with inhomogeneous magnetic field and inhomogeneous density. Our calculations show that the inhomogeneity has a critical effect on the EH dynamics. EHs propagating into stronger (weaker) magnetic field are decelerated (accelerated) with deceleration (acceleration) rate dependent on the magnetic field gradient. During the deceleration of EH, the potential drop (weak double layer) along EH is generated. Such a potential drop might be experimentally observable even for single EH in the reconnecting current sheets. The same holds for the propagation in the plasma with inhomogeneous density. For some parameters of the system, the deceleration results in the turning of the hole. The interesting feature of this process is that the turning point depends only on the EH parameters, being independent of the average inhomogeneity scale. Our calculations also demonstrate the significant difference between "quasi-particle" concept and real evolution of the hole. Indeed, the EH is accelerated (decelerated) faster than it follows from a quasi-particle energy conservation law. It indicates

WKB solution 4×4 for electromagnetic waves in a planar magnetically anisotropic inhomogeneous layer

Science.gov (United States)

Moiseeva, Natalya Michailovna; Moiseev, Anton Vladimirovich

2018-04-01

In the paper, an oblique incidence of a plane electromagnetic wave on a planar magnetically anisotropic inhomogeneous layer is considered. We consider the case when all the components of the magnetic permeability tensor are non zero and vary with distance from the interface of media. The WKB method gives a matrix 4 × 4 solution for the projections of the electromagnetic wave fields during its propagation. The dependence of the cross-polarized components on the orientation of the anisotropic medium relative to the plane of incidence of the medium is analyzed.

Inhomogeneous neutrino degeneracy and big bang nucleosynthesis

International Nuclear Information System (INIS)

Whitmire, Scott E.; Scherrer, Robert J.

2000-01-01

We examine big bang nucleosynthesis (BBN) in the case of inhomogeneous neutrino degeneracy, in the limit where the fluctuations are sufficiently small on large length scales that the present-day element abundances are homogeneous. We consider two representative cases: degeneracy of the electron neutrino alone and equal chemical potentials for all three neutrinos. We use a linear programming method to constrain an arbitrary distribution of the chemical potentials. For the current set of (highly restrictive) limits on the primordial element abundances, homogeneous neutrino degeneracy barely changes the allowed range of the baryon-to-photon ratio η. Inhomogeneous degeneracy allows for little change in the lower bound on η, but the upper bound in this case can be as large as η=1.1x10 -8 (only ν e degeneracy) or η=1.0x10 -9 (equal degeneracies for all three neutrinos). For the case of inhomogeneous neutrino degeneracy, we show that there is no BBN upper bound on the neutrino energy density, which is bounded in this case only by limits from structure formation and the cosmic microwave background. (c) 2000 The American Physical Society

Current sheets with inhomogeneous plasma temperature: Effects of polarization electric field and 2D solutions

International Nuclear Information System (INIS)

Catapano, F.; Zimbardo, G.; Artemyev, A. V.; Vasko, I. Y.

2015-01-01

We develop current sheet models which allow to regulate the level of plasma temperature and density inhomogeneities across the sheet. These models generalize the classical Harris model via including two current-carrying plasma populations with different temperature and the background plasma not contributing to the current density. The parameters of these plasma populations allow regulating contributions of plasma density and temperature to the pressure balance. A brief comparison with spacecraft observations demonstrates the model applicability for describing the Earth magnetotail current sheet. We also develop a two dimensional (2D) generalization of the proposed model. The interesting effect found for 2D models is the nonmonotonous profile (along the current sheet) of the magnetic field component perpendicular to the current sheet. Possible applications of the model are discussed

Current sheets with inhomogeneous plasma temperature: Effects of polarization electric field and 2D solutions

Energy Technology Data Exchange (ETDEWEB)

Catapano, F., E-mail: menacata3@gmail.com; Zimbardo, G. [Dipartimento di Fisica, Università della Calabria, Rende, Cosenza (Italy); Artemyev, A. V., E-mail: ante0226@gmail.com; Vasko, I. Y. [Space Research Institute, RAS, Moscow (Russian Federation)

2015-09-15

We develop current sheet models which allow to regulate the level of plasma temperature and density inhomogeneities across the sheet. These models generalize the classical Harris model via including two current-carrying plasma populations with different temperature and the background plasma not contributing to the current density. The parameters of these plasma populations allow regulating contributions of plasma density and temperature to the pressure balance. A brief comparison with spacecraft observations demonstrates the model applicability for describing the Earth magnetotail current sheet. We also develop a two dimensional (2D) generalization of the proposed model. The interesting effect found for 2D models is the nonmonotonous profile (along the current sheet) of the magnetic field component perpendicular to the current sheet. Possible applications of the model are discussed.

Cosmic acceleration driven by mirage inhomogeneities

Energy Technology Data Exchange (ETDEWEB)

Galfard, Christophe [DAMTP, Centre for Mathematical Sciences, University of Cambridge, Wilberforce road, Cambridge CB3 0WA (United Kingdom); Germani, Cristiano [DAMTP, Centre for Mathematical Sciences, University of Cambridge, Wilberforce road, Cambridge CB3 0WA (United Kingdom); Kehagias, Alex [Physics Division, National Technical University of Athens, 15780 Zografou Campus, Athens (Greece)

2006-03-21

A cosmological model based on an inhomogeneous D3-brane moving in an AdS{sub 5} x S{sub 5} bulk is introduced. Although there are no special points in the bulk, the brane universe has a centre and is isotropic around it. The model has an accelerating expansion and its effective cosmological constant is inversely proportional to the distance from the centre, giving a possible geometrical origin for the smallness of a present-day cosmological constant. Besides, if our model is considered as an alternative of early-time acceleration, it is shown that the early stage accelerating phase ends in a dust-dominated FRW homogeneous universe. Mirage-driven acceleration thus provides a dark matter component for the brane universe final state. We finally show that the model fulfils the current constraints on inhomogeneities.

Nonlocality and optics of inhomogeneous systems : The role of quantum induction

NARCIS (Netherlands)

Wijers, C.M.J.; de Boeij, P.L.

2002-01-01

Nonlocal interactions play a prominent role in the optics of inhomogeneous systems. Classical discrete dipole descriptions take into account only electro-magnetic nonlocality. This is insufficient to describe correctly the inhomogeneous optical response (e.g., reflectance anisotropy) for covalently

Corrections to the apparent value of the cosmological constant due to local inhomogeneities

International Nuclear Information System (INIS)

Romano, Antonio Enea; Chen, Pisin

2011-01-01

Supernovae observations strongly support the presence of a cosmological constant, but its value, which we will call apparent, is normally determined assuming that the Universe can be accurately described by a homogeneous model. Even in the presence of a cosmological constant we cannot exclude nevertheless the presence of a small local inhomogeneity which could affect the apparent value of the cosmological constant. Neglecting the presence of the inhomogeneity can in fact introduce a systematic misinterpretation of cosmological data, leading to the distinction between an apparent and true value of the cosmological constant. We establish the theoretical framework to calculate the corrections to the apparent value of the cosmological constant by modeling the local inhomogeneity with a ΛLTB solution. Our assumption to be at the center of a spherically symmetric inhomogeneous matter distribution correspond to effectively calculate the monopole contribution of the large scale inhomogeneities surrounding us, which we expect to be the dominant one, because of other observations supporting a high level of isotropy of the Universe around us. By performing a local Taylor expansion we analyze the number of independent degrees of freedom which determine the local shape of the inhomogeneity, and consider the issue of central smoothness, showing how the same correction can correspond to different inhomogeneity profiles. Contrary to previous attempts to fit data using large void models our approach is quite general. The correction to the apparent value of the cosmological constant is in fact present for local inhomogeneities of any size, and should always be taken appropriately into account both theoretically and observationally

Inhomogeneous chiral symmetry breaking in isospin-asymmetric strong-interaction matter

Energy Technology Data Exchange (ETDEWEB)

Nowakowski, Daniel

2017-07-01

In this thesis we investigate the effects of an isospin asymmetry on inhomogeneous chiral symmetry breaking phases, which are characterized by spatially modulated quarkantiquark condensates. In order to determine the relevance of such phases for the phase diagram of strong-interaction matter, a two-flavor Nambu-Jona-Lasinio model is used to study the properties of the ground state of the system. Confirming the presence of inhomogeneous chiral symmetry breaking in isospin-asymmetric matter for a simple Chiral Density Wave, we generalize the modulation of the quark-antiquark pairs to more complicated shapes and study the effects of different degrees of flavor-mixing on the inhomogeneous phase at non-zero isospin asymmetry. Then, we investigate the occurrence of crystalline chiral symmetry breaking phases in charge-neutral matter, from which we determine the influence of crystalline phases on a quark star by calculating mass-radius sequences. Finally, our model is extended through color-superconducting phases and we study the interplay of these phases with inhomogeneous chiral-symmetry breaking at non-vanishing isospin asymmetry, before we discuss our findings.

Inhomogeneous anisotropic cosmology

International Nuclear Information System (INIS)

Kleban, Matthew; Senatore, Leonardo

2016-01-01

In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with “flat” (including toroidal) and “open” (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are “flat” or “open”. Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with “flat” or “open” topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.

Dose inhomogeneities at various levels of biological organization

International Nuclear Information System (INIS)

Bond, V.P.

1988-01-01

Dose inhomogeneities in both tumor and normal tissue, inherent to the application of boron neutron capture therapy (BNCT), can be the result not only of ununiform distribution of 10 B at various levels of biological organization, but also of the distribution of the thermal neutrons and of the energy depositions from more energetic neutrons and other radiations comprising the externally-applied beams. The severity of the problems resulting from such inhomogeneities, and approaches to evaluating them, are illustrated by three examples, at the macro, micro and intermediate levels

Spectral properties of waves in superlattices with 2D and 3D inhomogeneities

International Nuclear Information System (INIS)

Ignatchenko, V. A.; Tsikalov, D. S.

2011-01-01

We investigate the dynamic susceptibility and one-dimensional density of states in an initially sinusoidal superlattice containing simultaneously 2D phase inhomogeneities simulating correlated rough-nesses of superlattice interfaces and 3D amplitude inhomogeneities of the superlattice layer materials. The analytic expression for the averaged Green’s function of the sinusoidal superlattice with two phase inhomogeneities is derived in the Bourret approximation. It is shown that the effect of increasing asymmetry in the peak heights of dynamic susceptibility at the Brillouin zone boundary of the superlattice, which was discovered earlier [15] upon an increase in root-mean-square (rms) fluctuations, also takes place upon an increase in the correlation wavenumber of inhomogeneities. However, the peaks in this case also become closer, and the width and depth of the gap in the density of states decrease thereby. It is shown that the enhancement of rms fluctuations of 3D amplitude inhomogeneities in a superlattice containing 2D phase inhomogeneities suppresses the effect of dynamic susceptibility asymmetry and leads to a slight broadening of the gap in the density of states and a decrease in its depth. Targeted experiments aimed at detecting the effects studied here would facilitate the development of radio-spectroscopic and optical methods for identifying the presence of inhomogeneities of various dimensions in multilayer magnetic and optical structures.

Off-center observers versus supernovae in inhomogeneous pressure universes

OpenAIRE

Balcerzak, Adam; Dabrowski, Mariusz P.; Denkiewicz, Tomasz

2013-01-01

Exact luminosity distance and apparent magnitude formulas are applied to Union2 557 supernovae sample in order to constrain possible position of an observer outside of the center of symmetry in spherically symmetric inhomogeneous pressure Stephani universes which are complementary to inhomogeneous density Lema\\^itre-Tolman-Bondi (LTB) void models. Two specific models are investigated. The first which allows a barotropic equation of state at the center of symmetry with no scale factor function...

Process Modeling With Inhomogeneous Thin Films

Science.gov (United States)

Machorro, R.; Macleod, H. A.; Jacobson, M. R.

1986-12-01

Designers of optical multilayer coatings commonly assume that the individual layers will be ideally homogeneous and isotropic. In practice, it is very difficult to control the conditions involved in the complex evaporation process sufficiently to produce such ideal films. Clearly, changes in process parameters, such as evaporation rate, chamber pressure, and substrate temperature, affect the microstructure of the growing film, frequently producing inhomogeneity in structure or composition. In many cases, these effects are interdependent, further complicating the situation. However, this process can be simulated on powerful, interactive, and accessible microcomputers. In this work, we present such a model and apply it to estimate the influence of an inhomogeneous layer on multilayer performance. Presently, the program simulates film growth, thermal expansion and contraction, and thickness monitoring procedures, and includes the effects of uncertainty in these parameters or noise. Although the model is being developed to cover very general cases, we restrict the present discussion to isotropic and nondispersive quarterwave layers to understand the particular effects of inhomogeneity. We studied several coating designs and related results and tolerances to variations in evaporation conditions. The model is composed of several modular subprograms, is written in Fortran, and is executed on an IBM-PC with 640 K of memory. The results can be presented in graphic form on a monochrome monitor. We are currently installing and implementing color capability to improve the clarity of the multidimensional output.

Analytical solution of electromagnetic radiation by a vertical electric dipole inside the earth and the effect of atmospheric electrical conductivity inhomogeneity

Science.gov (United States)

Mosayebidorcheh, Taha; Hosseinibalam, Fahimeh; Hassanzadeh, Smaeyl

2017-11-01

In this paper, the effect of atmospheric electrical conductivity on the electromagnetic waves radiated by a vertical electric dipole located in the earth, near the surface of the earth, is investigated. As far as electrical conductivity is concerned, the atmosphere is divided into three areas, in which the electrical conductivity changes with altitude. The Maxwell equations in these areas are investigated as well. Using the differential transform method, the differential equation is solved in a way that atmospheric electrical conductivity is variable. Solving the problem in these areas indicates that electrical conductivity in the middle and lower areas of atmosphere may be ignored. However, in the upper areas of atmosphere, the magnitude of the magnetic field in the ionosphere at a frequency of 10 kHz at night is five times smaller when electrical conductivity is considered compared to when it is neglected.

Thermal activation of current in an inhomogeneous Schottky diode with a Gaussian distribution of barrier height

International Nuclear Information System (INIS)

Guo-Ping, Ru; Rong, Yu; Yu-Long, Jiang; Gang, Ruan

2010-01-01

This paper investigates the thermal activation behaviour of current in an inhomogeneous Schottky diode with a Gaussian distribution of barrier height by numerical simulation. The analytical Gaussian distribution model predicted that the I-V-T curves may intersect with the possibility of the negative thermal activation of current, but may be contradictory to the thermionic emission mechanism in a Schottky diode. It shows that the cause of the unphysical phenomenon is related to the incorrect calculation of current across very low barriers. It proposes that junction voltage V j , excluding the voltage drop across series resistance from the external bias, is a crucial parameter for correct calculation of the current across very low barriers. For correctly employing the thermionic emission model, V j needs to be smaller than the barrier height ø. With proper scheme of series resistance connection where the condition of V j > ø is guaranteed, I-V-T curves of an inhomogeneous Schottky diode with a Gaussian distribution of barrier height have been simulated, which demonstrate normal thermal activation. Although the calculated results exclude the intersecting possibility of I-V-T curves with an assumption of temperature-independent series resistance, it shows that the intersecting is possible when the series resistance has a positive temperature coefficient. Finally, the comparison of our numerical and analytical results indicates that the analytical Gaussian distribution model is valid and accurate in analysing I-V-T curves only for small barrier height inhomogeneity. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Non-conventional rule of making a periodically varying different-pole magnetic field in low-power alternating current electrical machines with using ring coils in multiphase armature winding

Science.gov (United States)

Plastun, A. T.; Tikhonova, O. V.; Malygin, I. V.

2018-02-01

The paper presents methods of making a periodically varying different-pole magnetic field in low-power electrical machines. Authors consider classical designs of electrical machines and machines with ring windings in armature, structural features and calculated parameters of magnetic circuit for these machines.

Inhomogeneities from quantum collapse scheme without inflation

Energy Technology Data Exchange (ETDEWEB)

Bengochea, Gabriel R., E-mail: gabriel@iafe.uba.ar [Instituto de Astronomía y Física del Espacio (IAFE), UBA-CONICET, CC 67, Suc. 28, 1428 Buenos Aires (Argentina); Cañate, Pedro, E-mail: pedro.canate@nucleares.unam.mx [Instituto de Ciencias Nucleares, UNAM, México D.F. 04510, México (Mexico); Sudarsky, Daniel, E-mail: sudarsky@nucleares.unam.mx [Instituto de Ciencias Nucleares, UNAM, México D.F. 04510, México (Mexico)

2015-04-09

In this work, we consider the problem of the emergence of seeds of cosmic structure in the framework of the non-inflationary model proposed by Hollands and Wald. In particular, we consider a modification to that proposal designed to account for breaking the symmetries of the initial quantum state, leading to the generation of the primordial inhomogeneities. This new ingredient is described in terms of a spontaneous reduction of the wave function. We investigate under which conditions one can recover an essentially scale free spectrum of primordial inhomogeneities, and which are the dominant deviations that arise in the model as a consequence of the introduction of the collapse of the quantum state into that scenario.

Inhomogeneous ensembles of radical pairs in chemical compasses

Science.gov (United States)

Procopio, Maria; Ritz, Thorsten

2016-11-01

The biophysical basis for the ability of animals to detect the geomagnetic field and to use it for finding directions remains a mystery of sensory biology. One much debated hypothesis suggests that an ensemble of specialized light-induced radical pair reactions can provide the primary signal for a magnetic compass sensor. The question arises what features of such a radical pair ensemble could be optimized by evolution so as to improve the detection of the direction of weak magnetic fields. Here, we focus on the overlooked aspect of the noise arising from inhomogeneity of copies of biomolecules in a realistic biological environment. Such inhomogeneity leads to variations of the radical pair parameters, thereby deteriorating the signal arising from an ensemble and providing a source of noise. We investigate the effect of variations in hyperfine interactions between different copies of simple radical pairs on the directional response of a compass system. We find that the choice of radical pair parameters greatly influences how strongly the directional response of an ensemble is affected by inhomogeneity.

Large Scale Cosmological Anomalies and Inhomogeneous Dark Energy

Directory of Open Access Journals (Sweden)

Leandros Perivolaropoulos

2014-01-01

Full Text Available A wide range of large scale observations hint towards possible modifications on the standard cosmological model which is based on a homogeneous and isotropic universe with a small cosmological constant and matter. These observations, also known as “cosmic anomalies” include unexpected Cosmic Microwave Background perturbations on large angular scales, large dipolar peculiar velocity flows of galaxies (“bulk flows”, the measurement of inhomogenous values of the fine structure constant on cosmological scales (“alpha dipole” and other effects. The presence of the observational anomalies could either be a large statistical fluctuation in the context of ΛCDM or it could indicate a non-trivial departure from the cosmological principle on Hubble scales. Such a departure is very much constrained by cosmological observations for matter. For dark energy however there are no significant observational constraints for Hubble scale inhomogeneities. In this brief review I discuss some of the theoretical models that can naturally lead to inhomogeneous dark energy, their observational constraints and their potential to explain the large scale cosmic anomalies.

Quantification of inhomogeneities in malignancy grading of non-Hodgkin lymphoma with MR imaging

International Nuclear Information System (INIS)

Rehn, S.; Sperber, G.O.; Nyman, R.; Glimelius, B.; Hagberg, H.; Hemmingsson, A.

1993-01-01

In a previous study of 50 patients with non-Hodgkin lymphoma (NHL) it was shown that the inhomogeneous appearance of a tumor at MR imaging strongly indicated a high malignancy grade. In this study of 33 patients with NHL, the administration of an i.v. contrast medium, Gadolinium-DTPA, improved the subjective detectability of the inhomogeneities. A method of quantifying the degree of inhomogeneity in the tumors (inhomogeneity index, IH-index) was developed and tested. The mean value of IH-index in the T2-weighted image before contrast medium administration, and of the T1-weighted image after contrast medium administration, as well as the IH-index value in the T2-weighted image before contrast medium administration alone, was able to discriminate well between low- and high-grade NHL. This method of quantifiying the degree of inhomogeneity in tumors improved sensitivity in detecting high-grade NHL. (orig.)

A storage ring for neutral molecules

NARCIS (Netherlands)

Crompvoets, F.M.H.

2005-01-01

Time-varying inhomogeneous electric fields can be used to manipulate the motion of neutral molecules in phase-space, i.e., position-momentum space, via their electric dipole moment. A theoretical background is given on the motion of the molecules in phase-space. As the forces exerted on the

Estimating functions for inhomogeneous spatial point processes with incomplete covariate data

DEFF Research Database (Denmark)

Waagepetersen, Rasmus

and this leads to parameter estimation error which is difficult to quantify. In this paper we introduce a Monte Carlo version of the estimating function used in "spatstat" for fitting inhomogeneous Poisson processes and certain inhomogeneous cluster processes. For this modified estimating function it is feasible...

Estimating functions for inhomogeneous spatial point processes with incomplete covariate data

DEFF Research Database (Denmark)

Waagepetersen, Rasmus

2008-01-01

and this leads to parameter estimation error which is difficult to quantify. In this paper, we introduce a Monte Carlo version of the estimating function used in spatstat for fitting inhomogeneous Poisson processes and certain inhomogeneous cluster processes. For this modified estimating function, it is feasible...

Characterisation of an inhomogeneously irradiated microstrip detector using a fine spot infrared laser

CERN Document Server

Casse, G; Bowcock, T J V; Greenall, A; Phillips, JP; Turner, PR; Wright, V

2001-01-01

A prototype silicon microstrip detector for the LHCb vertex locator (VELO) has been partially irradiated using a 24 GeV/c proton beam at the CERN-PS accelerator. The detector possesses a radial strip geometry designed to measure the azimuthal coordinate (Phi) of tracks within the VELO. The peak fluence received by the detector was measured to be 4.6×10 14 p/cm 2 though the non-uniform nature of the exposure left part of the detector unirradiated. The inhomogeneous irradiation introduced a damage profile in the detector approximating to that expected in the VELO. High irradiation gradients are important to study as they can modify the electric field within the silicon. Of special interest are changes in the component of the electric field parallel to the strip plane but perpendicular to the strips which lead to systematic shifts in the reconstructed cluster position. If these (flux and position dependent) shifts are sufficiently large they could contribute to a degraded spatial resolution of the detector. In ...

Love waves in a structure with an inhomogeneous layer

International Nuclear Information System (INIS)

Ghazaryan, K.B.; Piliposyan, D.G.

2011-01-01

The problem of the propagation of Love type waves in a structure consisting of a finite inhomogeneous layer sandwiched between two isotropic homogeneous half spaces is investigated. Two types of inhomogeneity are considered. It is shown that in one case the amplitude of vibrations in the middle layer is a sinusoidal function of distance from the plane of symmetry, but that in the other case it may be non-sinusoidal for certain values of the parameters of the problem

Solutions of the chemical kinetic equations for initially inhomogeneous mixtures.

Science.gov (United States)

Hilst, G. R.

1973-01-01

Following the recent discussions by O'Brien (1971) and Donaldson and Hilst (1972) of the effects of inhomogeneous mixing and turbulent diffusion on simple chemical reaction rates, the present report provides a more extensive analysis of when inhomogeneous mixing has a significant effect on chemical reaction rates. The analysis is then extended to the development of an approximate chemical sub-model which provides much improved predictions of chemical reaction rates over a wide range of inhomogeneities and pathological distributions of the concentrations of the reacting chemical species. In particular, the development of an approximate representation of the third-order correlations of the joint concentration fluctuations permits closure of the chemical sub-model at the level of the second-order moments of these fluctuations and the mean concentrations.

A new scheme for solving inhomogeneous Boltzmann equation for electrons in weakly ionised gases

International Nuclear Information System (INIS)

Mahmoud, M.O.M.; Yousfi, M.

1995-01-01

In the case of weakly ionized gases, the numerical treatment of non-hydrodynamic regime involving spatial variation of distribution function due to boundaries (walls, electrodes, electron source, etc hor-ellipsis) by using direct Boltzmann equation always constitute a challenge if the main collisional processes occurring in non thermal plasmas are to be considered (elastic, inelastic and super-elastic collisions, Penning ionisation, Coulomb interactions, etc hor-ellipsis). In the non-thermal discharge modelling, the inhomogeneous electron Boltzmann equation is needed in order to be coupled for example to a fluid model to take into account the electron non-hydrodynamic effects. This is for example the case of filamentary discharge, in which the space charge electric field due to streamer propagation has a very sharp spatial profile thus leading to important space non-hydrodynamic effects. It is also the case of the cathodic zone of glow discharge where electric field has a rapid spatial decrease until the negative glow. In the present work, a new numerical scheme is proposed to solve the inhomogeneous Boltzmann equation for electrons in the framework of two-term approximation (TTA) taking into account elastic and inelastic processes. Such a method has the usual drawbacks associated with the TTA i.e. not an accurate enough at high E/N values or in presence of high inelastic processes. But the accuracy of this method is considered sufficient because in a next step it is destinated to be coupled to fluid model for charged particles and a chemical kinetic model where the accuracy is of the same order of magnitude or worse. However there are numerous advantages of this method concerning time computing, treatment of non-linear collision processes (Coulomb, Penning, etc hor-ellipsis)

Effective permittivity of finite inhomogeneous objects

NARCIS (Netherlands)

Raghunathan, S.B.; Budko, N.V.

2010-01-01

A generalization of the S-parameter retrieval method for finite three-dimensional inhomogeneous objects under arbitrary illumination and observation conditions is presented. The effective permittivity of such objects may be rigorously defined as a solution of a nonlinear inverse scattering problem.

Impact of inhomogeneity on SH-type wave propagation in an initially stressed composite structure

Science.gov (United States)

Saha, S.; Chattopadhyay, A.; Singh, A. K.

2018-02-01

The present analysis has been made on the influence of distinct form of inhomogeneity in a composite structure comprised of double superficial layers lying over a half-space, on the phase velocity of SH-type wave propagating through it. Propagation of SH-type wave in the said structure has been examined in four distinct cases of inhomogeneity viz. when inhomogeneity in double superficial layer is due to exponential variation in density only (Case I); when inhomogeneity in double superficial layers is due to exponential variation in rigidity only (Case II); when inhomogeneity in double superficial layer is due to exponential variation in rigidity, density and initial stress (Case III) and when inhomogeneity in double superficial layer is due to linear variation in rigidity, density and initial stress (Case IV). Closed-form expression of dispersion relation has been accomplished for all four aforementioned cases through extensive application of Debye asymptotic analysis. Deduced dispersion relations for all the cases are found in well-agreement to the classical Love-wave equation. Numerical computation has been carried out to graphically demonstrate the effect of inhomogeneity parameters, initial stress parameters as well as width ratio associated with double superficial layers in the composite structure for each of the four aforesaid cases on dispersion curve. Meticulous examination of distinct cases of inhomogeneity and initial stress in context of considered problem has been carried out with detailed analysis in a comparative approach.

Brownian motion probe for water-ethanol inhomogeneous mixtures

Science.gov (United States)

Furukawa, Kazuki; Judai, Ken

2017-12-01

Brownian motion provides information regarding the microscopic geometry and motion of molecules, insofar as it occurs as a result of molecular collisions with a colloid particle. We found that the mobility of polystyrene beads from the Brownian motion in a water-ethanol mixture is larger than that predicted from the liquid shear viscosity. This indicates that mixing water and ethanol is inhomogeneous in micron-sized probe beads. The discrepancy between the mobility of Brownian motion and liquid mobility can be explained by the way the rotation of the beads in an inhomogeneous viscous solvent converts the translational movement.

Phase synchronization in inhomogeneous globally coupled map lattices

International Nuclear Information System (INIS)

Ho Mingchung; Hung Yaochen; Jiang, I-M.

2004-01-01

The study of inhomogeneous-coupled chaotic systems has attracted a lot of attention recently. With simple definition of phase, we present the phase-locking behavior in ensembles of globally coupled non-identical maps. The inhomogeneous globally coupled maps consist of logistic map and tent map simultaneously. Average phase synchronization ratios, which are used to characterize the phase coherent phenomena, depend on different coupling coefficients and chaotic parameters. By using interdependence, the relationship between a single unit and the mean field is illustrated. Moreover, we take the effect of external noise and parameter mismatch into consideration and present the results by numerical simulation

Spatial Inhomogeneity of Kinetic and Magnetic Dissipations in Thermal Convection

Energy Technology Data Exchange (ETDEWEB)

Hotta, H. [Department of Physics, Graduate School of Science, Chiba university, 1-33 Yayoi-cho, Inage-ku, Chiba, 263-8522 (Japan)

2017-08-20

We investigate the inhomogeneity of kinetic and magnetic dissipations in thermal convection using high-resolution calculations. In statistically steady turbulence, the injected and dissipated energies are balanced. This means that a large amount of energy is continuously converted into internal energy via dissipation. As in thermal convection, downflows are colder than upflows and the inhomogeneity of the dissipation potentially changes the convection structure. Our investigation of the inhomogeneity of the dissipation shows the following. (1) More dissipation is seen around the bottom of the calculation domain, and this tendency is promoted with the magnetic field. (2) The dissipation in the downflow is much larger than that in the upflow. The dissipation in the downflow is more than 80% of the total at maximum. This tendency is also promoted with the magnetic field. (3) Although 2D probability density functions of the kinetic and magnetic dissipations versus the vertical velocity are similar, the kinetic and magnetic dissipations are not well correlated. Our result suggests that the spatial inhomogeneity of the dissipation is significant and should be considered when modeling a small-scale strong magnetic field generated with an efficient small-scale dynamo for low-resolution calculations.

Chemical inhomogeneity populations in various zircaloy claddings and their association with SCC and corrosion resistance

International Nuclear Information System (INIS)

Tasooji, A.; Miller, A.K.; Cheung, T.Y.; Brooks, M.; Santucci, J.

1987-01-01

A technique has been developed that permits detection and characterization of sparsely distributed chemical inhomogeneities in Zircaloy. These inhomogeneities have previously been observed at the origins of iodine stress-corrosion cracks but are not detectable by, for example, simple scanning electron microscopy (SEM) examination. The technique uses radioactive iodine to ''label'' the chemical inhomogeneities, autoradiography to detect their locations, and SEM and energy-dispersive X-ray analysis (EDAX) to further characterize them. Large areas of surface have been surveyed and statistically meaningful populations of chemical inhomogeneities measured for five different lots of Zircaloy cladding. Inner surfaces and cladding cross-sectional surfaces have been studied. There are clear differences in chemical inhomogeneity size distribution and composition between the various claddings. For three of the claddings characterized in this work, the previously measured stress-corrosion cracking (SCC) threshold stresses correlate well (inversely) with the new data on their average chemical inhomogeneity sizes. Of special interest is the fact that the most SCC-resistant cladding contains far fewer iron-bearing inhomogeneities than the other claddings

Quasilinear diffusion in inhomogeneous plasmas

International Nuclear Information System (INIS)

Hooley, D.L.

1975-05-01

The problem of inhomogeneous diffusion in a plasma is considered with emphasis on its possible application to relativistic electron beams. A one-dimensional model with a background electrostatic field is used to illustrate the basic approach, which is then extended to a two-dimensional plasma with a background magnetic field. Only preliminary results are available. (U.S.)

High-speed imaging of inhomogeneous ignition in a shock tube

Science.gov (United States)

Tulgestke, A. M.; Johnson, S. E.; Davidson, D. F.; Hanson, R. K.

2018-05-01

Homogeneous and inhomogeneous ignition of real and surrogate fuels were imaged in two Stanford shock tubes, revealing the influence of small particle fragmentation. n-Heptane, iso-octane, and Jet A were studied, each mixed in an oxidizer containing 21% oxygen and ignited at low temperatures (900-1000 K), low pressures (1-2 atm), with an equivalence ratio of 0.5. Visible images (350-1050 nm) were captured through the shock tube endwall using a high-speed camera. Particles were found to arrive near the endwalls of the shock tubes approximately 5 ms after reflection of the incident shock wave. Reflected shock wave experiments using diaphragm materials of Lexan and steel were investigated. Particles collected from the shock tubes after each experiment were found to match the material of the diaphragm burst during the experiment. Following each experiment, the shock tubes were cleaned by scrubbing with cotton cloths soaked with acetone. Particles were observed to fragment after arrival near the endwall, often leading to inhomogeneous ignition of the fuel. Distinctly more particles were observed during experiments using steel diaphragms. In experiments exhibiting inhomogeneous ignition, flames were observed to grow radially until all the fuel within the cross section of the shock tube had been consumed. The influence of diluent gas (argon or helium) was also investigated. The use of He diluent gas was found to suppress the number of particles capable of causing inhomogeneous flames. The use of He thus allowed time history studies of ignition to extend past the test times that would have been limited by inhomogeneous ignition.

Unified formulation for inhomogeneity-driven instabilities in the lower-hybrid range

International Nuclear Information System (INIS)

Silveira, O.J.G.; Ziebell, L.F.; Gaelzer, R.; Yoon, Peter H.

2002-01-01

A local dispersion relation that describes inhomogeneity-driven instabilities in the lower-hybrid range is derived following a procedure that correctly describes energy exchange between waves and particles in inhomogeneous media, correcting some inherent ambiguities associated with the standard formalism found in the literature. Numerical solutions of this improved dispersion relation show that it constitutes a unified formulation for the instabilities in the lower-hybrid range, describing the so-called modified two-stream instability, excited by the ion cross-field drift, including the ion Weibel instability, and also describing the lower-hybrid drift instability, which is due to inhomogeneity effects on the electron population

Attosecond extreme ultraviolet generation in cluster by using spatially inhomogeneous field

Energy Technology Data Exchange (ETDEWEB)

Feng, Liqiang, E-mail: lqfeng-lngy@126.com [College of Science, Liaoning University of Technology, Jinzhou, 121000 (China); State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics Chinese Academy of Sciences, Dalian 116023 (China); Liu, Hang [School of Chemical and Environmental Engineering, Liaoning University of Technology, Jinzhou 121000 (China)

2015-01-15

A promising method to generate the attosecond extreme ultraviolet (XUV) sources has been theoretically investigated emerging from the two-dimensional Ar{sup +} cluster driven by the spatially inhomogeneous field. The results show that with the introduction of the Ar{sup +} cluster model, not only the harmonic cutoffs are enhanced, but also the harmonic yields are reinforced. Furthermore, by properly moderating the inhomogeneity as well as the laser parameters of the inhomogeneous field, the harmonic cutoff can be further extended. As a result, three almost linearly polarized XUV pulses with durations of 40 as, 42 as, and 45 as can be obtained.

Critical behavior in inhomogeneous random graphs

NARCIS (Netherlands)

Hofstad, van der R.W.

2009-01-01

We study the critical behavior of inhomogeneous random graphs where edges are present independently but with unequal edge occupation probabilities. We show that the critical behavior depends sensitively on the properties of the asymptotic degrees. Indeed, when the proportion of vertices with degree

A systematic study of head tissue inhomogeneity and anisotropy on EEG forward problem computing

International Nuclear Information System (INIS)

Bashar, M.R.; Li, Y.; Wen, P.

2010-01-01

Full text: In this study, we propose a stochastic method to analyze the effects of inhomogeneous anisotropic tissue conductivity on electroencephalogram (EEG) in forward computation. We apply this method to an inhomogeneous and anisotropic spherical human head model. We apply stochastic finite element method based on Legendre polynomials, Karhunen-Loeve expansion and stochastic Galerkin methods. We apply Volume and Wang's constraints to restrict the anisotropic conductivities for both the white matter (WM) and the skull tissue compartments. The EEGs resulting from deterministic and stochastic FEMs are compared using statistical measurement techniques. Based on these comparisons, we find that EEGs generated by incorporating WM and skull inhomogeneous anisotropic tissue properties individually result in an average of 56.5 and 57.5% relative errors, respectively. Incorporating these tissue properties for both layers together generate 43.5% average relative error. Inhomogeneous scalp tissue causes 27% average relative error and a full inhomogeneous anisotropic model brings in an average of 45.5% relative error. The study results demonstrate that the effects of inhomogeneous anisotropic tissue conductivity are significant on EEG.

Time-dependent inhomogeneous jet models for BL Lac objects

Science.gov (United States)

Marlowe, A. T.; Urry, C. M.; George, I. M.

1992-05-01

Relativistic beaming can explain many of the observed properties of BL Lac objects (e.g., rapid variability, high polarization, etc.). In particular, the broadband radio through X-ray spectra are well modeled by synchrotron-self Compton emission from an inhomogeneous relativistic jet. We have done a uniform analysis on several BL Lac objects using a simple but plausible inhomogeneous jet model. For all objects, we found that the assumed power-law distribution of the magnetic field and the electron density can be adjusted to match the observed BL Lac spectrum. While such models are typically unconstrained, consideration of spectral variability strongly restricts the allowed parameters, although to date the sampling has generally been too sparse to constrain the current models effectively. We investigate the time evolution of the inhomogeneous jet model for a simple perturbation propagating along the jet. The implications of this time evolution model and its relevance to observed data are discussed.

Vesicle biomechanics in a time-varying magnetic field.

Science.gov (United States)

Ye, Hui; Curcuru, Austen

2015-01-01

Cells exhibit distortion when exposed to a strong electric field, suggesting that the field imposes control over cellular biomechanics. Closed pure lipid bilayer membranes (vesicles) have been widely used for the experimental and theoretical studies of cellular biomechanics under this electrodeformation. An alternative method used to generate an electric field is by electromagnetic induction with a time-varying magnetic field. References reporting the magnetic control of cellular mechanics have recently emerged. However, theoretical analysis of the cellular mechanics under a time-varying magnetic field is inadequate. We developed an analytical theory to investigate the biomechanics of a modeled vesicle under a time-varying magnetic field. Following previous publications and to simplify the calculation, this model treated the inner and suspending media as lossy dielectrics, the membrane thickness set at zero, and the electric resistance of the membrane assumed to be negligible. This work provided the first analytical solutions for the surface charges, electric field, radial pressure, overall translational forces, and rotational torques introduced on a vesicle by the time-varying magnetic field. Frequency responses of these measures were analyzed, particularly the frequency used clinically by transcranial magnetic stimulation (TMS). The induced surface charges interacted with the electric field to produce a biomechanical impact upon the vesicle. The distribution of the induced surface charges depended on the orientation of the coil and field frequency. The densities of these charges were trivial at low frequency ranges, but significant at high frequency ranges. The direction of the radial force on the vesicle was dependent on the conductivity ratio between the vesicle and the medium. At relatively low frequencies (biomechanics under a time-varying magnetic field. Biological effects of clinical TMS are not likely to occur via alteration of the biomechanics of brain

Evaluation of planning dose accuracy in case of radiation treatment on inhomogeneous organ structure

Energy Technology Data Exchange (ETDEWEB)

Kim, Chan Yong; Lee, Jae Hee; Kwak, Yong Kook; Ha, Min Yong [Dept. of Radiation Oncology, Seoul National University Hospital, Seoul (Korea, Republic of)

2013-09-15

We are to find out the difference of calculated dose of treatment planning system (TPS) and measured dose in case of inhomogeneous organ structure. Inhomogeneous phantom is made with solid water phantom and cork plate. CT image of inhomogeneous phantom is acquired. Treatment plan is made with TPS (Pinnacle3 9.2. Royal Philips Electronics, Netherlands) and calculated dose of point of interest is acquired. Treatment plan was delivered in the inhomogeneous phantom by ARTISTE (Siemens AG, Germany) measured dose of each point of interest is obtained with Gafchromic EBT2 film (International Specialty Products, US) in the gap between solid water phantom or cork plate. To simulate lung cancer radiation treatment, artificial tumor target of paraffin is inserted in the cork volume of inhomogeneous phantom. Calculated dose and measured dose are acquired as above. In case of inhomogeneous phantom experiment, dose difference of calculated dose and measured dose is about -8.5% at solid water phantom-cork gap and about -7% lower in measured dose at cork-solid water phantom gap. In case of inhomogeneous phantom inserted paraffin target experiment, dose difference is about 5% lower in measured dose at cork-paraffin gap. There is no significant difference at same material gap in both experiments. Radiation dose at the gap between two organs with different electron density is significantly lower than calculated dose with TPS. Therefore, we must be aware of dose calculation error in TPS and great care is suggested in case of radiation treatment planning on inhomogeneous organ structure.

Evaluation of planning dose accuracy in case of radiation treatment on inhomogeneous organ structure

International Nuclear Information System (INIS)

Kim, Chan Yong; Lee, Jae Hee; Kwak, Yong Kook; Ha, Min Yong

2013-01-01

We are to find out the difference of calculated dose of treatment planning system (TPS) and measured dose in case of inhomogeneous organ structure. Inhomogeneous phantom is made with solid water phantom and cork plate. CT image of inhomogeneous phantom is acquired. Treatment plan is made with TPS (Pinnacle3 9.2. Royal Philips Electronics, Netherlands) and calculated dose of point of interest is acquired. Treatment plan was delivered in the inhomogeneous phantom by ARTISTE (Siemens AG, Germany) measured dose of each point of interest is obtained with Gafchromic EBT2 film (International Specialty Products, US) in the gap between solid water phantom or cork plate. To simulate lung cancer radiation treatment, artificial tumor target of paraffin is inserted in the cork volume of inhomogeneous phantom. Calculated dose and measured dose are acquired as above. In case of inhomogeneous phantom experiment, dose difference of calculated dose and measured dose is about -8.5% at solid water phantom-cork gap and about -7% lower in measured dose at cork-solid water phantom gap. In case of inhomogeneous phantom inserted paraffin target experiment, dose difference is about 5% lower in measured dose at cork-paraffin gap. There is no significant difference at same material gap in both experiments. Radiation dose at the gap between two organs with different electron density is significantly lower than calculated dose with TPS. Therefore, we must be aware of dose calculation error in TPS and great care is suggested in case of radiation treatment planning on inhomogeneous organ structure

Inhomogeneous Pre-Big Bang String Cosmology

OpenAIRE

Veneziano, Gabriele

1997-01-01

An inhomogeneous version of pre--Big Bang cosmology emerges, within string theory, from quite generic initial conditions, provided they lie deeply inside the weak-coupling, low-curvature regime. Large-scale homogeneity, flatness, and isotropy appear naturally as late-time outcomes of such an evolution.

Electrical Impedance Spectroscopic Studies on Broiler Chicken Tissue Suitable for the Development of Practical Phantoms in Multifrequency EIT

Directory of Open Access Journals (Sweden)

Tushar Kanti Bera

2011-06-01

Full Text Available Phantoms are essential for assessing the system performance in Electrical Impedance Tomography (EIT. Saline phantoms with insulator inhomogeneity fail to mimic the physiological structure of real body tissue in several aspects. Saline or any other salt solutions are purely resistive and hence studying multifrequency EIT systems cannot be assessed with saline phantoms because the response of the purely resistive materials do not change over frequency. Animal tissues show a variable response over a wide band of signal frequency due to their complex physiological and physiochemical structures and hence they can suitably be used as bathing medium and inhomogeneity in the phantoms of multifrequency EIT system. An efficient assessment of a multifrequency EIT system with real tissue phantom needs a prior knowledge of the impedance profile of the bathing medium as well as the inhomogeneity. In this direction Electrical Impedance Spectroscopy (EIS of broiler chicken muscle tissue paste and broiler chicken fat tissue is conducted from 10 Hz to 2 MHz using an impedance analyzer and their impedance profiles are thoroughly studied. Results show that the broiler chicken muscle tissue paste is less resistive than the fat tissue and hence it can be successfully used as the bathing medium of the phantoms for resistivity imaging in multifrequency EIT. Fat tissue is found more resistive than the muscle tissue which makes it more suitable for the inhomogeneity in phantoms of resistivity imaging study. doi:10.5617/jeb.174 J Electr Bioimp, vol. 2, pp. 48-63, 2011

Time-Varying Value of Energy Efficiency in Michigan

Energy Technology Data Exchange (ETDEWEB)

Mims, Natalie; Eckman, Tom; Schwartz, Lisa C.

2018-04-02

Quantifying the time-varying value of energy efficiency is necessary to properly account for all of its benefits and costs and to identify and implement efficiency resources that contribute to a low-cost, reliable electric system. Historically, most quantification of the benefits of efficiency has focused largely on the economic value of annual energy reduction. Due to the lack of statistically representative metered end-use load shape data in Michigan (i.e., the hourly or seasonal timing of electricity savings), the ability to confidently characterize the time-varying value of energy efficiency savings in the state, especially for weather-sensitive measures such as central air conditioning, is limited. Still, electric utilities in Michigan can take advantage of opportunities to incorporate the time-varying value of efficiency into their planning. For example, end-use load research and hourly valuation of efficiency savings can be used for a variety of electricity planning functions, including load forecasting, demand-side management and evaluation, capacity planning, long-term resource planning, renewable energy integration, assessing potential grid modernization investments, establishing rates and pricing, and customer service (KEMA 2012). In addition, accurately calculating the time-varying value of efficiency may help energy efficiency program administrators prioritize existing offerings, set incentive or rebate levels that reflect the full value of efficiency, and design new programs.

Detection of Buried Inhomogeneous Elliptic Cylinders by a Memetic Algorithm

OpenAIRE

Caorsi, Salvatore; Massa, Andrea; Pastorino, Matteo; Raffetto, Mirco; Randazzo, Andrea

2003-01-01

The application of a global optimization procedure to the detection of buried inhomogeneities is studied in the present paper. The object inhomogeneities are schematized as multilayer infinite dielectric cylinders with elliptic cross sections. An efficient recursive analytical procedure is used for the forward scattering computation. A functional is constructed in which the field is expressed in series solution of Mathieu functions. Starting by the input scattered data, the iterative minimiza...

The phase transition to an inhomogeneous condensate state

International Nuclear Information System (INIS)

Voskresensky, D.N.

1984-01-01

The Lagrangian (free energy) of the model with a complex scalar order parameter in which the phase transition to an inhomogeneous condensate state exists is constructed in the coordinate representation. In the case of condensation of charged particles (for example paired electrons) interaction with the electromagnetic field is included. The excitation spectrum in the presence of the condensate is found. The oscillations are strongly anisotropic. It is shown that superfluidity is absent for an uncharged system but that the charged one has the property of superconductivity. The important role of thermal fluctuations is demonstrated. They drastically change the behaviour of the condensate system. The condensation in a finite system is considered. A study is carried out for the behaviour of an inhomogeneous condensate in magnetic field. It is shown that the inhomogeneous condensate is a type II superconductor with Ginzburg-Landau parameter kappa >> 1, but that the structure of the mixed state of the system is unusual - consisting of plane layers of the normal phase, when Hsub(c1)< H< H'sub(c2). The distribution of condensate in the strong magnetic field H'sub(c2)< H< Hsub(c2) is also studied. (Auth.)

Strong dopant dependence of electric transport in ion-gated MoS2

NARCIS (Netherlands)

Piatti, Erik; Chen, Qihong; Ye, Jianting

2017-01-01

We report modifications of the temperature-dependent transport properties of MoS2 thin flakes via field-driven ion intercalation in an electric double layer transistor. We find that intercalation with Li+ ions induces the onset of an inhomogeneous superconducting state. Intercalation with K+ leads

How the effects of winds and electric fields in F2-layer storms vary with latitude and longitude - A theoretical study

Science.gov (United States)

Mendillo, M.; He, X.-Q.; Rishbeth, H.

1992-01-01

The effects of thermospheric winds and electric fields on the ionospheric F2-layer are controlled by the geometry of the magnetic field, and so vary with latitude and longitude. A simple model of the daytime F2-layer is adopted and the effects at midlatitudes (25-65 deg geographic) of three processes that accompany geomagnetic storms: (1) thermospheric changes due to auroral heating; (2) equatorward winds that tend to cancel the quiet-day poleward winds; and (3) the penetration of magnetospheric electric fields are studied. At +/- 65 deg, the effects of heating and electric fields are strongest in the longitudes toward which the geomagnetic dipole is tilted, i.e., the North American and the South Indian Ocean sectors. Because of the proximity of the geomagnetic equator to the East Asian and South American sectors, the reverse is true at +/- 25 deg.

Electron Beam interaction with an inhomogeneous

Energy Technology Data Exchange (ETDEWEB)

Zaki, N G; El-Shorbagy, Kh H [Plasma physics and Nuclear Fusion Dept. Nuclear Research Centre Atomic Energy Authority, Cairo, (Egypt)

1997-12-31

The linear and nonlinear interaction of an electron beam with an inhomogeneous semi bounded warm plasma is investigated. The amount of energy absorbed by the plasma is obtained. The formation of waves at double frequency at the inlet of the beam into the plasma is also considered.

Inhomogeneity driven by Higgs instability in a gapless superconductor

International Nuclear Information System (INIS)

Giannakis, Ioannis; Hou Defu; Huang Mei; Ren Haicang

2007-01-01

The fluctuations of the Higgs and pseudo Nambu-Goldstone fields in the 2-flavor color superconductivity (2SC) phase with mismatched pairing are described in the nonlinear realization framework of the gauged Nambu-Jona-Lasinio model. In the gapless 2SC phase, not only Nambu-Goldstone currents can be spontaneously generated, but also the Higgs field exhibits instablity. The Nambu-Goldstone currents generation indicates the formation of the single plane wave Larkin-Ovchinnikov-Fulde-Ferrel state and breaks rotation symmetry, while the Higgs instability favors spatial inhomogeneity and breaks translation invariance. In this paper, we focus on the Higgs instability which has not drawn much attention yet. The Higgs instability cannot be removed without a long range force, thus it persists in the gapless superfluidity and induces phase separation. In the case of gapless 2-flavor color superconductivity state, the Higgs instability can only be partially removed by the electric Coulomb energy. However, it is not excluded that the Higgs instability might be completely removed in the charge neutral gapless color-flavor locked phase by the color Coulomb energy

Optical Modeling of Sea Salt Aerosols: The Effects of Nonsphericity and Inhomogeneity

Science.gov (United States)

Bi, Lei; Lin, Wushao; Wang, Zheng; Tang, Xiaoyun; Zhang, Xiaoyu; Yi, Bingqi

2018-01-01

The nonsphericity and inhomogeneity of marine aerosols (sea salts) have not been addressed in pertinent radiative transfer calculations and remote sensing studies. This study investigates the optical properties of nonspherical and inhomogeneous sea salts using invariant imbedding T-matrix simulations. Dry sea salt aerosols are modeled based on superellipsoidal geometries with a prescribed aspect ratio and roundness parameter. Wet sea salt particles are modeled as coated superellipsoids, as spherical particles with a superellipsoidal core, and as homogeneous spheres depending on the level of relative humidity. Aspect ratio and roundness parameters are found to be critical to interpreting the linear depolarization ratios (LDRs) of NaCl crystals from laboratory measurements. The optimal morphology parameters of NaCl necessary to reproduce the measurements are found to be consistent with data gleaned from an electron micrograph. The LDRs of wet sea salts are computed based on inhomogeneous models and compared with the measured data from ground-based LiDAR. The dependence of the LDR on relative humidity is explicitly considered. The increase in the LDR with relative humidity at the initial phase of deliquescence is attributed to both the size increase and the inhomogeneity effect. For large humidity values, the LDR substantially decreases because the overall particle shape becomes more spherical and the inhomogeneity effect in a particle on the LDR is suppressed for submicron sea salts. However, the effect of inhomogeneity on optical properties is pronounced for coarse-mode sea salts. These findings have important implications for atmospheric radiative transfer and remote sensing involving sea salt aerosols.

Equilibrium and stability in strongly inhomogeneous plasmas

International Nuclear Information System (INIS)

Mynick, H.E.

1978-10-01

The equilibrium of strongly inhomogeneous, collisionless, slab plasmas, is studied using a generalized version of a formalism previously developed, which permits the generation of self-consistent equilibria, for plasmas with arbitrary magnetic shear, and variation of magnetic field strength. A systematic procedure is developed for deriving the form of the guiding-center Hamiltonian K, for finite eta, in an axisymmetric geometry. In the process of obtaining K, an expression for the first adiabatic invariant (the gyroaction) is obtained, which generalizes the usual expression 1/2 mv/sub perpendicular/ 2 /Ω/sub c/ (Ω/sub c/ = eB/mc), to finite eta and magnetic shear. A formalism is developed for the study of the stability of strongly-inhomogeneous, magnetized slab plasmas; it is then applied to the ion-drift-cyclotron instability

How Forest Inhomogeneities Affect the Edge Flow

DEFF Research Database (Denmark)

Boudreault, Louis-Étienne; Dupont, Sylvain; Bechmann, Andreas

2016-01-01

Most of our knowledge on forest-edge flows comes from numerical and wind-tunnel experiments where canopies are horizontally homogeneous. To investigate the impact of tree-scale heterogeneities (>1 m) on the edge-flow dynamics, the flow in an inhomogeneous forest edge on Falster island in Denmark...... is investigated using large-eddy simulation. The three-dimensional forest structure is prescribed in the model using high resolution helicopter-based lidar scans. After evaluating the simulation against wind measurements upwind and downwind of the forest leading edge, the flow dynamics are compared between...... the scanned forest and an equivalent homogeneous forest. The simulations reveal that forest inhomogeneities facilitate flow penetration into the canopy from the edge, inducing important dispersive fluxes in the edge region as a consequence of the flow spatial variability. Further downstream from the edge...

Primordial inhomogeneities from massive defects during inflation

Energy Technology Data Exchange (ETDEWEB)

Firouzjahi, Hassan; Karami, Asieh; Rostami, Tahereh, E-mail: firouz@ipm.ir, E-mail: karami@ipm.ir, E-mail: t.rostami@ipm.ir [School of Astronomy, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)

2016-10-01

We consider the imprints of local massive defects, such as a black hole or a massive monopole, during inflation. The massive defect breaks the background homogeneity. We consider the limit that the physical Schwarzschild radius of the defect is much smaller than the inflationary Hubble radius so a perturbative analysis is allowed. The inhomogeneities induced in scalar and gravitational wave power spectrum are calculated. We obtain the amplitudes of dipole, quadrupole and octupole anisotropies in curvature perturbation power spectrum and identify the relative configuration of the defect to CMB sphere in which large observable dipole asymmetry can be generated. We observe a curious reflection symmetry in which the configuration where the defect is inside the CMB comoving sphere has the same inhomogeneous variance as its mirror configuration where the defect is outside the CMB sphere.

Line broadening interference for high-resolution nuclear magnetic resonance spectra under inhomogeneous magnetic fields

International Nuclear Information System (INIS)

Wei, Zhiliang; Yang, Jian; Lin, Yanqin; Chen, Zhong; Chen, Youhe

2015-01-01

Nuclear magnetic resonance spectroscopy serves as an important tool for analyzing chemicals and biological metabolites. However, its performance is subject to the magnetic-field homogeneity. Under inhomogeneous fields, peaks are broadened to overlap each other, introducing difficulties for assignments. Here, we propose a method termed as line broadening interference (LBI) to provide high-resolution information under inhomogeneous magnetic fields by employing certain gradients in the indirect dimension to interfere the magnetic-field inhomogeneity. The conventional spectral-line broadening is thus interfered to be non-diagonal, avoiding the overlapping among adjacent resonances. Furthermore, an inhomogeneity correction algorithm is developed based on pattern recognition to recover the high-resolution information from LBI spectra. Theoretical deductions are performed to offer systematic and detailed analyses on the proposed method. Moreover, experiments are conducted to prove the feasibility of the proposed method for yielding high-resolution spectra in inhomogeneous magnetic fields

Transformation instability of oscillations in inhomogeneous beam-plasma system

International Nuclear Information System (INIS)

Kitsenko, A.B.

1985-01-01

Wave transformation is studied in a plasma system which was weak-inhomogeneous along beam velocity, in absence of external magnetic field. For the case of small density beam formulae are obtained which have set a coupling between the charge density beam wave amplitudes and the Langmuir wave on both sides of transformation point. It is shown that in collisionless plasma the wave production is a cause of the absorption of the charge density beam waves. Transformation mechanism of the absolute instability in the weak-inhomogeneous beam-plasma system is revealed

Annealing effect on Schottky barrier inhomogeneity of graphene/n-type Si Schottky diodes

International Nuclear Information System (INIS)

Lin, Yow-Jon; Lin, Jian-Huang

2014-01-01

Highlights: • The current–voltage characteristics of graphene/n-type Si devices were measured. • The ideality factor increases with the decrease measurement temperatures. • Such behavior is attributed to Schottky barrier inhomogeneities. • Both Schottky barrier inhomogeneity and the T 0 effect are affected by annealing. • Stoichiometry of SiO x has a noticeable effect on the inhomogeneous barriers. - Abstract: The current–voltage characteristics of graphene/n-type Si (n-Si) Schottky diodes with and without annealing were measured in the temperature range of −120 to 30 °C and analyzed on the basis of thermionic emission theory. It is found that the barrier height decreases and the ideality factor increases with the decrease measurement temperatures. Such behavior is attributed to Schottky barrier inhomogeneities. It is shown that both the barrier height and the ideality factor can be tuned by changing the annealing temperature. Through the analysis, it can be suspected that a SiO x layer at the graphene/n-Si interfaces influences the electronic conduction through the device and stoichiometry of SiO x is affected by annealing treatment. In addition, both Schottky barrier inhomogeneity and the T 0 effect are affected by annealing treatment, implying that stoichiometry of SiO x has a noticeable effect on the inhomogeneous barriers of graphene/n-Si Schottky diodes

Experimental analysis on stress wave in inhomogeneous multi-layered structures

International Nuclear Information System (INIS)

Cho, Yun Ho; Ham, Hyo Sick

1998-01-01

The guided wave propagation in inhomogeneous multi-layered structures is experimentally explored based on theoretical dispersion curves. It turns out that proper selection of incident angle and frequency is critical for guided wave generation in multi-layered structures. Theoretical dispersion curves greatly depend on adhesive zone thickness, layer thickness and material properties. It was possible to determine the adhesive zone thickness of an inhomogeneous multi-layered structure by monitoring experimentally the change of dispersion curves.

Electrical properties of Au/perylene-monoimide/p-Si Schottky diode

International Nuclear Information System (INIS)

Yüksel, Ö.F.; Tuğluoğlu, N.; Gülveren, B.; Şafak, H.; Kuş, M.

2013-01-01

Graphical abstract: In this work, we have fabricated an Au/perylene-monoimide (PMI)/p-Si Schottky barrier diode. An emphasis is placed on how electrical and interface characteristics like current–voltage (I–V) variation, ideality factor (n), barrier height (Φ B ) and series resistance (R s ) of Au/PMI/p-Si diode structure change with the temperatures between 100 and 300 K. The temperature dependence of barrier height shows that the Schottky barrier height is inhomogeneous in nature at the interface. Such inhomogeneous behavior was explained on the basis of thermionic emission mechanism by assuming the existence of a Gaussian distribution of barrier heights. -- Highlights: •An Au/perylene-monoimide (PMI)/p-Si Schottky diode having an organic interlayer has been fabricated. •I–V characteristics have been investigated over a wide temperature range 100–300 K. •C–V measurements have been analyzed at room temperature. -- Abstract: In this work, we have fabricated an Au/perylene-monoimide (PMI)/p-Si Schottky barrier diode. We have investigated how electrical and interface characteristics like current–voltage characteristics (I–V), ideality factor (n), barrier height (Φ B ) and series resistance (R s ) of diode change with temperature over a wide range of 100–300 K. Detailed analysis on the electrical properties of structure is performed by assuming the standard thermionic emission (TE) model. Possible mechanisms such as image force lowering, generation–recombination processes and interface states which cause deviations of n values from the unity have been discussed. Cheung–Cheung method is also employed to analysis the current–voltage characteristics and a good agreement is observed between the results. It is shown that the electronic properties of Schottky diode are very sensitive to the modification of perylene-monoimide (PMI) interlayer organic material and also to the temperature. The ideality factor was found to decrease and the barrier

Critical behavior in inhomogeneous random graphs

NARCIS (Netherlands)

Hofstad, van der R.W.

2013-01-01

We study the critical behavior of inhomogeneous random graphs in the so-called rank-1 case, where edges are present independently but with unequal edge occupation probabilities. The edge occupation probabilities are moderated by vertex weights, and are such that the degree of vertex i is close in

Cirrus Cloud Optical Thickness and Effective Diameter Retrieved by MODIS: Impacts of Single Habit Assumption, 3-D Radiative Effects, and Cloud Inhomogeneity

Science.gov (United States)

Zhou, Yongbo; Sun, Xuejin; Mielonen, Tero; Li, Haoran; Zhang, Riwei; Li, Yan; Zhang, Chuanliang

2018-01-01

For inhomogeneous cirrus clouds, cloud optical thickness (COT) and effective diameter (De) provided by the Moderate Resolution Imaging Spectrometer (MODIS) Collection 6 cloud products are associated with errors due to the single habit assumption (SHA), independent pixel assumption (IPA), photon absorption effect (PAE), and plane-parallel assumption (PPA). SHA means that every cirrus cloud is assumed to have the same shape habit of ice crystals. IPA errors are caused by three-dimensional (3D) radiative effects. PPA and PAE errors are caused by cloud inhomogeneity. We proposed a method to single out these different errors. These errors were examined using the Spherical Harmonics Discrete Ordinate Method simulations done for the MODIS 0.86 μm and 2.13 μm bands. Four midlatitude and tropical cirrus cases were studied. For the COT retrieval, the impacts of SHA and IPA were especially large for optically thick cirrus cases. SHA errors in COT varied distinctly with scattering angles. For the De retrieval, SHA decreased De under most circumstances. PAE decreased De for optically thick cirrus cases. For the COT and De retrievals, the dominant error source was SHA for overhead sun whereas for oblique sun, it could be any of SHA, IPA, and PAE, varying with cirrus cases and sun-satellite viewing geometries. On the domain average, the SHA errors in COT (De) were within -16.1%-42.6% (-38.7%-2.0%), whereas the 3-D radiative effects- and cloud inhomogeneity-induced errors in COT (De) were within -5.6%-19.6% (-2.9%-8.0%) and -2.6%-0% (-3.7%-9.8%), respectively.

Active Appearance Segmentation for Intensity Inhomogeneity in Light Sheet Fluorescence Microscopy

DEFF Research Database (Denmark)

Jensen, Casper Bo; Lyksborg, Mark; Hecksher-Sørensen, J.

2016-01-01

inhomogeneities which are often seen in Light Sheet Fluorescence Microscopy (LSFM) images. This robustness is achieved by modelling the appearance of an image as a regularized Normalized Gradient Field (rNGF). We perform two experiments to challenge the model. First it is tested using a repeated leave......Active Appearance Models (AAM) are used for annotating or segmenting shapes in biomedical images. Performance relies heavily on the image data used to train the AAM. In this paper we improve the generalization properties of the model by making it robust to slowly varying spatial intensity......-one-out approach on images with minimal imperfections where the left out images are corrupted by a simulated bias field and segmented using the AAM. Secondly we test the model on LSFM images with common acquisition problems. In both experiments the proposed approach outperforms the often used AAM implementation...

Dielectric polarization and electric field distortion due to heavy ions impinging on silicon detectors

International Nuclear Information System (INIS)

Parlog, M.; Wieleczko, J.P.; Parlog, M.; Hamrita, H.; Borderie, B.; Lavergne, L.; Rivet, M.F.

2003-01-01

The polarization of the electron-hole pairs induced by 80 MeV 12 C in a silicon detector was considered and connected to the relative dielectric permittivity, locally increased. The exact coordinate dependence of the modified electric field - inside and outside the ion range - was found as the solution of the one dimension Poisson's equation for the electric potential in this inhomogeneous medium. The improvement of the signal simulation is encouraging, as compared to an undisturbed electric field case. (authors)

Three-dimensional distribution of random velocity inhomogeneities at the Nankai trough seismogenic zone

Science.gov (United States)

Takahashi, T.; Obana, K.; Yamamoto, Y.; Nakanishi, A.; Kaiho, Y.; Kodaira, S.; Kaneda, Y.

2012-12-01

The Nankai trough in southwestern Japan is a convergent margin where the Philippine sea plate is subducted beneath the Eurasian plate. There are major faults segments of huge earthquakes that are called Tokai, Tonankai and Nankai earthquakes. According to the earthquake occurrence history over the past hundreds years, we must expect various rupture patters such as simultaneous or nearly continuous ruptures of plural fault segments. Japan Agency for Marine-Earth Science and Technology (JAMSTEC) conducted seismic surveys at Nankai trough in order to clarify mutual relations between seismic structures and fault segments, as a part of "Research concerning Interaction Between the Tokai, Tonankai and Nankai Earthquakes" funded by Ministry of Education, Culture, Sports, Science and Technology, Japan. This study evaluated the spatial distribution of random velocity inhomogeneities from Hyuga-nada to Kii-channel by using velocity seismograms of small and moderate sized earthquakes. Random velocity inhomogeneities are estimated by the peak delay time analysis of S-wave envelopes (e.g., Takahashi et al. 2009). Peak delay time is defined as the time lag from the S-wave onset to its maximal amplitude arrival. This quantity mainly reflects the accumulated multiple forward scattering effect due to random inhomogeneities, and is quite insensitive to the inelastic attenuation. Peak delay times are measured from the rms envelopes of horizontal components at 4-8Hz, 8-16Hz and 16-32Hz. This study used the velocity seismograms that are recorded by 495 ocean bottom seismographs and 378 onshore seismic stations. Onshore stations are composed of the F-net and Hi-net stations that are maintained by National Research Institute for Earth Science and Disaster Prevention (NIED) of Japan. It is assumed that the random inhomogeneities are represented by the von Karman type PSDF. Preliminary result of inversion analysis shows that spectral gradient of PSDF (i.e., scale dependence of

Dynamically assisted Sauter-Schwinger effect in inhomogeneous electric fields

Energy Technology Data Exchange (ETDEWEB)

Schneider, Christian; Schützhold, Ralf [Fakultät für Physik, Universität Duisburg-Essen,Lotharstrasse 1, 47057 Duisburg (Germany)

2016-02-24

Via the world-line instanton method, we study electron-positron pair creation by a strong (but sub-critical) electric field of the profile E/cosh{sup 2} (kx) superimposed by a weaker pulse E{sup ′}/cosh{sup 2} (ωt). If the temporal Keldysh parameter γ{sub ω}=mω/(qE) exceeds a threshold value γ{sub ω}{sup crit} which depends on the spatial Keldysh parameter γ{sub k}=mk/(qE), we find a drastic enhancement of the pair creation probability — reporting on what we believe to be the first analytic non-perturbative result for the interplay between temporal and spatial field dependences E(t,x) in the Sauter-Schwinger effect. Finally, we speculate whether an analogous effect (drastic enhancement of tunneling probability) could occur in other scenarios such as stimulated nuclear decay, for example.

Dielectric tensor elements for the description of waves in rotating inhomogeneous magnetized plasma spheroids

Science.gov (United States)

Abdoli-Arani, A.; Ramezani-Arani, R.

2012-11-01

The dielectric permittivity tensor elements of a rotating cold collisionless plasma spheroid in an external magnetic field with toroidal and axial components are obtained. The effects of inhomogeneity in the densities of charged particles and the initial toroidal velocity on the dielectric permittivity tensor and field equations are investigated. The field components in terms of their toroidal components are calculated and it is shown that the toroidal components of the electric and magnetic fields are coupled by two differential equations. The influence of thermal and collisional effects on the dielectric tensor and field equations in the rotating plasma spheroid are also investigated. In the limiting spherical case, the dielectric tensor of a stationary magnetized collisionless cold plasma sphere is presented.

Polymers undergoing inhomogeneous adsorption: exact results and Monte Carlo simulations

Energy Technology Data Exchange (ETDEWEB)

Iliev, G K [Department of Mathematics, University of Melbourne, Parkville, Victoria (Australia); Orlandini, E [Dipartimento di Fisica, CNISM, Universita di Padova, Via Marzolo 8, 35131 Padova (Italy); Whittington, S G, E-mail: giliev@yorku.ca [Department of Chemistry, University of Toronto, Toronto (Canada)

2011-10-07

We consider several types of inhomogeneous polymer adsorption. In each case, the inhomogeneity is regular and resides in the surface, in the polymer or in both. We consider two different polymer models: a directed walk model that can be solved exactly and a self-avoiding walk model which we investigate using Monte Carlo methods. In each case, we compute the phase diagram. We compare and contrast the phase diagrams and give qualitative arguments about their forms. (paper)

Torsional surface waves in an inhomogeneous layer over a gravitating anisotropic porous half-space

International Nuclear Information System (INIS)

Gupta, Shishir; Pramanik, Abhijit

2015-01-01

The present work aims to deal with the propagation of torsional surface wave in an inhomogeneous layer over a gravitating anisotropic porous half space. The inhomogeneous layer exhibits the inhomogeneity of quadratic type. In order to show the effect of gravity the equation for the velocity of torsional wave has been obtained. It is also observed that for a layer over a homogeneous half space without gravity, the torsional surface wave does not propagate. An attempt is also made to assess the possible propagation of torsional surface waves in that medium in the absence of the upper layer. The effects of inhomogeneity factors and porosity on the phase velocity are depicted by means of graphs. (paper)

INHOMOGENEOUS NEARLY INCOMPRESSIBLE DESCRIPTION OF MAGNETOHYDRODYNAMIC TURBULENCE

International Nuclear Information System (INIS)

Hunana, P.; Zank, G. P.

2010-01-01

The nearly incompressible theory of magnetohydrodynamics (MHD) is formulated in the presence of a static large-scale inhomogeneous background. The theory is an inhomogeneous generalization of the homogeneous nearly incompressible MHD description of Zank and Matthaeus and a polytropic equation of state is assumed. The theory is primarily developed to describe solar wind turbulence where the assumption of a composition of two-dimensional (2D) and slab turbulence with the dominance of the 2D component has been used for some time. It was however unclear, if in the presence of a large-scale inhomogeneous background, the dominant component will also be mainly 2D and we consider three distinct MHD regimes for the plasma beta β > 1. For regimes appropriate to the solar wind (β 2 s δp is not valid for the leading-order O(M) density fluctuations, and therefore in observational studies, the density fluctuations should not be analyzed through the pressure fluctuations. The pseudosound relation is valid only for higher order O(M 2 ) density fluctuations, and then only for short-length scales and fast timescales. The spectrum of the leading-order density fluctuations should be modeled as k -5/3 in the inertial range, followed by a Bessel function solution K ν (k), where for stationary turbulence ν = 1, in the viscous-convective and diffusion range. Other implications for solar wind turbulence with an emphasis on the evolution of density fluctuations are also discussed.

Nonequilibrium statistical Zubarev's operator and Green's functions for an inhomogeneous electron gas

Directory of Open Access Journals (Sweden)

P.Kostrobii

2006-01-01

Full Text Available Nonequilibrium properties of an inhomogeneous electron gas are studied using the method of the nonequilibrium statistical operator by D.N. Zubarev. Generalized transport equations for the mean values of inhomogeneous operators of the electron number density, momentum density, and total energy density for weakly and strongly nonequilibrium states are obtained. We derive a chain of equations for the Green's functions, which connects commutative time-dependent Green's functions "density-density", "momentum-momentum", "enthalpy-enthalpy" with reduced Green's functions of the generalized transport coefficients and with Green's functions for higher order memory kernels in the case of a weakly nonequilibrium spatially inhomogeneous electron gas.

Plasma waves in an inhomogeneous cylindrical plasma

International Nuclear Information System (INIS)

Pesic, S.S.

1976-01-01

The complete dispersion equation governing small amplitude plasma waves propagating in an inhomogeneous cylindrical plasma confined by a helical magnetic field is solved numerically. The efficiency of the wave energy thermalization in the lower hybrid frequency range is studied

Electron-Bernstein Waves in Inhomogeneous Magnetic Fields

DEFF Research Database (Denmark)

Armstrong, R. J.; Frederiksen, Å.; Pécseli, Hans

1984-01-01

The propagation of small amplitude electron-Bernstein waves in different inhomogeneous magnetic field geometries is investigated experimentally. Wave propagation towards both cut-offs and resonances are considered. The experimental results are supported by a numerical ray-tracing analysis. Spatia...

Baryon inhomogeneity from the cosmic quark-hadron phase transition

International Nuclear Information System (INIS)

Kurki-Suonio, H.

1991-01-01

We discuss the generation of inhomogeneity in the baryon-number density during the cosmic quark-hadron phase transition. We use a simple model with thin-wall phase boundaries and ideal-gas equations of state. The nucleation of the phase transition introduces a new distance scale into the universe which will be the scale of the generated inhomogeneity. We review the estimate of this scale. During the transition baryon number is likely to collect onto a layer at the phase boundary. These layers may in the end be deposited as small regions of very high baryon density. 21 refs., 1 fig

Inhomogeneities in a Friedmann universe

International Nuclear Information System (INIS)

Tauber, G.E.

1987-08-01

One of the outstanding problems in cosmology is the growth of inhomogeneities, which are characterized by an anisotropic pressure and density distribution. Following a method developed by McVittie (1967, 1968) it has been possible to find time-dependent spherically symmetric solutions of Einstein's field equations containing an arbitrary pressure and density distribution which connect smoothly to a Friedmann universe for any desired equation of state. (author). 5 refs

Granule fraction inhomogeneity of calcium carbonate/sorbitol in roller compacted granules

DEFF Research Database (Denmark)

Bacher, Charlotte; Olsen, P.M.; Bertelsen, P.

2008-01-01

The granule fraction inhomogeneity of roller compacted granules was examined on mixtures of three different morphologic forms of calcium carbonate and three particle sizes of sorbitol. The granule fraction inhomogeneity was determined by the distribution of the calcium carbonate in each of the 10...... size fractions between 0 and 2000 µm and by calculating the demixing potential. Significant inhomogeneous occurrence of calcium carbonate in the size fractions was demonstrated, depending mostly on the particles sizes of sorbitol but also on the morphological forms of calcium carbonate......, the ability of the powder to agglomerate in the roller compactor was demonstrated to be related to the ability of the powder to be compacted into a tablet, thus the most compactable calcium carbonate and the smallest sized sorbitol improved the homogeneity by decreasing the demixing potential....

Change in the radiation dose at a point where an inhomogeneity partly covers the radiation field from a 60Co-γ-source

International Nuclear Information System (INIS)

Helmrot, E.

1976-04-01

Measurements and calculations have been made in order to study the change of the radiation dose in a point when an inhomogeneity covers parts of the radiation field from a Co 60-source. An ionization chamber, placed in a water phantom, was used for the measurements. As inhomogeneity an air cavity was used. The measuring point was placed on the central axis of the radiation field during the measurement. The air cavity was moved in front of the measuring point 0.5 - 1 cm by steps laterally, i.e. along a line perpendicular to the radiation direction. Measurements were made at different depths behind the air cavity. The air cavity was placed at different distances from the front plate of the water phantom. Measurements and calculations show that the change of the radiation dose, when the edge of the air cavity passes the measuring point, varies with the depth distance to the air cavity. The greatest deviation is near the air cavity and at a great distance behind this. The change of the radiation dose is less than 2 percent at distances greater than 2 cm from the edge of the air cavity laterally. This change is independent of the depth distance to the air cavity. The maximum deviation 1 cm from the edge of the air cavity is 5 percent independent of the distance tothe air cavity. Used methods of calculation can be extended to be used for irregular inhomogeneities but this requires knowledge of the three-dimensional extension of the inhomogeneity. (M.S.)

A theoretical description of inhomogeneous turbulence

International Nuclear Information System (INIS)

Turner, L.

2000-01-01

This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). In this LDRD, we have developed a highly compact and descriptive formalism that allows us to broach the theoretically formidable morass of inhomogeneous turbulence. Our formalism has two novel aspects: (a) an adaptation of helicity basis functions to represent an arbitrary incompressible channel flow and (b) the invocation of a hypothesis of random phase. A result of this compact formalism is that the mathematical description of inhomogeneous turbulence looks much like that of homogeneous turbulence--at the moment, the most rigorously explored terrain in turbulence research. As a result, we can explore the effect of boundaries on such important quantities as the gradients of mean flow, mean pressure, triple-velocity correlations and pressure velocity correlations, all of which vanish under the conventional, but artificial, assumption that the turbulence is statistically spatially uniform. Under suitable conditions, we have predicted that a mean flow gradient can develop even when none is initially present

Limits to the primordial helium abundance in the baryon-inhomogeneous big bang

Science.gov (United States)

Mathews, G. J.; Schramm, D. N.; Meyer, B. S.

1993-01-01

The parameter space for baryon inhomogeneous big bang models is explored with the goal of determining the minimum helium abundance obtainable in such models while still satisfying the other light-element constraints. We find that the constraint of (D + He-3)/H less than 10 exp -4 restricts the primordial helium mass fraction from baryon-inhomogeneous big bang models to be greater than 0.231 even for a scenario which optimizes the effects of the inhomogeneities and destroys the excess lithium production. Thus, this modification to the standard big bang as well as the standard homogeneous big bang model itself would be falsifiable by observation if the primordial He-4 abundance were observed to be less than 0.231. Furthermore, a present upper limit to the observed helium mass fraction of Y(obs)(p) less than 0.24 implies that the maximum baryon-to-photon ratio allowable in the inhomogeneous models corresponds to eta less than 2.3 x 10 exp -9 (omega(b) h-squared less than 0.088) even if all conditions are optimized.

Dissipation of Alfven waves in compressible inhomogeneous media

International Nuclear Information System (INIS)

Malara, F.; Primavera, L.; Veltri, P.

1997-01-01

In weakly dissipative media governed by the magnetohydrodynamics (MHD) equations, any efficient mechanism of energy dissipation requires the formation of small scales. Using numerical simulations, we study the properties of Alfven waves propagating in a compressible inhomogeneous medium, with an inhomogeneity transverse to the direction of wave propagation. Two dynamical effects, energy pinching and phase mixing, are responsible for the small-scales formation, similarly to the incompressible case. Moreover, compressive perturbations, slow waves and a static entropy wave are generated; the former are subject to steepening and form shock waves, which efficiently dissipate their energy, regardless of the Reynolds number. Rough estimates show that the dissipation times are consistent with those required to dissipate Alfven waves of photospheric origin inside the solar corona

On dislocation inhomogeneity of electroerosion crater zone in molybdenum single crystals

International Nuclear Information System (INIS)

Larikov, L.N.; Dubovitskaya, N.V.; Zakharov, S.M.

1979-01-01

Methods of diffraction electron microscopy, X-ray analysis and microhardness measurements have been applied to study the inhomogeneity of dislocation structure of the electroerosion crater zone in molybdenum single crystals. Microhardness inhomogeneous distribution in this zone is established, conditioned by changes in dislocation structure as a result of the development of thermally activated processes of the plastic deformation and dynamic recovery. Dislocationless channels are detected in predeformed crystals

Modeling of electron cyclotron resonance acceleration in a stationary inhomogeneous magnetic field

Directory of Open Access Journals (Sweden)

Valeri D. Dougar-Jabon

2008-04-01

Full Text Available In this paper, the cyclotron autoresonance acceleration of electrons in a stationary inhomogeneous magnetic field is studied. The trajectory and energy of electrons are found through a numerical solution of the relativistic Newton-Lorentz equation by a finite difference method. The electrons move along a TE_{112} cylinder cavity in a steady-state magnetic field whose axis coincides with the cavity axis. The magnetic field profile is such that it keeps the phase difference between the electric microwave field and the electron velocity vector within the acceleration phase band. The microwaves amplitude of 6  kV/cm is used for numerical calculations. It is shown that an electron with an initial longitudinal energy of 8 keV can be accelerated up to 260 keV by 2.45 GHz microwaves at a distance of 17 cm.

No hair theorem for inhomogeneous cosmologies

International Nuclear Information System (INIS)

Jensen, L.G.; Stein-Schabes, J.A.

1986-03-01

We show that under very general conditions any inhomogeneous cosmological model with a positive cosmological constant, that can be described in a synchronous reference system will tend asymptotically in time towards the de Sitter solution. This is shown to be relevant in the context of inflationary models as it makes inflation very weakly dependent on initial conditions. 8 refs

Approximate P-wave ray tracing and dynamic ray tracing in weakly orthorhombic media of varying symmetry orientation

KAUST Repository

Masmoudi, Nabil; Pšenčí k, Ivan

2014-01-01

We present an approximate, but efficient and sufficiently accurate P-wave ray tracing and dynamic ray tracing procedure for 3D inhomogeneous, weakly orthorhombic media with varying orientation of symmetry planes. In contrast to commonly used approaches, the orthorhombic symmetry is preserved at any point of the model. The model is described by six weak-anisotropy parameters and three Euler angles, which may vary arbitrarily, but smoothly, throughout the model. We use the procedure for the calculation of rays and corresponding two-point traveltimes in a VSP experiment in a part of the BP benchmark model generalized to orthorhombic symmetry.

On the radio source scintillations caused by plasma inhomogeneities behind a shock wave

International Nuclear Information System (INIS)

Pimenov, S.F.

1984-01-01

The turbulence in the interplanetary and interstellar medium is shown to become anisotropic and statistically inhomogeneous after a shock wave passing. Scintillation intensity spectra of radio sources are estimated. The possibilities to derive the inhomogeneity spectra and source brightness distribution from scintillation changes are discussed

The acceleration of a gaseous plasma by intense microwave fields in a constant inhomogeneous magnetic field

International Nuclear Information System (INIS)

Mourier, Georges

1971-01-01

A gaseous plasma excited by a powerful microwave source (up to 300 kW) was studied theoretically and experimentally. The large amplitude electric field excites, in a constant inhomogeneous magnetic field, a plasma near to the electron cyclotron resonance. These particles are accelerated to energies of between 100 and 10000 eV and subsequently drift to the regions of lower magnetic field. The ions are accelerated by the resulting electrostatic forces. Ion and electron currents of some tens of milli-amperes to a few amperes are obtained. The energy of the electrons is limited by their relativistic mass; a three-dimensional of space charge model is set up to describe the particle flow. (author) [fr

Scattering of electromagnetic wave by the layer with one-dimensional random inhomogeneities

Science.gov (United States)

Kogan, Lev; Zaboronkova, Tatiana; Grigoriev, Gennadii., IV.

A great deal of attention has been paid to the study of probability characteristics of electro-magnetic waves scattered by one-dimensional fluctuations of medium dielectric permittivity. However, the problem of a determination of a density of a probability and average intensity of the field inside the stochastically inhomogeneous medium with arbitrary extension of fluc-tuations has not been considered yet. It is the purpose of the present report to find and to analyze the indicated functions for the plane electromagnetic wave scattered by the layer with one-dimensional fluctuations of permittivity. We assumed that the length and the amplitude of individual fluctuations as well the interval between them are random quantities. All of indi-cated fluctuation parameters are supposed as independent random values possessing Gaussian distribution. We considered the stationary time cases both small-scale and large-scale rarefied inhomogeneities. Mathematically such problem can be reduced to the solution of integral Fred-holm equation of second kind for Hertz potential (U). Using the decomposition of the field into the series of multiply scattered waves we obtained the expression for a probability density of the field of the plane wave and determined the moments of the scattered field. We have shown that all odd moments of the centered field (U-¡U¿) are equal to zero and the even moments depend on the intensity. It was obtained that the probability density of the field possesses the Gaussian distribution. The average field is small compared with the standard fluctuation of scattered field for all considered cases of inhomogeneities. The value of average intensity of the field is an order of a standard of fluctuations of field intensity and drops with increases the inhomogeneities length in the case of small-scale inhomogeneities. The behavior of average intensity is more complicated in the case of large-scale medium inhomogeneities. The value of average intensity is the

Random field assessment of nanoscopic inhomogeneity of bone.

Science.gov (United States)

Dong, X Neil; Luo, Qing; Sparkman, Daniel M; Millwater, Harry R; Wang, Xiaodu

2010-12-01

Bone quality is significantly correlated with the inhomogeneous distribution of material and ultrastructural properties (e.g., modulus and mineralization) of the tissue. Current techniques for quantifying inhomogeneity consist of descriptive statistics such as mean, standard deviation and coefficient of variation. However, these parameters do not describe the spatial variations of bone properties. The objective of this study was to develop a novel statistical method to characterize and quantitatively describe the spatial variation of bone properties at ultrastructural levels. To do so, a random field defined by an exponential covariance function was used to represent the spatial uncertainty of elastic modulus by delineating the correlation of the modulus at different locations in bone lamellae. The correlation length, a characteristic parameter of the covariance function, was employed to estimate the fluctuation of the elastic modulus in the random field. Using this approach, two distribution maps of the elastic modulus within bone lamellae were generated using simulation and compared with those obtained experimentally by a combination of atomic force microscopy and nanoindentation techniques. The simulation-generated maps of elastic modulus were in close agreement with the experimental ones, thus validating the random field approach in defining the inhomogeneity of elastic modulus in lamellae of bone. Indeed, generation of such random fields will facilitate multi-scale modeling of bone in more pragmatic details. Copyright © 2010 Elsevier Inc. All rights reserved.

The influence of inhomogeneities on the dose distribution of fast electrons in radiotherapy

International Nuclear Information System (INIS)

Windemuth, M.

1985-01-01

Simple models are used to make a principal comparison between measured fast-electron dose distributions behind tissue inhomogeneities and those calculated by means of an irradiation planning system. The different organs were represented by water (for muscle), by cork (for the lungs) and by graphite (for bone). Corresponding to their density, inhomogeneities result, in principle, in a dose shift to a greater or smaller body depth which is correctly considered by the irradiation planning system. However, electron scattering transversal to beam direction will occur behind inhomogeneity edges which, in general, are not covered by the irradiation planning system, but which result in dose distributions deviating strongly from those expected as due to the shift. This is the reason for the limited accuracy of irradiation planning systems in complicated inhomogeneity distribution. The thesis demonstrates those cases which justify irradiation planning and those cases where they are not a reliable basis for irradiation. (orig./HP) [de

Reflection of oblique electron thermal modes in an inhomogeneous plasma

International Nuclear Information System (INIS)

Ohnuma, T.; Watanabe, T.; Sanuki, H.

1980-04-01

In an inhomogeneous magnetoplasma, reflection of an oblique electron thermal mode radiated from a local source is investigated experimentally and theoretically near the electron plasma frequency layer. The experimental observation of reflection in the lower plasma density region than the f sub(p)-layer is found to be in qualitative accord with the theoretical reflection, which is obtained from a kinetic theory in an inhomogeneous magnetoplasma. The reflection of the thermal mode is also compared with that of an electromagnetic mode at the f sub(p)-layer. (author)

Vector electric field measurement via position-modulated Kelvin probe force microscopy

Science.gov (United States)

Dwyer, Ryan P.; Smieska, Louisa M.; Tirmzi, Ali Moeed; Marohn, John A.

2017-10-01

High-quality spatially resolved measurements of electric fields are critical to understanding charge injection, charge transport, and charge trapping in semiconducting materials. Here, we report a variation of frequency-modulated Kelvin probe force microscopy that enables spatially resolved measurements of the electric field. We measure electric field components along multiple directions simultaneously by employing position modulation and lock-in detection in addition to numeric differentiation of the surface potential. We demonstrate the technique by recording linescans of the in-plane electric field vector in the vicinity of a patch of trapped charge in a 2,7-diphenyl[1]benzothieno[3,2-b][1]benzothiophene (DPh-BTBT) organic field-effect transistor. This technique is simple to implement and should be especially useful for studying electric fields in spatially inhomogeneous samples like organic transistors and photovoltaic blends.

Modulated magnetic structure of an inhomogeneous stressed single crystal FeBO3

International Nuclear Information System (INIS)

Sharipiv, M.Z.; Dzhuraev, D.R.; Sokolov, B.Yu.; Kurbanov, M.

2010-01-01

With the help of low-symmetry mechanical stresses, we induced an additional spatially inhomogeneous anisotropy in the basal plane of a single crystal FeBO 3 . By the magnetooptical method, we study the effect of an inhomogeneous magnetic anisotropy on the magnetic state of this easy-plane weak ferromagnetic. It is established that, at the magnetization of inhomogeneously stressed FeBO 3 in the basal plane near some separated direction, the crystal transits from the homogeneous state into a spatially modulated magnetic state. The latter can be represented in the form of a static spin wave, in which a local vector of ferromagnetism oscillates near the direction of the mean magnetization of a crystal, by remaining in the basal plane.

Non collinear magnetic phase of the inhomogeneously stressed FeBO3 monocrystals

International Nuclear Information System (INIS)

Sharipov, M.Z.

2011-01-01

With the help of low-symmetry mechanical stresses, an additional spatially inhomogeneous anisotropy in the basal plane of a single crystal FeBO 3 has been induced. By the magnetooptical method, an effect of the inhomogeneous magnetic anisotropy on the magnetic state of this easy-plane weak ferromagnetic has been investigated. It is established that at the magnetization of inhomogeneously stressed FeBO 3 in the basal plane near the separated direction, the crystal turns from the homogeneous state into a spatially modulated magnetic state. The latter can be represented in the form of a static spin wave, in which a local vector of ferromagnetism oscillates near the direction of the mean magnetization of a crystal, remaining in the basal plane. (authors)

Symbolic-computation study of the perturbed nonlinear Schrodinger model in inhomogeneous optical fibers

International Nuclear Information System (INIS)

Tian Bo; Gao Yitian

2005-01-01

A realistic, inhomogeneous fiber in the optical communication systems can be described by the perturbed nonlinear Schrodinger model (also named as the normalized nonlinear Schrodinger model with periodically varying coefficients, dispersion managed nonlinear Schrodinger model or nonlinear Schrodinger model with variable coefficients). Hereby, we extend to this model a direct method, perform symbolic computation and obtain two families of the exact, analytic bright-solitonic solutions, with or without the chirp respectively. The parameters addressed include the shape of the bright soliton, soliton amplitude, inverse width of the soliton, chirp, frequency, center of the soliton and center of the phase of the soliton. Of optical and physical interests, we discuss some previously-published special cases of our solutions. Those solutions could help the future studies on the optical communication systems. ms

Control of inhomogeneous atomic ensembles of hyperfine qudits

DEFF Research Database (Denmark)

Mischuck, Brian Edward; Merkel, Seth T.; Deutsch, Ivan H.

2012-01-01

We study the ability to control d-dimensional quantum systems (qudits) encoded in the hyperfine spin of alkali-metal atoms through the application of radio- and microwave-frequency magnetic fields in the presence of inhomogeneities in amplitude and detuning. Such a capability is essential...... to the design of robust pulses that mitigate the effects of experimental uncertainty and also for application to tomographic addressing of particular members of an extended ensemble. We study the problem of preparing an arbitrary state in the Hilbert space from an initial fiducial state. We prove...... that inhomogeneous control of qudit ensembles is possible based on a semianalytic protocol that synthesizes the target through a sequence of alternating rf and microwave-driven SU(2) rotations in overlapping irreducible subspaces. Several examples of robust control are studied, and the semianalytic protocol...

Electric fields in nonhomogeneously doped silicon. Summary of simulations

International Nuclear Information System (INIS)

Kotov, I.V.; Humanic, T.J.; Nouais, D.; Randel, J.; Rashevsky, A.

2006-01-01

Variations of the doping concentration inside a silicon device result in electric field distortions. These distortions, 'parasitic' fields, have been observed in Silicon Drift Detectors [D. Nouais, et al., Nucl. Instr. and Meth. A 501 (2003) 119; E. Crescio, et al., Nucl. Instr. and Meth. A 539 (2005) 250]. Electric fields inside a silicon device can be calculated for a given doping profile. In this study, the ATLAS device simulator. [Silvaco International, 4701 Patrick Henry Drive, Bldg.2, Santa Clara, CA 95054, USA and s imulation/atlas.html>] was used to calculate the electric field inside an inhomogeneously doped device. Simulations were performed for 1D periodic doping profiles. Results show strong dependence of the parasitic field strength on the 'smoothness' of the doping profile

Theory of Thomson scattering in inhomogeneous media.

Science.gov (United States)

Kozlowski, P M; Crowley, B J B; Gericke, D O; Regan, S P; Gregori, G

2016-04-12

Thomson scattering of laser light is one of the most fundamental diagnostics of plasma density, temperature and magnetic fields. It relies on the assumption that the properties in the probed volume are homogeneous and constant during the probing time. On the other hand, laboratory plasmas are seldom uniform and homogeneous on the temporal and spatial dimensions over which data is collected. This is particularly true for laser-produced high-energy-density matter, which often exhibits steep gradients in temperature, density and pressure, on a scale determined by the laser focus. Here, we discuss the modification of the cross section for Thomson scattering in fully-ionized media exhibiting steep spatial inhomogeneities and/or fast temporal fluctuations. We show that the predicted Thomson scattering spectra are greatly altered compared to the uniform case, and may lead to violations of detailed balance. Therefore, careful interpretation of the spectra is necessary for spatially or temporally inhomogeneous systems.

Stabilization of the dissipation-free current transport in inhomogeneous MgB2 thin films

International Nuclear Information System (INIS)

Treiber, S.; Stahl, C.; Schütz, G.; Soltan, S.; Albrecht, J.

2014-01-01

Highlights: • We investigate transport properties of inhomogeneous MgB 2 films. • An inhomogeneous microstructure stabilizes supercurrents. • Vortex pinning forces and energies have been analyzed experimentally. • In inhomogeneous films the increase of the pinning energy is responsible for stable supercurrents. - Abstract: In type-II superconductors at T = 0 the critical current density is determined by the pinning of flux lines. Considering an arbitrarily shaped energy landscape the pinning force at each pinning site is given by the derivative of the flux line energy with respect to the considered direction. At finite temperatures, in addition, thermal activation can lead to a depinning of flux lines. The governing property in this case is the depth of the corresponding pinning potential, i.e. the pinning energy. We show a detailed analysis of both pinning forces and pinning energies of MgB 2 films with inhomogeneous microstructure. We show that a pronounced increase of the pinning energy is responsible for the significantly enhanced stability of the dissipation-free current transport in thin inhomogeneous MgB 2 films. This is found even if the corresponding pinning forces are small

Laser Beam Propagation Through Inhomogeneous Media with Shock-Like Profiles: Modeling and Computing

Science.gov (United States)

Adamovsky, Grigory; Ida, Nathan

1997-01-01

Wave propagation in inhomogeneous media has been studied for such diverse applications as propagation of radiowaves in atmosphere, light propagation through thin films and in inhomogeneous waveguides, flow visualization, and others. In recent years an increased interest has been developed in wave propagation through shocks in supersonic flows. Results of experiments conducted in the past few years has shown such interesting phenomena as a laser beam splitting and spreading. The paper describes a model constructed to propagate a laser beam through shock-like inhomogeneous media. Numerical techniques are presented to compute the beam through such media. The results of computation are presented, discussed, and compared with experimental data.

Propagation of dispersion-nonlinearity-managed solitons in an inhomogeneous erbium-doped fiber system

International Nuclear Information System (INIS)

Mahalingam, A; Porsezian, K; Mani Rajan, M S; Uthayakumar, A

2009-01-01

In this paper, a generalized nonlinear Schroedinger-Maxwell-Bloch model with variable dispersion and nonlinearity management functions, which describes the propagation of optical pulses in an inhomogeneous erbium-doped fiber system under certain restrictive conditions, is under investigation. We derive the Lax pair with a variable spectral parameter and the exact soliton solution is generated from the Baecklund transformation. It is observed that stable solitons are possible only under a very restrictive condition for the spectral parameter and other inhomogeneous functions. For various forms of the inhomogeneous dispersion, nonlinearity and gain/loss functions, construction of different types of solitary waves like classical solitons, breathers, etc is discussed

Direct prediction of spatially and temporally varying physical properties from time-lapse electrical resistance data

Science.gov (United States)

Hermans, Thomas; Oware, Erasmus; Caers, Jef

2016-09-01

Time-lapse applications of electrical methods have grown significantly over the last decade. However, the quantitative interpretation of tomograms in terms of physical properties, such as salinity, temperature or saturation, remains difficult. In many applications, geophysical models are transformed into hydrological models, but this transformation suffers from spatially and temporally varying resolution resulting from the regularization used by the deterministic inversion. In this study, we investigate a prediction-focused approach (PFA) to directly estimate subsurface physical properties with electrical resistance data, circumventing the need for classic tomographic inversions. First, we generate a prior set of resistance data and physical property forecast through hydrogeological and geophysical simulations mimicking the field experiment. We reduce the dimension of both the data and the forecast through principal component analysis in order to keep the most informative part of both sets in a reduced dimension space. Then, we apply canonical correlation analysis to explore the relationship between the data and the forecast in their reduced dimension space. If a linear relationship can be established, the posterior distribution of the forecast can be directly sampled using a Gaussian process regression where the field data scores are the conditioning data. In this paper, we demonstrate PFA for various physical property distributions. We also develop a framework to propagate the estimated noise level in the reduced dimension space. We validate the results by a Monte Carlo study on the posterior distribution and demonstrate that PFA yields accurate uncertainty for the cases studied.

Integrability and soliton solutions for an inhomogeneous generalized fourth-order nonlinear Schrödinger equation describing the inhomogeneous alpha helical proteins and Heisenberg ferromagnetic spin chains

International Nuclear Information System (INIS)

Wang, Pan; Tian, Bo; Jiang, Yan; Wang, Yu-Feng

2013-01-01

For describing the dynamics of alpha helical proteins with internal molecular excitations, nonlinear couplings between lattice vibrations and molecular excitations, and spin excitations in one-dimensional isotropic biquadratic Heisenberg ferromagnetic spin with the octupole–dipole interactions, we consider an inhomogeneous generalized fourth-order nonlinear Schrödinger equation. Based on the Ablowitz–Kaup–Newell–Segur system, infinitely many conservation laws for the equation are derived. Through the auxiliary function, bilinear forms and N-soliton solutions for the equation are obtained. Interactions of solitons are discussed by means of the asymptotic analysis. Effects of linear inhomogeneity on the interactions of solitons are also investigated graphically and analytically. Since the inhomogeneous coefficient of the equation h=α x+β, the soliton takes on the parabolic profile during the evolution. Soliton velocity is related to the parameter α, distance scale coefficient and biquadratic exchange coefficient, but has no relation with the parameter β. Soliton amplitude and width are only related to α. Soliton position is related to β

Electron dynamics in solid state via time varying wavevectors

Science.gov (United States)

Khaneja, Navin

2018-06-01

In this paper, we study electron wavepacket dynamics in electric and magnetic fields. We rigorously derive the semiclassical equations of electron dynamics in electric and magnetic fields. We do it both for free electron and electron in a periodic potential. We do this by introducing time varying wavevectors k(t). In the presence of magnetic field, our wavepacket reproduces the classical cyclotron orbits once the origin of the Schröedinger equation is correctly chosen to be center of cyclotron orbit. In the presence of both electric and magnetic fields, our equations for wavepacket dynamics differ from classical Lorentz force equations. We show that in a periodic potential, on application of electric field, the electron wave function adiabatically follows the wavefunction of a time varying Bloch wavevector k(t), with its energies suitably shifted with time. We derive the effective mass equation and discuss conduction in conductors and insulators.

Ordering dynamics of self-propelled particles in an inhomogeneous medium

Science.gov (United States)

Das, Rakesh; Mishra, Shradha; Puri, Sanjay

2018-02-01

Ordering dynamics of self-propelled particles in an inhomogeneous medium in two dimensions is studied. We write coarse-grained hydrodynamic equations of motion for density and polarisation fields in the presence of an external random disorder field, which is quenched in time. The strength of inhomogeneity is tuned from zero disorder (clean system) to large disorder. In the clean system, the polarisation field grows algebraically as LP ∼ t0.5 . The density field does not show clean power-law growth; however, it follows Lρ ∼ t0.8 approximately. In the inhomogeneous system, we find a disorder-dependent growth. For both the density and the polarisation, growth slows down with increasing strength of disorder. The polarisation shows a disorder-dependent power-law growth LP(t,Δ) ∼ t1/\\bar zP(Δ) for intermediate times. At late times, there is a crossover to logarithmic growth LP(t,Δ) ∼ (\\ln t)1/\\varphi , where φ is a disorder-independent exponent. Two-point correlation functions for the polarisation show dynamical scaling, but the density does not.

Spatial inhomogeneity in spectra and exciton dynamics in porphyrin ...

Indian Academy of Sciences (India)

inhomogeneity. This is elucidated by time-resolved confocal microscopy. ... dynamics of such supramolecular aggregates. Weisman ... protein scaffold and faithfully represents a biomimetic reminiscent .... increased intermolecular interactions.

Effect of layerwise structural inhomogeneity on stress- corrosion cracking of steel tubes

Science.gov (United States)

Perlovich, Yu A.; Krymskaya, O. A.; Isaenkova, M. G.; Morozov, N. S.; Fesenko, V. A.; Ryakhovskikh, I. V.; Esiev, T. S.

2016-04-01

Based on X-ray texture and structure analysis data of the material of main gas pipelines it was shown that the layerwise inhomogeneity of tubes is formed during their manufacturing. The degree of this inhomogeneity affects on the tendency of tubes to stress- corrosion cracking under exploitation. Samples of tubes were cut out from gas pipelines located under various operating conditions. Herewith the study was conducted both for sections with detected stress-corrosion defects and without them. Distributions along tube wall thickness for lattice parameters and half-width of X-ray lines were constructed. Crystallographic texture analysis of external and internal tube layers was also carried out. Obtained data testifies about considerable layerwise inhomogeneity of all samples. Despite the different nature of the texture inhomogeneity of gas pipeline tubes, the more inhomogeneous distribution of texture or structure features causes the increasing of resistance to stress- corrosion. The observed effect can be explained by saturation with interstitial impurities of the surface layer of the hot-rolled sheet and obtained therefrom tube. This results in rising of lattice parameters in the external layer of tube as compared to those in underlying metal. Thus, internal layers have a compressive effect on external layers in the rolling plane that prevents cracks opening at the tube surface. Moreover, the high mutual misorientation of grains within external and internal layers of tube results in the necessity to change the moving crack plane, so that the crack growth can be inhibited when reaching the layer with a modified texture.

The effect of utility time-varying pricing and load control strategies on residential summer peak electricity use. A review

International Nuclear Information System (INIS)

Newsham, Guy R.; Bowker, Brent G.

2010-01-01

Peak demand for electricity in North America is expected to grow, challenging electrical utilities to supply this demand in a cost-effective, reliable manner. Therefore, there is growing interest in strategies to reduce peak demand by eliminating electricity use, or shifting it to non-peak times. This strategy is commonly called 'demand response'. In households, common strategies are time-varying pricing, which charge more for energy use on peak, or direct load control, which allows utilities to curtail certain loads during high demand periods. We reviewed recent North American studies of these strategies. The data suggest that the most effective strategy is a critical peak price (CPP) program with enabling technology to automatically curtail loads on event days. There is little evidence that this causes substantial hardship for occupants, particularly if they have input into which loads are controlled and how, and have an override option. In such cases, a peak load reduction of at least 30% is a reasonable expectation. It might be possible to attain such load reductions without enabling technology by focusing on household types more likely to respond, and providing them with excellent support. A simple time-of-use (TOU) program can only expect to realise on-peak reductions of 5%. (author)

Modelling altered revenue function based on varying power consumption distribution and electricity tariff charge using data analytics framework

Science.gov (United States)

Zainudin, W. N. R. A.; Ramli, N. A.

2017-09-01

In 2010, Energy Commission (EC) had introduced Incentive Based Regulation (IBR) to ensure sustainable Malaysian Electricity Supply Industry (MESI), promotes transparent and fair returns, encourage maximum efficiency and maintains policy driven end user tariff. To cater such revolutionary transformation, a sophisticated system to generate policy driven electricity tariff structure is in great need. Hence, this study presents a data analytics framework that generates altered revenue function based on varying power consumption distribution and tariff charge function. For the purpose of this study, the power consumption distribution is being proxy using proportion of household consumption and electricity consumed in KwH and the tariff charge function is being proxy using three-tiered increasing block tariff (IBT). The altered revenue function is useful to give an indication on whether any changes in the power consumption distribution and tariff charges will give positive or negative impact to the economy. The methodology used for this framework begins by defining the revenue to be a function of power consumption distribution and tariff charge function. Then, the proportion of household consumption and tariff charge function is derived within certain interval of electricity power. Any changes in those proportion are conjectured to contribute towards changes in revenue function. Thus, these changes can potentially give an indication on whether the changes in power consumption distribution and tariff charge function are giving positive or negative impact on TNB revenue. Based on the finding of this study, major changes on tariff charge function seems to affect altered revenue function more than power consumption distribution. However, the paper concludes that power consumption distribution and tariff charge function can influence TNB revenue to some great extent.

Effects of dipole magnet inhomogeneities on the beam ellipsoid

International Nuclear Information System (INIS)

Tsoupas, N.; Colman, J.; Levine, M.; McKenzie-Wilson, R.; Ward, T.; Grand, P.

1986-01-01

The RAYTRACE computer code has been modified to accept magnetic fields measured in the median plane of a dipole magnet. This modification allows one to study the effects of a non-ideal dipole magnet on the beam ellipsoid (as defined by the TRANSPORT code manual). The effects on the beam ellipsoid are due to: field inhomogeneities in the interior region of the dipole, and discrepancies from design conditions of the magnetic field values in the fringe field region. The results of the RAYTRACE code calculations based on experimentally measured fields will be compared with the results derived using both an ideal (no inhomogeneities) dipole with SCOFF boundaries and an ideal dipole with perfect (according to design) fringe fields

Thermal domains in inhomogeneous current-carrying superconductors. Current-voltage characteriscs and dynamics of domain formation after current jumps

International Nuclear Information System (INIS)

Bezuglyj, A.I.; Shklovskij, V.A.

1984-01-01

The static and dynamic behavior of thermal domains in inhomogeneous superconducting films, where the inhomogeneity behaves like a portion of the film with a reduced critical current, have been studied theoretically within the framework of the phenomenological approach, using the heat balance equation and the dependence of the superconductor critical current on temperature. Depending on the size of the inhomogeneity (local or extended) and on the relative values of parameters of the homogeneous and inhomogeneous regions, different types of current-voltage characteristics are obtained. The nonstationary problem of thermal domain formation near the inhomogeneity after a current jump has been solved, and the domain boundary (kink) dynamics at a distance from the inhomogeneity has been analyzed. A combination of the results allows one to describe the whole process of normal phase formation and its spread throughout the superconducting film

Laser dynamics in transversely inhomogeneous plasma and its relevance to wakefield acceleration

Science.gov (United States)

Pathak, V. B.; Vieira, J.; Silva, L. O.; Nam, Chang Hee

2018-05-01

We present full set of coupled equations describing the weakly relativistic dynamics of a laser in a plasma with transverse inhomogeneity. We apply variational principle approach to obtain these coupled equations governing laser spot-size, transverse wavenumber, curvature, transverse centroid, etc. We observe that such plasma inhomogeneity can lead to stronger self-focusing. We further discuss the guiding conditions of laser in parabolic plasma channels. With the help of multi-dimensional particle in cell simulations the study is extended to the blowout regime of laser wakefield acceleration to show laser as well as self-injected electron bunch steering in plasma to generate unconventional particle trajectories. Our simulation results demonstrate that such transverse inhomogeneities due to asymmetric self focusing lead to asymmetric bubble excitation, thus inducing off-axis self-injection.

Excitation of magnetic inhomogeneities in three-layer ferromagnetic structure with different parameters of the magnetic anisotropy and exchange

Energy Technology Data Exchange (ETDEWEB)

Ekomasov, E.G., E-mail: EkomasovEG@gmail.com [Bashkir State University, 32, Validy Str., Ufa, 450076 (Russian Federation); Murtazin, R.R. [Bashkir State University, 32, Validy Str., Ufa, 450076 (Russian Federation); Nazarov, V.N. [Institute of Molecule and Crystal Physics Ufa Research Centre of Russian Academy of Sciences, Prospekt Oktyabrya 151, Ufa, 450075 (Russian Federation)

2015-07-01

The generation and evolution of magnetic inhomogeneities, emerging in a thin flat layer with the parameters of the magnetic anisotropy and exchange interaction, with the parameters different from other two thick layers of the three-layer ferromagnetic structure, were investigated. The parameters ranges that determine the possibility of their existence were found. The possibility of the external magnetic field influence on the structure and dynamic properties of localized magnetic inhomogeneities was shown. - Highlights: • The generation of magnetic inhomogeneities in the three-layer ferromagnetic. • The influence of an external field on the parameters of magnetic inhomogeneities. • Numerical study of the structure and dynamics of magnetic inhomogeneities.

Relationship between the Amplitude and Phase of a Signal Scattered by a Point-Like Acoustic Inhomogeneity

Science.gov (United States)

Burov, V. A.; Morozov, S. A.

2001-11-01

Wave scattering by a point-like inhomogeneity, i.e., a strong inhomogeneity with infinitesimal dimensions, is described. This type of inhomogeneity model is used in investigating the point-spread functions of different algorithms and systems. Two approaches are used to derive the rigorous relationship between the amplitude and phase of a signal scattered by a point-like acoustic inhomogeneity. The first approach is based on a Marchenko-type equation. The second approach uses the scattering by a scatterer whose size decreases simultaneously with an increase in its contrast. It is shown that the retarded and advanced waves are scattered differently despite the relationship between the phases of the corresponding scattered waves.

Transient growth of a Vlasov plasma in a weakly inhomogeneous magnetic field

KAUST Repository

Ratushnaya, Valeria

2016-12-17

We investigate the stability properties of a collisionless Vlasov plasma in a weakly inhomogeneous magnetic field using non-modal stability analysis. This is an important topic in a physics of tokamak plasma rich in various types of instabilities. We consider a thin tokamak plasma in a Maxwellian equilibrium, subjected to a small arbitrary perturbation. Within the framework of kinetic theory, we demonstrate the emergence of short time scale algebraic instabilities evolving in a stable magnetized plasma. We show that the linearized governing operator (Vlasov operator) is non-normal leading to the transient growth of the perturbations on the time scale of several plasma periods that is subsequently followed by Landau damping. We calculate the first-order distribution function and the electric field and study the dependence of the transient growth characteristics on the magnetic field strength and perturbation parameters of the system. We compare our results with uniformly magnetized plasma and field-free Vlasov plasma.

Transient growth of a Vlasov plasma in a weakly inhomogeneous magnetic field

KAUST Repository

Ratushnaya, Valeria; Samtaney, Ravi

2016-01-01

We investigate the stability properties of a collisionless Vlasov plasma in a weakly inhomogeneous magnetic field using non-modal stability analysis. This is an important topic in a physics of tokamak plasma rich in various types of instabilities. We consider a thin tokamak plasma in a Maxwellian equilibrium, subjected to a small arbitrary perturbation. Within the framework of kinetic theory, we demonstrate the emergence of short time scale algebraic instabilities evolving in a stable magnetized plasma. We show that the linearized governing operator (Vlasov operator) is non-normal leading to the transient growth of the perturbations on the time scale of several plasma periods that is subsequently followed by Landau damping. We calculate the first-order distribution function and the electric field and study the dependence of the transient growth characteristics on the magnetic field strength and perturbation parameters of the system. We compare our results with uniformly magnetized plasma and field-free Vlasov plasma.

Inhomogeneous vortex tangles in counterflow superfluid turbulence: flow in convergent channels

Directory of Open Access Journals (Sweden)

Saluto Lidia

2016-06-01

Full Text Available We investigate the evolution equation for the average vortex length per unit volume L of superfluid turbulence in inhomogeneous flows. Inhomogeneities in line density L andincounterflowvelocity V may contribute to vortex diffusion, vortex formation and vortex destruction. We explore two different families of contributions: those arising from asecondorder expansionofthe Vinenequationitself, andthose whichare notrelated to the original Vinen equation but must be stated by adding to it second-order terms obtained from dimensional analysis or other physical arguments.

Cliques in dense inhomogenous random graphs

Czech Academy of Sciences Publication Activity Database

Doležal, Martin; Hladký, Jan; Máthé, A.

2017-01-01

Roč. 51, č. 2 (2017), s. 275-314 ISSN 1042-9832 R&D Projects: GA ČR GA16-07378S EU Projects: European Commission(XE) 628974 - PAECIDM Institutional support: RVO:67985840 Keywords : inhomogeneous random graphs * clique number Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 1.243, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/ rsa .20715/abstract

Cliques in dense inhomogenous random graphs

Czech Academy of Sciences Publication Activity Database

Doležal, Martin; Hladký, Jan; Máthé, A.

2017-01-01

Roč. 51, č. 2 (2017), s. 275-314 ISSN 1042-9832 R&D Projects: GA ČR GA16-07378S EU Projects: European Commission(XE) 628974 - PAECIDM Institutional support: RVO:67985840 Keywords : inhomogeneous random graphs * clique number Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 1.243, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/rsa.20715/abstract

Measurements of the electron dose distribution near inhomogeneities using a plastic scintillation detector

International Nuclear Information System (INIS)

Wells, C.M.M.; Mackie, T.R.; Podgorsak, M.B.; Holmes, M.A.; Papanikolaou, N.; Reckwerdt, P.J.; Cygler, J.; Rogers, D.W.O.; Bielajew, A.F.; Schmidt, D.G.

1994-01-01

Accurate measurement of the electron dose distribution near an inhomogeneity is difficult with traditional dosimeters which themselves perturb the electron field. The authors tested the performance of a new high resolution, water-equivalent plastic scintillation detector which has ideal properties for this application. A plastic scintillation detector with a 1 mm diameter, 3 mm long cylindrical sensitive volume was used to measure the dose distributions behind standard benchmark inhomogeneities in water phantoms. The plastic scintillator material is more water equivalent than polystyrene in terms of its mass collision stopping power and mass scattering power. Measurements were performed for beams of electrons having initial energies of 6 and 18 MeV at depths from 0.2-4.2 cm behind the inhomogeneities. The detector reveals hot and cold spots behind heterogeneities at resolutions equivalent to typical film digitizer spot sizes. Plots of the dose distributions behind air, aluminum, lead, and formulations for cortical and inner bone-equivalent materials are presented. The plastic scintillation detector is suited for measuring the electron dose distribution near an inhomogeneity. 14 refs., 9 figs

Artificial blood-flow controlling effects of inhomogeneity of twisted magnetic fields

Science.gov (United States)

Nakagawa, Hidenori; Ohuchi, Mikio

2017-06-01

We developed a blood-flow controlling system using magnetic therapy for some types of nervous diseases. In our research, we utilized overlapped extremely low frequency (ELF) fields for the most effective blood-flow for the system. Results showed the possibility that the inhomogeneous region obtained by overlapping the fields at 50 Hz, namely, a desirably twisted field revealed a significant difference in induced electromotive forces at the insertion points of electrodes. In addition, ELF exposures with a high inhomogeneity of the twisted field at 50 Hz out of phase were more effective in generating an induced electromotive difference by approximately 31%, as contrasted with the difference generated by the exposure in phase. We expect that the increase of the inhomogeneity of the twisted field around a blood vessel can produce the most effective electromotive difference in the blood, and also moderately affect the excitable cells relating to the autonomic nervous system for an outstanding blood-flow control in vivo.

Inhomogeneous ozone doping and heat induced defects in graphene studied by infrared near-field microscopy

Science.gov (United States)

Wang, Wenjie; Zhang, Jiawei; Deng, Haiming; Liu, Megnkun; Xu, Du

With the potential use of surface plasmon such as transfer data many orders faster than traditional wires, it has been very popular in research. The fact is that the wavelength of of plasmon is much shorter than the one of free space radiation. The UV ozone doping level can be fine controlled in room temperature creating selected plasmon circuit. We study inhomogeneous graphene plasmonics in ozone doped graphene using scattering-type scanning near-field infrared microscopy and spectroscopy. The single layer and bilayer graphene are doped with different dosage of ozone under UV exposure, which lead to surface inhomogeneity and inhomogeneous graphene plasmon polarition excitation under tip. After annealing the ozone doped graphene in air, the inhomogeneous doping induced plasmons disappear, together with the occurrence of local defects after high temperature annealing.

The equilibrium theory of inhomogeneous polymers (international series of monographs on physics)

CERN Document Server

Fredrickson, Glenn

2013-01-01

The Equilibrium Theory of Inhomogeneous Polymers provides an introduction to the field-theoretic methods and computer simulation techniques that are used in the design of structured polymeric fluids. By such methods, the principles that dictate equilibrium self-assembly in systems ranging from block and graft copolymers, to polyelectrolytes, liquid crystalline polymers, and polymer nanocomposites can be established. Building on an introductory discussion of single-polymer statistical mechanics, the book provides a detailed treatment of analytical and numerical techniques for addressing the conformational properties of polymers subjected to spatially-varying potential fields. This problem is shown to be central to the field-theoretic description of interacting polymeric fluids, and models for a number of important polymer systems are elaborated. Chapter 5 serves to unify and expound the topic of self-consistent field theory, which is a collection of analytical and numerical techniques for obtaining solutions o...

Inhomogeneous target-dose distributions: a dimension more for optimization?

International Nuclear Information System (INIS)

Gersem, Werner R.T. de; Derycke, Sylvie; Colle, Christophe O.; Wagter, Carlos de; Neve, Wilfried J. de

1999-01-01

Purpose: To evaluate if the use of inhomogeneous target-dose distributions, obtained by 3D conformal radiotherapy plans with or without beam intensity modulation, offers the possibility to decrease indices of toxicity to normal tissues and/or increase indices of tumor control stage III non-small cell lung cancer (NSCLC). Methods and Materials: Ten patients with stage III NSCLC were planned using a conventional 3D technique and a technique involving noncoplanar beam intensity modulation (BIM). Two planning target volumes (PTVs) were defined: PTV1 included macroscopic tumor volume and PTV2 included macroscopic and microscopic tumor volume. Virtual simulation defined the beam shapes and incidences as well as the wedge orientations (3D) and segment outlines (BIM). Weights of wedged beams, unwedged beams, and segments were determined by optimization using an objective function with a biological and a physical component. The biological component included tumor control probability (TCP) for PTV1 (TCP1), PTV2 (TCP2), and normal tissue complication probability (NTCP) for lung, spinal cord, and heart. The physical component included the maximum and minimum dose as well as the standard deviation of the dose at PTV1. The most inhomogeneous target-dose distributions were obtained by using only the biological component of the objective function (biological optimization). By enabling the physical component in addition to the biological component, PTV1 inhomogeneity was reduced (biophysical optimization). As indices for toxicity to normal tissues, NTCP-values as well as maximum doses or dose levels to relevant fractions of the organ's volume were used. As indices for tumor control, TCP-values as well as minimum doses to the PTVs were used. Results: When optimization was performed with the biophysical as compared to the biological objective function, the PTV1 inhomogeneity decreased from 13 (8-23)% to 4 (2-9)% for the 3D-(p = 0.00009) and from 44 (33-56)% to 20 (9-34)% for the BIM

Inhomogeneous compact extra dimensions

Energy Technology Data Exchange (ETDEWEB)

Bronnikov, K.A. [Center of Gravity and Fundamental Metrology, VNIIMS, 46 Ozyornaya st., Moscow 119361 (Russian Federation); Budaev, R.I.; Grobov, A.V.; Dmitriev, A.E.; Rubin, Sergey G., E-mail: kb20@yandex.ru, E-mail: buday48@mail.ru, E-mail: alexey.grobov@gmail.com, E-mail: alexdintras@mail.ru, E-mail: sergeirubin@list.ru [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 115409 Moscow (Russian Federation)

2017-10-01

We show that an inhomogeneous compact extra space possesses two necessary features— their existence does not contradict the observable value of the cosmological constant Λ{sub 4} in pure f ( R ) theory, and the extra dimensions are stable relative to the 'radion mode' of perturbations, the only mode considered. For a two-dimensional extra space, both analytical and numerical solutions for the metric are found, able to provide a zero or arbitrarily small Λ{sub 4}. A no-go theorem has also been proved, that maximally symmetric compact extra spaces are inconsistent with 4D Minkowski space in the framework of pure f ( R ) gravity.

Head-on collision between positron acoustic waves in homogeneous and inhomogeneous plasmas

Science.gov (United States)

Alam, M. S.; Hafez, M. G.; Talukder, M. R.; Ali, M. Hossain

2018-05-01

The head-on collision between positron acoustic solitary waves (PASWs) as well as the production of rogue waves (RWs) in homogeneous and PASWs in inhomogeneous unmagnetized plasma systems are investigated deriving the nonlinear evolution equations. The plasmas are composed of immobile positive ions, mobile cold and hot positrons, and hot electrons, where the hot positrons and hot electrons are assumed to follow the Kappa distributions. The evolution equations are derived using the appropriate coordinate transformation and the reductive perturbation technique. The effects of concentrations, kappa parameters of hot electrons and positrons, and temperature ratios on the characteristics of PASWs and RWs are examined. It is found that the kappa parameters and temperature ratios significantly modify phase shifts after head-on collisions and RWs in homogeneous as well as PASWs in inhomogeneous plasmas. The amplitudes of the PASWs in inhomogeneous plasmas are diminished with increasing kappa parameters, concentration and temperature ratios. Further, the amplitudes of RWs are reduced with increasing charged particles concentration, while it enhances with increasing kappa- and temperature parameters. Besides, the compressive and rarefactive solitons are produced at critical densities from KdV equation for hot and cold positrons, while the compressive solitons are only produced from mKdV equation for both in homogeneous and inhomogeneous plasmas.

Effect of Inhomogeneity on s-wave Superconductivity in the Attractive Hubbard Model

Energy Technology Data Exchange (ETDEWEB)

Aryanpour, K. A. [University of California, Davis; Dagotto, Elbio R [ORNL; Mayr, Matthias [Max-Planck-Institut fur Feskorperforschung, Stuttgart, Germany; Paiva, T. [Universidade Federal do Rio de Janeiro, Brazil; Pickett, W. E. [University of California, Davis; Scalettar, Richard T [ORNL

2006-01-01

Inhomogeneous s-wave superconductivity is studied in the two-dimensional, square lattice attractive Hubbard Hamiltonian using the Bogoliubov-de Gennes BdG mean field approximation. We find that at weak coupling, and for densities mainly below half-filling, an inhomogeneous interaction in which the on-site interaction Ui takes on two values, Ui=0, 2U results in a larger zero temperature pairing amplitude, and that the superconducting Tc can also be significantly increased, relative to a uniform system with Ui=U on all sites. These effects are observed for stripe, checkerboard, and even random patterns of the attractive centers, suggesting that the pattern of inhomogeneity is unimportant. Monte Carlo calculations which reintroduce some of the fluctuations neglected within the BdG approach see the same effect, both for the attractive Hubbard model and a Hamiltonian with d-wave pairing symmetry.

Friction, slip and structural inhomogeneity of the buried interface

International Nuclear Information System (INIS)

Dong, Y; Wu, J; Martini, A; Li, Q

2011-01-01

An atomistic model of metallic contacts using realistic interatomic potentials is used to study the connection between friction, slip and the structure of the buried interface. Incommensurability induced by misalignment and lattice mismatch is modeled with contact sizes that are large enough to observe superstructures formed by the relative orientations of the surfaces. The periodicity of the superstructures is quantitatively related to inhomogeneous shear stress distributions in the contact area, and a reduced order model is used to clarify the connection between friction and structural inhomogeneity. Finally, the movement of atoms is evaluated before, during and after slip in both aligned and misaligned contacts to understand how the interfacial structure affects the mechanisms of slip and the corresponding frictional behavior

Fluence inhomogeneities due to a ripple filter induced Moiré effect.

Science.gov (United States)

Ringbæk, Toke Printz; Brons, Stephan; Naumann, Jakob; Ackermann, Benjamin; Horn, Julian; Latzel, Harald; Scheloske, Stefan; Galonska, Michael; Bassler, Niels; Zink, Klemens; Weber, Uli

2015-02-07

At particle therapy facilities with pencil beam scanning, the implementation of a ripple filter (RiFi) broadens the Bragg peak, so fewer energy steps from the accelerator are required for a homogeneous dose coverage of the planning target volume (PTV). However, sharply focusing the scanned pencil beams at the RiFi plane by ion optical settings can lead to a Moiré effect, causing fluence inhomogeneities at the isocenter. This has been experimentally proven at the Heidelberg Ionenstrahl-Therapiezentrum (HIT), Universitätsklinikum Heidelberg, Germany. 150 MeV u(-1) carbon-12 ions are used for irradiation with a 3 mm thick RiFi. The beam is focused in front of and as close to the RiFi plane as possible. The pencil beam width is estimated to be 0.78 mm at a 93 mm distance from the RiFi. Radiographic films are used to obtain the fluence profile 30 mm in front of the isocenter, 930 mm from the RiFi. The Monte Carlo (MC) code SHIELD-HIT12A is used to determine the RiFi-induced inhomogeneities in the fluence distribution at the isocenter for a similar setup, pencil beam widths at the RiFi plane ranging from σχ(RiFi to 1.2 mm and for scanning step sizes ranging from 1.5 to 3.7 mm. The beam application and monitoring system (BAMS) used at HIT is modelled and simulated. When the width of the pencil beams at the RiFi plane is much smaller than the scanning step size, the resulting inhomogeneous fluence distribution at the RiFi plane interfers with the inhomogeneous RiFi mass distribution and fluence inhomogeneity can be observed at the isocenter as large as an 8% deviation from the mean fluence. The inverse of the fluence ripple period at the isocenter is found to be the difference between the inverse of the RiFi period and the inverse of the scanning step size. We have been able to use MC simulations to reproduce the spacing of the ripple stripes seen in films irradiated at HIT. Our findings clearly indicate that pencil beams sharply focused near the RiFi plane result in

Radiation transport in statistically inhomogeneous rocks

International Nuclear Information System (INIS)

Lukhminskij, B.E.

1975-01-01

A study has been made of radiation transfer in statistically inhomogeneous rocks. Account has been taken of the statistical character of rock composition through randomization of density. Formulas are summarized for sigma-distribution, homogeneous density, the Simpson and Cauchy distributions. Consideration is given to the statistics of mean square ranges in a medium, simulated by the jump Markov random function. A quantitative criterion of rock heterogeneity is proposed

Spectroscopy and Raman imaging of inhomogeneous materials

International Nuclear Information System (INIS)

Maslova, Olga

2014-01-01

This thesis is aimed at developing methodologies in Raman spectroscopy and imaging. After reviewing the statistical instruments which allow treating giant amount of data (multivariate analysis and classification), the study is applied to two families of well-known materials which are used as models for testing the limits of the implemented developments. The first family is a series of carbon materials pyrolyzed at various temperatures and exhibiting inhomogeneities at a nm scale which is suitable for Raman-X-ray diffraction combination. Another results concern the polishing effect on carbon structure. Since it is found to induce Raman artifacts leading to the overestimation of the local structural disorder, a method based on the use of the G band width is therefore proposed in order to evaluate the crystallite size in both unpolished and polished nano-graphites. The second class of materials presents inhomogeneities at higher (micrometric) scales by the example of uranium dioxide ceramics. Being well adapted in terms of spatial scale, Raman imaging is thus used for probing their surfaces. Data processing is implemented via an approach combining the multivariate (principal component) analysis and the classical fitting procedure with Lorentzian profiles. The interpretation of results is supported via electron backscattering diffraction (EBSD) analysis which enables us to distinguish the orientation effects of ceramic grains from other underlying contributions. The last ones are mainly localized at the grain boundaries, that is testified by the appearance of a specific Raman mode. Their origin seems to be caused by stoichiometric oxygen variations or impurities, as well as strain inhomogeneities. The perspectives of this work include both the implementation of other mathematical methods and in-depth analysis of UO 2 structure damaged by irradiation (anisotropic effects, role of grain boundaries). (author) [fr

Network-derived inhomogeneity in monthly rainfall analyses over western Tasmania

International Nuclear Information System (INIS)

Fawcett, Robert; Trewin, Blair; Barnes-Keoghan, Ian

2010-01-01

Monthly rainfall in the wetter western half of Tasmania was relatively poorly observed in the early to middle parts of the 20th century, and this causes a marked inhomogeneity in the operational gridded monthly rainfall analyses generated by the Australian Bureau of Meteorology up until the end of 2009. These monthly rainfall analyses were generated for the period 1900 to 2009 in two forms; a national analysis at 0.25 0 latitude-longitude resolution, and a southeastern Australia regional analysis at 0.1 0 resolution. For any given month, they used all the monthly data from the standard Bureau rainfall gauge network available in the Australian Data Archive for Meteorology. Since this network has changed markedly since Federation (1901), there is obvious scope for network-derived inhomogeneities in the analyses. In this study, we show that the topography-resolving techniques of the new Australian Water Availability Project analyses, adopted as the official operational analyses from the start of 2010, substantially diminish those inhomogeneities, while using largely the same observation network. One result is an improved characterisation of recent rainfall declines across Tasmania. The new analyses are available at two resolutions, 0.25 0 and 0.05 0 .

Inhomogeneous Spin Diffusion in Traps with Cold Atoms

DEFF Research Database (Denmark)

Heiselberg, Henning

2012-01-01

increases. The inhomogeneity and the smaller nite trap size signicantly reduce the spin diusion rate at low temperatures. The resulting spin diusion rates and spin drag at longer time scales are compatible with measurements at low to high temperatures for resonant attractive interactions...

Physical model of optical inhomogeneities of water

Science.gov (United States)

Shybanov, E. B.

2017-11-01

The paper is devoted to theoretical aspects of the light scattering of water that does not contain suspended particles. To be consistent with current physical point of view the water as far as any liquid is regarded as a complex unstable nonergodic media. It was proposed that at fixed time the water as a condensed medium had global inhomogeneities similar to linear and planar defects in a solid. Anticipated own global inhomogeneities of water have been approximated by the system randomly distributed spherical clusters filling the entire water bulk. An analytical expression for the single scattered light has been derived. The formula simultaneously describes both the high anisotropy of light scattering and the high degree of polarization which one close to those for molecular scattering. It is shown that at general angles there is a qualitative coincidence with the two-component Kopelevich's model for the light scattering by marine particles. On the contrary towards to forwards angles the spectral law becomes much more prominent i.e. it corresponds to results for model of optically soft particles.

Heating and acceleration of solar wind ions by turbulent wave spectrum in inhomogeneous expanding plasma

Energy Technology Data Exchange (ETDEWEB)

Ofman, Leon, E-mail: Leon.Ofman@nasa.gov [Department of Physics, The Catholic University of America, Washington, DC (United States); NASA Goddard Space Flight Center, Greenbelt, MD (United States); Visiting, Department of Geosciences, Tel Aviv University, Tel Aviv (Israel); Ozak, Nataly [Centre for mathematical Plasma Astrophysics, KU Leuven, Celestijnenlaan 200B, 3001 Leuven (Belgium); Viñas, Adolfo F. [NASA Goddard Space Flight Center, Greenbelt, MD (United States)

2016-03-25

Near the Sun (< 10R{sub s}) the acceleration, heating, and propagation of the solar wind are likely affected by the background inhomogeneities of the magnetized plasma. The heating and the acceleration of the solar wind ions by turbulent wave spectrum in inhomogeneous plasma is studied using a 2.5D hybrid model. The hybrid model describes the kinetics of the ions, while the electrons are modeled as massless neutralizing fluid in an expanding box approach. Turbulent magnetic fluctuations dominated by power-law frequency spectra, which are evident from in-situ as well as remote sensing measurements, are used in our models. The effects of background density inhomogeneity across the magnetic field on the resonant ion heating are studied. The effect of super-Alfvénic ion drift on the ion heating is investigated. It is found that the turbulent wave spectrum of initially parallel propagating waves cascades to oblique modes, and leads to enhanced resonant ion heating due to the inhomogeneity. The acceleration of the solar wind ions is achieved by the parametric instability of large amplitude waves in the spectrum, and is also affected by the inhomogeneity. The results of the study provide the ion temperature anisotropy and drift velocity temporal evolution due to relaxation of the instability. The non-Maxwellian velocity distribution functions (VDFs) of the ions are modeled in the inhomogeneous solar wind plasma in the acceleration region close to the Sun.

Parallel application of plasma equilibrium fitting based on inhomogeneous platforms

International Nuclear Information System (INIS)

Liao Min; Zhang Jinhua; Chen Liaoyuan; Li Yongge; Pan Wei; Pan Li

2008-01-01

An online analysis and online display platform EFIT, which is based on the equilibrium-fitting mode, is inducted in this paper. This application can realize large data transportation between inhomogeneous platforms by designing a communication mechanism using sockets. It spends approximately one minute to complete the equilibrium fitting reconstruction by using a finite state machine to describe the management node and several node computers of cluster system to fulfill the parallel computation, this satisfies the online display during the discharge interval. An effective communication model between inhomogeneous platforms is provided, which could transport the computing results from Linux platform to Windows platform for online analysis and display. (authors)

Inhomogeneous Relaxation of a Molecular Layer on an Insulator due to Compressive Stress

Science.gov (United States)

Bocquet, F.; Nony, L.; Mannsfeld, S. C. B.; Oison, V.; Pawlak, R.; Porte, L.; Loppacher, Ch.

2012-05-01

We discuss the inhomogeneous stress relaxation of a monolayer of hexahydroxytriphenylene (HHTP) which adopts the rare line-on-line (LOL) coincidence on KCl(001) and forms moiré patterns. The fact that the hexagonal HHTP layer is uniaxially compressed along the LOL makes this system an ideal candidate to discuss the influence of inhomogeneous stress relaxation. Our work is a combination of noncontact atomic force microscopy experiments, density functional theory and potential energy calculations, and a thorough interpretation by means of the Frenkel-Kontorova model. We show that the assumption of a homogeneous molecular layer is not valid for this organic-inorganic heteroepitaxial system since the best calculated energy configuration correlates with the experimental data only if inhomogeneous relaxations of the layer are taken into account.

Multi-layer composite mechanical modeling for the inhomogeneous biofilm mechanical behavior.

Science.gov (United States)

Wang, Xiaoling; Han, Jingshi; Li, Kui; Wang, Guoqing; Hao, Mudong

2016-08-01

Experiments showed that bacterial biofilms are heterogeneous, for example, the density, the diffusion coefficient, and mechanical properties of the biofilm are different along the biofilm thickness. In this paper, we establish a multi-layer composite model to describe the biofilm mechanical inhomogeneity based on unified multiple-component cellular automaton (UMCCA) model. By using our model, we develop finite element simulation procedure for biofilm tension experiment. The failure limit and biofilm extension displacement obtained from our model agree well with experimental measurements. This method provides an alternative theory to study the mechanical inhomogeneity in biological materials.

Magnetostatic modes in ferromagnetic samples with inhomogeneous internal fields

Science.gov (United States)

Arias, Rodrigo

2015-03-01

Magnetostatic modes in ferromagnetic samples are very well characterized and understood in samples with uniform internal magnetic fields. More recently interest has shifted to the study of magnetization modes in ferromagnetic samples with inhomogeneous internal fields. The present work shows that under the magnetostatic approximation and for samples of arbitrary shape and/or arbitrary inhomogeneous internal magnetic fields the modes can be classified as elliptic or hyperbolic, and their associated frequency spectrum can be delimited. This results from the analysis of the character of the second order partial differential equation for the magnetostatic potential under these general conditions. In general, a sample with an inhomogeneous internal field and at a given frequency, may have regions of elliptic and hyperbolic character separated by a boundary. In the elliptic regions the magnetostatic modes have a smooth monotonic character (generally decaying form the surfaces (a ``tunneling'' behavior)) and in hyperbolic regions an oscillatory wave-like character. A simple local criterion distinguishes hyperbolic from elliptic regions: the sign of a susceptibility parameter. This study shows that one may control to some extent magnetostatic modes via external fields or geometry. R.E.A. acknowledges Financiamiento Basal para Centros Cientificos y Tecnologicos de Excelencia under Project No. FB 0807 (Chile), Grant No. ICM P10-061-F by Fondo de Innovacion para la Competitividad-MINECON, and Proyecto Fondecyt 1130192.

Microstructural evolution in inhomogeneous elastic media

International Nuclear Information System (INIS)

Jou, H.J.; Leo, P.H.; Lowengrub, J.S.

1997-01-01

We simulate the diffusional evolution of microstructures produced by solid state diffusional transformations in elastically stressed binary alloys in two dimensions. The microstructure consists of arbitrarily shaped precipitates embedded coherently in an infinite matrix. The precipitate and matrix are taken to be elastically isotropic, although they may have different elastic constants (elastically inhomogeneous). Both far-field applied strains and mismatch strains between the phases are considered. The diffusion and elastic fields are calculated using the boundary integral method, together with a small scale preconditioner to remove ill-conditioning. The precipitate-matrix interfaces are tracked using a nonstiff time updating method. The numerical method is spectrally accurate and efficient. Simulations of a single precipitate indicate that precipitate shapes depend strongly on the mass flux into the system as well as on the elastic fields. Growing shapes (positive mass flux) are dendritic while equilibrium shapes (zero mass flux) are squarish. Simulations of multiparticle systems show complicated interactions between precipitate morphology and the overall development of microstructure (i.e., precipitate alignment, translation, merging, and coarsening). In both single and multiple particle simulations, the details of the microstructural evolution depend strongly o the elastic inhomogeneity, misfit strain, and applied fields. 57 refs., 24 figs

Inhomogeneous Big Bang Nucleosynthesis Revisited

OpenAIRE

Lara, J. F.; Kajino, T.; Mathews, G. J.

2006-01-01

We reanalyze the allowed parameters for inhomogeneous big bang nucleosynthesis in light of the WMAP constraints on the baryon-to-photon ratio and a recent measurement which has set the neutron lifetime to be 878.5 +/- 0.7 +/- 0.3 seconds. For a set baryon-to-photon ratio the new lifetime reduces the mass fraction of He4 by 0.0015 but does not significantly change the abundances of other isotopes. This enlarges the region of concordance between He4 and deuterium in the parameter space of the b...

Catheter visualisation in MR tomography: first animal experimental experiences with field inhomogeneity catheters

International Nuclear Information System (INIS)

Adam, G.; Glowinski, A.; Neuerburg, J.; Buecker, A.; Vaals, J.J. van; Hurtak, W.; Guenther, R.W.

1997-01-01

Purpose: To assess the feasibility of a new developed field inhomogeneity catheter for interventional MR imaging in vivo. Materials and methods: Three different prototypes of a field inhomogeneity catheter were investigated in 6 pigs. The catheters were introduced in Seldinger technique via the femoral vessels over a guide wire on an interventional MR system (Philips Gyroscan NT combined with a C-arm fluoroscopy unit [Philips BV 212[). Catheters were placed in veins and arteries. The catheter position was controlled by a fast gradient echo sequence (Turbo Field Echo [TEF[). Results: Catheters were introduced over a guide wire without complications in all cases. Using the field inhomogeneity concept, catheters were easily visualised in the inferior vena cava and the aorta by the fast gradient echo technique on MR in all cases. Although aortic branches were successfully cannulated, the catheters were not displayed by the TFE technique due to the complex and tortuous anatomy. All animals survived the experiments without complications. Conclusion: MR guided visualisation of a field inhomogeneity catheter is a simple concept which can be realised on each MR scanner and may allow intravascular MR guided interventions in future. (orig.) [de

Inhomogeneous strain induced by fast neutron irradiation in NaKSO4 crystals

International Nuclear Information System (INIS)

Kandil, S.H.; Kassem, M.E.; El-Khatib, A.; El-Gamal, M.A.; El-Wahidy, E.F.

1987-01-01

The paper reports the effect of fast neutron irradiation on the thermal properties of NaKSO 4 crystals in the temperature range 400-475 K. Results are presented for the thermal expansion, tensile strain and specific heat of NaKSO 4 , as a function of neutron irradiation dose. All these results revealed an inhomogeneous strain induced by the radiation. It is suggested that this induced inhomogeneous strain could be used to detect neutron exposure doses. (UK)

Modeling of the anode of a liquid-feed DMFC: Inhomogeneous compression effects and two-phase transport phenomena

Science.gov (United States)

García-Salaberri, Pablo A.; Vera, Marcos; Iglesias, Immaculada

2014-01-01

An isothermal two-phase 2D/1D across-the-channel model for the anode of a liquid-feed Direct Methanol Fuel Cell (DMFC) is presented. The model takes into account the effects of the inhomogeneous assembly compression of the Gas Diffusion Layer (GDL), including the spatial variations of porosity, diffusivity, permeability, capillary pressure, and electrical conductivity. The effective anisotropic properties of the GDL are evaluated from empirical data reported in the literature corresponding to Toray carbon paper TGP-H series. Multiphase transport is modeled according to the classical theory of porous media (two-fluid model), considering the effect of non-equilibrium evaporation and condensation of methanol and water. The numerical results evidence that the hydrophobic Leverett J-function approach is physically inconsistent to describe capillary transport in the anode of a DMFC when assembly compression effects are considered. In contrast, more realistic results are obtained when GDL-specific capillary pressure curves reflecting the mixed-wettability characteristics of GDLs are taken into account. The gas coverage factor at the GDL/channel interface also exhibits a strong influence on the gas-void fraction distribution in the GDL, which in turn depends on the relative importance between the capillary resistance induced by the inhomogeneous compression, Rc(∝ ∂pc / ∂ ε) , and the capillary diffusivity, Dbarc(∝ ∂pc / ∂ s) .

Effect of natural aging on quench-induced inhomogeneity of microstructure and hardness in high strength 7055 aluminum alloy

International Nuclear Information System (INIS)

Liu, Shengdan; Li, Chengbo; Han, Suqi; Deng, Yunlai; Zhang, Xinming

2015-01-01

Highlights: • The quench-induced hardness inhomogeneity in 7055 Al alloy decreases by natural aging. • The reason is discussed based on natural aging effect on microstructural inhomogeneity. • Natural aging decreases the difference of hardening precipitates due to slow quenching. • GPII zones appear in the rapidly-quenched sample after natural aging for 17,280 h. - Abstract: The effect of natural aging on quench-induced inhomogeneity of microstructure and hardness in high strength 7055 aluminum alloy was investigated by means of end quenching technique, transmission electron microscopy and differential scanning calorimetry thermal analysis. The hardness inhomogeneity in the end-quenched specimens after artificial aging decreases with the increase of natural aging time prior to artificial aging. The quench-induced differences in the amount and size of η′ phase are large in the end-quenched specimen after artificial aging at 120 °C for 24 h, leading to high hardness inhomogeneity. Natural aging for a long time results in a larger amount of stable GPI zones in the slowly-quenched sample, and thus decreases such differences in the end-quenched specimens after subsequent artificial aging, leading to lower hardness inhomogeneity. The hardness inhomogeneity can be reduced from 14% to be 4% by natural aging for 17,280 h prior to artificial aging

Multiple scattering of elliptically polarized light in two-dimensional medium with large inhomogeneities

Energy Technology Data Exchange (ETDEWEB)

Gorodnichev, E. E., E-mail: gorodn@theor.mephi.ru [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) (Russian Federation)

2016-12-15

For elliptically polarized light incident on a two-dimensional medium with large inhomogeneities, the Stokes parameters of scattered waves are calculated. Multiple scattering is assumed to be sharply anisotropic. The degree of polarization of scattered radiation is shown to be a nonmonotonic function of depth when the incident wave is circularly polarized or its polarization vector is not parallel to the symmetry axis of the inhomogeneities.

Karlin–McGregor-like formula in a simple time-inhomogeneous birth–death process

International Nuclear Information System (INIS)

Ohkubo, Jun

2014-01-01

Algebraic discussions are developed to derive transition probabilities for a simple time-inhomogeneous birth–death process. Algebraic probability theory and Lie algebraic treatments make it easy to treat the time-inhomogeneous cases. As a result, an expression based on the Charlier polynomials is obtained, which can be considered as an extension of a famous Karlin–McGregor representation for a time-homogeneous birth–death process. (paper)

Flame spread over inclined electrical wires with AC electric fields

KAUST Repository

Lim, Seung J.; Park, Sun H.; Park, Jeong; Fujita, Osamu; Keel, Sang I.; Chung, Suk-Ho

2017-01-01

Flame spread over polyethylene-insulated electrical wires was studied experimentally with applied alternating current (AC) by varying the inclination angle (θ), applied voltage (VAC), and frequency (fAC). For the baseline case with no electric field

Inhomogeneities in dusty universe — a possible alternative to dark energy?

International Nuclear Information System (INIS)

Chatterjee, S.

2011-01-01

There have been of late renewed debates on the role of inhomogeneities to explain the observed late acceleration of the universe. We have looked into the problem analytically with the help of the well known spherically symmetric but inhomogeneous Lemaitre-Tolman-Bondi(LTB) model generalised to higher dimensions. It is observed that in contrast to the claim made by Kolb et al. the presence of inhomogeneities as well as extra dimensions can not reverse the signature of the deceleration parameter if the matter field obeys the energy conditions. The well known Raychaudhuri equation also points to the same result. Without solving the field equations explicitly it can, however, be shown that although the total deceleration is positive everywhere nevertheless it does not exclude the possibility of having radial acceleration, even in the pure dust universe, if the angular scale factor is decelerating fast enough and vice versa. Moreover it is found that introduction of extra dimensions can not reverse the scenario. To the contrary it actually helps the decelerating process

Negative refraction of inhomogeneous waves in lossy isotropic media

International Nuclear Information System (INIS)

Fedorov, V Yu; Nakajima, T

2014-01-01

We theoretically study negative refraction of inhomogeneous waves at the interface of lossy isotropic media. We obtain explicit (up to the sign) expressions for the parameters of a wave transmitted through the interface between two lossy media characterized by complex permittivity and permeability. We show that the criterion of negative refraction that requires negative permittivity and permeability can be used only in the case of a homogeneous incident wave at the interface between a lossless and lossy media. In a more general situation, when the incident wave is inhomogeneous, or both media are lossy, the criterion of negative refraction becomes dependent on an incidence angle. Most interestingly, we show that negative refraction can be realized in conventional lossy materials (such as metals) if their interfaces are properly oriented. (paper)

The Prediction of Wave Competitions in Inhomogeneous Brusselator Systems

International Nuclear Information System (INIS)

Cui Xiao-Hua; Dong Yun-Xia; Huang Xiao-Qing; Li Ning

2015-01-01

The competition of waves has remained a hot topic in physics over the past few decades, especially the area of pattern control. Because of improved understanding of various dynamic behaviors, many practical applications have sprung up recently. The prediction of wave competitions is also very important and quite useful in these fields. This paper considers the behaviors of wave competitions in simple, inhomogeneous media which is modeled by Brusselator equations. We present a simple rule to judge the results of wave competitions utilizing the dispersion relation curves and the waves coming from different wave sources. Moreover, this rule can also be used to predict the results of wave propagation. It provides methods of obtaining the desired waves with given frequencies in inhomogeneous media. All our results are concluded and verified by computer simulations. (paper)

Sensitivity of resistive and Hall measurements to local inhomogeneities

DEFF Research Database (Denmark)

Koon, Daniel W.; Wang, Fei; Petersen, Dirch Hjorth

2014-01-01

We derive exact, analytic expressions for the sensitivity of sheet resistance and Hall sheet resistance measurements to local inhomogeneities for the cases of nonzero magnetic fields, strong perturbations, and perturbations over a finite area, extending our earlier results on weak perturbations. ...... simulations on both a linear four-point probe array on a large circular disc and a van der Pauw square geometry. Furthermore, the results also agree well with Náhlík et al. published experimental results for physical holes in a circular copper foil disc.......We derive exact, analytic expressions for the sensitivity of sheet resistance and Hall sheet resistance measurements to local inhomogeneities for the cases of nonzero magnetic fields, strong perturbations, and perturbations over a finite area, extending our earlier results on weak perturbations. We...

Evolution of a Diffusion Channel in an Inhomogeneous Electric Field of the KrF-Laser Pump Discharge

Science.gov (United States)

Yampol'skaya, S. A.; Yastremsky, A. G.; Panchenko, Yu. N.; Puchikin, A. V.; Bobrovnikov, S. M.

2018-01-01

The results of studying the 2D-simulation of evolution of a diffusion channel in the KrF-laser pump discharge initiated by the pin on the cathode surface are presented. It is shown that during the pump pulse, the inhomogeneity passes successively through three stages: a plasma spot on the cathode surface, a diffuse channel, and a high-conductivity channel. From the analysis of the dynamics of spatial distribution of spontaneous emission on the B0-X transition of the KrF molecule in such a discharge, it is obtained that the channel can work as an amplifying medium while the volumetric form of its glow is maintained. Despite the contraction of the channel into a narrow cord at the end of the pump pulse, the distribution of the radiation energy over the entire pulse has the shape of a torch with the width at the anode of 0.6 cm.

Modeling groundwater flow to elliptical lakes and through multi-aquifer elliptical inhomogeneities

Science.gov (United States)

Bakker, Mark

2004-05-01

Two new analytic element solutions are presented for steady flow problems with elliptical boundaries. The first solution concerns groundwater flow to shallow elliptical lakes with leaky lake beds in a single-aquifer. The second solution concerns groundwater flow through elliptical cylinder inhomogeneities in a multi-aquifer system. Both the transmissivity of each aquifer and the resistance of each leaky layer may differ between the inside and the outside of an inhomogeneity. The elliptical inhomogeneity may be bounded on top by a shallow elliptical lake with a leaky lake bed. Analytic element solutions are obtained for both problems through separation of variables of the Laplace and modified-Helmholtz differential equations in elliptical coordinates. The resulting equations for the discharge potential consist of infinite sums of products of exponentials, trigonometric functions, and modified-Mathieu functions. The series are truncated but still fulfill the differential equation exactly; boundary conditions are met approximately, but up to machine accuracy provided enough terms are used. The head and flow may be computed analytically at any point in the aquifer. Examples are given of uniform flow through an elliptical lake, a well pumping near two elliptical lakes, and uniform flow through three elliptical inhomogeneities in a multi-aquifer system. Mathieu functions may be applied in a similar fashion to solve other groundwater flow problems in semi-confined aquifers and leaky aquifer systems with elliptical internal or external boundaries.

Exploring entropic uncertainty relation in the Heisenberg XX model with inhomogeneous magnetic field

Science.gov (United States)

Huang, Ai-Jun; Wang, Dong; Wang, Jia-Ming; Shi, Jia-Dong; Sun, Wen-Yang; Ye, Liu

2017-08-01

In this work, we investigate the quantum-memory-assisted entropic uncertainty relation in a two-qubit Heisenberg XX model with inhomogeneous magnetic field. It has been found that larger coupling strength J between the two spin-chain qubits can effectively reduce the entropic uncertainty. Besides, we observe the mechanics of how the inhomogeneous field influences the uncertainty, and find out that when the inhomogeneous field parameter b1. Intriguingly, the entropic uncertainty can shrink to zero when the coupling coefficients are relatively large, while the entropic uncertainty only reduces to 1 with the increase of the homogeneous magnetic field. Additionally, we observe the purity of the state and Bell non-locality and obtain that the entropic uncertainty is anticorrelated with both the purity and Bell non-locality of the evolution state.

Regular Bulk Solutions in Brane-Worlds with Inhomogeneous Dust and Generalized Dark Radiation

International Nuclear Information System (INIS)

Rocha, Roldão da; Kuerten, A. M.; Herrera-Aguilar, A.

2015-01-01

From the dynamics of a brane-world with matter fields present in the bulk, the bulk metric and the black string solution near the brane are generalized, when both the dynamics of inhomogeneous dust/generalized dark radiation on the brane-world and inhomogeneous dark radiation in the bulk as well are considered as exact dynamical collapse solutions. Based on the analysis on the inhomogeneous static exterior of a collapsing sphere of homogeneous dark radiation on the brane, the associated black string warped horizon is studied, as well as the 5D bulk metric near the brane. Moreover, the black string and the bulk are shown to be more regular upon time evolution, for suitable values for the dark radiation parameter in the model, by analyzing the soft physical singularities

Material inhomogeneities and their evolution a geometric approach

CERN Document Server

Epstein, Marcelo

2007-01-01

Presents a unified treatment of the inhomogeneity theory using some of the tools of modern differential geometry. This book deals with the geometrical description of uniform bodies and their homogeneity conditions. It also develops a theory of material evolution and discusses its relevance in various applied contexts.

Radiance intensity enhanced by thin inhomogeneous lossy films

International Nuclear Information System (INIS)

Ben-Abdallah, Philippe; Ni Bo

2004-01-01

Basically, the classical radiative transfer theory assumes that the coherent component of the radiation field is equal to zero and heuristic considerations about energy conservation are used in the phenomenological derivation of the RTE. Here a self-consistent theory is presented to investigate radiative transport in the presence of diffraction processes within thin inhomogeneous films. The problem of linear optics about the transport of scalar radiation within film is solved, a new definition of the radiance is introduced in agreement with earlier definitions and a corresponding radiative transfer equation is derived. The influence of spatial variations of the bulk properties on the propagating mode is described in detail. It is analytically predicted that, unlike homogeneous media, an inhomogeneous film can enhance the radiance intensity in spite of the diffraction and the local extinction. From a practical point of view, the results of this work should be useful to perform the optimal design for many thermoelectric devices such as the new generations of photovoltaiec cells

Big bang nucleosynthesis with Gaussian inhomogeneous neutrino degeneracy

International Nuclear Information System (INIS)

Stirling, Spencer D.; Scherrer, Robert J.

2002-01-01

We consider the effect of inhomogeneous neutrino degeneracy on big bang nucleosynthesis for the case where the distribution of neutrino chemical potentials is given by a Gaussian. The chemical potential fluctuations are taken to be isocurvature, so that only inhomogeneities in the electron chemical potential are relevant. Then the final element abundances are a function only of the baryon-photon ratio η, the effective number of additional neutrinos ΔN ν , the mean electron neutrino degeneracy parameter ξ-bar, and the rms fluctuation of the degeneracy parameter, σ ξ . We find that for fixed η, ΔN ν , and ξ-bar, the abundances of 4 He, D, and 7 Li are, in general, increasing functions of σ ξ . Hence, the effect of adding a Gaussian distribution for the electron neutrino degeneracy parameter is to decrease the allowed range for η. We show that this result can be generalized to a wide variety of distributions for ξ

Trace element evidence for a laterally inhomogeneous moon

International Nuclear Information System (INIS)

Jovanovic, S.; Reed, G.W. Jr.

1978-01-01

A number of trace element interrelations support the concept of a laterally inhomogeneous moon based orginally in Cl/sub r//P 2 O 5 ratios. The correspondence between Cl/sub r//P 2 O 5 and Rb/Sr ratios in basalts are of special interest since the isotopic evolution of the latter pair of elements relates to the earliest history of the moon. This implies the times when the Cl/sub r//P 2 O 5 relations were established. The early magma ocean is conjectured to have been made up of nonintermixing seas resulting either from large convection cells or large body accretion. These mutually exclusive regions could be lunar geological provinces. It is proposed that the diversity of basalts from the Apollo 17 site is related to the lateral inhomogeneity of the moon. Ca/Na ratios in basalts show a trend which parallels that of Ru/Os and in a corresponding fashion may serve as a depth indicator. 4 figures, 4 tables, 12 references

The Optimal Inhomogeneity for Superconductivity: Finite Size Studies

Energy Technology Data Exchange (ETDEWEB)

Tsai, W-F.

2010-04-06

We report the results of exact diagonalization studies of Hubbard models on a 4 x 4 square lattice with periodic boundary conditions and various degrees and patterns of inhomogeneity, which are represented by inequivalent hopping integrals t and t{prime}. We focus primarily on two patterns, the checkerboard and the striped cases, for a large range of values of the on-site repulsion U and doped hole concentration, x. We present evidence that superconductivity is strongest for U of order the bandwidth, and intermediate inhomogeneity, 0 < t{prime} < t. The maximum value of the 'pair-binding energy' we have found with purely repulsive interactions is {Delta}{sub pb} = 0.32t for the checkerboard Hubbard model with U = 8t and t{prime} = 0.5t. Moreover, for near optimal values, our results are insensitive to changes in boundary conditions, suggesting that the correlation length is sufficiently short that finite size effects are already unimportant.

Electrical conductivity of polytetrafluoroethylene in dc and ac electric fields under continuous electron bombardment

International Nuclear Information System (INIS)

Khatipov, S.A.; Turdybekov, K.M.; Milinchuk, V.K.

1993-01-01

A study has been made of the time of the radiation current density in dc and ac (10 2 -5-10 3 Hz) electric fields (10 3 -5-10 5 V/cm) at temperatures from 80 to 393 K and dose rates from 5-10 3 Gy/sec, for PTFE films (50-180 μm) with various thermal prehistories, when exposed to continuous bombardment by 9-MeV electrons. It has been shown that the experimental results cannot be interpreted from the standpoint of free-charge conduction; they can be explained qualitatively within the framework of concepts of inhomogeneous ionization of the substance, due to the formation of short tracks

Intermittency for stochastic partial differential equations driven by strongly inhomogeneous space-time white noises

Science.gov (United States)

Xie, Bin

2018-01-01

In this paper, the main topic is to investigate the intermittent property of the one-dimensional stochastic heat equation driven by an inhomogeneous Brownian sheet, which is a noise deduced from the study of the catalytic super-Brownian motion. Under some proper conditions on the catalytic measure of the inhomogeneous Brownian sheet, we show that the solution is weakly full intermittent based on the estimates of moments of the solution. In particular, it is proved that the second moment of the solution grows at the exponential rate. The novelty is that the catalytic measure relative to the inhomogeneous noise is not required to be absolutely continuous with respect to the Lebesgue measure on R.

The effect of dust charge inhomogeneity on low-frequency modes in a strongly coupled plasma

International Nuclear Information System (INIS)

Farid, T.; Mamun, A.A.; Shukla, P.K.

2000-01-01

An analysis of low-frequency modes accounting for dust grain charge fluctuation and equilibrium grain charge inhomogeneity in a strongly coupled dusty plasma is presented. The existence of an extremely low frequency mode, which is due to the inhomogeneity in the equilibrium dust grain charge, is reported. Besides, the equilibrium dust grain charge inhomogeneity makes the dust-acoustic mode unstable. The strong correlations in the dust fluid significantly drive a new mode as well as the existing dust-acoustic mode. The applications of these results to recent experimental and to some space and astrophysical situations are discussed

TRANSMISSION AND ABSORPTION OF MICROWAVES BY AN INHOMOGENEOUS SPHERE PLASMA

Institute of Scientific and Technical Information of China (English)

SONG Falun; CAO Jinxiang; WANG Ge

2004-01-01

The numerical calculation of the transmission and absorption of microwaves at an arbitrarily incident angle to the inhomogeneous spherically symmetric plasma is presented.The nonuniform sphere is modeled by a series of concentric spherical shells, and the electron density is constant in each shell. The overall density profile follows any given distribution function. By using the geometrical optics approximation and considering the propagation coefficient is complex, as well as the attenuation and phase coefficients are vectors, the detailed evaluation shows that the transmission and absorption of microwaves in the inhomogeneous spherically symmetric plasma depend on the electron and neutral particle collision frequency, central density, incident angle of the microwaves and density distribution profiles.

Toroidal inhomogeneity of the vertical field in a tokamak apparatus

International Nuclear Information System (INIS)

Sometani, Taro; Takashima, Hidekazu

1977-01-01

An experiment with a model device has been made on the toroidal inhomogeneity of the vertical field in a Tokamak with an iron core. The D.C. vertical field is increased near the yokes of the iron core, while the gross plasma image field (consisting of the components due to the plasma current, the primary current, and its image) is reduced there. These two vertical fields, when superposed, exert force on the plasma as a less inhomogeneous external vertical field. The vertical field can be homogenized satisfactorily by using a compensation winding wound at a proper position on the iron core even if the shielding plates, which are mounted on some Tokamaks, are dispensed with. (auth.)

Heating and Acceleration of Solar Wind Ions by Turbulent Wave Spectrum in Inhomogeneous Expanding Plasma

Science.gov (United States)

Ofman, Leon; Ozak, Nataly; Vinas, Adolfo F.

2016-01-01

Near the Sun (plasma. The heating and the acceleration of the solar wind ions by turbulent wave spectrum in inhomogeneous plasma is studied using a 2.5D hybrid model. The hybrid model describes the kinetics of the ions, while the electrons are modeled as massless neutralizing fluid in an expanding box approach. Turbulent magnetic fluctuations dominated by power-law frequency spectra, which are evident from in-situ as well as remote sensing measurements, are used in our models. The effects of background density inhomogeneity across the magnetic field on the resonant ion heating are studied. The effect of super- Alfvenic ion drift on the ion heating is investigated. It is found that the turbulent wave spectrum of initially parallel propagating waves cascades to oblique modes, and leads to enhanced resonant ion heating due to the inhomogeneity. The acceleration of the solar wind ions is achieved by the parametric instability of large amplitude waves in the spectrum, and is also affected by the inhomogeneity. The results of the study provide the ion temperature anisotropy and drift velocity temporal evolution due to relaxation of the instability. The non-Maxwellian velocity distribution functions (VDFs) of the ions are modeled in the inhomogeneous solar wind plasma in the acceleration region close to the Sun.

Optical inhomogeneity developing in flashlamp photolysis lasers

Energy Technology Data Exchange (ETDEWEB)

Alekhin, B V; Borovkov, V V; Brodskii, A Ya; Lazhintsev, B V; Nor-Arevian, V A; Sukhanov, L V

1980-07-01

The paper discusses the dynamics of optical inhomogenity developing in the active medium of a high-power flashlamp-pumped photolysis laser in inverse population storage, fast inversion suppression, and free-running lasing regimes. A chemical component of the refractive index was found in a C3F7I photolysis experiment, along with the anomalous growth of a gas refractive index.

Generation of Nonlinear Electric Field Bursts in the Outer Radiation Belt through Electrons Trapping by Oblique Whistler Waves

Science.gov (United States)

Agapitov, Oleksiy; Drake, James; Mozer, Forrest

2016-04-01

Huge numbers of different nonlinear structures (double layers, electron holes, non-linear whistlers, etc. referred to as Time Domain Structures - TDS) have been observed by the electric field experiment on board the Van Allen Probes. A large part of the observed non-linear structures are associated with whistler waves and some of them can be directly driven by whistlers. The parameters favorable for the generation of TDS were studied experimentally as well as making use of 2-D particle-in-cell (PIC) simulations for the system with inhomogeneous magnetic field. It is shown that an outward propagating front of whistlers and hot electrons amplifies oblique whistlers which collapse into regions of intense parallel electric field with properties consistent with recent observations of TDS from the Van Allen Probe satellites. Oblique whistlers seed the parallel electric fields that are driven by the beams. The resulting parallel electric fields trap and heat the precipitating electrons. These electrons drive spikes of intense parallel electric field with characteristics similar to the TDSs seen in the VAP data. The decoupling of the whistler wave and the nonlinear electrostatic component is shown in PIC simulation in the inhomogeneous magnetic field system. These effects are observed by the Van Allen Probes in the radiation belts. The precipitating hot electrons propagate away from the source region in intense bunches rather than as a smooth flux.

Amplification of Frequency-Modulated Similariton Pulses in Length-Inhomogeneous Active Fibers

Directory of Open Access Journals (Sweden)

I. O. Zolotovskii

2012-01-01

Full Text Available The possibility of an effective gain of the self-similar frequency-modulated (FM wave packets is studied in the length-inhomogeneous active fibers. The dynamics of parabolic pulses with the constant chirp has been considered. The optimal profile for the change of the group-velocity dispersion corresponding to the optimal similariton pulse amplification has been obtained. It is shown that the use of FM pulses in the active (gain and length-inhomogeneous optical fibers with the normal group-velocity dispersion can provide subpicosecond optical pulse amplification up to the energies higher than 1 nJ.

Electric fields in nonhomogeneously doped silicon. Summary of simulations

Energy Technology Data Exchange (ETDEWEB)

Kotov, I.V. [Ohio State University, Columbus, OH 43210 (United States)]. E-mail: kotov@mps.ohio-state.edu; Humanic, T.J. [Ohio State University, Columbus, OH 43210 (United States); Nouais, D. [INFN, Sezione di Torino, I-10125 Turin (Italy); Randel, J. [Ohio State University, Columbus, OH 43210 (United States); Rashevsky, A. [INFN, Sezione di Triste, I-34127 Trieste (Italy)

2006-11-30

Variations of the doping concentration inside a silicon device result in electric field distortions. These distortions, 'parasitic' fields, have been observed in Silicon Drift Detectors [D. Nouais, et al., Nucl. Instr. and Meth. A 501 (2003) 119; E. Crescio, et al., Nucl. Instr. and Meth. A 539 (2005) 250]. Electric fields inside a silicon device can be calculated for a given doping profile. In this study, the ATLAS device simulator. [Silvaco International, 4701 Patrick Henry Drive, Bldg.2, Santa Clara, CA 95054, USA and ] was used to calculate the electric field inside an inhomogeneously doped device. Simulations were performed for 1D periodic doping profiles. Results show strong dependence of the parasitic field strength on the 'smoothness' of the doping profile.

Effect of active medium inhomogeneity on lasing characteristics of InAs/InP quantum-dash lasers

KAUST Repository

Khan, Mohammed Zahed Mustafa

2010-01-01

The authors report on the effect of quantum-dash (Qdash) inhomogeneity on the characteristics of InAs/InP Qdash laser utilizing a single state rate equation model. The inhomogeneity is assumed to follow the Gaussian approximation. From our observation, an increased in Qdash inhomogeneity results in increasing of threshold current density and redshifting of the peak lasing wavelength. The lasing linewidth of the Qdash lasers has also found to increase under large injection current, attaining a full width at half maximum (FWHM) of ~ 17 nm.

Polarized optical scattering by inhomogeneities and surface roughness in an anisotropic thin film.

Science.gov (United States)

Germer, Thomas A; Sharma, Katelynn A; Brown, Thomas G; Oliver, James B

2017-11-01

We extend the theory of Kassam et al. [J. Opt. Soc. Am. A12, 2009 (1995)JOAOD60740-323210.1364/JOSAA.12.002009] for scattering by oblique columnar structure thin films to include the induced form birefringence and the propagation of radiation in those films. We generalize the 4×4 matrix theory of Berreman [J. Opt. Soc. Am.62, 502 (1972)JOSAAH0030-394110.1364/JOSA.62.000502] to include arbitrary sources in the layer, which are necessary to determine the Green function for the inhomogeneous wave equation. We further extend first-order vector perturbation theory for scattering by roughness in the smooth surface limit, when the layer is anisotropic. Scattering by an inhomogeneous medium is approximated by a distorted Born approximation, where effective medium theory is used to determine the effective properties of the medium, and strong fluctuation theory is used to determine the inhomogeneous sources. In this manner, we develop a model for scattering by inhomogeneous films, with anisotropic correlation functions. The results are compared with Mueller matrix bidirectional scattering distribution function measurements for a glancing-angle deposition (GLAD) film. While the results are applied to the GLAD film example, the development of the theory is general enough that it can guide simulations for scattering in other anisotropic thin films.

ION HEATING IN INHOMOGENEOUS EXPANDING SOLAR WIND PLASMA: THE ROLE OF PARALLEL AND OBLIQUE ION-CYCLOTRON WAVES

International Nuclear Information System (INIS)

Ozak, N.; Ofman, L.; Viñas, A.-F.

2015-01-01

Remote sensing observations of coronal holes show that heavy ions are hotter than protons and their temperature is anisotropic. In-situ observations of fast solar wind streams provide direct evidence for turbulent Alfvén wave spectrum, left-hand polarized ion-cyclotron waves, and He ++ - proton drift in the solar wind plasma, which can produce temperature anisotropies by resonant absorption and perpendicular heating of the ions. Furthermore, the solar wind is expected to be inhomogeneous on decreasing scales approaching the Sun. We study the heating of solar wind ions in inhomogeneous plasma with a 2.5D hybrid code. We include the expansion of the solar wind in an inhomogeneous plasma background, combined with the effects of a turbulent wave spectrum of Alfvénic fluctuations and initial ion-proton drifts. We study the influence of these effects on the perpendicular ion heating and cooling and on the spectrum of the magnetic fluctuations in the inhomogeneous background wind. We find that inhomogeneities in the plasma lead to enhanced heating compared to the homogenous solar wind, and the generation of significant power of oblique waves in the solar wind plasma. The cooling effect due to the expansion is not significant for super-Alfvénic drifts, and is diminished further when we include an inhomogeneous background density. We reproduce the ion temperature anisotropy seen in observations and previous models, which is present regardless of the perpendicular cooling due to solar wind expansion. We conclude that small scale inhomogeneities in the inner heliosphere can significantly affect resonant wave ion heating

Turbulent structure of stably stratified inhomogeneous flow

Science.gov (United States)

Iida, Oaki

2018-04-01

Effects of buoyancy force stabilizing disturbances are investigated on the inhomogeneous flow where disturbances are dispersed from the turbulent to non-turbulent field in the direction perpendicular to the gravity force. Attaching the fringe region, where disturbances are excited by the artificial body force, a Fourier spectral method is used for the inhomogeneous flow stirred at one side of the cuboid computational box. As a result, it is found that the turbulent kinetic energy is dispersed as layered structures elongated in the streamwise direction through the vibrating motion. A close look at the layered structures shows that they are flanked by colder fluids at the top and hotter fluids at the bottom, and hence vertically compressed and horizontally expanded by the buoyancy related to the countergradient heat flux, though they are punctuated by the vertical expansion of fluids at the forefront of the layered structures, which is related to the downgradient heat flux, indicating that the layered structures are gravity currents. However, the phase between temperature fluctuations and vertical velocity is shifted by π/2 rad, indicating that temperature fluctuations are generated by the propagation of internal gravity waves.

Glauber theory and the quantum coherence of curvature inhomogeneities

CERN Document Server

Giovannini, Massimo

2017-01-12

The curvature inhomogeneities are systematically scrutinized in the framework of the Glauber approach. The amplified quantum fluctuations of the scalar and tensor modes of the geometry are shown to be first-order coherent while the interference of the corresponding intensities is larger than in the case of Bose-Einstein correlations. After showing that the degree of second-order coherence does not suffice to characterize unambiguously the curvature inhomogeneities, we argue that direct analyses of the degrees of third and fourth-order coherence are necessary to discriminate between different correlated states and to infer more reliably the statistical properties of the large-scale fluctuations. We speculate that the moments of the multiplicity distributions of the relic phonons might be observationally accessible thanks to new generations of instruments able to count the single photons of the Cosmic Microwave Background in the THz region.

Spatial inhomogeneity in Schottky barrier height at graphene/MoS2 Schottky junctions

Science.gov (United States)

Tomer, D.; Rajput, S.; Li, L.

2017-04-01

Transport properties of graphene semiconductor Schottky junctions strongly depend on interfacial inhomogeneities due to the inherent formation of ripples and ridges. Here, chemical vapor deposited graphene is transferred onto multilayer MoS2 to fabricate Schottky junctions. These junctions exhibit rectifying current-voltage behavior with the zero bias Schottky barrier height increases and ideality factor decreases with increasing temperature between 210 and 300 K. Such behavior is attributed to the inhomogeneous interface that arises from graphene ripples and ridges, as revealed by atomic force and scanning tunneling microscopy imaging. Assuming a Gaussian distribution of the barrier height, a mean value of 0.96  ±  0.14 eV is obtained. These findings indicate a direct correlation between temperature dependent Schottky barrier height and spatial inhomogeneity in graphene/2D semiconductor Schottky junctions.

Spatial inhomogeneity in Schottky barrier height at graphene/MoS2 Schottky junctions

International Nuclear Information System (INIS)

Tomer, D; Rajput, S; Li, L

2017-01-01

Transport properties of graphene semiconductor Schottky junctions strongly depend on interfacial inhomogeneities due to the inherent formation of ripples and ridges. Here, chemical vapor deposited graphene is transferred onto multilayer MoS 2 to fabricate Schottky junctions. These junctions exhibit rectifying current–voltage behavior with the zero bias Schottky barrier height increases and ideality factor decreases with increasing temperature between 210 and 300 K. Such behavior is attributed to the inhomogeneous interface that arises from graphene ripples and ridges, as revealed by atomic force and scanning tunneling microscopy imaging. Assuming a Gaussian distribution of the barrier height, a mean value of 0.96  ±  0.14 eV is obtained. These findings indicate a direct correlation between temperature dependent Schottky barrier height and spatial inhomogeneity in graphene/2D semiconductor Schottky junctions. (paper)

Phase function of a spherical particle when scattering an inhomogeneous electromagnetic plane wave

DEFF Research Database (Denmark)

Frisvad, Jeppe Revall

2018-01-01

of the complex hypergeometric function 2F1 for every term of a series expansion. In this work, I develop a simpler solution based on associated Legendre functions with argument zero. It is similar to the solution for homogeneous plane waves but with new explicit expressions for the angular dependency of the far......In absorbing media, electromagnetic plane waves are most often inhomogeneous. Existing solutions for the scattering of an inhomogeneous plane wave by a spherical particle provide no explicit expressions for the scattering components. In addition, current analytical solutions require evaluation......-field scattering components, that is, the phase function. I include recurrence formulae for practical evaluation and provide numerical examples to evaluate how well the new expressions match previous work in some limiting cases. The predicted difference in the scattering phase function due to inhomogeneity...

Modeling of inhomogeneous mixing of plasma species in argon-steam arc discharge

Science.gov (United States)

Jeništa, J.; Takana, H.; Uehara, S.; Nishiyama, H.; Bartlová, M.; Aubrecht, V.; Murphy, A. B.

2018-01-01

This paper presents numerical simulation of mixing of argon- and water-plasma species in an argon-steam arc discharge generated in a thermal plasma generator with the combined stabilization of arc by axial gas flow (argon) and water vortex. The diffusion of plasma species itself is described by the combined diffusion coefficients method in which the coefficients describe the diffusion of argon ‘gas,’ with respect to water vapor ‘gas.’ Diffusion processes due to the gradients of mass density, temperature, pressure, and an electric field have been considered in the model. Calculations for currents 150-400 A with 15-22.5 standard liters per minute (slm) of argon reveal inhomogeneous mixing of argon and oxygen-hydrogen species with the argon species prevailing near the arc axis. All the combined diffusion coefficients exhibit highly nonlinear distribution of their values within the discharge, depending on the temperature, pressure, and argon mass fraction of the plasma. The argon diffusion mass flux is driven mainly by the concentration and temperature space gradients. Diffusions due to pressure gradients and due to the electric field are of about 1 order lower. Comparison with our former calculations based on the homogeneous mixing assumption shows differences in temperature, enthalpy, radiation losses, arc efficiency, and velocity at 400 A. Comparison with available experiments exhibits very good qualitative and quantitative agreement for the radial temperature and velocity profiles 2 mm downstream of the exit nozzle.

Accretion from an inhomogeneous medium

International Nuclear Information System (INIS)

Livio, M.; Soker, N.; Koo, M. de; Savonije, G.J.

1986-01-01

The problem of accretion by a compact object from an inhomogeneous medium is studied in the general γnot=1 case. The mass accretion rate is found to decrease with increasing γ. The rate of accretion of angular momentum is found to be significantly lower than the rate at which angular momentum is deposited into the Bondi-Hoyle, symmetrical, accretion cylinder. The consequences of the results are studied for the cases of neutron stars accreting from the winds of early-type companions and white dwarfs and main-sequence stars accreting from winds of cool giants. (author)

geometric optics and WKB method for electromagnetic wave propagation in an inhomogeneous plasma near cutoff

Energy Technology Data Exchange (ETDEWEB)

Light, Max Eugene [Los Alamos National Laboratory

2017-04-13

This report outlines the theory underlying electromagnetic (EM) wave propagation in an unmagnetized, inhomogeneous plasma. The inhomogeneity is given by a spatially nonuniform plasma electron density n_e(r), which will modify the wave propagation in the direction of the gradient rn_e(r).

Flux and polarization signals of spatially inhomogeneous gaseous exoplanets

NARCIS (Netherlands)

Karalidi, T.; Stam, D.M.; Guirado, D.

2013-01-01

Aims. We present numerically calculated, disk-integrated, spectropolarimetric signals of starlight that is reflected by vertically and horizontally inhomogeneous gaseous exoplanets. We include various spatial features that are present on Solar System’s gaseous planets: belts and zones, cyclonic

Effects of inhomogeneity on the Shukla-Nambu-Salimullah potential in a magnetized plasma

International Nuclear Information System (INIS)

Salimullah, M.; Shah, H.A.; Murtaza, G.; Nitta, H.; Tessarotto, M.

2007-01-01

Detailed properties of the electrostatic Shukla-Nambu-Salimullah potential in an inhomogeneous magnetoplasma in the presence of ion streaming due to diamagnetic drift as in a laboratory discharge plasma have been examined analytically. The potential becomes a sensitive function of the external static magnetic field, the scalelength of inhomogeneity, and the diamagnetic ion streaming velocity. For a decreasing ion density gradient, there is a limit of existence of this static modified shielding potential

Effect of active medium inhomogeneity on lasing characteristics of InAs/InP quantum-dash lasers

KAUST Repository

Khan, Mohammed Zahed Mustafa; Ng, Tien Khee; Ooi, Boon S.; Schwingenschlö gl, Udo

2010-01-01

The authors report on the effect of quantum-dash (Qdash) inhomogeneity on the characteristics of InAs/InP Qdash laser utilizing a single state rate equation model. The inhomogeneity is assumed to follow the Gaussian approximation. From our

Magnetic response of localized spins coupled to itinerant electrons in an inhomogeneous crystal field

International Nuclear Information System (INIS)

Iannarella, L.; Guimaraes, A.P.; Silva, X.A. da.

1990-01-01

The magnetic behavior at T = O K of a system consisting of conduction electrons coupled to localized electrons, the latter submitted to an inhomogeneous crystal field distribution, is studied. The study implies that the inhomogeneity of the crystal field attenuates the quenching effects. The model is interesting to the study of disordered rare-earth intermetallic compounds. (A.C.A.S.) [pt

Optical and electrical phenomena in dielectric materials under irradiation

CERN Document Server

Plaksin, O A; Stepanov, P A; Demenkov, P V; Chernov, V M; Krutskikh, A O

2002-01-01

Optical and acoustic properties of the materials based on Al sub 2 O sub 3 , SiO sub 2 and BN under 8 MeV proton irradiation (<10 sup 4 Gy/s) have been measured. Electric charge partitioning has been shown to result in charging the microscopic regions in the bulk of the dielectrics under irradiation, which is due to different mobility of free electrons and holes (sapphire), concentration inhomogeneity in the system of charge carrier traps (alumina), or thermodynamic instability of the homogeneous distribution of the filled traps (silica glasses). Prevalent charge carrier recombination in the grain boundaries causes re-crystallization of pyrolytic boron nitride under irradiation, which shows up as simultaneous decrease of the intensity of radiation-induced luminescence (RIL) of the centres in the grain boundaries and the BN. The local charging results in optical inhomogeneity of the silica glasses which is sustained by the optical loss spectra of the irradiated glasses, features of kinetics of bleaching, RI...

Genomic mid-range inhomogeneity correlates with an abundance of RNA secondary structures

Directory of Open Access Journals (Sweden)

Song Jun

2008-06-01

Full Text Available Abstract Background Genomes possess different levels of non-randomness, in particular, an inhomogeneity in their nucleotide composition. Inhomogeneity is manifest from the short-range where neighboring nucleotides influence the choice of base at a site, to the long-range, commonly known as isochores, where a particular base composition can span millions of nucleotides. A separate genomic issue that has yet to be thoroughly elucidated is the role that RNA secondary structure (SS plays in gene expression. Results We present novel data and approaches that show that a mid-range inhomogeneity (~30 to 1000 nt not only exists in mammalian genomes but is also significantly associated with strong RNA SS. A whole-genome bioinformatics investigation of local SS in a set of 11,315 non-redundant human pre-mRNA sequences has been carried out. Four distinct components of these molecules (5'-UTRs, exons, introns and 3'-UTRs were considered separately, since they differ in overall nucleotide composition, sequence motifs and periodicities. For each pre-mRNA component, the abundance of strong local SS ( Conclusion We demonstrate that the excess of strong local SS in pre-mRNAs is linked to the little explored phenomenon of genomic mid-range inhomogeneity (MRI. MRI is an interdependence between nucleotide choice and base composition over a distance of 20–1000 nt. Additionally, we have created a public computational resource to support further study of genomic MRI.

Controlling Charged Particles with Inhomogeneous Electrostatic Fields

Science.gov (United States)

Herrero, Federico A. (Inventor)

2016-01-01

An energy analyzer for a charged-particle spectrometer may include a top deflection plate and a bottom deflection plate. The top and bottom deflection plates may be non-symmetric and configured to generate an inhomogeneous electrostatic field when a voltage is applied to one of the top or bottom deflection plates. In some instances, the top and bottom deflection plates may be L-shaped deflection plates.

Inhomogeneous MUSIG Model - a population balance approach for polydispersed bubbly flows

International Nuclear Information System (INIS)

Frank, T.; Zwart, P.J.; Shi, J.; Krepper, E.; Lucas, D.; Rohde, U.

2005-01-01

Many flow regimes in Nuclear Reactor Safety (NRS) Research are characterized by multiphase flows, with one phase being a continuous liquid and the other phase consisting of gas or vapour of the liquid phase. In the range of low to intermediate volume fraction of the gaseous phase the multiphase flow under consideration is a bubbly or slug flow, where the disperse phase is characterized by an evolving bubble size distribution due to bubble breakup and coalescence processes. The paper presents a generalized inhomogeneous Multiple Size Group (MUSIG) Model. Within this model the disperse gaseous phase is divided into N inhomogeneous velocity groups (phases) and each of these groups is subdivided into M bubble size classes. Bubble breakup and coalescence processes between all bubble size classes are taken into account by appropriate models. The derived inhomogeneous MUSIG model has been validated against experimental data from the TOPFLOW test facility at the Research Center Rossendorf (FZR). Comparisons of gas volume fraction and velocity profiles with TOPFLOW-074 test case data are provided, showing the applicability and accuracy of the model for polydispersed bubbly flow in large diameter vertical pipe flow. (author)

Jeans instability of an inhomogeneous streaming dusty plasma

Indian Academy of Sciences (India)

The dynamics of a self-gravitating unmagnetized, inhomogeneous, streaming dusty plasma is studied in the present work. The presence of the shear flow causes the coupling between gravitational and electrostatic forces. In the absence of self-gravity, the fluctuations in the plasma may grow at the expense of the density ...

An optimal power-dispatching system using neural networks for the electrochemical process of zinc depending on varying prices of electricity.

Science.gov (United States)

Yang, Chunhua; Deconinck, G; Gui, Weihua; Li, Yonggang

2002-01-01

Depending on varying prices of electricity, an optimal power-dispatching system (OPDS) is developed to minimize the cost of power consumption in the electrochemical process of zinc (EPZ). Due to the complexity of the EPZ, the main factors influencing the power consumption are determined by qualitative analysis, and a series of conditional experiments is conducted to acquire sufficient data, then two backpropagation neural networks are used to describe these relationships quantitatively. An equivalent Hopfield neural network is constructed to solve the optimization problem where a penalty function is introduced into the network energy function so as to meet the equality constraints, and inequality constraints are removed by alteration of the Sigmoid function. This OPDS was put into service in a smeltery in 1998. The cost of power consumption has decreased significantly, the total electrical energy consumption is reduced, and it is also beneficial to balancing the load of the power grid. The actual results show the effectiveness of the OPDS. This paper introduces a successful industrial application and mainly presents how to utilize neural networks to solve particular problems for the real world.

Inhomogeneous strain induced by fast neutron irradiation in NaKSO/sub 4/ crystals

Energy Technology Data Exchange (ETDEWEB)

Kandil, S.H.; Kassem, M.E.; El-Khatib, A.; El-Gamal, M.A.; El-Wahidy, E.F.

1987-11-01

The paper reports the effect of fast neutron irradiation on the thermal properties of NaKSO/sub 4/ crystals in the temperature range 400-475 K. Results are presented for the thermal expansion, tensile strain and specific heat of NaKSO/sub 4/, as a function of neutron irradiation dose. All these results revealed an inhomogeneous strain induced by the radiation. It is suggested that this induced inhomogeneous strain could be used to detect neutron exposure doses.

Investigation of small-scale optical inhomogeneities in an electroionization CO/sub 2/-laser

Energy Technology Data Exchange (ETDEWEB)

Borovkov, V V; Kornilov, V G; Lazhintsev, B V; Nor-arevian, V A; Sukhanov, L V

1987-08-01

A technique for the interferometer investigation of optical inhomogeneities in an electroionization CO/sub 2/-laser in the free-oscillation regime is developed which involves active-medium sounding that is coaxial with the laser resonator. Experimental results are presented on small-scale optical inhomogeneities for a pulsed electroionization laser pumped by a nonself-sustained discharge in a CO/sub 2/:N/sub 2/:He = 1:3:6 mixture at a total pressure of 1 atm. 11 references.

Lie Symmetry Analysis of the Inhomogeneous Toda Lattice Equation via Semi-Discrete Exterior Calculus

International Nuclear Information System (INIS)

Liu Jiang; Wang Deng-Shan; Yin Yan-Bin

2017-01-01

In this work, the Lie point symmetries of the inhomogeneous Toda lattice equation are obtained by semi-discrete exterior calculus, which is a semi-discrete version of Harrison and Estabrook’s geometric approach. A four-dimensional Lie algebra and its one-, two- and three-dimensional subalgebras are given. Two similarity reductions of the inhomogeneous Toda lattice equation are obtained by using the symmetry vectors. (paper)

Energy transfer rates in inhomogeneous van der Waals clusters

International Nuclear Information System (INIS)

Desfrancois, C.; Schermann, J.P.

1991-01-01

The internal energy exchange inside an inhomogeneous van der Waals cluster are investigated by means of molecular dynamic calculations. The very long time scales for relaxation of the high frequency degrees of freedom are examined within the framework of Nekhoroshev's theorem. (orig.)

Anisotropic modelling of the electrical conductivity of fractured bedrock

International Nuclear Information System (INIS)

Flykt, M.J.; Sihvola, A.H.; Eloranta, E.H.

1995-01-01

The electromagnetic characterization of fractured bedrock is of importance when studying the final disposal of nuclear waste. The different types of discontinuities at all scales in rocks can be viewed as an inhomogeneity. In some cases there are reasons to assume the influence of the discontinuities on electrical conductivity is anisotropic in character. The effort has been made to use electromagnetic mixing rules in the definition of an equivalent homogeneous anisotropic conductivity tensor for such fractured rock mass. (author) (16 refs., 6 figs.)

Laser Meter of Atmospheric Inhomogeneity Properties in UV Spectral Range

Directory of Open Access Journals (Sweden)

S. E. Ivanov

2015-01-01

Full Text Available Development of laser systems designed to operate in conditions of the terrestrial atmosphere demands reliable information about the atmosphere condition. The aerosol lidars for operational monitoring of the atmosphere allow us to define remotely characteristics of atmospheric aerosol and cloudy formations in the atmosphere.Today the majority of aerosol lidars run in the visible range. However, in terms of safety (first of all to eyes also ultra-violet (UF range is of interest. A range of the wavelengths of the harmful effect on the eye retina is from 0.38 to 1.4 mμ. Laser radiation with the wavelengths less than 0.38 mμ and over 1.4 mμ influences the anterior ambient of an eye and is safer, than laser radiation with the wavelengths of 0.38 – 1.4 mμ.The paper describes a laser meter to measure characteristics of atmospheric inhomogeneity propertis in UF spectral range at the wavelength of 0.355 mμ.As a radiation source, the meter uses a semiconductor-pumped pulse solid-state Nd:YAG laser. As a receiving lens, Kassegren's scheme-implemented mirror lens with a socket to connect optical fibre is used in the laser meter. Radiation from the receiving lens is transported through the optical fibre to the optical block. The optical block provides spectral selection of useful signal and conversion of optical radiation into electric signal.To ensure a possibility for alignment of the optical axes of receiving lens and laser radiator the lens is set on the alignment platform that enables changing lens inclination and turn with respect to the laser.The software of the laser meter model is developed in the NI LabVIEW 2012 graphic programming environment.The paper gives the following examples: a typical laser echo signal, which is back scattered by the atmosphere and spatiotemporal distribution of variation coefficient of the volumetric factor of the back scattered atmosphere. Results of multi-day measurements show that an extent of the recorded aerosol

Electric field tuning of phase separation in manganite thin films

KAUST Repository

Lourembam, James; Wu, Jianchun; Ding, Junfeng; Lin, Weinan; Wu, Tao

2014-01-01

In this paper, we investigate the electric field effect on epitaxial Pr0.65(Ca0.75Sr0.25)0.35MnO3 thin films in electric double-layer transistors. Different from the conventional transistors with semiconducting channels, the sub(micrometer)-scale phase separation in the manganite channels is expected to result in inhomogeneous distribution of mobile carriers and local enhancement of electric field. The field effect is much larger in the low-temperature phase separation region compared to that in the high-temperature polaron transport region. Further enhancement of electroresistance is achieved by applying a magnetic field, and a 250% modulation of resistance is observed at 80 K, equivalent to an increase of the ferromagnetic metallic phase fraction by 0.51%, as estimated by the general effective medium model. Our results illustrate the complementary nature of electric and magnetic field effects in phase-separated manganites, providing insights on such novel electronic devices based on complex oxides.

Electric field tuning of phase separation in manganite thin films

KAUST Repository

Lourembam, James

2014-01-29

In this paper, we investigate the electric field effect on epitaxial Pr0.65(Ca0.75Sr0.25)0.35MnO3 thin films in electric double-layer transistors. Different from the conventional transistors with semiconducting channels, the sub(micrometer)-scale phase separation in the manganite channels is expected to result in inhomogeneous distribution of mobile carriers and local enhancement of electric field. The field effect is much larger in the low-temperature phase separation region compared to that in the high-temperature polaron transport region. Further enhancement of electroresistance is achieved by applying a magnetic field, and a 250% modulation of resistance is observed at 80 K, equivalent to an increase of the ferromagnetic metallic phase fraction by 0.51%, as estimated by the general effective medium model. Our results illustrate the complementary nature of electric and magnetic field effects in phase-separated manganites, providing insights on such novel electronic devices based on complex oxides.

EBL Inhomogeneity and Hard-Spectrum Gamma-Ray Sources

Energy Technology Data Exchange (ETDEWEB)

Abdalla, Hassan; Böttcher, Markus [Centre for Space Research, North-West University, Potchefstroom 2520 (South Africa)

2017-02-01

The unexpectedly hard very-high-energy (VHE; E > 100 GeV) γ -ray spectra of a few distant blazars have been interpreted as evidence of a reduction of the γγ opacity of the universe due to the interaction of VHE γ -rays with the extragalactic background light (EBL) compared to the expectation from current knowledge of the density and cosmological evolution of the EBL. One of the suggested solutions to this problem involves the inhomogeneity of the EBL. In this paper, we study the effects of such inhomogeneity on the energy density of the EBL (which then also becomes anisotropic) and the resulting γγ opacity. Specifically, we investigate the effects of cosmic voids along the line of sight to a distant blazar. We find that the effect of such voids on the γγ opacity, for any realistic void size, is only of the order of ≲1% and much smaller than expected from a simple linear scaling of the γγ opacity with the line-of-sight galaxy underdensity due to a cosmic void.

Spatially inhomogeneous acceleration of electrons in solar flares

Science.gov (United States)

Stackhouse, Duncan J.; Kontar, Eduard P.

2018-04-01

The imaging spectroscopy capabilities of the Reuven Ramaty high energy solar spectroscopic imager (RHESSI) enable the examination of the accelerated electron distribution throughout a solar flare region. In particular, it has been revealed that the energisation of these particles takes place over a region of finite size, sometimes resolved by RHESSI observations. In this paper, we present, for the first time, a spatially distributed acceleration model and investigate the role of inhomogeneous acceleration on the observed X-ray emission properties. We have modelled transport explicitly examining scatter-free and diffusive transport within the acceleration region and compare with the analytic leaky-box solution. The results show the importance of including this spatial variation when modelling electron acceleration in solar flares. The presence of an inhomogeneous, extended acceleration region produces a spectral index that is, in most cases, different from the simple leaky-box prediction. In particular, it results in a generally softer spectral index than predicted by the leaky-box solution, for both scatter-free and diffusive transport, and thus should be taken into account when modelling stochastic acceleration in solar flares.

The two-qubit quantum Rabi model: inhomogeneous coupling

International Nuclear Information System (INIS)

Mao, Lijun; Huai, Sainan; Zhang, Yunbo

2015-01-01

We revisit the analytic solution of the two-qubit quantum Rabi model with inhomogeneous coupling and transition frequencies using a displaced oscillator basis. This approach enables us to apply the same truncation rules and techniques adopted in the Rabi model to the two qubits system. The derived analytical spectra match perfectly with the numerical solutions in the parameter regime where the qubits’ transition frequencies are far off-resonance with the field frequency and the interaction strengths reach the ultrastrong coupling regime. We further explore the dynamical behavior of the two qubits as well as the evolution of entanglement. The analytical methods provide unexpectedly accurate results in describing the dynamics of the two qubits in the present experimentally accessible coupling regime. The time evolutions of the probability for the qubits show that the collapse-revival phenomena emerge, survive and finally disappear when one coupling strength increases from weak to strong coupling regimes and the other coupling strength is well into the ultrastrong coupling regime. The inhomogeneous coupling system exhibits new dynamics, which are different from the homogeneous coupling case. (paper)

Non-Linear Instabilities in an Inhomogeneous Plasma

International Nuclear Information System (INIS)

Coppi, B.; Laval, G.; Pellat, R.; Khiet, Tu

1969-01-01

The low-frequency drift modes of a low-pressure isothermal inhomogeneous plasma can be stabilized if the shear of the magnetic field lines exceeds a critical value given by the expression r/L s = (1/2 √2) (a/r), where L s is the shear length, r the characteristic length of density variation, and a the ion Larmor radius. The authors first show that, even if r/L s [fr

Dose distributions in thorax inhomogeneity for fast neutron beam from NIRS cyclotron

International Nuclear Information System (INIS)

Kutsutani-Nakamura, Yuzuru; Furukawa, Shigeo; Iinuma, T.A.; Kawashima, Katsuhiro; Hoshino, Kazuo; Hiraoka, Takeshi; Maruyama, Takashi; Sakashita, Kunio; Tsunemoto, Hiroshi

1990-01-01

The power law tissue-air ratio (TAR) method developed by Batho appears to be practical use for inhomogeneity corrections to the dose calculated in a layered media for photon beam therapy. The validity was examined in applying the modified power law TAR and the isodose shift methods to the dose calculation in thorax tissue inhomogeneity containing the boundary region for fast neutron beam. The neutron beam is produced by bombarding a thick beryllium target with 30 MeV deuterons. Lung phantom was made of granulated tissue equivalent plastic, which resulted in density of 0.30 and 0.60 g/cm 3 . Depth dose distributions for neutron beam were measured in thorax phantom by an air-filled cylindrical ionization chamber with TE plastic wall. The power law TAR method considering TAR of zero depth at boundary was compared with the measured data and a good result was obtained that the calculated dose was within ±3 % against the measured. But the isodose shift method is not so good for dose calculation in thorax tissue inhomogeneity using fast neutron beam. (author)

Constitutive model of friction stir weld with consideration of its inhomogeneous mechanical properties

Science.gov (United States)

Zhang, Ling; Min, Junying; Wang, Bin; Lin, Jianping; Li, Fangfang; Liu, Jing

2016-03-01

In practical engineering, finite element(FE) modeling for weld seam is commonly simplified by neglecting its inhomogeneous mechanical properties. This will cause a significant loss in accuracy of FE forming analysis, in particular, for friction stir welded(FSW) blanks due to the large width and good formability of its weld seam. The inhomogeneous mechanical properties across weld seam need to be well characterized for an accurate FE analysis. Based on a similar AA5182 FSW blank, the metallographic observation and micro-Vickers hardness analysis upon the weld cross-section are performed to identify the interfaces of different sub-zones, i.e., heat affected zone(HAZ), thermal-mechanically affected zone(TMAZ) and weld nugget(WN). Based on the rule of mixture and hardness distribution, a constitutive model is established for each sub-zone to characterize the inhomogeneous mechanical properties across the weld seam. Uniaxial tensile tests of the AA5182 FSW blank are performed with the aid of digital image correlation(DIC) techniques. Experimental local stress-strain curves are obtained for different weld sub-zones. The experimental results show good agreement with those derived from the constitutive models, which demonstrates the feasibility and accuracy of these models. The proposed research gives an accurate characterization of inhomogeneous mechanical properties across the weld seam produced by FSW, which provides solutions for improving the FE simulation accuracy of FSW sheet forming.

Examples of backreaction of small-scale inhomogeneities in cosmology

Science.gov (United States)

Green, Stephen R.; Wald, Robert M.

2013-06-01

In previous work, we introduced a new framework to treat large-scale backreaction effects due to small-scale inhomogeneities in general relativity. We considered one-parameter families of spacetimes for which such backreaction effects can occur, and we proved that, provided the weak energy condition on matter is satisfied, the leading effect of small-scale inhomogeneities on large-scale dynamics is to produce a traceless effective stress-energy tensor that itself satisfies the weak energy condition. In this work, we illustrate the nature of our framework by providing two explicit examples of one-parameter families with backreaction. The first, based on previous work of Berger, is a family of polarized vacuum Gowdy spacetimes on a torus, which satisfies all of the assumptions of our framework. As the parameter approaches its limiting value, the metric uniformly approaches a smooth background metric, but spacetime derivatives of the deviation of the metric from the background metric do not converge uniformly to zero. The limiting metric has nontrivial backreaction from the small-scale inhomogeneities, with an effective stress energy that is traceless and satisfies the weak energy condition, in accord with our theorems. Our second one-parameter family consists of metrics which have a uniform Friedmann-Lemaître-Robertson-Walker limit. This family satisfies all of our assumptions with the exception of the weak energy condition for matter. In this case, the limiting metric has an effective stress-energy tensor which is not traceless. We emphasize the importance of imposing energy conditions on matter in studies of backreaction.

Spectral Analysis of Quantum-Dash Lasers: Effect of Inhomogeneous Broadening of the Active-Gain Region

KAUST Repository

Khan, Mohammed Zahed Mustafa

2012-05-01

The effect of the active region inhomogeneity on the spectral characteristics of InAs/InP quantum-dash (Qdash) lasers is examined theoretically by solving the coupled set of carrier-photon rate equations. The inhomogeneity due to dash size or composition fluctuation is included in the model by considering dispersive energy states and characterized by a Gaussian envelope. In addition, the technique incorporates multilongitudinal photon modes and homogeneous broadening of the optical gain. The results predict a red shift in the central lasing wavelength of Qdash lasers on increasing the inhomogeneous broadening either explicitly or implicitly, which supports various experimental observations. The threshold current density and the lasing bandwidth are also found to increase. © 2012 IEEE.

Spectral Analysis of Quantum-Dash Lasers: Effect of Inhomogeneous Broadening of the Active-Gain Region

KAUST Repository

Khan, Mohammed Zahed Mustafa; Ng, Tien Khee; Ooi, Boon S.; Schwingenschlö gl, Udo

2012-01-01

The effect of the active region inhomogeneity on the spectral characteristics of InAs/InP quantum-dash (Qdash) lasers is examined theoretically by solving the coupled set of carrier-photon rate equations. The inhomogeneity due to dash size or composition fluctuation is included in the model by considering dispersive energy states and characterized by a Gaussian envelope. In addition, the technique incorporates multilongitudinal photon modes and homogeneous broadening of the optical gain. The results predict a red shift in the central lasing wavelength of Qdash lasers on increasing the inhomogeneous broadening either explicitly or implicitly, which supports various experimental observations. The threshold current density and the lasing bandwidth are also found to increase. © 2012 IEEE.

Visualizing time-varying harmonics using filter banks

NARCIS (Netherlands)

Duque, C.A.; Da Silveira, P.M.; Ribeiro, P.F.

2011-01-01

Although it is well known that Fourier analysis is in reality only accurately applicable to steady state waveforms, it is a widely used tool to study and monitor time-varying signals, such as are commonplace in electrical power systems. The disadvantages of Fourier analysis, such as frequency

Rate-optimal Bayesian intensity smoothing for inhomogeneous Poisson processes

NARCIS (Netherlands)

Belitser, E.; Andrade Serra, De P.J.; Zanten, van J.H.

2013-01-01

We apply nonparametric Bayesian methods to study the problem of estimating the intensity function of an inhomogeneous Poisson process. We exhibit a prior on intensities which both leads to a computationally feasible method and enjoys desirable theoretical optimality properties. The prior we use is

An inhomogeneous wave equation and non-linear Diophantine approximation

DEFF Research Database (Denmark)

Beresnevich, V.; Dodson, M. M.; Kristensen, S.

2008-01-01

A non-linear Diophantine condition involving perfect squares and arising from an inhomogeneous wave equation on the torus guarantees the existence of a smooth solution. The exceptional set associated with the failure of the Diophantine condition and hence of the existence of a smooth solution...

Structural and electrical properties of co-evaporated Cu(In,Ga)Se{sub 2} thin films with varied Cu contents

Energy Technology Data Exchange (ETDEWEB)

Kim, Min Young; Kim, Girim; Kim, Jongwan; Park, Jae Hwan; Lim, Donggun, E-mail: dglim@ut.ac.kr

2013-11-01

Cu(In,Ga)Se{sub 2} (CIGS) thin films were fabricated with varying Cu contents. Cu/(Ga + In) ratios were varied between 0.4 and 1.02. Solar cells were then fabricated by co-evaporation using the CIGS layers as absorbers. The influences of Cu content on the cells' structural, optical and electrical properties were studied. The CIGS thin films were characterized by X-ray diffractometer, scanning electron microscopy, energy-dispersive spectroscopy, four-point probe measurement and Hall measurement. Grain size in the films increased with increasing Cu content. At a Cu/(Ga + In) ratio of 0.86, the (220/204) peak was stronger than the (112) peak and carrier concentration was 1.49 × 10{sup 16} cm{sup −3}. Optimizing the Cu content resulted in a CIGS solar cell with an efficiency of 16.5%. - Highlights: • Improvement of technique to form Cu(In,Ga)Se{sub 2} (CIGS) film by co-evaporation method • Cu/(In + Ga) ratio to improve the efficiency for CIGS thin film solar cell • Cu content effects have been analyzed. • Optimum condition of CIGS layer as an absorber of thin film solar cells.

Second-order analysis of structured inhomogeneous spatio-temporal point processes

DEFF Research Database (Denmark)

Møller, Jesper; Ghorbani, Mohammad

Statistical methodology for spatio-temporal point processes is in its infancy. We consider second-order analysis based on pair correlation functions and K-functions for first general inhomogeneous spatio-temporal point processes and second inhomogeneous spatio-temporal Cox processes. Assuming...... spatio-temporal separability of the intensity function, we clarify different meanings of second-order spatio-temporal separability. One is second-order spatio-temporal independence and relates e.g. to log-Gaussian Cox processes with an additive covariance structure of the underlying spatio......-temporal Gaussian process. Another concerns shot-noise Cox processes with a separable spatio-temporal covariance density. We propose diagnostic procedures for checking hypotheses of second-order spatio-temporal separability, which we apply on simulated and real data (the UK 2001 epidemic foot and mouth disease data)....

Subspace-based optimization method for inverse scattering problems with an inhomogeneous background medium

International Nuclear Information System (INIS)

Chen, Xudong

2010-01-01

This paper proposes a version of the subspace-based optimization method to solve the inverse scattering problem with an inhomogeneous background medium where the known inhomogeneities are bounded in a finite domain. Although the background Green's function at each discrete point in the computational domain is not directly available in an inhomogeneous background scenario, the paper uses the finite element method to simultaneously obtain the Green's function at all discrete points. The essence of the subspace-based optimization method is that part of the contrast source is determined from the spectrum analysis without using any optimization, whereas the orthogonally complementary part is determined by solving a lower dimension optimization problem. This feature significantly speeds up the convergence of the algorithm and at the same time makes it robust against noise. Numerical simulations illustrate the efficacy of the proposed algorithm. The algorithm presented in this paper finds wide applications in nondestructive evaluation, such as through-wall imaging

Integrability and soliton in a classical one dimensional site dependent biquadratic Heisenberg spin chain and the effect of nonlinear inhomogeneity

International Nuclear Information System (INIS)

Kavitha, L.; Daniel, M.

2002-07-01

The integrability of one dimensional classical continuum inhomogeneous biquadratic Heisenberg spin chain and the effect of nonlinear inhomogeneity on the soliton of an underlying completely integrable spin model are studied. The dynamics of the spin system is expressed in terms of a higher order generalized nonlinear Schroedinger equation through a differential geometric approach which becomes integrable for a particular choice of the biquadratic exchange interaction and for linear inhomogeneity. The effect of nonlinear inhomogeneity on the spin soliton is studied by carrying out a multiple scale perturbation analysis. (author)

Calculation of Prestressed Pressure Vessel Taking into Account the Concrete Temperature Inhomogeneity

Science.gov (United States)

Andreev, Vladimir

2018-03-01

The paper deals with the problem of determining the stress state of the pressure vessel (PV) with considering the concrete temperature inhomogeneity. Such structures are widely used in heat power engineering, for example, in nuclear power engineering. The structures of such buildings are quite complex and a comprehensive analysis of the stress state in them can be carried out either by numerical or experimental methods. However, a number of fundamental questions can be solved on the basis of simplified models, in particular, studies of the effect on the stressed state of the inhomogeneity caused by the temperature field.

Validation of Micro-Meso Electrical Relations for Laminates with Varying Anisotropy

KAUST Repository

Selvakumaran, Lakshmi; Lubineau, Gilles

2015-01-01

For electrical impedance tomography (EIT) to be useful in monitoring transverse cracks in composites, it is imperative to establish the relation between conductivity and cracking density. Micro to meso scale homogenization has been developed

Aspects of second-order analysis of structured inhomogeneous spatio-temporal processes

DEFF Research Database (Denmark)

Møller, Jesper; Ghorbani, Mohammad

2012-01-01

Statistical methodology for spatio-temporal point processes is in its infancy. We consider second-order analysis based on pair correlation functions and K-functions for general inhomogeneous spatio-temporal point processes and for inhomogeneous spatio-temporal Cox processes. Assuming spatio......-temporal separability of the intensity function, we clarify different meanings of second-order spatio-temporal separability. One is second-order spatio-temporal independence and relates to log-Gaussian Cox processes with an additive covariance structure of the underlying spatio-temporal Gaussian process. Another...... concerns shot-noise Cox processes with a separable spatio-temporal covariance density. We propose diagnostic procedures for checking hypotheses of second-order spatio-temporal separability, which we apply on simulated and real data....

GENERAL P, TYPE-I S, AND TYPE-II S WAVES IN ANELASTIC SOLIDS; INHOMOGENEOUS WAVE FIELDS IN LOW-LOSS SOLIDS.

Science.gov (United States)

Borcherdt, Roger D.; Wennerberg, Leif

1985-01-01

The physical characteristics for general plane-wave radiation fields in an arbitrary linear viscoelastic solid are derived. Expressions for the characteristics of inhomogeneous wave fields, derived in terms of those for homogeneous fields, are utilized to specify the characteristics and a set of reference curves for general P and S wave fields in arbitrary viscoelastic solids as a function of wave inhomogeneity and intrinsic material absorption. The expressions show that an increase in inhomogeneity of the wave fields cause the velocity to decrease, the fractional-energy loss (Q** minus **1) to increase, the deviation of maximum energy flow with respect to phase propagation to increase, and the elliptical particle motions for P and type-I S waves to approach circularity. Q** minus **1 for inhomogeneous type-I S waves is shown to be greater than that for type-II S waves, with the deviation first increasing then decreasing with inhomogeneity. The mean energy densities (kinetic, potential, and total), the mean rate of energy dissipation, the mean energy flux, and Q** minus **1 for inhomogeneous waves are shown to be greater than corresponding characteristics for homogeneous waves, with the deviations increasing as the inhomogeneity is increased for waves of fixed maximum displacement amplitude.

Field distribution of a source and energy absorption in an inhomogeneous magneto-active plasma

International Nuclear Information System (INIS)

Galushko, N.P.; Erokhin, N.S.; Moiseev, S.S.

1975-01-01

In the present paper the distribution of source fields in in a magnetoactive plasma is studied from the standpoint of the possibility of an effective SHF heating of an inhomogeneous plasma in both high (ωapproximatelyωsub(pe) and low (ωapproximatelyωsub(pi) frequency ranges, where ωsub(pe) and ωsub(pi) are the electron and ion plasma frequencies. The localization of the HF energy absorption regions in cold and hot plasma and the effect of plasma inhomogeneity and source dimensions on the absorption efficiency are investigated. The linear wave transformation in an inhomogeneous hot plasma is taken into consideration. Attention is paid to the difference between the region localization for collisional and non-collisional absorption. It has been shown that the HF energy dissipation in plasma particle collisions is localized in the region of thin jets going from the source; the radiation field has a sharp peak in this region. At the same time, non-collisional HF energy dissipation is spread over the plasma volume as a result of Cherenkov and cyclotron wave attenuation. The essential contribution to the source field from resonances due to standing wave excitation in an inhomogeneous plasma shell near the source is pointed out

Stable dissipative optical vortex clusters by inhomogeneous effective diffusion.

Science.gov (United States)

Li, Huishan; Lai, Shiquan; Qui, Yunli; Zhu, Xing; Xie, Jianing; Mihalache, Dumitru; He, Yingji

2017-10-30

We numerically show the generation of robust vortex clusters embedded in a two-dimensional beam propagating in a dissipative medium described by the generic cubic-quintic complex Ginzburg-Landau equation with an inhomogeneous effective diffusion term, which is asymmetrical in the two transverse directions and periodically modulated in the longitudinal direction. We show the generation of stable optical vortex clusters for different values of the winding number (topological charge) of the input optical beam. We have found that the number of individual vortex solitons that form the robust vortex cluster is equal to the winding number of the input beam. We have obtained the relationships between the amplitudes and oscillation periods of the inhomogeneous effective diffusion and the cubic gain and diffusion (viscosity) parameters, which depict the regions of existence and stability of vortex clusters. The obtained results offer a method to form robust vortex clusters embedded in two-dimensional optical beams, and we envisage potential applications in the area of structured light.

Relativistic acceleration of captured particles by a longitudinal wave in a slightly inhomogeneous plasma

International Nuclear Information System (INIS)

Erokhin, N.S.; Zol'nikova, N.N.; Mikhajlovskaya, L.A.

1991-01-01

Relativistic acceleration of charged particles, captured by a longitudinal wave in a slightly inhomogeneous plasma without an external magnetic field is considered numerically and analytically. It is shown that with the growth of the plasma inhomogeneity parameter the maximum energy of accelerated captured particles exponentially increases. Attention is paid to the possibility of 'eternal' confinement and, respectively, unlimited acceleration of captured particles by an undamped longitudinal wave in a plasma without a magnetic field

Anomalous transient behavior from an inhomogeneous initial optical vortex density

CSIR Research Space (South Africa)

Roux, FS

2011-04-01

Full Text Available . However, the decay curves contain oscillatory features that are counterintuitive: for a short while, the inhomogeneity actually increases. The author provides numerical simulations and analytic calculations to study the appearance of the anomalous features...

Rate-optimal Bayesian intensity smoothing for inhomogeneous Poisson processes

NARCIS (Netherlands)

Belitser, E.N.; Serra, P.; van Zanten, H.

2015-01-01

We apply nonparametric Bayesian methods to study the problem of estimating the intensity function of an inhomogeneous Poisson process. To motivate our results we start by analyzing count data coming from a call center which we model as a Poisson process. This analysis is carried out using a certain

Numerical analysis of the stability of inhomogeneous slopes considering partially saturated conditions

Directory of Open Access Journals (Sweden)

Pichler Patrick P.

2016-01-01

Full Text Available It is well accepted that rainfall could play a significant role in instability of slopes. The main objective of the presented study is to quantify the influence of varying characteristics of water flow, its associated changes of pore-water pressures and shear strength on the stability of simplified, but inhomogeneous, slope geometries. The commonly used van Genuchten model was used to describe the Soil Water Characteristic Curve (SWCC mathematically. In the context of this study, the influence of different hydraulic behaviour of soil layers, i.e. different SWCC, on the factor of safety (FoS is evaluated by means of fully coupled flow-deformation analyses employing the finite element method. To quantify the slopes’ factor of safety during rainfall events after specified times of infiltration or evaporation, the strength reduction method was applied. In addition to various combinations of soil layers, the influence of a water bearing high permeable soil layer between two less permeable soil layers, a situation which is often encountered in practice, on the factor of safety has been investigated.

Characterization of the inhomogeneous barrier distribution in a Pt/(100)β-Ga2O3 Schottky diode via its temperature-dependent electrical properties

Science.gov (United States)

Jian, Guangzhong; He, Qiming; Mu, Wenxiang; Fu, Bo; Dong, Hang; Qin, Yuan; Zhang, Ying; Xue, Huiwen; Long, Shibing; Jia, Zhitai; Lv, Hangbing; Liu, Qi; Tao, Xutang; Liu, Ming

2018-01-01

β-Ga2O3 is an ultra-wide bandgap semiconductor with applications in power electronic devices. Revealing the transport characteristics of β-Ga2O3 devices at various temperatures is important for improving device performance and reliability. In this study, we fabricated a Pt/β-Ga2O3 Schottky barrier diode with good performance characteristics, such as a low ON-resistance, high forward current, and a large rectification ratio. Its temperature-dependent current-voltage and capacitance-voltage characteristics were measured at various temperatures. The characteristic diode parameters were derived using thermionic emission theory. The ideality factor n was found to decrease from 2.57 to 1.16 while the zero-bias barrier height Φb0 increased from 0.47 V to 1.00 V when the temperature was increased from 125 K to 350 K. This was explained by the Gaussian distribution of barrier height inhomogeneity. The mean barrier height Φ ¯ b0 = 1.27 V and zero-bias standard deviation σ0 = 0.13 V were obtained. A modified Richardson plot gave a Richardson constant A* of 36.02 A.cm-2.K-2, which is close to the theoretical value of 41.11 A.cm-2.K-2. The differences between the barrier heights determined using the capacitance-voltage and current-voltage curves were also in line with the Gaussian distribution of barrier height inhomogeneity.

Characterization of the inhomogeneous barrier distribution in a Pt/(100β-Ga2O3 Schottky diode via its temperature-dependent electrical properties

Directory of Open Access Journals (Sweden)

Guangzhong Jian

2018-01-01

Full Text Available β-Ga2O3 is an ultra-wide bandgap semiconductor with applications in power electronic devices. Revealing the transport characteristics of β-Ga2O3 devices at various temperatures is important for improving device performance and reliability. In this study, we fabricated a Pt/β-Ga2O3 Schottky barrier diode with good performance characteristics, such as a low ON-resistance, high forward current, and a large rectification ratio. Its temperature-dependent current–voltage and capacitance–voltage characteristics were measured at various temperatures. The characteristic diode parameters were derived using thermionic emission theory. The ideality factor n was found to decrease from 2.57 to 1.16 while the zero-bias barrier height Φb0 increased from 0.47 V to 1.00 V when the temperature was increased from 125 K to 350 K. This was explained by the Gaussian distribution of barrier height inhomogeneity. The mean barrier height Φ ¯ b0 = 1.27 V and zero-bias standard deviation σ0 = 0.13 V were obtained. A modified Richardson plot gave a Richardson constant A* of 36.02 A·cm−2·K−2, which is close to the theoretical value of 41.11 A·cm−2·K−2. The differences between the barrier heights determined using the capacitance–voltage and current–voltage curves were also in line with the Gaussian distribution of barrier height inhomogeneity.

Time varying voltage combustion control and diagnostics sensor

Science.gov (United States)

Chorpening, Benjamin T [Morgantown, WV; Thornton, Jimmy D [Morgantown, WV; Huckaby, E David [Morgantown, WV; Fincham, William [Fairmont, WV

2011-04-19

A time-varying voltage is applied to an electrode, or a pair of electrodes, of a sensor installed in a fuel nozzle disposed adjacent the combustion zone of a continuous combustion system, such as of the gas turbine engine type. The time-varying voltage induces a time-varying current in the flame which is measured and used to determine flame capacitance using AC electrical circuit analysis. Flame capacitance is used to accurately determine the position of the flame from the sensor and the fuel/air ratio. The fuel and/or air flow rate (s) is/are then adjusted to provide reduced flame instability problems such as flashback, combustion dynamics and lean blowout, as well as reduced emissions. The time-varying voltage may be an alternating voltage and the time-varying current may be an alternating current.

Time-varying output performances of piezoelectric vibration energy harvesting under nonstationary random vibrations

Science.gov (United States)

Yoon, Heonjun; Kim, Miso; Park, Choon-Su; Youn, Byeng D.

2018-01-01

Piezoelectric vibration energy harvesting (PVEH) has received much attention as a potential solution that could ultimately realize self-powered wireless sensor networks. Since most ambient vibrations in nature are inherently random and nonstationary, the output performances of PVEH devices also randomly change with time. However, little attention has been paid to investigating the randomly time-varying electroelastic behaviors of PVEH systems both analytically and experimentally. The objective of this study is thus to make a step forward towards a deep understanding of the time-varying performances of PVEH devices under nonstationary random vibrations. Two typical cases of nonstationary random vibration signals are considered: (1) randomly-varying amplitude (amplitude modulation; AM) and (2) randomly-varying amplitude with randomly-varying instantaneous frequency (amplitude and frequency modulation; AM-FM). In both cases, this study pursues well-balanced correlations of analytical predictions and experimental observations to deduce the relationships between the time-varying output performances of the PVEH device and two primary input parameters, such as a central frequency and an external electrical resistance. We introduce three correlation metrics to quantitatively compare analytical prediction and experimental observation, including the normalized root mean square error, the correlation coefficient, and the weighted integrated factor. Analytical predictions are in an excellent agreement with experimental observations both mechanically and electrically. This study provides insightful guidelines for designing PVEH devices to reliably generate electric power under nonstationary random vibrations.

Varying constants, black holes, and quantum gravity

International Nuclear Information System (INIS)

Carlip, S.

2003-01-01

Tentative observations and theoretical considerations have recently led to renewed interest in models of fundamental physics in which certain 'constants' vary in time. Assuming fixed black hole mass and the standard form of the Bekenstein-Hawking entropy, Davies, Davis and Lineweaver have argued that the laws of black hole thermodynamics disfavor models in which the fundamental electric charge e changes. I show that with these assumptions, similar considerations severely constrain 'varying speed of light' models, unless we are prepared to abandon cherished assumptions about quantum gravity. Relaxation of these assumptions permits sensible theories of quantum gravity with ''varying constants,'' but also eliminates the thermodynamic constraints, though the black hole mass spectrum may still provide some restrictions on the range of allowable models

Fractal behaviour of flow of an inhomogeneous fluid over a smooth inclined surface

International Nuclear Information System (INIS)

Rouhani, S.; Maleki Jirsarani, N.; Ghane Motlagh, B.; Baradaran, S.; Shokrian, E.

2001-01-01

We have observed and analyzed fractal patterns made by the flow of an inhomogeneous fluid (a suspension) over an inclined smooth surface. We observed that if the angle of inclination is above a threshold (10 d eg C - 12 d eg C), the length of fractal clusters become infinity. We measured a fractal dimension of df=1.40 ± 0.05. This falls within the same general class of patterns of flow of water over an inhomogeneous surface. This observation is consistent with the results of theoretical modes for nonlinear fluid flow in random media

EPR dosimetry of radiotherapy photon beams in inhomogeneous media using alanine films

Energy Technology Data Exchange (ETDEWEB)

Oesteraas, Bjoern Helge [Department of Radiation Biology, Institute for Cancer Research, Norwegian Radium Hospital, Montebello, N-0310 Oslo (Norway); Hole, Eli Olaug [Department of Physics, University of Oslo, PO Box 1048 Blindern, N-0316 Oslo (Norway); Olsen, Dag Rune [Department of Radiation Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, N-0310 Oslo (Norway); Malinen, Eirik [Department of Radiation Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, N-0310 Oslo (Norway)

2006-12-21

In the current work, EPR (electron paramagnetic resonance) dosimetry using alanine films (134 {mu}m thick) was utilized for dose measurements in inhomogeneous phantoms irradiated with radiotherapy photon beams. The main phantom material was PMMA, while either Styrofoam or aluminium was introduced as an inhomogeneity. The phantoms were irradiated to a maximum dose of about 30 Gy with 6 or 15 MV photons. The performance of the alanine film dosimeters was investigated and compared to results from ion chamber dosimetry, Monte Carlo simulations and radiotherapy treatment planning calculations. It was found that the alanine film dosimeters had a linear dose response above approximately 5 Gy, while a background signal obscured the response at lower dose levels. For doses between 5 and 60 Gy, the standard deviation of single alanine film dose estimates was about 2%. The alanine film dose estimates yielded results comparable to those from the Monte Carlo simulations and the ion chamber measurements, with absolute differences between estimates in the order of 1-15%. The treatment planning calculations exhibited limited applicability. The current work shows that alanine film dosimetry is a method suitable for estimating radiotherapeutical doses and for dose measurements in inhomogeneous media.

EPR dosimetry of radiotherapy photon beams in inhomogeneous media using alanine films

International Nuclear Information System (INIS)

Oesteraas, Bjoern Helge; Hole, Eli Olaug; Olsen, Dag Rune; Malinen, Eirik

2006-01-01

In the current work, EPR (electron paramagnetic resonance) dosimetry using alanine films (134 μm thick) was utilized for dose measurements in inhomogeneous phantoms irradiated with radiotherapy photon beams. The main phantom material was PMMA, while either Styrofoam or aluminium was introduced as an inhomogeneity. The phantoms were irradiated to a maximum dose of about 30 Gy with 6 or 15 MV photons. The performance of the alanine film dosimeters was investigated and compared to results from ion chamber dosimetry, Monte Carlo simulations and radiotherapy treatment planning calculations. It was found that the alanine film dosimeters had a linear dose response above approximately 5 Gy, while a background signal obscured the response at lower dose levels. For doses between 5 and 60 Gy, the standard deviation of single alanine film dose estimates was about 2%. The alanine film dose estimates yielded results comparable to those from the Monte Carlo simulations and the ion chamber measurements, with absolute differences between estimates in the order of 1-15%. The treatment planning calculations exhibited limited applicability. The current work shows that alanine film dosimetry is a method suitable for estimating radiotherapeutical doses and for dose measurements in inhomogeneous media

Common features of a vortex structure in long exponentially shaped Josephson junctions and Josephson junctions with inhomogeneities

International Nuclear Information System (INIS)

Boyadjiev, T.L.; Semerdjieva, E.G.; Shukrinov, Yu.M.

2007-01-01

We study the vortex structure in three different models of the long Josephson junction: the exponentially shaped Josephson junction and the Josephson junctions with the resistor and the shunt inhomogeneities in the barrier layer. For these three models the critical curves 'critical current-magnetic field' are numerically constructed. We develop the idea of the equivalence of the exponentially shaped Josephson junction and the rectangular junction with the distributed inhomogeneity and demonstrate that at some parameters of the shunt and the resistor inhomogeneities in the ends of the junction the corresponding critical curves are very close to the exponentially shaped one

Analytical transition-matrix treatment of electric multipole polarizabilities of hydrogen-like atoms

International Nuclear Information System (INIS)

Kharchenko, V.F.

2015-01-01

The direct transition-matrix approach to the description of the electric polarization of the quantum bound system of particles is used to determine the electric multipole polarizabilities of the hydrogen-like atoms. It is shown that in the case of the bound system formed by the Coulomb interaction the corresponding inhomogeneous integral equation determining an off-shell scattering function, which consistently describes virtual multiple scattering, can be solved exactly analytically for all electric multipole polarizabilities. Our method allows to reproduce the known Dalgarno–Lewis formula for electric multipole polarizabilities of the hydrogen atom in the ground state and can also be applied to determine the polarizability of the atom in excited bound states. - Highlights: • A new description for electric polarization of hydrogen-like atoms. • Expression for multipole polarizabilities in terms of off-shell scattering functions. • Derivation of integral equation determining the off-shell scattering function. • Rigorous analytic solving the integral equations both for ground and excited states. • Study of contributions of virtual multiple scattering to electric polarizabilities

Physical Mechanisms Responsible for Electrical Conduction in Pt/GaN Schottky Diodes

OpenAIRE

H. MAZARI; K. AMEUR; N. BENSEDDIK; Z. BENAMARA; R. KHELIFI; M. MOSTEFAOUI; N. ZOUGAGH; N. BENYAHYA; R. BECHAREF; G. BASSOU; B. GRUZZA; J. M. BLUET; C. BRU-CHEVALLIER

2014-01-01

The current-voltage (I-V) characteristics of Pt/(n.u.d)-GaN and Pt/Si-doped-GaN diodes Schottky are investigated. Based on these measurements, physical mechanisms responsible for electrical conduction have been suggested. The contribution of thermionic-emission current and various other current transport mechanisms were assumed when evaluating the Schottky barrier height. Thus the generation-recombination, tunneling and leakage currents caused by inhomogeneities and defects at metal-semicondu...

Optical coherent control in semiconductors: Fringe contrast and inhomogeneous broadening

DEFF Research Database (Denmark)

Østergaard, John Erland; Vadim, Lyssenko; Hvam, Jørn Märcher

2001-01-01

in the interplay between the homogeneous and inhomogeneous broadenings are measured. Based on these experiments, a coherent control model describing the optical fringe contrast using different detection schemes, such as photoluminescence or four-wave mixing, is established. Significant spectral modulation...

Acoustic Force Density Acting on Inhomogeneous Fluids in Acoustic Fields

DEFF Research Database (Denmark)

Karlsen, Jonas Tobias; Augustsson, Per; Bruus, Henrik

2016-01-01

, the theory predicts a relocation of the inhomogeneities into stable field-dependent configurations, which are qualitatively different from the horizontally layered configurations due to gravity. Experimental validation is obtained by confocal imaging of aqueous solutions in a glass-silicon microchip....

Approximating transcranial magnetic stimulation with electric stimulation in mouse: a simulation study.

Science.gov (United States)

Barnes, Walter L; Lee, Won Hee; Peterchev, Angel V

2014-01-01

Rodent models are valuable for preclinical examination of novel therapeutic techniques, including transcranial magnetic stimulation (TMS). However, comparison of TMS effects in rodents and humans is confounded by inaccurate scaling of the spatial extent of the induced electric field in rodents. The electric field is substantially less focal in rodent models of TMS due to the technical restrictions of making very small coils that can handle the currents required for TMS. We examine the electric field distributions generated by various electrode configurations of electric stimulation in an inhomogeneous high-resolution finite element mouse model, and show that the electric field distributions produced by human TMS can be approximated by electric stimulation in mouse. Based on these results and the limits of magnetic stimulation in mice, we argue that the most practical and accurate way to model focal TMS in mice is electric stimulation through either cortical surface electrodes or electrodes implanted halfway through the mouse cranium. This approach could allow much more accurate approximation of the human TMS electric field focality and strength than that offered by TMS in mouse, enabling, for example, focal targeting of specific cortical regions, which is common in human TMS paradigms.

Electric field control of magnon-induced magnetization dynamics in multiferroics.

Science.gov (United States)

Risinggård, Vetle; Kulagina, Iryna; Linder, Jacob

2016-08-24

We consider theoretically the effect of an inhomogeneous magnetoelectric coupling on the magnon-induced dynamics of a ferromagnet. The magnon-mediated magnetoelectric torque affects both the homogeneous magnetization and magnon-driven domain wall motion. In the domains, we predict a reorientation of the magnetization, controllable by the applied electric field, which is almost an order of magnitude larger than that observed in other physical systems via the same mechanism. The applied electric field can also be used to tune the domain wall speed and direction of motion in a linear fashion, producing domain wall velocities several times the zero field velocity. These results show that multiferroic systems offer a promising arena to achieve low-dissipation magnetization rotation and domain wall motion by exciting spin-waves.

Measurement of the anisotropy of inhomogeneities in the auroral ionosphere by means of signals from satellites

International Nuclear Information System (INIS)

Bogolyobov, A.A.; Erukhimov, L.M.; Kryazhev, V.A.; Myasnikov, E.N.

1985-01-01

The authors show how it is possible to determine the shapes of inhomogeneities by using a method of correlation analysis of the fluctuations in signals from orbiting satellites. The authors show that when this method is used, the finite thickness of the layer containing the inhomogeneity must be taken into accout. It is established that the inhomogeneities in the auroral ionosphere which are responsible for the amplitude fluctuations in the signals are extended along the lines of force of the geomagnetic field and that they have a shape which is close to being axially symmetric in the plane orthogonal to the geomagnetic field and that the fluctuations in the signals may be concentrated in localized regions

Effects of inhomogeneity on the Shukla-Nambu-Salimullah and wake potentials in a streaming dusty magnetoplasma

International Nuclear Information System (INIS)

Salimullah, M.; Khan, M.I.U.; Amin, R.; Nitta, H.; Shukla, P.K.

2005-10-01

Detailed properties of the electrostatic Shukla-Nambu-Salimullah and the dynamical oscillatory wake potentials in an inhomogeneous dusty magnetoplasma in the presence of ion streaming, as in a laboratory discharge plasma, have been examined analytically. The potentials become sensitive functions of the external static magnetic field, the scale-length of inhomogeneity, and the deviation from the linear ion streaming velocity. For a decreasing ion density gradient, there is a limit of existence of the static modified shielding potential. For a strongly inhomogeneous dusty plasma, the effective length of the oscillatory wake potential increases with increasing deviation of the ion streaming velocity (u i0y ), but it does not depend on the external magnetic field. (author)

Neuron matters: electric activation of neuronal tissue is dependent on the interaction between the neuron and the electric field.

Science.gov (United States)

Ye, Hui; Steiger, Amanda

2015-08-12

In laboratory research and clinical practice, externally-applied electric fields have been widely used to control neuronal activity. It is generally accepted that neuronal excitability is controlled by electric current that depolarizes or hyperpolarizes the excitable cell membrane. What determines the amount of polarization? Research on the mechanisms of electric stimulation focus on the optimal control of the field properties (frequency, amplitude, and direction of the electric currents) to improve stimulation outcomes. Emerging evidence from modeling and experimental studies support the existence of interactions between the targeted neurons and the externally-applied electric fields. With cell-field interaction, we suggest a two-way process. When a neuron is positioned inside an electric field, the electric field will induce a change in the resting membrane potential by superimposing an electrically-induced transmembrane potential (ITP). At the same time, the electric field can be perturbed and re-distributed by the cell. This cell-field interaction may play a significant role in the overall effects of stimulation. The redistributed field can cause secondary effects to neighboring cells by altering their geometrical pattern and amount of membrane polarization. Neurons excited by the externally-applied electric field can also affect neighboring cells by ephaptic interaction. Both aspects of the cell-field interaction depend on the biophysical properties of the neuronal tissue, including geometric (i.e., size, shape, orientation to the field) and electric (i.e., conductivity and dielectricity) attributes of the cells. The biophysical basis of the cell-field interaction can be explained by the electromagnetism theory. Further experimental and simulation studies on electric stimulation of neuronal tissue should consider the prospect of a cell-field interaction, and a better understanding of tissue inhomogeneity and anisotropy is needed to fully appreciate the neural

Comprehension of the Electric Polarization as a Function of Low Temperature

Science.gov (United States)

Liu, Changshi

2017-01-01

Polarization response to warming plays an increasingly important role in a number of ferroelectric memory devices. This paper reports on the theoretical explanation of the relationship between polarization and temperature. According to the Fermi-Dirac distribution, the basic property of electric polarization response to temperature in magnetoelectric multiferroic materials is theoretically analyzed. The polarization in magnetoelectric multiferroic materials can be calculated by low temperature using a phenomenological theory suggested in this paper. Simulation results revealed that the numerically calculated results are in good agreement with experimental results of some inhomogeneous multiferroic materials. Numerical simulations have been performed to investigate the influences of both electric and magnetic fields on the polarization in magnetoelectric multiferroic materials. Furthermore, polarization behavior of magnetoelectric multiferroic materials can be predicted by low temperature, electric field and magnetic induction using only one function. The calculations offer an insight into the understanding of the effects of heating and magnetoelectric field on electrical properties of multiferroic materials and offer a potential to use similar methods to analyze electrical properties of other memory devices.

Inhomogeneous effects in the quantum free electron laser

International Nuclear Information System (INIS)

Piovella, N.; Bonifacio, R.

2006-01-01

We include inhomogeneous effects in the quantum model of a free electron laser taking into account the initial energy spread of the electron beam. From a linear analysis, we obtain a generalized dispersion relation, from which the exponential gain can be explicitly calculated. We determine the maximum allowed initial energy spread in the quantum exponential regime and we discuss the limit of large energy spread

Phase function of a spherical particle when scattering an inhomogeneous electromagnetic plane wave.

Science.gov (United States)

Frisvad, Jeppe Revall

2018-04-01

In absorbing media, electromagnetic plane waves are most often inhomogeneous. Existing solutions for the scattering of an inhomogeneous plane wave by a spherical particle provide no explicit expressions for the scattering components. In addition, current analytical solutions require evaluation of the complex hypergeometric function F 1 2 for every term of a series expansion. In this work, I develop a simpler solution based on associated Legendre functions with argument zero. It is similar to the solution for homogeneous plane waves but with new explicit expressions for the angular dependency of the far-field scattering components, that is, the phase function. I include recurrence formulas for practical evaluation and provide numerical examples to evaluate how well the new expressions match previous work in some limiting cases. The predicted difference in the scattering phase function due to inhomogeneity is not negligible for light entering an absorbing medium at an oblique angle. The presented theory could thus be useful for predicting scattering behavior in dye-based random lasing and in solar cell absorption enhancement.

Lower hybrid waves instability in a velocity–sheared inhomogenous ...

African Journals Online (AJOL)

An electrostatic linear kinetic analysis of velocity-sheared inhomogeneous charged dust streaming parallel to a magnetic field in plasma is presented. Excited mode and the growth rates are derived in the lower hybrid-like mode regime, with collisional effects included. In the case where the drift velocity u is very small the ...

Structural and electrical characterization of AuPtAlTi ohmic contacts to AlGaN/GaN with varying annealing temperature and Al content

OpenAIRE

Fay, Mike W.; Han, Y.; Brown, Paul D.; Harrison, Ian; Hilton, K.P.; Munday, A.; Wallis, D.; Balmer, R.S.; Uren, M.J.; Martin, T.

2008-01-01

The effect of varying annealing temperature and Al layer thickness on the structural and electrical characteristics of AuPtAlTi/AlGaN/GaN ohmic contact structures has been systematically investigated. The relationship between annealing temperature, Al content, interfacial microstructure, surface planarity and contact resistance is\\ud examined. In particular, the presence of a detrimental low temperature Pt-Al reaction is identified. This is implicated in both the requirement for a higher Al:T...

Measuring size dependent electrical properties from nanoneedle structures: Pt/ZnO Schottky diodes

International Nuclear Information System (INIS)

Mao, Shimin; Anderson, Daniel D.; Shang, Tao; Park, Byoungnam; Dillon, Shen J.

2014-01-01

This work reports the fabrication and testing of nanoneedle devices with well-defined interfaces that are amenable to a variety of structural and electrical characterization, including transmission electron microscopy. Single Pt/ZnO nanoneedle Schottky diodes were fabricated by a top down method using a combination of electro-polishing, sputtering, and focused ion beam milling. The resulting structures contained nanoscale planar heterojunctions with low ideality factors, the dimensions of which were tuned to study size-dependent electrical properties. The diameter dependence of the Pt/ZnO diode barrier height is explained by a joule heating effect and/or electronic inhomogeneity in the Pt/ZnO contact area

Influence of spatial beam inhomogeneities on the parameters of a petawatt laser system based on multi-stage parametric amplification

International Nuclear Information System (INIS)

Frolov, S A; Trunov, V I; Pestryakov, Efim V; Leshchenko, V E

2013-01-01

We have developed a technique for investigating the evolution of spatial inhomogeneities in high-power laser systems based on multi-stage parametric amplification. A linearised model of the inhomogeneity development is first devised for parametric amplification with the small-scale self-focusing taken into account. It is shown that the application of this model gives the results consistent (with high accuracy and in a wide range of inhomogeneity parameters) with the calculation without approximations. Using the linearised model, we have analysed the development of spatial inhomogeneities in a petawatt laser system based on multi-stage parametric amplification, developed at the Institute of Laser Physics, Siberian Branch of the Russian Academy of Sciences (ILP SB RAS). (control of laser radiation parameters)

Spherically symmetric inhomogeneous bianisotropic media: Wave propagation and light scattering

DEFF Research Database (Denmark)

Novitsky, Andrey; Shalin, Alexander S.; Lavrinenko, Andrei

2017-01-01

We develop a technique for finding closed-form expressions for electromagnetic fields in radially inhomogeneous bianisotropic media, both the solutions of the Maxwell equations and material tensors being defined by the set of auxiliary two-dimensional matrices. The approach is applied to determine...

Effect of Inhomogeneity of the Universe on a Gravitationally Bound ...

Indian Academy of Sciences (India)

2012-04-16

Apr 16, 2012 ... on a gravitationally bound local system such as the solar system. We con- ... method to describe the large-scale inhomogeneity of the Universe. ..... is regular at the origin r = 0 where the central body is located, and that the test.

Measurements of weak localization of graphene in inhomogeneous magnetic fields

DEFF Research Database (Denmark)

Lindvall, N.; Shivayogimath, Abhay; Yurgens, A.

2015-01-01

attribute this to the inhomogeneous field caused by vortices in the superconductor. The deviation, which depends on the carrier concentration in graphene, can be tuned by the gate voltage. In addition, collective vortex motion, known as vortex avalanches, is observed through magnetoresistance measurements...

Multiple solutions for inhomogeneous nonlinear elliptic problems arising in astrophyiscs

Directory of Open Access Journals (Sweden)

Marco Calahorrano

2004-04-01

Full Text Available Using variational methods we prove the existence and multiplicity of solutions for some nonlinear inhomogeneous elliptic problems on a bounded domain in $mathbb{R}^n$, with $ngeq 2$ and a smooth boundary, and when the domain is $mathbb{R}_+^n$

Poster – 12: Radiological assessment of the secondary barrier shielding for IMRT treatments delivered through patient inhomogeneities

International Nuclear Information System (INIS)

Haseeb, Syed Abdul; Ahmad, Syed Bilal; Mirza, Sikander Majid

2016-01-01

Purpose: To assess the impact of radiation treatment delivery through patient inhomogeneities on the secondary barrier shielding requirements in IMRT treatments using Monte Carlo Simulations. Materials and Methods: Scatter factors were calculated at a distance of 1m from the center of a virtual phantom in Geant4.10.01. Phantom (30×30×30 cm 3 ) was inserted with lung (30×30×8 cm 3 ), stainless steel (5×5×5 cm 3 ) and aluminum (5×5×5 cm 3 ) to represent the inhomogeneities. Scatter factor was defined according to the NCRP-151 recommendations and was calculated for angles of 3° to 120° with respect to the beam’s central axis. A virtual radiation source, with energy sampled from a histogram representing 6 MV FFF beam, was used for irradiation with a field size of 15×15 cm 2 and SSD of 100 cm. Results: Irradiation through the inhomogeneity affects the patient scattered dose. For high Z material inhomogeneities the scattered dose is reduced due to significant attenuation of the primary radiation. On the other hand if the inhomogeneity is a low Z material such as lung the scattered dose is higher by a maximum of 26%. The average increase in scatter factors for the lung phantom was 17% for angles between 3° and 63° compared to the homogeneous water phantom. Conclusions: In IMRT type treatments delivered through low density patient inhomogeneities (lung) the scattered dose increases significantly. Considering a large proportion of patients receiving radiation therapy for lung cancers the increase in the scattered dose should be incorporated in the shielding calculations for the secondary barriers.

Practical Model for First Hyperpolarizability Dispersion Accounting for Both Homogeneous and Inhomogeneous Broadening Effects.

Science.gov (United States)

Campo, Jochen; Wenseleers, Wim; Hales, Joel M; Makarov, Nikolay S; Perry, Joseph W

2012-08-16

A practical yet accurate dispersion model for the molecular first hyperpolarizability β is presented, incorporating both homogeneous and inhomogeneous line broadening because these affect the β dispersion differently, even if they are indistinguishable in linear absorption. Consequently, combining the absorption spectrum with one free shape-determining parameter Ginhom, the inhomogeneous line width, turns out to be necessary and sufficient to obtain a reliable description of the β dispersion, requiring no information on the homogeneous (including vibronic) and inhomogeneous line broadening mechanisms involved, providing an ideal model for practical use in extrapolating experimental nonlinear optical (NLO) data. The model is applied to the efficient NLO chromophore picolinium quinodimethane, yielding an excellent fit of the two-photon resonant wavelength-dependent data and a dependable static value β0 = 316 × 10(-30) esu. Furthermore, we show that including a second electronic excited state in the model does yield an improved description of the NLO data at shorter wavelengths but has only limited influence on β0.

On the study of the interaction of inhomogeneous electron beam with plasma. Vol. 2

Energy Technology Data Exchange (ETDEWEB)

Amein, W H; Sayed, Y A [Plasma Physics and Nuclear Fusion Department, Nuclear Research Center, Atomic Energy Aurhority, Cairo (Egypt); El-Waraki, S A [Faculty of Science, Physics Department, Mansura University, Damuitta, (Egypt)

1996-03-01

The treatment of the beam-plasma instability usually studies the behaviour of the growth rate as a function of the parameters of the problem for one two oscillation modes which have the largest growth rate. however, these studies have not been completed, they did not investigate the effect of inhomogeneity of the electron beam-plasma interaction. In the present work, the linear interaction between the cold inhomogeneous electron beam-plasma system was considered. The field equation which describes the system is a differential equation of third order. In order to solve this equation to obtain the dispersion relation, the density and velocity of inhomogeneous beam in such form was considered. n{sub ob} = n{sub o} (1+X/L); V{sub ob} (X) = V{sub o} (1+X/L). Where; L is the length scale of the variation (L >>X). The growth rate of the instability was calculated. It is shown that waves are excited more strongly in this case compared to that for homogeneous beam.

Restoration of longitudinal laser tomography target image from inhomogeneous medium degradation under common conditions.

Science.gov (United States)

Yi, WenJun; Wang, Ping; Fu, MeiCheng; Tan, JiChun; Zhu, Jubo; Li, XiuJian

2017-07-10

In order to overcome the shortages of the target image restoration method for longitudinal laser tomography using self-calibration, a more general restoration method through backscattering medium images associated with prior parameters is developed for common conditions. The system parameters are extracted from pre-calibration, and the LIDAR ratio is estimated according to the medium types. Assisted by these prior parameters, the degradation caused by inhomogeneous turbid media can be established with the backscattering medium images, which can further be used for removal of the interferences of turbid media. The results of simulations and experiments demonstrate that the proposed image restoration method can effectively eliminate the inhomogeneous interferences of turbid media and achieve exactly the reflectivity distribution of targets behind inhomogeneous turbid media. Furthermore, the restoration method can work beyond the limitation of the previous method that only works well under the conditions of localized turbid attenuations and some types of targets with fairly uniform reflectivity distributions.

Compression behavior of cellular metals with inhomogeneous mass distribution

International Nuclear Information System (INIS)

Foroughi, B.

2001-05-01

Mechanical behavior of two types of closed cell metals (ALULIGHT and ALPORAS) is investigated experimentally and numerically. Compressive tests performed on prismatic specimens indicate that inhomogeneities in the mass density distribution are a key factor in the deformation behavior of cellular metals. The three dimensional cellular structure of the investigated specimens is recorded using x-ray medical computed tomography (CT). A special procedure called density mapping method has been used to transfer the recorded CT data into a continuum by averaging over a certain domain (averaging domain). This continuum model is implemented using finite elements to study the effect of variations in local mass densities. The finite element model is performed by a simple regular discretization of a specimen's volume with elements which have constant edge length. Mechanical properties derived from compression tests of ALPORAS samples are assigned to the corresponding mesoscopic density value of each element. The effect of averaging domain size is studied to obtain a suitable dimension which fulfils the homogenization requirements and allows the evaluation of inhomogenities in the specimens. The formation and propagation of deformation band(s) and stress-strain responses of tested cellular metals are modeled with respect to their mass distribution. It is shown that the inhomogeneous density distribution leads to plastic strain localization and causes a monotonically increase of the stress in the plateau regime although no hardening response was considered for homogeneous material in this regime. The simulated plastic strain localization and the calculated stress-strain responses are compared with the experimental results. The stiffness values of experiment and simulation agree very well for both cellular materials. The values of plateau strength as well, but it differs in some cases of ALULIGHT samples, where the hardening response can be predicted at least qualitatively

Particle shape inhomogeneity and plasmon-band broadening of solar-control LaB{sub 6} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Machida, Keisuke; Adachi, Kenji, E-mail: kenji-adachi@ni.smm.co.jp [Ichikawa Research Laboratories, Sumitomo Metal Mining Co., Ltd., Ichikawa 272-8588 (Japan)

2015-07-07

An ensemble inhomogeneity of non-spherical LaB{sub 6} nanoparticles dispersion has been analyzed with Mie theory to account for the observed broad plasmon band. LaB{sub 6} particle shape has been characterized using small-angle X-ray scattering (SAXS) and electron tomography (ET). SAXS scattering intensity is found to vary exponentially with exponent −3.10, indicating the particle shape of disk toward sphere. ET analysis disclosed dually grouped distribution of nanoparticle dispersion; one is large-sized at small aspect ratio and the other is small-sized with scattered high aspect ratio, reflecting the dual fragmentation modes during the milling process. Mie extinction calculations have been integrated for 100 000 particles of varying aspect ratio, which were produced randomly by using the Box-Muller method. The Mie integration method has produced a broad and smooth absorption band expanded towards low energy, in remarkable agreement with experimental profiles by assuming a SAXS- and ET-derived shape distribution, i.e., a majority of disks with a little incorporation of rods and spheres for the ensemble. The analysis envisages a high potential of LaB{sub 6} with further-increased visible transparency and plasmon peak upon controlled particle-shape and its distribution.

Control of inhomogeneous materials strength by method of acoustic emission

Directory of Open Access Journals (Sweden)

В. В. Носов

2017-08-01

Full Text Available The ambiguous connection between the results of acoustic emission control and the strength of materials makes acoustic-emission diagnosis ineffective and actualizes the problem of strength and metrological heterogeneity. Inhomogeneity is some deviation from a certain norm. The real object is always heterogeneous, homogeneity is an assumption that simplifies the image of the object and the solution of the tasks associated with it. The need to consider heterogeneity is due to the need to clarify a particular task and is a transition to a more complex level of research. Accounting for heterogeneity requires the definition of its type, criterion and method of evaluation. The type of heterogeneity depends on the problem being solved and should be related to the property that determines the function of the real object, the criterion should be informative, and the way of its evaluation is non-destructive. The complexity of predicting the behavior of heterogeneous materials necessitates the modeling of the destructive process that determines the operability, the formulation of the inhomogeneity criterion, the interpretation of the Kaiser effect, as showing inhomogeneity of the phenomenon of non-reproduction of acoustic emission (AE activity upon repeated loading of the examined object.The article gives an example of modeling strength and metrological heterogeneity, analyzes and estimates the informative effect of the Kaiser effect on the danger degree of state of diagnosed object from the positions of the micromechanical model of time dependencies of AE parameters recorded during loading of structural materials and technical objects.

Cluster tails for critical power-law inhomogeneous random graphs

NARCIS (Netherlands)

van der Hofstad, R.; Kliem, S.; van Leeuwaarden, J.S.H.

2018-01-01

Recently, the scaling limit of cluster sizes for critical inhomogeneous random graphs of rank-1 type having finite variance but infinite third moment degrees was obtained in Bhamidi et al. (Ann Probab 40:2299–2361, 2012). It was proved that when the degrees obey a power law with exponent τ∈ (3 , 4)

Electrical power system integrated thermal/electrical system simulation

International Nuclear Information System (INIS)

Freeman, W.E.

1992-01-01

This paper adds thermal properties to previously developed electrical Saber templates and incorporates these templates into a functional Electrical Power Subsystem (EPS) simulation. These combined electrical and thermal templates enable the complete and realistic simulation of a vehicle EPS on-orbit. Applications include on-orbit energy balance determinations for system load changes, initial array and battery EPS sizing for new EPS development, and array and battery technology trade studies. This effort proves the versatility of the Saber simulation program in handling varied and complex simulations accurately and in a reasonable amount of computer time. 9 refs

Dynamical stability for finite quantum spin chains against a time-periodic inhomogeneous perturbation

International Nuclear Information System (INIS)

Kudo, Kazue; Nakamura, Katsuhiro

2009-01-01

We investigate dynamical stability of the ground state against a time-periodic and spatially-inhomogeneous magnetic field for finite quantum XXZ spin chains. We use the survival probability as a measure of stability and demonstrate that it decays as P(t) ∝ t -1/2 under a certain condition. The dynamical properties should also be related to the level statistics of the XXZ spin chains with a constant spatially-inhomogeneous magnetic field. The level statistics depends on the anisotropy parameter and the field strength. We show how the survival probability depends on the anisotropy parameter, the strength and frequency of the field.

Cluster Tails for Critical Power-Law Inhomogeneous Random Graphs

Science.gov (United States)

van der Hofstad, Remco; Kliem, Sandra; van Leeuwaarden, Johan S. H.

2018-04-01

Recently, the scaling limit of cluster sizes for critical inhomogeneous random graphs of rank-1 type having finite variance but infinite third moment degrees was obtained in Bhamidi et al. (Ann Probab 40:2299-2361, 2012). It was proved that when the degrees obey a power law with exponent τ \\in (3,4), the sequence of clusters ordered in decreasing size and multiplied through by n^{-(τ -2)/(τ -1)} converges as n→ ∞ to a sequence of decreasing non-degenerate random variables. Here, we study the tails of the limit of the rescaled largest cluster, i.e., the probability that the scaling limit of the largest cluster takes a large value u, as a function of u. This extends a related result of Pittel (J Combin Theory Ser B 82(2):237-269, 2001) for the Erdős-Rényi random graph to the setting of rank-1 inhomogeneous random graphs with infinite third moment degrees. We make use of delicate large deviations and weak convergence arguments.

NONLINEAR EVOLUTION OF BEAM-PLASMA INSTABILITY IN INHOMOGENEOUS MEDIUM

International Nuclear Information System (INIS)

Ziebell, L. F.; Pavan, J.; Yoon, P. H.; Gaelzer, R.

2011-01-01

The problem of electron-beam propagation in inhomogeneous solar wind is intimately related to the solar type II and/or type III radio bursts. Many scientists have addressed this issue in the past by means of quasi-linear theory, but in order to fully characterize the nonlinear dynamics, one must employ weak-turbulence theory. Available numerical solutions of the weak-turbulence theory either rely on only one nonlinear process (either decay or scattering), or when both nonlinear terms are included, the inhomogeneity effect is generally ignored. The present paper reports the full solution of weak-turbulence theory that includes both decay and scattering processes, and also incorporating the effects of density gradient. It is found that the quasi-linear effect sufficiently accounts for the primary Langmuir waves, but to properly characterize the back-scattered Langmuir wave, which is important for eventual radiation generation, it is found that both nonlinear decay and scattering processes make comparable contributions. Such a finding may be important in the quantitative analysis of the plasma emission process with application to solar type II and/or type III radio bursts.

Plasmons in inhomogeneously doped neutral and charged graphene nanodisks

Energy Technology Data Exchange (ETDEWEB)

Silveiro, Iván [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, 08860 Castelldefels (Barcelona) (Spain); Javier García de Abajo, F., E-mail: javier.garciadeabajo@icfo.es [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, 08860 Castelldefels (Barcelona) (Spain); ICREA-Institució Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys, 23, 08010 Barcelona (Spain)

2014-03-31

We study plasmons in graphene nanodisks including the effect of inhomogeneity in the distribution of the doping charge. Specifically, we discuss the following two configurations: charged disks containing a fixed amount of additional carriers, which are self-consistently distributed along the surface to produce a uniform DC potential; and neutral disks exposed to a neighboring external point charge. A suitable finite-element method is elaborated to compute the charge density associated with the plasmons in the electrostatic limit. For charged disks, we find dipolar plasmons similar to those of uniformly doped graphene structures, in which the plasmon induced charge piles up near the edges. In contrast, in neutral disks placed near an external point charge, plasmons are strongly localized away from the edges. Surprisingly, a single external electron is enough to trap plasmons. The disks also display axially symmetric dark-plasmons, which can be excited through external illumination by coupling them to a neighboring metallic element. Our results have practical relevance for graphene nanophotonics under inhomogeneous doping conditions.

Percolation for a model of statistically inhomogeneous random media

International Nuclear Information System (INIS)

Quintanilla, J.; Torquato, S.

1999-01-01

We study clustering and percolation phenomena for a model of statistically inhomogeneous two-phase random media, including functionally graded materials. This model consists of inhomogeneous fully penetrable (Poisson distributed) disks and can be constructed for any specified variation of volume fraction. We quantify the transition zone in the model, defined by the frontier of the cluster of disks which are connected to the disk-covered portion of the model, by defining the coastline function and correlation functions for the coastline. We find that the behavior of these functions becomes largely independent of the specific choice of grade in volume fraction as the separation of length scales becomes large. We also show that the correlation function behaves in a manner similar to that of fractal Brownian motion. Finally, we study fractal characteristics of the frontier itself and compare to similar properties for two-dimensional percolation on a lattice. In particular, we show that the average location of the frontier appears to be related to the percolation threshold for homogeneous fully penetrable disks. copyright 1999 American Institute of Physics

INHOMOGENEITY IN SPATIAL COX POINT PROCESSES – LOCATION DEPENDENT THINNING IS NOT THE ONLY OPTION

Directory of Open Access Journals (Sweden)

Michaela Prokešová

2010-11-01

Full Text Available In the literature on point processes the by far most popular option for introducing inhomogeneity into a point process model is the location dependent thinning (resulting in a second-order intensity-reweighted stationary point process. This produces a very tractable model and there are several fast estimation procedures available. Nevertheless, this model dilutes the interaction (or the geometrical structure of the original homogeneous model in a special way. When concerning the Markov point processes several alternative inhomogeneous models were suggested and investigated in the literature. But it is not so for the Cox point processes, the canonical models for clustered point patterns. In the contribution we discuss several other options how to define inhomogeneous Cox point process models that result in point patterns with different types of geometric structure. We further investigate the possible parameter estimation procedures for such models.

IEA Statistics 1993: electricity information

International Nuclear Information System (INIS)

1994-01-01

Gross electricity production in 1993 in the OECD (including generation from pumped storage plants) was 7 466 TWh, a rise of 1.2 per cent from the level of gross production in 1992 (Tables 1 and 3). Nuclear plants accounted for 24.2 per cent of total gross electricity production in 1993, hydroelectric plants 16.7 per cent, total thermal plants 58.7 per cent and geothermal and other renewables 0.4 per cent. In 1992 total OECD heat production that is sold to third parties by public producers was 25 Mtoe (Table 6). About 86 per cent of this heat (21.6 Mtoe) was produced in CHP plants, about 12 per cent (3.1 Mtoe) in heat plants, and the remainder (0.3 Mtoe) in nuclear power plants (in Canada and Switzerland only). Based on preliminary data, apparent consumption of electricity (gross production plus imports less exports) in 1993 in OECD was 7 474 TWh. The corresponding figure for 1992 was 7 379 TWh, indicating a rise of 1.3 per cent in apparent electricity consumption in OECD countries in 1993. OECD countries imported a total of 219 TWh of electricity in 1993 (including from other OECD countries) and exported 211 TWh (including to other OECD countries). Accordingly, net imports of electricity in 1993 amounted to 7.7 TWh. Real electricity prices (as measured by the indices of real energy prices) in the OECD fell slightly in 1993 from 1992 levels for both industry and household end-users (Table 20). Electricity prices for industrial consumers vary widely across OECD countries. Based on data that are available for 1993, prices varied from 3.3 US cents per kWh in New Zealand to 12.1 US cents per kWh in Portugal. Electricity prices for industry are reported in Tables 24 and 25. Electricity prices for domestic consumers also vary widely across OECD countries. Based on data that are available for 1993, prices varied from 5.8 US cents per kWh in New Zealand to 18.0 US cents per kWh in Denmark (Tables 26 and 27)

Perfectly matched layers for radio wave propagation in inhomogeneous magnetized plasmas

International Nuclear Information System (INIS)

Gondarenko, Natalia A.; Guzdar, Parvez N.; Ossakow, Sidney L.; Bernhardt, Paul A.

2004-01-01

We present 1D and 2D numerical models of the propagation of high-frequency (HF) radio waves in inhomogeneous magnetized plasmas. The simulations allow one to describe the process of linear conversion of HF electromagnetic waves into electrostatic waves. The waves, launched from the lower boundary normally or at a specified angle on a layer of a magnetoactive plasma, can undergo linear conversion of the incident O-mode into a Z-mode at appropriate locations in an inhomogeneous prescribed plasma density. The numerical scheme for solving 2D HF wave propagation equations is described. The model employed the Maxwellian perfectly matched layers (PML) technique for approximating nonreflecting boundary conditions. Our numerical studies demonstrate the effectiveness of the PML technique for transparent boundary conditions for an open-domain problem

An algorithm of computing inhomogeneous differential equations for definite integrals

OpenAIRE

Nakayama, Hiromasa; Nishiyama, Kenta

2010-01-01

We give an algorithm to compute inhomogeneous differential equations for definite integrals with parameters. The algorithm is based on the integration algorithm for $D$-modules by Oaku. Main tool in the algorithm is the Gr\\"obner basis method in the ring of differential operators.

Emergence of curved light-cones in a class of inhomogeneous Luttinger liquids

Directory of Open Access Journals (Sweden)

Jérôme Dubail, Jean-Marie Stéphan, Pasquale Calabrese

2017-09-01

Full Text Available The light-cone spreading of entanglement and correlation is a fundamental and ubiquitous feature of homogeneous extended quantum systems. Here we point out that a class of inhomogenous Luttinger liquids (those with a uniform Luttinger parameter $K$ at low energy display the universal phenomenon of curved light cones: gapless excitations propagate along the geodesics of the metric $ds^2=dx^2+v(x^2 d\\tau^2$, with $v(x$ being the calculable spatial dependent velocity induced by the inhomogeneity. We confirm our findings with explicit analytic and numerical calculations both in- and out-of-equilibrium for a Tonks-Girardeau gas in a harmonic potential and in lattice systems with artificially tuned hamiltonian density.

VIE-FG-FFT for Analyzing EM Scattering from Inhomogeneous Nonmagnetic Dielectric Objects

Directory of Open Access Journals (Sweden)

Shu-Wen Chen

2014-01-01

Full Text Available A new realization of the volume integral equation (VIE in combination with the fast Fourier transform (FFT is established by fitting Green’s function (FG onto the nodes of a uniform Cartesian grid for analyzing EM scattering from inhomogeneous nonmagnetic dielectric objects. The accuracy of the proposed method is the same as that of the P-FFT and higher than that of the AIM and the IE-FFT especially when increasing the grid spacing size. Besides, the preprocessing time of the proposed method is obviously less than that of the P-FFT for inhomogeneous nonmagnetic dielectric objects. Numerical examples are provided to demonstrate the accuracy and efficiency of the proposed method.

Asymptotic solution of the Vlasov and Poisson equations for an inhomogeneous plasma

International Nuclear Information System (INIS)

Croci, R.

1991-01-01

The asymptotic solutions to a class of inhomogeneous integral equations that reduce to algebraic equations when a parameter η goes to zero (the kernel becoming proportional to a Dirac δ function) are derived. This class includes the integral equations obtained from the system of Vlasov and Poisson equations for the Fourier transform in space and the Laplace transform in time of the electrostatic potential, when the equilibrium magnetic field is uniform and the equilibrium plasma density depends on ηx, with the co-ordinate z being the direction of the magnetic field. In this case the inhomogeneous term is given by the initial conditions and possibly by sources, and the Laplace-transform variable ω is the eigenvalue parameter. (Author)

The nonlinear distortion of propagation cones of lower hybrid wave in an inhomogeneous plasma

International Nuclear Information System (INIS)

Sanuki, Heiji; Ogino, Tatsuki.

1976-12-01

Nonlinear propagation of externally driven waves in the lower hybrid frequency range in an inhomogeneous plasma are investigated. The results of finite temperature, inhomogeneity of the plasma and density depression due to the ponderomotive force are emphasized since these effects are responsible for the propagation characteristics of the waves. The results shows that the waves are localized in a spatial wave packet that propagates into the plasma center along the conical trajectory which makes a small angle with respect to the confining magnetic field. (auth.)

Scattering cross-section of an inhomogeneous plasma cylinder

International Nuclear Information System (INIS)

Jiaming Shi; Lijian Qiu; Ling, Y.

1995-01-01

Scattering of em waves by the plasma cylinder is of significance in radar target detection, plasma diagnosis, etc. This paper discusses the general method to calculate the scattering cross-section of em waves from a plasma cylinder which is radially inhomogeneous and infinitely long. Numerical results are also provided for several plasma density profiles. The effect of the electron density distribution on the scattering cross-section is investigated

Local sensor based on nanowire field effect transistor from inhomogeneously doped silicon on insulator

Science.gov (United States)

Presnov, Denis E.; Bozhev, Ivan V.; Miakonkikh, Andrew V.; Simakin, Sergey G.; Trifonov, Artem S.; Krupenin, Vladimir A.

2018-02-01

We present the original method for fabricating a sensitive field/charge sensor based on field effect transistor (FET) with a nanowire channel that uses CMOS-compatible processes only. A FET with a kink-like silicon nanowire channel was fabricated from the inhomogeneously doped silicon on insulator wafer very close (˜100 nm) to the extremely sharp corner of a silicon chip forming local probe. The single e-beam lithographic process with a shadow deposition technique, followed by separate two reactive ion etching processes, was used to define the narrow semiconductor nanowire channel. The sensors charge sensitivity was evaluated to be in the range of 0.1-0.2 e /√{Hz } from the analysis of their transport and noise characteristics. The proposed method provides a good opportunity for the relatively simple manufacture of a local field sensor for measuring the electrical field distribution, potential profiles, and charge dynamics for a wide range of mesoscopic objects. Diagnostic systems and devices based on such sensors can be used in various fields of physics, chemistry, material science, biology, electronics, medicine, etc.

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

Foerster resonance energy transfer in inhomogeneous non-dispersive nanophotonic environments

DEFF Research Database (Denmark)

Wubs, Martijn; Vos, Willem L.

A nondispersive inhomogeneous dielectric environment of a donor-acceptor pair of quantum emitters affects their Foerster resonance energy transfer (FRET) rate. We find that this rate does not depend on the emission frequency and hence not on the local optical density of states (LDOS) at that freq...

Tissue characterization using electrical impedance spectroscopy data: a linear algebra approach.

Science.gov (United States)

Laufer, Shlomi; Solomon, Stephen B; Rubinsky, Boris

2012-06-01

In this study, we use a new linear algebra manipulation on electrical impedance spectroscopy measurements to provide real-time information regarding the nature of the tissue surrounding the needle in minimal invasive procedures. Using a Comsol Multiphysics three-dimensional model, a phantom based on ex vivo animal tissue and in vivo animal data, we demonstrate how tissue inhomogeneity can be characterized without any previous knowledge of the electrical properties of the different tissues, except that they should not be linearly dependent on a certain frequency range. This method may have applications in needle biopsies, radiation seeds, or minimally invasive surgery and can reduce the number of computer tomography or magnetic resonance imaging images. We conclude by demonstrating how this mathematical approach can be useful in other applications.

Poster – 12: Radiological assessment of the secondary barrier shielding for IMRT treatments delivered through patient inhomogeneities

Energy Technology Data Exchange (ETDEWEB)

Haseeb, Syed Abdul; Ahmad, Syed Bilal; Mirza, Sikander Majid [Pakistan Institute of Engineering and Applied Science, Nilore, Islamabad, Pakistan, Sunnybrook Health Sciences Center, Toronto, ON, Canada & Pakistan Institute of Engineering and Applied Science, Nilore, Islamabad, Pakistan, Pakistan Institute of Engineering and Applied Science, Nilore, Islamabad (Pakistan)

2016-08-15

Purpose: To assess the impact of radiation treatment delivery through patient inhomogeneities on the secondary barrier shielding requirements in IMRT treatments using Monte Carlo Simulations. Materials and Methods: Scatter factors were calculated at a distance of 1m from the center of a virtual phantom in Geant4.10.01. Phantom (30×30×30 cm{sup 3}) was inserted with lung (30×30×8 cm{sup 3}), stainless steel (5×5×5 cm{sup 3}) and aluminum (5×5×5 cm{sup 3}) to represent the inhomogeneities. Scatter factor was defined according to the NCRP-151 recommendations and was calculated for angles of 3° to 120° with respect to the beam’s central axis. A virtual radiation source, with energy sampled from a histogram representing 6 MV FFF beam, was used for irradiation with a field size of 15×15 cm{sup 2} and SSD of 100 cm. Results: Irradiation through the inhomogeneity affects the patient scattered dose. For high Z material inhomogeneities the scattered dose is reduced due to significant attenuation of the primary radiation. On the other hand if the inhomogeneity is a low Z material such as lung the scattered dose is higher by a maximum of 26%. The average increase in scatter factors for the lung phantom was 17% for angles between 3° and 63° compared to the homogeneous water phantom. Conclusions: In IMRT type treatments delivered through low density patient inhomogeneities (lung) the scattered dose increases significantly. Considering a large proportion of patients receiving radiation therapy for lung cancers the increase in the scattered dose should be incorporated in the shielding calculations for the secondary barriers.

Solar energy thermally powered electrical generating system

Science.gov (United States)

Owens, William R. (Inventor)

1989-01-01

A thermally powered electrical generating system for use in a space vehicle is disclosed. The rate of storage in a thermal energy storage medium is controlled by varying the rate of generation and dissipation of electrical energy in a thermally powered electrical generating system which is powered from heat stored in the thermal energy storage medium without exceeding a maximum quantity of heat. A control system (10) varies the rate at which electrical energy is generated by the electrical generating system and the rate at which electrical energy is consumed by a variable parasitic electrical load to cause storage of an amount of thermal energy in the thermal energy storage system at the end of a period of insolation which is sufficient to satisfy the scheduled demand for electrical power to be generated during the next period of eclipse. The control system is based upon Kalman filter theory.