Confinement of a self-stabilized tokamak under average magnetic well conditions
International Nuclear Information System (INIS)
It is well known that the average favorable magnetic curvature of a tokamak is stabilizing with respect to pressure-driven magnetohydrodynamic instabilities at low beta and that self-stabilization occurs at finite beta in the so-called second stability regime. Here we self-consistently investigate how these two effects, viz., the mean magnetic well and the self-stabilization, influence the energy confinement time in a tokamak, using the ballooning mode transport model
Bayesian Averaging is Well-Temperated
DEFF Research Database (Denmark)
Hansen, Lars Kai
2000-01-01
Bayesian predictions are stochastic just like predictions of any other inference scheme that generalize from a finite sample. While a simple variational argument shows that Bayes averaging is generalization optimal given that the prior matches the teacher parameter distribution the situation is l...
Small scale magnetic flux-averaged magnetohydrodynamics
International Nuclear Information System (INIS)
By relaxing exact magnetic flux conservation below a scale λ a system of flux-averaged magnetohydrodynamic equations are derived from Hamilton's principle with modified constraints. An energy principle can be derived from the linearized averaged system because the total system energy is conserved. This energy principle is employed to treat the resistive tearing instability and the exact growth rate is recovered when λ is identified with the resistive skin depth. A necessary and sufficient stability criteria of the tearing instability with line tying at the ends for solar coronal loops is also obtained. The method is extended to both spatial and temporal averaging in Hamilton's principle. The resulting system of equations not only allows flux reconnection but introduces irreversibility for appropriate choice of the averaging function. Except for boundary contributions which are modified by the time averaging process total energy and momentum are conserved over times much longer than the averaging time τ but not for less than τ. These modified boundary contributions correspond to the existence, also, of damped waves and shock waves in this theory. Time and space averaging is applied to electron magnetohydrodynamics and in one-dimensional geometry predicts solitons and shocks in different limits
Magnetic well for plasma confinement
International Nuclear Information System (INIS)
A multipole magnetic well for plasma confinement includes a plurality of current-carrying coils placed on planes corresponding to the facets of a regular polyhedron that can be symmetrically circumscribed about a sphere. The direction of current in the coils is such as to minimize the flux density at the center of the polyhedron, thereby providing a confinement well with three-dimensional symmetry having an increasing flux density in all directions from the center. 16 claims, 18 figures
The B-dot Earth Average Magnetic Field
Capo-Lugo, Pedro A.; Rakoczy, John; Sanders, Devon
2013-01-01
The average Earth's magnetic field is solved with complex mathematical models based on mean square integral. Depending on the selection of the Earth magnetic model, the average Earth's magnetic field can have different solutions. This paper presents a simple technique that takes advantage of the damping effects of the b-dot controller and is not dependent of the Earth magnetic model; but it is dependent on the magnetic torquers of the satellite which is not taken into consideration in the known mathematical models. Also the solution of this new technique can be implemented so easily that the flight software can be updated during flight, and the control system can have current gains for the magnetic torquers. Finally, this technique is verified and validated using flight data from a satellite that it has been in orbit for three years.
Averaging and sampling for magnetic-observatory hourly data
Directory of Open Access Journals (Sweden)
J. J. Love
2010-11-01
Full Text Available A time and frequency-domain analysis is made of the effects of averaging and sampling methods used for constructing magnetic-observatory hourly data values. Using 1-min data as a proxy for continuous, geomagnetic variation, we construct synthetic hourly values of two standard types: instantaneous "spot" measurements and simple 1-h "boxcar" averages. We compare these average-sample types with others: 2-h average, Gaussian, and "brick-wall" low-frequency-pass. Hourly spot measurements provide a statistically unbiased representation of the amplitude range of geomagnetic-field variation, but as a representation of continuous field variation over time, they are significantly affected by aliasing, especially at high latitudes. The 1-h, 2-h, and Gaussian average-samples are affected by a combination of amplitude distortion and aliasing. Brick-wall values are not affected by either amplitude distortion or aliasing, but constructing them is, in an operational setting, relatively more difficult than it is for other average-sample types. It is noteworthy that 1-h average-samples, the present standard for observatory hourly data, have properties similar to Gaussian average-samples that have been optimized for a minimum residual sum of amplitude distortion and aliasing. For 1-h average-samples from medium and low-latitude observatories, the average of the combination of amplitude distortion and aliasing is less than the 5.0 nT accuracy standard established by Intermagnet for modern 1-min data. For medium and low-latitude observatories, average differences between monthly means constructed from 1-min data and monthly means constructed from any of the hourly average-sample types considered here are less than the 1.0 nT resolution of standard databases. We recommend that observatories and World Data Centers continue the standard practice of reporting simple 1-h-average hourly values.
Spin spatial splitter based on a magnetic nanostructure with zero average magnetic field
International Nuclear Information System (INIS)
Highlights: • The lateral displacement of spin electron is investigated theoretically in a new magnetic nanostructure with a zero average magnetic field. • The lateral displacement is found to be dependent strongly on the spins. • Such a magnetic nanostructure can serve as a spin spatial splitter for spintronics applications. - Abstract: We report a theoretical study on spin-polarized lateral displacement for the electron across a magnetic nanostructure with a zero average magnetic field, which can be experimentally realized by depositing a ferromagnetic stripe with a plumb magnetization on the top of a semiconductor heterostructure. It is shown that, the lateral displacement depends strongly on the electron spins due to the Zeeman coupling and the intrinsic symmetry, though the average magnetic field is vanishing in the nanostructure. It is also shown that the spin-polarized lateral displacement is related closely to the structural parameters. Therefore, such a novel magnetic nanostructure may be used as a spin spatial splitter for spintronics applications
Helical Fields Possessing Mean Magnetic Wells
International Nuclear Information System (INIS)
Recently Furth and Rosenbluth pointed out that a particular magnetic field having helical symmetry could provide a mean magnetic well, that is provide regions in which ∫dℓ/B decreases away from a magnetic axis (or equivalently a region in which V'' is negative). In this paper we examine helical fields in general and the circumstances in which they may exhibit the negative V'' property. This investigation is made possible by the use of the stream function formalism which provides a simple picture of the field geometry, The existence of negative V'' is related to the topology of the magnetic surfaces which in turn is connected with the positions of the stationary points of the stream function ψ. Detailed calculations are given of the shape of the flux surfaces and of the shape of the magnetic well (the variation of ∫dℓ/B across it) for several examples of helical fields. These include the Furth-Rosenbluth configuration and a new configuration which provides a mean magnetic well without the necessity for a central conductor. A survey is also made of the magnetic well properties of these two classes of helical field in terms of two simple criteria: (1) the ratio Q of the field strength on the axis and on the separatrix (which provides an estimate of the overall well depth); and (2) the value of V'' on the magnetic axis (which provides a measure of the ''curvature'' of the well). This latter quantity is calculated analytically by using a general expression for the value of V'' on an arbitrary magnetic axis; It is pointed out that Q alone does not provide a realistic indication of the well shape. (author)
Average dimension and magnetic structure of the distant Venus magnetotail
Saunders, M. A.; Russell, C. T.
1986-01-01
The first major statistical investigation of the far wake of an unmagnetized object embedded in the solar wind is reported. The investigation is based on Pioneer Venus Orbiter magnetometer data from 70 crossings of the Venus wake at altitudes between 5 and 11 Venus radii during reasonably steady IMF conditions. It is found that Venus has a well-developed-tail, flaring with altitude and possibly broader in the direction parallel to the IMF cross-flow component. Tail lobe field polarities and the direction of the cross-tail field are consistent with tail accretion from the solar wind. Average values for the cross-tail field (2 nT) and the distant tail flux (3 MWb) indicate that most distant tail field lines close across the center of the tail and are not rooted in the Venus ionosphere. The findings are illustrated in a three-dimensional schematic.
Squeezed potato orbits in a magnetic well
International Nuclear Information System (INIS)
It is shown that potato orbits in the near-axis region of a high beta tokamak are squeezed in a magnetic well. The squeezing factor is the same as that for the banana orbits derived in an earlier work [Phys. Plasmas 3, 2843 (1996)]. It depends on the energy of the particle. For high-energy particles, the size of the squeezed orbits is independent of their energy. This implies improved confinement for high-energy particles and for high beta tokamaks with advanced fuels
Permeability averaging for well tests in 3D stochastic reservoir models
Energy Technology Data Exchange (ETDEWEB)
Noetinger, B.; Haas, A.
1996-12-31
Geostatistical models are useful to generate equiprobable realizations of oil reservoirs that allow the study uncertainties in the production forecasts. A key problem is the constraint of these models according to known production data, to reduce uncertainties. Due to the relative simplicity of well tests, numerous authors attempted to include those in the geostatistical models, especially in a 2D context. The goal of this work is to propose a simple analytical formula which relates the apparent permeability given by a well test interpretation and the original permeability map around the well for 3D heterogeneous reservoirs. The pressure derivative is used to interpret drawdowns. Assuming that this permeability is related to the original permeability map in the drainage volume by a simple power averaging formula, the best value of the averaging exponent is computed using perturbation methods. It depends on time, and on the vertical to horizontal permeability ratio k{sub v}/k{sub h}, and geostatistical anisotropy. For sufficiently long times, when the apparent permeability is stabilized, we obtain an apparent permeability equal to the well-known steady-state equivalent permeability of the medium. This regime occurs when the investigation radius of the well test is larger than the correlation length. Numerical simulations of well tests performed in this regime are in good agreement with the calculation and demonstrate the validity and robustness of the proposed formula.
A two-region hydraulic averaging model for cuttings transport during horizontal well drilling
Energy Technology Data Exchange (ETDEWEB)
Salazar-Mendoza, R. [Inst. Mexicano del Petrolio (Mexico); Centro Nacional de Investigacion y Desarrollo Technologico (Mexico); Garcia-Gutierrez, A. [Inst. de Investigaciones Electricas (Mexico); Centro Nacional de Investigacion y Desarrollo Technologico (Mexico)
2008-03-15
The problem of cuttings transport for a two-region system was investigated to better understand the cuttings transport phenomena for horizontal well drilling applications. The complex hydraulic transport of solid particles in horizontal pipes must be well understood by the oil industry where horizontal drilling is commonly used to exploit reservoirs exhibiting thin pay zones. The two-region hydraulic averaging model for cuttings transport is a newly developed mathematical model for use during horizontal well drilling. The model considers a two-phase two region system composed of a moving bed and a stationary bed of drill cuttings modelled as a porous medium. The volume averaging method was used to obtain the volume-averaged transport equations for both the moving bed and the porous medium regions. Three main flow patterns of the horizontal cuttings transport process were analyzed. These included fully suspended flow; flow with a stationary bed; and, flow with a moving bed. The finite difference technique with an implicit scheme was used to numerically solve the one-dimensional models for all patterns. Numerical and experimental results were found to be in good agreement. 26 refs., 9 figs.
Thiel, Thorsten; Czisch, Michael; Elbel, Gregor K; Hennig, Juergen
2002-06-01
The quality of spectra in (1)H magnetic resonance spectroscopy (MRS) is strongly affected by temporal signal instabilities during the acquisition. One reason for these instabilities are hardware imperfections, e.g., drifts of the main magnetic field in superconducting magnets. This is of special concern in high-field systems where the specification of the field stability is close to the spectral linewidth. A second major potential source of artifacts, particularly in clinical MRS, is patient motion. Using standard acquisition schemes of phase-cycled averaging of the individual acquisitions, long-term effects (field drifts) as well as changes on a shorter time scale (motion) can severely reduce spectral quality. The new technique for volume-selective MRS presented here is based on the additional interleaved acquisition of a navigator signal during the recovery time of the metabolite acquisition. It corrects for temporal signal instabilities by means of a deconvolution of the metabolite and the navigator signal. This leads to phase-corrected individual metabolite scans and upon summation to a phase-coherent averaging scheme. The interleaved navigator acquisition does not require any user interaction or supervision, while sequence efficiency is maintained. PMID:12111954
Anisotropy of the solar network magnetic field around the average supergranule
Langfellner, J.; Gizon, L.; Birch, A. C.
2015-07-01
Supergranules in the quiet Sun are outlined by a web-like structure of enhanced magnetic field strength, the so-called magnetic network. We aim to map the magnetic network field around the average supergranule near disk center. We use observations of the line-of-sight component of the magnetic field from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). The average supergranule is constructed by coaligning and averaging over 3000 individual supergranules. We determine the positions of the supergranules with an image segmentation algorithm that we apply to maps of the horizontal flow divergence measured using time-distance helioseismology. In the center of the average supergranule, the magnetic (intranetwork) field is weaker by about 2.2 Gauss than the background value (3.5 Gauss), whereas it is enhanced in the surrounding ring of horizontal inflows (by about 0.6 Gauss on average). We find that this network field is significantly stronger west (prograde) of the average supergranule than in the east (by about 0.3 Gauss). With time-distance helioseismology, we find a similar anisotropy. The observed anisotropy of the magnetic field adds to the mysterious dynamical properties of solar supergranulation.
Anisotropy of the solar network magnetic field around the average supergranule
Langfellner, J; Birch, A C
2015-01-01
Supergranules in the quiet Sun are outlined by a web-like structure of enhanced magnetic field strength, the so-called magnetic network. We aim to map the magnetic network field around the average supergranule near disk center. We use observations of the line-of-sight component of the magnetic field from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). The average supergranule is constructed by coaligning and averaging over 3000 individual supergranules. We determine the positions of the supergranules with an image segmentation algorithm that we apply on maps of the horizontal flow divergence measured using time-distance helioseismology. In the center of the average supergranule the magnetic (intranetwork) field is weaker by about 2.2 Gauss than the background value (3.5 Gauss), whereas it is enhanced in the surrounding ring of horizontal inflows (by about 0.6 Gauss on average). We find that this network field is significantly stronger west (prograde) of the average sup...
Directory of Open Access Journals (Sweden)
Saeedeh Ghafourian
2011-01-01
Full Text Available Single wall carbon nanotubes (SWCNT extensively are attractive from both theoretical and experimental point of view, due to its technological applications such as nano electronics devises. SWCNT are created by rolling a graphen sheet into a cyclindrical form. We have investigated the possibility of making a ferromagnetic semiconductor zigzag SWCNT by doping magnetic impurities. We found by increasing magnetic impurities doping on a zigzag SWCNT, average magnetization is increased and one can make a ferromagnetic semiconductor
Thinking About One's Subjective Well-Being: Average Trends and Individual Differences.
Luhmann, Maike; Hawkley, Louise C; Cacioppo, John T
2014-08-01
In two studies, participants reported what they had been thinking about while completing measures of subjective well-being (SWB). These thought reports were analyzed with respect to life domain, valence, and how strongly they were related to actual levels of SWB. Most people focused on their life circumstances (e.g., career) rather than on dispositional predictors (e.g., personality) of SWB. The domains mentioned most frequently (career, family, romantic life) were also the ones that were most strongly related to actual SWB, indicating that most of people think about things that actually contribute to their SWB. Some domains are predominantly mentioned in positive contexts (e.g., family) whereas others are predominantly mentioned in negative contexts (e.g., money). On average, people thought more about positive than about negative things, a result that is magnified for respondents high in extraversion or emotional stability. In sum, these findings provide insight into what people think contributes to their SWB; beliefs that may guide them as they make important decisions. PMID:25332682
Thinking About One’s Subjective Well-Being: Average Trends and Individual Differences
Luhmann, Maike; Hawkley, Louise C.; Cacioppo, John T.
2013-01-01
In two studies, participants reported what they had been thinking about while completing measures of subjective well-being (SWB). These thought reports were analyzed with respect to life domain, valence, and how strongly they were related to actual levels of SWB. Most people focused on their life circumstances (e.g., career) rather than on dispositional predictors (e.g., personality) of SWB. The domains mentioned most frequently (career, family, romantic life) were also the ones that were most strongly related to actual SWB, indicating that most of people think about things that actually contribute to their SWB. Some domains are predominantly mentioned in positive contexts (e.g., family) whereas others are predominantly mentioned in negative contexts (e.g., money). On average, people thought more about positive than about negative things, a result that is magnified for respondents high in extraversion or emotional stability. In sum, these findings provide insight into what people think contributes to their SWB; beliefs that may guide them as they make important decisions. PMID:25332682
On averaging the Kubo-Hall conductivity of magnetic Bloch bands leading to Chern numbers
International Nuclear Information System (INIS)
The authors re-examine the topological approach to the integer quantum Hall effect in its original form where an average of the Kubo-Hall conductivity of a magnetic Bloch band has been considered. For the precise definition of this average it is crucial to make a sharp distinction between the discrete Bloch wave numbers k1, k2 and the two continuous integration parameters α1, α2. The average over the parameter domain 0 ≤ αj 1, k2. They show how this can be transformed into a single integral over the continuous magnetic Brillouin zone 0 ≤ αj j, j = 1, 2, nj = number of unit cells in j-direction, keeping k1, k2 fixed. This average prescription for the Hall conductivity of a magnetic Bloch band is exactly the same as the one used for a many-body system in the presence of disorder
Shu, Di; Guo, Lei; Yin, Liang; Chen, Zhaoyang; Chen, Juan; Qi, Xin
2015-11-01
The average volume of magnetic Barkhausen jump (AVMBJ) v bar generated by magnetic domain wall irreversible displacement under the effect of the incentive magnetic field H for ferromagnetic materials and the relationship between irreversible magnetic susceptibility χirr and stress σ are adopted in this paper to study the theoretical relationship among AVMBJ v bar(magneto-elasticity noise) and the incentive magnetic field H. Then the numerical relationship among AVMBJ v bar, stress σ and the incentive magnetic field H is deduced. Utilizing this numerical relationship, the displacement process of magnetic domain wall for single crystal is analyzed and the effect of the incentive magnetic field H and the stress σ on the AVMBJ v bar (magneto-elasticity noise) is explained from experimental and theoretical perspectives. The saturation velocity of Barkhausen jump characteristic value curve is different when tensile or compressive stress is applied on ferromagnetic materials, because the resistance of magnetic domain wall displacement is different. The idea of critical magnetic field in the process of magnetic domain wall displacement is introduced in this paper, which solves the supersaturated calibration problem of AVMBJ - σ calibration curve.
The average magnetic field draping and consistent plasma properties of the Venus magnetotail
Mccomas, D. J.; Spence, H. E.; Russell, C. T.; Saunders, M. A.
1986-01-01
The detailed average draping pattern of the magnetic field in the deep Venus magnetotail is examined. The variability of the data ordered by spatial location is studied, and the groundwork is laid for developing a coordinate system which measured locations with respect to the tail structures. The reconstruction of the tail in the presence of flapping using a new technique is shown, and the average variations in the field components are examined, including the average field vectors, cross-tail current density distribution, and J x B forces as functions of location across the tail. The average downtail velocity is derived as a function of distance, and a simple model based on the field variations is defined from which the average plasma acceleration is obtained as a function of distance, density, and temperature.
2010 Kids Count in Colorado! Far from Average: Growing Gaps in Child Well-Being
Colorado Children's Campaign, 2010
2010-01-01
"Kids Count in Colorado!" is an annual publication of the Colorado Children's Campaign, which provides the best available state- and county-level data to measure and track the education, health and general well-being of the state's children. "Kids Count in Colorado!" informs policy debates and community discussions, serving as a valuable resource…
Thinking About One’s Subjective Well-Being: Average Trends and Individual Differences
Luhmann, Maike; Hawkley, Louise C.; Cacioppo, John T.
2013-01-01
In two studies, participants reported what they had been thinking about while completing measures of subjective well-being (SWB). These thought reports were analyzed with respect to life domain, valence, and how strongly they were related to actual levels of SWB. Most people focused on their life circumstances (e.g., career) rather than on dispositional predictors (e.g., personality) of SWB. The domains mentioned most frequently (career, family, romantic life) were also the ones that were mos...
A new solar signal: Average maximum sunspot magnetic fields independent of activity cycle
Livingston, William
2016-01-01
Over the past five years, 2010-2015, we have observed, in the near infrared (IR), the maximum magnetic field strengths for 4145 sunspot umbrae. Herein we distinguish field strengths from field flux. (Most solar magnetographs measure flux). Maximum field strength in umbrae is co-spatial with the position of umbral minimum brightness (Norton and Gilman, 2004). We measure field strength by the Zeeman splitting of the Fe 15648.5 A spectral line. We show that in the IR no cycle dependence on average maximum field strength (2050 G) has been found +/- 20 Gauss. A similar analysis of 17,450 spots observed by the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory reveal the same cycle independence +/- 0.18 G., or a variance of 0.01%. This is found not to change over the ongoing 2010-2015 minimum to maximum cycle. Conclude the average maximum umbral fields on the Sun are constant with time.
Use of induction linacs with nonlinear magnetic drive as high average power accelerators
International Nuclear Information System (INIS)
The marriage of induction linac technology with Nonlinear Magnetic Modulators has produced some unique capabilities. It appears possible to produce electron beams with average currents measured in amperes, at gradients exceeding 1 Mev/meter, and with power efficiencies approaching 50%. A 2 MeV, 5 kA electron accelerator is under construction at Lawrence Livermore National Laboratory (LLNL) to allow us to demonstrate some of these concepts. Progress on this project is reported here
Quantum-well-driven magnetism in thin films
DEFF Research Database (Denmark)
Mirbt, S.; Johansson, B.; Skriver, Hans Lomholt
1996-01-01
We have performed local spin-density calculations for an fee (100) Ag substrate covered by 1 to 16 monolayers (ML) of Pd. We find that thin films of Pd are magnetic with a moment of the order of 0.3 mu(B) except for films of 1-2 ML and 5-7 ML where magnetism is completely suppressed. We present a...... physically transparent explanation of this behavior in terms of the Stoner picture and magnetic quantum-well states....
International Nuclear Information System (INIS)
Backus averaging is often applied to well logs in order to estimate the elastic properties of a stack of thin layers at a longer wavelength to be used in seismic data analysis. Schoenberg and Muir extended Backus's method to layers with arbitrary anisotropy, but simple analytical equations are available for isotropic and transversely isotropic layers only. There is growing exploration interest in shale reservoirs, which exhibit lower symmetry seismic anisotropy if the reservoir is fractured. Here, simple analytical equations for Backus averaging are presented for symmetries up to monoclinic, of which averaging equations for orthorhombic and monoclinic layers are new. After Backus averaging, a stack of isotropic layers results in a vertical transverse isotropy (VTI), a stack of VTI layers results in a VTI, a stack of horizontal transverse isotropy layers results in an orthorhombic, a stack of orthorhombic layers results in an orthorhombic and a stack of monoclinic layers results in a monoclinic. Workflows for Backus averaging are presented along with numerical examples using well-log data from the Haynesville shale play in East Texas, USA. (paper)
Shen, Li-Hua; Ma, Wen-Yue; Zhang, Gui-Lian; Yang, Shi-Peng
2015-07-01
We report on a theoretical investigation of spin-polarized transport in a δ-doped magnetically modulated semiconductor nanostructure, which can be experimentally realized by depositing a ferromagnetic stripe on the top of a semiconductor heterostructure and by using the atomic layer doping technique such as molecular beam epitaxy (MBE). It is shown that although such a nanostructure has a zero average magnetic filed, a sizable spin polarization exists due to the Zeeman splitting mechanism. It is also shown that the degree of spin polarization varies sensitively with the weight and/or position of the δ-doping. Therefore, one can conveniently tailor the behaviour of the spin-polarized electron by tuning the δ -doping, and such a device can be employed as a controllable spin filter for spintronics.
International Nuclear Information System (INIS)
Aim: To evaluate the diagnostic performance of an interactive, adaptively averaged (AA) two-dimensional (2D) magnetic resonance cholangiography (MRC) technique in patients with suspected biliary disease by comparison to the standard MRC technique. Materials and methods: The AA 2D MRC method registers the images after acquisition, allowing summation of multiple images to improve the signal:noise ratio (SNR) and thereby potentially improve the visualization of bile ducts. One hundred and twenty-eight patients underwent both 2D conventional and AA magnetic resonance cholangiopancreatography (MRCP). Twenty-seven patients were excluded from the analysis as AA images could not be properly obtained due to technical failures. All examinations were performed using a 1.5 T whole-body MR system and a four-channel torso phased array coil. Images of 101 patients were adaptively averaged using an in-house developed program written in IDL. Two readers qualitatively evaluated the studies in consensus, blinded to acquisition details and without knowledge of clinical information. Results: The AA technique was significantly better than the conventional 2D MRC for the visualization of the second-order branch intrahepatic ducts (p < 00001). Overall, there was no significant difference in the diagnostic confidence between two techniques (p = 0.12). However, the AA technique showed a trend towards more confident diagnosis of biliary strictures (p = 0.055), likely due to better diagnostic confidence in identifying second order branch intrahepatic duct strictures (p = 0.054). Conclusion: Excluding those patients those patients in whom either satisfactory respiratory gating or a suitable kernel placement was not achieved, AA 2D MRC demonstrated a significant improvement in visualization of intrahepatic duct branches compared to standard MRC
Song, Hongqiang; Chen, Yao; Zhang, Jie; Cheng, Xin; Zhao, Liang; Hu, Qiang; Li, Gang
2016-01-01
Magnetic clouds (MCs) are the interplanetary counterpart of coronal magnetic flux ropes. They can provide valuable information to reveal the flux rope characteristics at their eruption stage in the corona, which are unable to be explored in situ at present. In this paper, we make a comprehensive survey of the average iron charge state (Fe) distributions inside 96 MCs for solar cycle 23 using ACE (Advanced Composition Explorer) data. As the Fe in the solar wind are typically around 9+ to 11+, the Fe charge state is defined as high when the Fe is larger than 12+, which implies the existence of a considerable amount of Fe ions with high charge states (e.g., \\geq 16+). The statistical results show that the Fe distributions of 92 (~ 96%) MCs can be classified into four groups with different characteristics. In group A (11 MCs), the Fe shows a bimodal distribution with both peaks higher than 12+. Group B (4 MCs) presents a unimodal distribution of Fe with its peak higher than 12+. In groups C (29 MCs) and D (48 MCs...
U.S. Department of Health & Human Services — A list of a variety of averages for each state or territory as well as the national average, including each quality measure, staffing, fine amount and number of...
Mallavajula, Rajesh K.; Archer, Lynden A.; Koch, Donald L.
2015-09-01
The effect of a homogeneous magnetic field (H) on the bulk stress in a dilute suspension of weakly Brownian, magnetic cubes suspended in a Newtonian fluid subjected to a linear shear flow is studied. The stresslet on each cube is anisotropic and depends on its orientation. Application of a magnetic field results in anisotropy in the orientation distribution. The steady-state orientation distribution is derived as a function of the angle between the directions of the magnetic field and the fluid vorticity vector and the ratio of the magnetic torque to the viscous torque. Knowledge of the distribution function is used to derive a general expression for the bulk stress in a general linear flow field and a magnetic field. Specific numerical results are obtained for the intrinsic viscosity in a simple shear flow when the magnetic field is either parallel or perpendicular to the vorticity. When the magnetic field is perpendicular to vorticity, we find that the intrinsic viscosity increases at first with increasing shear rate passes through a maximum and then shear thins. The intrinsic viscosity can vary from 3.25 to 5.5 in response to changes in the relative strengths of the shear and magnetic fields. The maximum value of 5.5 is obtained when the magnetic moment of the cube, which is assumed to be parallel to the normal of one of the faces, lies in the flow gradient plane at an angle of π/4 from the flow direction.
Statistical Average of Spin Operators for Calculation of Three-Component Magnetization
Institute of Scientific and Technical Information of China (English)
WANG Huai-Yu; ZHOU Bin; CHEN Nan-Xian
2005-01-01
When one wants to calculate all the three components of magnetization of Heisenberg model under random phase approximation, at least one of the components should be the solution of an ordinary differential equation. In this paper such an equation is established. It is argued that the general expressions of magnetization for any spin quantum number S suggested before are the solution of the ordinary differential equation.
Depth Estimates and Its Implications from Second Moving Average Residual Magnetic Anomalies on Mars
Czech Academy of Sciences Publication Activity Database
Essa, K. S.; Kletetschka, Günther
Houston: Lunar and Planetary Institute, 2015. [Lunar and Planetary Science Conference /46./. 16.03.2015-20.03.2015, Woodlands] Institutional support: RVO:67985831 Keywords : astrophysics * Mars * magnetic anomalies Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics http://www.hou.usra.edu/meetings/lpsc2015/pdf/3006.pdf
Shukla-Dave, Amita; Lee, Nancy; Stambuk, Hilda; Wang, YA; Huang, Wei; Howard T Thaler; Patel, Snehal G.; Shah, Jatin P.; Koutcher, Jason A
2009-01-01
Background The present study determines the feasibility of generating an average arterial input function (Avg-AIF) from a limited population of patients with neck nodal metastases to be used for pharmacokinetic modeling of dynamic contrast-enhanced MRI (DCE-MRI) data in clinical trials of larger populations. Methods Twenty patients (mean age 50 years [range 27–77 years]) with neck nodal metastases underwent pretreatment DCE-MRI studies with a temporal resolution of 3.75 to 7.5 sec on a 1.5T c...
On the XFEL Schrödinger Equation: Highly Oscillatory Magnetic Potentials and Time Averaging
Antonelli, Paolo
2014-01-14
We analyse a nonlinear Schrödinger equation for the time-evolution of the wave function of an electron beam, interacting selfconsistently through a Hartree-Fock nonlinearity and through the repulsive Coulomb interaction of an atomic nucleus. The electrons are supposed to move under the action of a time dependent, rapidly periodically oscillating electromagnetic potential. This can be considered a simplified effective single particle model for an X-ray free electron laser. We prove the existence and uniqueness for the Cauchy problem and the convergence of wave-functions to corresponding solutions of a Schrödinger equation with a time-averaged Coulomb potential in the high frequency limit for the oscillations of the electromagnetic potential. © 2014 Springer-Verlag Berlin Heidelberg.
Munoz-Menendez, Cristina; Conde-Leboran, Ivan; Baldomir, Daniel; Chubykalo-Fesenko, Oksana; Serantes, David
2015-11-01
An efficient and safe hyperthermia cancer treatment requires the accurate control of the heating performance of magnetic nanoparticles, which is directly related to their size. However, in any particle system the existence of some size polydispersity is experimentally unavoidable, which results in a different local heating output and consequently a different hyperthermia performance depending on the size of each particle. With the aim to shed some light on this significant issue, we have used a Monte Carlo technique to study the role of size polydispersity in heat dissipation at both the local (single particle) and global (macroscopic average) levels. We have systematically varied size polydispersity, temperature and interparticle dipolar interaction conditions, and evaluated local heating as a function of these parameters. Our results provide a simple guide on how to choose, for a given polydispersity degree, the more adequate average particle size so that the local variation in the released heat is kept within some limits that correspond to safety boundaries for the average-system hyperthermia performance. All together we believe that our results may help in the design of more effective magnetic hyperthermia applications. PMID:26437746
Containment of Plasma Trapped in a Magnetic Well
International Nuclear Information System (INIS)
Plasma from a coaxial gun is guided along an injection line by a converging magnetic field into a central glass vacuum chamber. Here part of the plasma is reflected from a magnetic mirror, and then trapped by the application of another rapidly-pulsed mirror field. Stabilising fields can also be applied by currents in six Ioffe bars parallel to the axis. The fields, of short rise time, are maintained roughly constant for 1 msec. In earlier experiments on plasma of mean density 4 x 1010 cm-3 and ion energy 1 keV, a rotating flute instability was present in simple mirror geometry, the plasma being lost in 60 μsec. With stabilising fields applied, the lifetime of energetic ions (measured by the emission of charge exchanged neutral atoms) increased to 250 -400 μsec. This decay rate was faster than that due to charge exchange at the background gas pressure of 3 x 10-7 Torr, indicating a large transient influx of gas from the walls of the chamber. Later experiments on higher density plasma (n ∼ 1013 cm-3, ϵ ∼ 5 keV) have confirmed these results. In these the fast atom flux lasted 140-200 μsec in both simple mirror and complex fields. The signal due to charge exchange emission peaked about 30 μsec after the instant of trapping. This signal measures the product of the fast ion and neutral gas densities. A deliberate increase of background pressure up to 10-5 Torr made little difference in the amplitude of the signal. Attempts to change the influx of gas by baking the chamber and evaporating lithium were unsuccessful, but the lithium coating showed signs of severe bombardment along the cusp lines between the Ioffe bars. A compensated diamagnetic loop placed inside the vacuum chamber showed that the value of β for the trapped plasma was at least 0.1; the diamagnetism fell sharply within 50 usee, confirming that the longer-lasting neutral atom signal must be due largely to the influx of neutral gas. (author)
International Nuclear Information System (INIS)
The present study determines the feasibility of generating an average arterial input function (Avg-AIF) from a limited population of patients with neck nodal metastases to be used for pharmacokinetic modeling of dynamic contrast-enhanced MRI (DCE-MRI) data in clinical trials of larger populations. Twenty patients (mean age 50 years [range 27–77 years]) with neck nodal metastases underwent pretreatment DCE-MRI studies with a temporal resolution of 3.75 to 7.5 sec on a 1.5T clinical MRI scanner. Eleven individual AIFs (Ind-AIFs) met the criteria of expected enhancement pattern and were used to generate Avg-AIF. Tofts model was used to calculate pharmacokinetic DCE-MRI parameters. Bland-Altman plots and paired Student t-tests were used to describe significant differences between the pharmacokinetic parameters obtained from individual and average AIFs. Ind-AIFs obtained from eleven patients were used to calculate the Avg-AIF. No overall significant difference (bias) was observed for the transfer constant (Ktrans) measured with Ind-AIFs compared to Avg-AIF (p = 0.20 for region-of-interest (ROI) analysis and p = 0.18 for histogram median analysis). Similarly, no overall significant difference was observed for interstitial fluid space volume fraction (ve) measured with Ind-AIFs compared to Avg-AIF (p = 0.48 for ROI analysis and p = 0.93 for histogram median analysis). However, the Bland-Altman plot suggests that as Ktrans increases, the Ind-AIF estimates tend to become proportionally higher than the Avg-AIF estimates. We found no statistically significant overall bias in Ktrans or ve estimates derived from Avg-AIF, generated from a limited population, as compared with Ind-AIFs. However, further study is needed to determine whether calibration is needed across the range of Ktrans. The Avg-AIF obtained from a limited population may be used for pharmacokinetic modeling of DCE-MRI data in larger population studies with neck nodal metastases. Further validation of the Avg
International Nuclear Information System (INIS)
It is observed that the recently developed magnetic flux-averaged magnetohydrodynamics (AMHD) [Phys. Plasmas 1, 2488 (1994)] is incompatible with Taylor close-quote s theorem, which states that the lowest-energy state of force-free equilibria based on the conservation of the helicity integral is absolutely stable for vanishingly small resistivity. By a modification of the Lagrangian from which AMHD is derived, a modified version of AMHD that is compatible with Taylor close-quote s theorem is obtained. It also provides an energy principle for examining the linear instability of resistive equilibria, which has a great advantage over resistive MHD. copyright 1996 American Institute of Physics
International Nuclear Information System (INIS)
Combining with the 1H and 13C nuclear magnetic resonance (NMR) determinations, elemental analysis and molecular weight measurement, average molecular formula of the chemical unit for the asphaltenes from Chinese Daqing crude oil were calculated. Thermal pyrolysis kinetics of the asphaltenes had been studied using thermogravimetric analysis (TGA). The distributed activation energy model (DAEM) was used to analyze these complex systems. The results show that the peak activation energy for pyrolysis of the asphaltenes is 245 kJ mol-1 and the pre-exponential factor is 5.88 x 1014 s-1. The DAEM method presented reasonably good results of the prediction of the weight loss curves. A linear relationship can be found from the plots of logarithm of the pre-exponential factor against the activation energy at selected conversion values. This phenomenon known as the compensation effect was explained and it was in agreement with the estimated chemical structure determined by NMR
George Chacko; Sanjiv Ranjan Das
1997-01-01
We develop analytic pricing models for options on averages by means of a state-space expansion method. These models augment the class of Asian options to markets where the underlying traded variable follows a mean-reverting process. The approach builds from the digital Asian option on the average and enables pricing of standard Asian calls and puts, caps and floors, as well as other exotica. The models may be used (i) to hedge long period interest rate risk cheaply, (ii) to hedge event risk (...
Magnetic oscillation of luminescence energy in modulation-doped quantum wells
Katayama, S.; Ando, T.
1989-04-01
Photoluminescence energy in strong magnetic fields is explored theoretically by taking into account many-body electron-electron and electron-hole interactions in modulation-doped GaAs/AlGaAs quantum wells. With use of the plasmon-pole approximation for dielectric function, we find the clear magnetic oscillation of the self-energy of a photo-excited hole in the lowest Landau level. The corresponding shift for electrons is nearly independent of the magnetic field. The calculation explains well the oscillatory behavior of luminescence energy observed experimentally.
Directory of Open Access Journals (Sweden)
R. P. Lepping
2008-01-01
Full Text Available We investigate the ability of the cylindrically symmetric force-free magnetic cloud (MC fitting model of Lepping et al. (1990 to faithfully reproduce actual magnetic field observations by examining two quantities: (1 a difference angle, called β, i.e., the angle between the direction of the observed magnetic field (B_{obs} and the derived force free model field (B_{mod} and (2 the difference in magnitudes between the observed and modeled fields, i.e., ΔB(=|B_{obs}|−|B_{mod}|, and a normalized ΔB (i.e., ΔB/<B> is also examined, all for a judiciously chosen set of 50 WIND interplanetary MCs, based on quality considerations. These three quantities are developed as a percent of MC duration and averaged over this set of MCs to obtain average profiles. It is found that, although <ΔB> and its normalize version are significantly enhanced (from a broad central average value early in an average MC (and to a lesser extent also late in the MC, the angle <β> is small (less than 8° and approximately constant all throughout the MC. The field intensity enhancements are due mainly to interaction of the MC with the surrounding solar wind plasma causing field compression at front and rear. For example, for a typical MC, ΔB/<B> is: 0.21±0.27 very early in the MC, −0.11±0.10 at the center (and −0.085±0.12 averaged over the full "central region," i.e., for 30% to 80% of duration, and 0.05±0.29 very late in the MC, showing a double sign change as we travel from front to center to back, in the MC. When individual MCs are examined we find that over 80% of them possess field enhancements within several to many hours of the front boundary, but only about 30% show such enhancements at their rear portions. The enhancement of the MC's front field is also due to MC expansion, but this is usually a lesser effect
Excitonic spin-splitting in quantum wells with a tilted magnetic field
International Nuclear Information System (INIS)
This work aims to investigate the effects of magnetic field strength and direction on the electronic properties and optical response of GaAs/AlGaAs-based heterostructures. An investigation of the excitonic spin-splitting of a disordered multiple quantum well embedded in a wide parabolic quantum well is presented. The results for polarization-resolved photoluminescence show that the magnetic field dependencies of the excitonic spin-splitting and photoluminescence linewidth are crucially sensitive to magnetic field orientation. Our experimental results are in good agreement with the calculated Zeeman splitting obtained by the Luttinger model, which predicts a hybridization of the spin character of states in the valence band under tilted magnetic fields. (paper)
Quantum-well states and induced magnetism in Fe/CuN/Fe bcc (001) trilayers
DEFF Research Database (Denmark)
Niklasson, A.M.N.; Mirbt, S.; Skriver, Hans Lomholt;
1996-01-01
profiles of two single Fe/Cu interfaces. The small deviations from this simple superposition are shown to be a consequence of quantum-well states confined within the paramagnetic spacer. This connection is confirmed by direct calculation of the state density. The results are of conceptual interest for the......We have used a first-principles Green's function technique to investigate the formation of magnetic moments in Fe/Cu-N/Fe bcc (001) trilayers. We show that the magnetic moment in the paramagnetic spacer material to a first approximation may be described as a linear superposition of the magnetic...
Energy Technology Data Exchange (ETDEWEB)
Kayanuma, K. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan); Seo, K. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan); Nishibayashi, K. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan); Murayama, A. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan); Oka, Y. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan)]. E-mail: oka@tagen.tohoku.ac.jp; Buyanova, I.A. [Department of Physics and Measurement Technology, Linkoeping University, 58183 Linkoeping (Sweden); Chen, W.M. [Department of Physics and Measurement Technology, Linkoeping University, 58183 Linkoeping (Sweden)
2006-07-15
Dynamics of spin injection has been studied in double quantum wells (DQWs) composed of diluted magnetic and non-magnetic semiconductors. Picosecond-transient photoluminescence (PL) of excitons in the DQWs has been measured in magnetic field. In the Cd{sub 1-} {sub x} Mn {sub x} Te-based DQWs, the PL intensity of the magnetic well (MW) excitons decays faster with decreasing barrier width from 12 to 2 nm. This provides the evidence for carrier tunneling from the MW to the non-magnetic well (NW) through the barrier layer. The degree of circular polarization in the transient PL of the NW exciton in magnetic field shows marked evidence for spin injection and rapid spin relaxation in the DQW system. In the Zn{sub 1-} {sub y} Mn {sub y} Se-based DQWs, the degree of circle polarization in the NW exciton PL at 3 T shows a rise with a time constant of 400 ps, while the PL of the MW exciton decays within 50 ps. The observed result is interpreted by the individual spin injection for electrons and holes from the MW to the NW. The results of the transient PL of excitons in the DQWs are compared with the transient absorptions of excitons studied by the pump-and-probe spectroscopy.
Exciton magnetic polarons in Cd1-xMnxTe quantum wells
International Nuclear Information System (INIS)
We study the exciton magnetic polaron system in semimagnetic quantum wells. The exact numerical solution of a non-linear Wannier equation describing this system allow us to analyse its stability as a function of temperature, well width and band offset. We find a decrease in the polaron energy with increasing temperature and/or well width. The calculated polaron properties are in good agreement with recent experimental results. (author)
International Nuclear Information System (INIS)
An epi-thermal instrumental neutron activation analysis (EINAA) method in conjunction with Compton suppression spectrometry (EINAA-CSS) was used for the determination of total iodine in eight different species of edible seaweeds from Japan. This method gave an absolute detection limit of about 2 μg. The accuracy of the method was evaluated using various reference materials and found to be generally in agreement within ±6% of the certified values. The longitudinal distributions of iodine at different growing stages in Japanese sea mustard and tangle seaweeds were investigated. For a 150-cm-high tangle, the highest concentration (5,360 mg/kg) of iodine was found at the root, then decreased slowly to 780 mg/kg in the middle portion (60-75 cm), and increased to 2,300 mg/kg at the apex. On the other hand, for a 190-cm-high sea mustard the highest levels of iodine were found both at the roots (164 mg/kg) and apex (152 mg/kg) with lower values (98 mg/kg) in the middle section. In order to estimate the bioaccessible fraction of iodine, seaweeds were digested by an in vitro enzymolysis method, dietary fibre separated from residue, and both fractions analyzed by EINAA-CSS. The average daily dietary intakes of total (0.14 mg) as well as bioaccessible fraction (0.12 mg) of iodine from the consumption of sea mustards were estimated. (author)
Strain and localization effects in InGaAs(N) quantum wells: Tuning the magnetic response
Energy Technology Data Exchange (ETDEWEB)
Lopes-Oliveira, V., E-mail: lopes@df.ufscar.br; Herval, L. K. S.; Orsi Gordo, V.; Cesar, D. F.; Godoy, M. P. F. de; Galvão Gobato, Y. [Departamento de Física, Universidade Federal de São Carlos, 13565-905, São Carlos, São Paulo (Brazil); Henini, M. [School of Physics and Astronomy, Nottingham Nanotechnology and Nanoscience Centre, University of Nottingham, NG7 2RD Nottingham (United Kingdom); Khatab, A. [School of Physics and Astronomy, Nottingham Nanotechnology and Nanoscience Centre, University of Nottingham, NG7 2RD Nottingham (United Kingdom); National Institute of Laser Enhanced Sciences, Cairo University (Egypt); Sadeghi, M.; Wang, S. [Photonics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Goteborg (Sweden); Schmidbauer, M. [Leibniz-Institute for Crystal Growth, Max-Born-Str. 2, D-12489 Berlin (Germany)
2014-12-21
We investigated effects of localization and strain on the optical and magneto-optical properties of diluted nitrogen III–V quantum wells theoretically and experimentally. High-resolution x-ray diffraction, photoluminescence (PL), and magneto-PL measurements under high magnetic fields up to 15 T were performed at low temperatures. Bir-Pikus Hamiltonian formalism was used to study the influence of strain, confinement, and localization effects. The circularly polarized magneto-PL was interpreted considering localization aspects in the valence band ground state. An anomalous behavior of the electron-hole pair magnetic shift was observed at low magnetic fields, ascribed to the increase in the exciton reduced mass due to the negative effective mass of the valence band ground state.
Influence of magnetic well on electromagnetic turbulence in the TJ-II stellarator
Castejón, F.; de Aguilera, M.; Ascasíbar, E.; Estrada, T.; Hidalgo, C.; López-Fraguas, A.; Ochando, M. A.; Yamamoto, S.; Melnikov, A. V.; Eliseev, L. G.; Krupnik, L. I.; the HIBP Team; the TJ-II Team
2016-09-01
A magnetic well scan has been performed in the TJ-II stellarator to investigate the confinement properties with different values of the well, or even of the hill, and to explore the properties of electromagnetic turbulence. Stable plasmas have been obtained in theoretically Mercier-unstable configurations, and the electrostatic turbulence levels in the edge are increased. Three families of modes appear during the experiments: (1) a family of modes of Alfvénic nature with high frequencies; (2) a second set of modes of middle frequencies (tens of kHz) and (3) an oscillation at f ≈ 10–20 kHz happens in several cases. In spite of the fact that the vacuum rotational transform is very similar in all of the cases, the Alfvénic mode family changes drastically when decreasing the magnetic well, showing a non-monotonic behaviour of the amplitude, and a decrease of the typical frequencies. This behaviour cannot be explained only by current or density variations, so the effect of the modification of the configuration is playing a key role. Regarding the intermediate frequencies, a coherent mode appears with decreasing frequency as the magnetic well decreases. This mode is a candidate for a GAM, which can survive in these TJ-II plasmas, despite of the strong damping these modes should suffer in this device.
Magnetic Logs from the Lopra-1/1A and Vestmanna-1 wells (Faroe Islands)
DEFF Research Database (Denmark)
Waagstein, R.; Abrahamsen, N.
2006-01-01
Susceptibility results from cores (representing basalt, lapilli-tuffs and tuffs) and magnetic logs from the Lopra-1/1A well are presented. The basalts fall into a high- and a low-susceptibility group with no overlap. The high-susceptibility basalts (7 cores) have susceptibilities between 4 and 85...... high-susceptibility basalts. The susceptibility of 9 volcaniclastites of lapilli-tuff or tuff varies from 0.4 to 4 x 10-3 SI. The cores reveal a bimodal distribution of magnetic susceptibily in the Lopra well. Low susceptibilities ranging from 0.4 to 4 in the well are characteristic to both altered...... 2381 m and sidewall cores of basalt from the Lopra-1/1A well have a mean susceptibility of 22.1 ± 3.5 ´ 10-3 SI (σ = 23.6, N = 46), while samples of hyaloclastite (lapilli-tuff and tuff) have a mean susceptibility of 0.85 ´ 10-3 SI (σ = 0.39, N = 17). The mean values of the rock magnetic parameters for...
Harbert, W.; Hammack, R.; Veloski, G.; Hodge, G.
2011-12-01
In this study Airborne magnetic data was collected by Fugro Airborne Surveys from a helicopter platform (Figure 1) using the Midas II system over the 39 km2 NPR3 (Naval Petroleum Reserve No. 3) oilfield in east-central Wyoming. The Midas II system employs two Scintrex CS-2 cesium vapor magnetometers on opposite ends of a transversely mounted, 13.4-m long horizontal boom located amidships (Fig. 1). Each magnetic sensor had an in-flight sensitivity of 0.01 nT. Real time compensation of the magnetic data for magnetic noise induced by maneuvering of the aircraft was accomplished using two fluxgate magnetometers mounted just inboard of the cesium sensors. The total area surveyed was 40.5 km2 (NPR3) near Casper, Wyoming. The purpose of the survey was to accurately locate wells that had been drilled there during more than 90 years of continuous oilfield operation. The survey was conducted at low altitude and with closely spaced flight lines to improve the detection of wells with weak magnetic response and to increase the resolution of closely spaced wells. The survey was in preparation for a planned CO2 flood to enhance oil recovery, which requires a complete well inventory with accurate locations for all existing wells. The magnetic survey was intended to locate wells that are missing from the well database and to provide accurate locations for all wells. The well location method used combined an input dataset (for example, leveled total magnetic field reduced to the pole), combined with first and second horizontal spatial derivatives of this input dataset, which were then analyzed using focal statistics and finally combined using a fuzzy combination operation. Analytic signal and the Shi and Butt (2004) ZS attribute were also analyzed using this algorithm. A parameter could be adjusted to determine sensitivity. Depending on the input dataset 88% to 100% of the wells were located, with typical values being 95% to 99% for the NPR3 field site.
International Nuclear Information System (INIS)
The present study quantified the volume-averaged in situ electric field in nerve tissues of anatomically based numeric Japanese male and female models for exposure to extremely low-frequency electric and magnetic fields. A quasi-static finite-difference time-domain method was applied to analyze this problem. The motivation of our investigation is that the dependence of the electric field induced in nerve tissue on the averaging volume/distance is not clear, while a cubical volume of 5 x 5 x 5 mm3 or a straight-line segment of 5 mm is suggested in some documents. The influence of non-nerve tissue surrounding nerve tissue is also discussed by considering three algorithms for calculating the averaged in situ electric field in nerve tissue. The computational results obtained herein reveal that the volume-averaged electric field in the nerve tissue decreases with the averaging volume. In addition, the 99th percentile value of the volume-averaged in situ electric field in nerve tissue is more stable than that of the maximal value for different averaging volume. When including non-nerve tissue surrounding nerve tissue in the averaging volume, the resultant in situ electric fields were not so dependent on the averaging volume as compared to the case excluding non-nerve tissue. In situ electric fields averaged over a distance of 5 mm were comparable or larger than that for a 5 x 5 x 5 mm3 cube depending on the algorithm, nerve tissue considered and exposure scenarios. (note)
Energy Technology Data Exchange (ETDEWEB)
Kassianov, Evgueni I.; Barnard, James C.; Flynn, Connor J.; Riihimaki, Laura D.; Marinovici, Maria C.
2015-10-15
Areal-averaged albedos are particularly difficult to measure in coastal regions, because the surface is not homogenous, consisting of a sharp demarcation between land and water. With this difficulty in mind, we evaluate a simple retrieval of areal-averaged surface albedo using ground-based measurements of atmospheric transmission alone under fully overcast conditions. To illustrate the performance of our retrieval, we find the areal-averaged albedo using measurements from the Multi-Filter Rotating Shadowband Radiometer (MFRSR) at five wavelengths (415, 500, 615, 673, and 870 nm). These MFRSR data are collected at a coastal site in Graciosa Island, Azores supported by the U.S. Department of Energy’s (DOE’s) Atmospheric Radiation Measurement (ARM) Program. The areal-averaged albedos obtained from the MFRSR are compared with collocated and coincident Moderate Resolution Imaging Spectroradiometer (MODIS) white-sky albedo at four nominal wavelengths (470, 560, 670 and 860 nm). These comparisons are made during a 19-month period (June 2009 - December 2010). We also calculate composite-based spectral values of surface albedo by a weighted-average approach using estimated fractions of major surface types observed in an area surrounding this coastal site. Taken as a whole, these three methods of finding albedo show spectral and temporal similarities, and suggest that our simple, transmission-based technique holds promise, but with estimated errors of about ±0.03. Additional work is needed to reduce this uncertainty in areas with inhomogeneous surfaces.
Magnetic control of Rashba splittings in symmetric InAs quantum wells
Matsuura, Toru; Faniel, Sébastien; Monta, Nozomu; Koga, Takaaki
2010-09-01
We propose a mechanism to control the Rashba-induced subband splitting by a magnetic field using a symmetric double quantum well (QW) system, where the lowest two subbands are coupled by a position-dependent Rashba parameter α(z). In such a system, all subbands are spin degenerate due to the time reversal symmetry and the spatial inversion symmetry at zero magnetic field, despite the presence of the Rashba spin-orbit interaction. Applying an external magnetic field parallel to the QW plane ( B∥y^) lifts this spin degeneracy breaking the time reversal symmetry, where the spin splitting energies are controllable in the range between zero and 2.9 meV, the latter being on the same order of magnitude as a typical Rashba splitting in a narrow asymmetric QW. We find that the first and second subband energy levels for a selected spin state with k∥=(kF,0,0) anticross each other, and that the energy of the subband splitting Δ0, equivalent to the Rashba splitting for the case of single QWs, can be determined from the value of the anticrossing magnetic field Bac. These results suggest that the investigation in the symmetric double QWs would provide useful approaches for quantitative understanding of the Rashba spin-orbit interaction.
AC transport in p-Ge/GeSi quantum well in high magnetic fields
Energy Technology Data Exchange (ETDEWEB)
Drichko, I. L.; Malysh, V. A.; Smirnov, I. Yu.; Golub, L. E.; Tarasenko, S. A. [A.F. Ioffe Physical Technical Institute of Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); Suslov, A. V. [National High Magnetic Field Laboratory, Tallahassee, FL 32310 (United States); Mironov, O. A. [Warwick SEMINANO R and D Center, University of Warwick Science Park, Coventry CV4 7EZ (United Kingdom); Kummer, M.; Känel, H. von [Laboratorium für Festkörperphysik ETH Zürich, CH-8093 Zürich (Switzerland)
2014-08-20
The contactless surface acoustic wave technique is implemented to probe the high-frequency conductivity of a high-mobility p-Ge/GeSi quantum well structure in the regime of integer quantum Hall effect (IQHE) at temperatures 0.3–5.8 K and magnetic fields up to 18 T. It is shown that, in the IQHE regime at the minima of conductivity, holes are localized and ac conductivity is of hopping nature and can be described within the “two-site” model. The analysis of the temperature and magnetic-field-orientation dependence of the ac conductivity at odd filing factors enables us to determine the effective hole g-factor, |g{sub zz}|≈4.5. It is shown that the in-plane component of the magnetic field leads to a decrease in the g-factor as well as increase in the cyclotron mass, which is explained by orbital effects in the complex valence band of germanium.
Markley, F. Landis; Cheng, Yang; Crassidis, John L.; Oshman, Yaakov
2007-01-01
Many applications require an algorithm that averages quaternions in an optimal manner. For example, when combining the quaternion outputs of multiple star trackers having this output capability, it is desirable to properly average the quaternions without recomputing the attitude from the the raw star tracker data. Other applications requiring some sort of optimal quaternion averaging include particle filtering and multiple-model adaptive estimation, where weighted quaternions are used to determine the quaternion estimate. For spacecraft attitude estimation applications, derives an optimal averaging scheme to compute the average of a set of weighted attitude matrices using the singular value decomposition method. Focusing on a 4-dimensional quaternion Gaussian distribution on the unit hypersphere, provides an approach to computing the average quaternion by minimizing a quaternion cost function that is equivalent to the attitude matrix cost function Motivated by and extending its results, this Note derives an algorithm that deterniines an optimal average quaternion from a set of scalar- or matrix-weighted quaternions. Rirthermore, a sufficient condition for the uniqueness of the average quaternion, and the equivalence of the mininiization problem, stated herein, to maximum likelihood estimation, are shown.
Transverse magnetic focussing of heavy holes in a (100) GaAs quantum well
International Nuclear Information System (INIS)
We perform magnetic focussing of high mobility holes confined in a shallow GaAs/Al0.33Ga0.67As quantum well grown on a (100) GaAs substrate. We observe ballistic focussing of holes over a path length of up to 4.9 μm with a large number of focussing peaks. We show that additional structure on the focussing peaks can be caused by a combination of the finite width of the injector quantum point contact and Shubnikov–de Haas oscillations. These results pave the way to studies of spin-dependent magnetic focussing and spin relaxation lengths in two-dimentional hole systems without complications of crystal anisotropies and anisotropic g-tensors. (fast track communication)
Institute of Scientific and Technical Information of China (English)
E. Kasapoglu; H. Sari; I. S(o)kmen
2004-01-01
@@ We have calculated variationally the ground state binding energy of a hydrogenic donor impurity in a parabolic quantum well in the presence of crossed electric and magnetic fields. These homogeneous crossed fields are such that the magnetic field is parallel to the heterostructure layers and the electric field is applied perpendicular to the magnetic field. The dependence of the donor impurity binding energy to the well width and the strength of the electric and magnetic fields are discussed. We hope that the obtained results will provide important improvements in device applications, especially for a suitable choice of both fields in the narrow well widths.
Institute of Scientific and Technical Information of China (English)
CHEN Chao; XIA Jianghai; XIA Sihao; David Laflen; Stephen L. Williams
2004-01-01
After successfully locating one abandoned brine well by an electromagnetic method during testing in 2001 and five abandoned brine wells by a high-resolution magnetic method during 2002, a high-resolution magnetic method was again proposed to search for wells in 2003 when a second sensor was employed to acquire data for calculating the pseudo-vertical gradient of magnetic fields. Total area surveyed in 2003 was 1,024,000 ft2, which was divided into grids with an average size of 10,000 ft2 and distributed across eight different sites. Magnetic anomalies and their vertical gradients from known brine wells were first recorded as signatures to identify anomalies caused by possible buried brine wells. Of fifty-one verified anomalies, thirtyone anomalies were due to wells buried at depths from 0 to 8.5 ft: twenty-one 6- to 9-inch abandoned brine wells, seven 1.5- to 3-inch probable water wells, one 16-inch dewatering well for a construction site at a depth of 3 ft, and two 4-inch wells on the ground surface. Approximate monopole shaped anomalies were observed from all these wells after data corrections. However, the range of amplitudes of magnetic anomalies from 7,000 to 28,000 nT from these abandoned brine wells was measured. This range of anomalies is mainly due to the thickness and depth of buried wells. Anomaly amplitudes from 1.5- to 3-inch wells are 4,000 to 8,000 nT and linearly correlate with the buried depth. One 3-inch well that caused an anomaly of 13,000 nT could be the inner pipe of a brine well. Gradient anomalies are roughly in a range of 100 to 200 nT/inch for 1.5-to 3-inch wells and 200 to 300 nT/inch for brine wells.As indicated by the potential-field theory, gradient data possess higher horizontal resolution than the magnetic field itself. Gradient data provide valuable assistance in determining horizontal locations of anomaly sources for excavation. In practice, however, improvement in the horizontal resolution is limited by surveyline spacing. If only
Can Hall drag be observed in Coulomb coupled quantum wells in a magnetic field?
DEFF Research Database (Denmark)
Hu, Ben Yu-Kuang
We study the transresistivity rho(21) (or equivalently, the drag rate) of two Coulomb-coupled quantum wells in the presence of a perpendicular magnetic field, using semi-classical transport theory. Elementary arguments seem to preclude any possibility of observation of ''Hall drag'' (i.e., a non......-zero off-diagonal component in rho(21)). We show that these arguments are specious, and in fact Hall drag can be observed at sufficiently high temperatures when the intralayer transport time tau has significant energy-dependence around the Fermi energy epsilon(F). The ratio of the Hall to longitudinal...
Luminescence of double quantum wells subject to in-plane magnetic fields
Orlita, M.; Grill, R.; Hlídek, P.; Zvára, M.; Döhler, G. H.; Malzer, S.; Byszewski, M.
2005-10-01
We report on photoluminescence (PL) measurements of a symmetric GaAs/AlGaAs double quantum well (DQW) in high magnetic fields. For this study, a selectively contacted p-δn-DQW-δn-p structure was chosen, allowing an independent tuning of the electron density in the DQW and thus a creation of a two-dimensional electron gas. Our attention was focused on phenomena in in-plane magnetic fields, where the field-induced depopulation of the antibonding subband observable in the PL spectra as a so-called N -type kink was predicted by Huang and Lyo (HL) [Phys. Rev. B 59, 7600 (1999)]. Whereas the equivalent behavior has been observed several times in the electric transport measurements and a proper theoretical description has been found, to the best of our knowledge, no PL experiment in a direct comparison with the theoretical model developed by HL has ever been published. We carried out a self-consistent calculation based on their model and achieved a good agreement with our experimental results. Additionally, the influence of the excitonic interaction on the PL spectra, not taken into account by HL, is also discussed. This enables us to explain small deviations from the HL theory. The interpretation of the in-plane magnetic field measurements is supported by the experiment with the magnetic field in the perpendicular orientation that allows a sufficiently accurate estimation of the electron density in the DQW. Distinctive renormalization effects of DQW subbands at various electron densities are also observed and discussed.
Effect of the magnetic field on optical properties of GaN/AlN multiple quantum wells
Energy Technology Data Exchange (ETDEWEB)
Solaimani, M.; Izadifard, Morteza [Faculty of Physics, Shahrood University of Technology, Shahrood (Iran, Islamic Republic of); Arabshahi, H., E-mail: arabshahi@um.ac.ir [Physics Department, Payame Noor University, Tehran (Iran, Islamic Republic of); Mohammad Reza, Sarkardei [Physics Department, Al-Zahra University, Vanak, Tehran (Iran, Islamic Republic of)
2013-02-15
In this paper, the effect of the magnetic field and well number on the optical properties of a GaN/AlN MQWs with different number of wells and the energy levels have been investigated. Our results showed that as the magnetic field increases the values of the absorption coefficient also increases while a blue shift in their peak positions is observed. The blue shift for MQWs with odd well number was larger than the system with the even well number and the biggest blue shifts were related to MQWs with three and four well numbers. As the magnetic field changed, the values of the refractive index changes have shifted towards higher energies. Finally, the effect of the magnetic field on the oscillator strength showed that as the magnetic field increases the oscillator strength decreases and it is also proportional to the number of wells. - Highlights: Black-Right-Pointing-Pointer Increase of absorption coefficient by increase of magnetic field will show a blue shift. Black-Right-Pointing-Pointer As the magnetic field increased the oscillator strength decreased. Black-Right-Pointing-Pointer Total effective intersubband oscillator strength was proportional to the number of wells. Black-Right-Pointing-Pointer Minibands form after 10 wells, thus our results are valid for systems with well width up to 3 nm.
Heuvel, Willem Van den; Soncini, Alessandro
2015-01-01
We present an ab initio methodology dedicated to the determination of the electronic structure and magnetic properties of ground and low-lying excited states, i.e., the crystal field levels, in lanthanide(III) complexes. Currently, the most popular and successful ab initio approach is the CASSCF/RASSI-SO method, consisting of the optimization of multiple complete active space self-consistent field (CASSCF) spin eigenfunctions, followed by full diagonalization of the spin--orbit coupling (SOC) Hamiltonian in the basis of the CASSCF spin states featuring spin-dependent orbitals. Based on two simple observations valid for Ln(III) complexes, namely: (i) CASSCF 4f atomic orbitals are expected to change very little when optimized for different multiconfigurational states belonging to the 4f-electronic configuration, (ii) due to strong SOC the total spin is not a good quantum number, we propose here an efficient ab initio strategy which completely avoids any multiconfigurational calculation, by optimizing a unique s...
International Nuclear Information System (INIS)
A reformulation of the Discrete Energy-Averaged model for the calculation of 3D hysteretic magnetization and magnetostriction of iron-gallium (Galfenol) alloys is presented in this paper. An analytical solution procedure based on an eigenvalue decomposition is developed. This procedure avoids the singularities present in the existing approximate solution by offering multiple local minimum energy directions for each easy crystallographic direction. This improved robustness is crucial for use in finite element codes. Analytical simplifications of the 3D model to 2D and 1D applications are also presented. In particular, the 1D model requires calculation for only one easy direction, while all six easy directions must be considered for general applications. Compared to the approximate solution procedure, it is shown that the resulting robustness comes at no expense for 1D applications, but requires almost twice the computational effort for 3D applications. To find model parameters, we employ the average of the hysteretic data, rather than anhysteretic curves, which would require additional measurements. An efficient optimization routine is developed that retains the dimensionality of the prior art. The routine decouples the parameters into exclusive sets, some of which are found directly through a fast preprocessing step to improve accuracy and computational efficiency. The effectiveness of the model is verified by comparison with existing measurement data. - Highlights: • The discrete energy-averaged model for Galfenol is reformulated. • An analytical solution for 3D magnetostriction and magnetization is developed from eigenvalue decomposition. • Improved robustness is achieved. • An efficient optimization routine is developed to identify parameters from averaged hysteresis curves. • The effectiveness of the model is demonstrated against experimental data
Yang, Huihui; Liu, Qiang; Masse, Sylvie; Zhang, Hao; Li, Laifeng; ,; Coradin, Thibaud
2015-01-01
Novel hierarchically-organized magnetic microspheres have been successfully developed that consist of an aqueous hollow core, a magnetic porous Fe3O4-carbon layer and a well-define hydroxyapatite (HAp) shell. The hollow magnetic carbon microspheres were prepared by ultrasonic spray pyrolysis and coated with HAp using a biomimetic approach. The resulting powders exhibit micro- and meso-porosity. The removal capacity of the composite spheres towards an antibiotic (ampicilin), a rare-earth ion (...
Sub-ns electrical spin control in a diluted magnetic semiconductor quantum well
International Nuclear Information System (INIS)
To gain control over the spin degree of freedom is a key issue in semiconductor spintronics. We present an approach to electrically control spins on a sub-ns time scale and on a micrometer length scale in a diluted magnetic semiconductor quantum well (DMS QW). Microscale Au coils are defined atop a CdMnTe/CdMgTe DMS QW and by introducing a short current pulse through the coil, a local magnetic field can be generated enabling an electrical control of Mn2+ spin dynamics in the DMS QW. Due to the strong sp-d exchange interaction, the Mn2+ spin dynamics can be effectively probed by means of time- and polarization-resolved micro-photoluminescence measurements. Thanks to our high time-resolution, we are able to clearly separate the field induced spin alignment and the Mn2+ spin heating process. At zero external field the Mn2+ spin polarization can be switched on a time-scale of several hundred picoseconds, i.e. clearly below typical time scales expected for spin-lattice relaxation. Applying an external field of 100 mT, an additional slow component appears with typical time constants in the few 100 ns regime.
Wang, Ranran; Hu, Yang; Zhao, Nana; Xu, Fu-Jian
2016-05-11
Due to their unique properties, one-dimensional (1D) magnetic nanostructures are of great significance for biorelated applications. A facile and straightforward strategy to fabricate 1D magnetic structure with special shapes is highly desirable. In this work, well-defined peapod-like 1D magnetic nanoparticles (Fe3O4@SiO2, p-FS) are readily synthesized by a facile method without assistance of any templates, magnetic string or magnetic field. There are few reports on 1D gene carriers based on Fe3O4 nanoparticles. BUCT-PGEA (ethanolamine-functionalized poly(glycidyl methacrylate) is subsequently grafted from the surface of p-FS nanoparticles by atom transfer radical polymerization to construct highly efficient gene vectors (p-FS-PGEA) for effective biomedical applications. Peapod-like p-FS nanoparticles were proven to largely improve gene transfection performance compared with ordinary spherical Fe3O4@SiO2 nanoparticles (s-FS). External magnetic field was also utilized to further enhance the transfection efficiency. Moreover, the as-prepared p-FS-PGEA gene carriers could combine the magnetic characteristics of p-FS to well achieve noninvasive magnetic resonance imaging (MRI). We show here novel and multifunctional magnetic nanostructures fabricated for biomedical applications that realized efficient gene delivery and real-time imaging at the same time. PMID:27100466
Energy Technology Data Exchange (ETDEWEB)
Babanli, Arif M. [Azerbaijan National Academy of Sciences, Baku (Azerbaijan). Inst. of Physics; Sueleyman Demirel Univ., Isparta (Turkey). Dept. of Physics; Artunc, Ekrem [Sueleyman Demirel Univ., Isparta (Turkey). Dept. of Physics; Kasalak, Turgut F. [Akdeniz Univ., Antalya (Turkey). Dept. of Informatics
2015-07-01
We have studied the Rashba spin-orbital effect on a diluted magnetic semiconductor (DMS) quantum well with parabolic potential in the presence of a magnetic field parallel to the z axis, taking into account the Zeeman coupling and the s-d exchange interaction between the carriers and the magnetic ions. We have obtained an analytical expression for the electron energy spectrum, which depends on the magnetic ion concentration, temperature, and strength of magnetic field. By using the obtained energy spectrum, we calculated the electron effective g{sup *}-factor. We have found that effective g{sup *}-factor increases when the magnetic field increases; by increasing the strength of spin-orbit interaction, the electron g{sup *}-factor decreases and by increasing the temperature, the electron g{sup *}-factor increases.
Energy Technology Data Exchange (ETDEWEB)
Restrepo, R.L., E-mail: pfrire@eia.edu.co [Department of Physics, Cumhuriyet University, 58140 Sivas (Turkey); Escuela de Ingeniería de Antioquia-EIA, Envigado (Colombia); Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia-UdeA, Calle 70 No. 52-21, Medellín (Colombia); Ungan, F.; Kasapoglu, E. [Department of Physics, Cumhuriyet University, 58140 Sivas (Turkey); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autonóma del Estado de Morelos, Ave. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Morales, A.L.; Duque, C.A. [Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia-UdeA, Calle 70 No. 52-21, Medellín (Colombia)
2015-01-15
This paper presents the results of the theoretical study of the effects of non-resonant intense laser field and electric and magnetic fields on the optical properties (the linear and third-order nonlinear refractive index and absorption coefficients) in an asymmetric quantum well. The electric field and intense laser field are applied along the growth direction of the asymmetric quantum well and the magnetic field is oriented perpendicularly. To calculate the energy and the wave functions of the electron in the asymmetric quantum well, the effective mass approximation and the method of envelope wave function are used. The asymmetric quantum well is constructed by using different aluminium concentrations in both right and left barriers. The confinement in the quantum well is changed drastically by either the effect of electric and magnetic fields or by the application of intense laser field. The optical properties are calculated using the compact density matrix approach. The results show that the effect of the intense laser field competes with the effects of the electric and magnetic fields. Consequently, peak position shifts to lower photon energies due to the effect of the intense laser field and it shifts to higher photon energies by the effects of electric and magnetic fields. In general, it is found that the concentration of aluminum, electric and magnetic fields and intense laser field are external agents that modify the optical responses in the asymmetric quantum well.
International Nuclear Information System (INIS)
This paper presents the results of the theoretical study of the effects of non-resonant intense laser field and electric and magnetic fields on the optical properties (the linear and third-order nonlinear refractive index and absorption coefficients) in an asymmetric quantum well. The electric field and intense laser field are applied along the growth direction of the asymmetric quantum well and the magnetic field is oriented perpendicularly. To calculate the energy and the wave functions of the electron in the asymmetric quantum well, the effective mass approximation and the method of envelope wave function are used. The asymmetric quantum well is constructed by using different aluminium concentrations in both right and left barriers. The confinement in the quantum well is changed drastically by either the effect of electric and magnetic fields or by the application of intense laser field. The optical properties are calculated using the compact density matrix approach. The results show that the effect of the intense laser field competes with the effects of the electric and magnetic fields. Consequently, peak position shifts to lower photon energies due to the effect of the intense laser field and it shifts to higher photon energies by the effects of electric and magnetic fields. In general, it is found that the concentration of aluminum, electric and magnetic fields and intense laser field are external agents that modify the optical responses in the asymmetric quantum well
Directory of Open Access Journals (Sweden)
M. Solaimani
2013-07-01
Full Text Available In this work, we have investigated the effect of an external magnetic field and, for the first time, number of wells with constant total effective length to study the degeneracy in electronic energy levels. We have used constant total effective length because it is technologically important. Then we have tried to remove the n-fold degeneracy of the n-well multiple quantum well by means of the external magnetic field but the two-fold degeneracy was remain and not removed. Finally, the effect of the external magnetic field on the number of bound states and the situation of unchanging absorption coefficient in a wide magnetic field interval are also investigated.
Energy Technology Data Exchange (ETDEWEB)
Nishibayashi, K. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan)]. E-mail: nishi@tagen.tohoku.ac.jp; Aoshima, I. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan); Souma, I. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan); Murayama, A. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan); Oka, Y. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan)
2006-07-15
Dynamics of spin injection has been investigated in a double quantum well (DQW) composed of a diluted magnetic semiconductor by the pump-probe transient absorption spectroscopy in magnetic field. The DQW consists of a non-magnetic well (NMW) of CdTe and a magnetic well (MW) of Cd{sub 0.92}Mn{sub 0.08}Te. The MW shows a transient absorption saturation in the exciton band for more than 200 ps after the optical pumping, while the exciton photoluminescence does not arise from the MW. In the NMW, the circular polarization degree of the transient absorption saturation shows an increase with increasing time. The results are interpreted by the individual tunneling of spin-polarized electrons and holes from the MW to the NMW with different tunneling times. Depolarization processes of the carrier spins in the MW and the NMW are also discussed.
Optical orientation of hole magnetic polarons in (Cd,Mn)Te/(Cd,Mn,Mg)Te quantum wells
Zhukov, E. A.; Kusrayev, Yu. G.; Kavokin, K. V.; Yakovlev, D. R.; Debus, J.; Schwan, A.; Akimov, I. A.; Karczewski, G.; Wojtowicz, T.; Kossut, J.; Bayer, M.
2016-06-01
The optically induced spin polarization in (Cd,Mn)Te/(Cd,Mn,Mg)Te diluted-magnetic-semiconductor quantum wells is investigated by means of picosecond pump-probe Kerr rotation. At 1.8 K temperature, additionally to the oscillatory signals from photoexcited electrons and manganese spins precessing about an external magnetic field, a surprisingly long-lived (up to 60 ns) nonoscillating spin polarization is detected. This polarization is related to optical orientation of equilibrium magnetic polarons involving resident holes. The suggested mechanism for the optical orientation of the equilibrium magnetic polarons indicates that the detected polaron dynamics originates from unexcited magnetic polarons. The polaron spin dynamics is controlled by the anisotropic spin structure of the heavy hole resulting in a freezing of the polaron magnetic moment in one of the two stable states oriented along the structure growth axis. Spin relaxation between these states is prohibited by a potential barrier, which depends on temperature and magnetic field. The magnetic polaron relaxation is accelerated with increasing temperature and in magnetic field.
Magnetic field interaction of exciton-polaritons in GaInAs quantum well-microcavities
Energy Technology Data Exchange (ETDEWEB)
Rahimi-Iman, Arash; Schneider, Christian; Fischer, Julian; Amthor, Matthias; Hoefling, Sven; Reitzenstein, Stephan; Kamp, Martin; Forchel, Alfred [Technische Physik, Universitaet Wuerzburg, D-97074 Wuerzburg (Germany)
2011-07-01
Polaritons formed by excitons and photons in strongly coupled quantum well (QW) semiconductor microcavities have initiated intensive studies of multiple particle physics in solids during the last decade. Bose-Einstein condensation of these quasi particles and the so-called polariton-lasing represent very interesting physical phenomena investigated in different material systems (Deng et al. 2002, Kasprzak et al. 2006). Since condensation is not feasible in ideal 2D systems, it only occurs in planar cavities if natural or artificial traps are provided. We have studied polariton emission from artificial traps in planar cavities in the presence of external magnetic fields up to 5 T, The work focuses on the interaction of the spin-resolved excitonic component of trapped polaritons due to the Zeeman effect. We report on trap-size dependent Zeeman splittings up to 100 {mu}eV and diamagnetic coefficients up to 0.025 meV/T{sup 2} of exciton-polaritons spatially confined by photonic quantum boxes in a planar single GaInAs QW-microcavity at 5 T. Providing a size variation of the traps ranging from 0.5 to 10 {mu}m on a wide detuning range, quantized polariton modes were observed under non-resonant optical pumping.
Demić, Aleksandar; Radovanović, Jelena; Milanović, Vitomir
2016-08-01
We present a method for modeling nonparabolicity effects (NPE) in quantum nanostructures in presence of external electric and magnetic field by using second order perturbation theory. The method is applied to analysis of quantum well structure and active region of a quantum cascade laser (QCL). This model will allow us to examine the influence of magnetic field on dipole matrix element in QCL structures, which will provide a better insight to how NPE can affect the gain of QCL structures.
A comparison between magnetic shear and flare shear in a well-observed M-class flare
Institute of Scientific and Technical Information of China (English)
Tuan-Hui Zhou; Hai-Sheng Ji
2009-01-01
We give an extensive multi-wavelength analysis of an eruptive M1.0/1N class solar flare, which occurred in the active region NOAA 10044 on 2002 July 26. Our empha-sis is on the relationship between magnetic shear and flare shear. Flare shear is defined as the angle formed between the line connecting the centroids of the two ribbons of the flare and the line perpendicular to the magnetic neutral line. The magnetic shear is computed from vector magnetograms observed at Big Bear Solar Observatory (BBSO), while the flare shear is computed from Transition Region and Coronal Explorer (TRACE) 1700A images. By a detailed comparison, we find that: 1) The magnetic shear and the flare shear of this event are basically consistent, as judged from the directions of the transverse mag-netic field and the line connecting the two ribbons' centroids. 2) During the period of the enhancement of magnetic shear, flare shear had a fast increase followed by a fluctuated decrease. 3) When the magnetic shear stopped its enhancement, the fluctuated decreasing behavior of the flare shear became very smooth. 4) Hard X-ray (HXR) spikes are well correlated with the unshearing peaks on the time profile of the rate of change of the flare shear. We give a discussion of the above phenomena.
International Nuclear Information System (INIS)
A procedure is proposed for precise scanning of the (Bperpendicular , Bparallel) plane between the magnetic field projections that are perpendicular and parallel to (quasi-)two-dimensional layers when measuring their longitudinal and Hall magnetoresistances. Investigations of a n-InxGa1-xAs/GaAs double quantum well (x ∼ 0.2) performed using this procedure make it possible to reveal a number of the features of the magnetoresistance, which appear due to a complex energy spectrum of the double quantum well in a parallel field, and to separate them from the structures associated with the magnetic breakdown. The trajectories representing the features of the magnetoresistance in the (Bperpendicular , Bparallel) plane are described by the semiclassical calculations of the quantization of the energy spectrum of the double quantum well under the action of the perpendicular field component. The structures appearing due to the magnetic breakdown are amplified with increasing the total magnetic field magnitude and, in the samples with low mobility, completely suppress the features caused by the motion of an electron with a constant pseudospin component. The peaks corresponding to the magnetic breakdown are split in a strong parallel field due to the spin splitting of the Landau levels. These splittings correspond to the effective Lande factor vertical bar g* vertical bar ∼ 3
Zhou, Y.; Yu, T.; Wu, M. W.
2013-06-01
We report an anomalous scaling of the D’yakonov-Perel’ spin relaxation with the momentum relaxation in semiconductor quantum wells under a strong magnetic field in the Voigt configuration. We focus on the case in which the external magnetic field is perpendicular to the spin-orbit-coupling-induced effective magnetic field and its magnitude is much larger than the latter one. It is found that the longitudinal spin relaxation time is proportional to the momentum relaxation time even in the strong-scattering limit, indicating that the D’yakonov-Perel’ spin relaxation demonstrates Elliott-Yafet-like behavior. Moreover, the transverse spin relaxation time is proportional (inversely proportional) to the momentum relaxation time in the strong- (weak-) scattering limit, both in the opposite trends against the well-established conventional D’yakonov-Perel’ spin relaxation behaviors. We further demonstrate that all the above anomalous scaling relations come from the unique form of the effective inhomogeneous broadening.
Iwamoto, D.; Sakuma, I.; Kitagawa, Y.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.
2012-10-01
In next step of fusion devices such as ITER, lifetime of plasma-facing materials (PFMs) is strongly affected by transient heat and particle loads during type I edge localized modes (ELMs) and disruption. To clarify damage characteristics of the PFMs, transient heat and particle loads have been simulated by using a plasma gun device. We have performed simulation experiments by using a magnetized coaxial plasma gun (MCPG) device at University of Hyogo. The line-averaged electron density measured by a He-Ne interferometer is 2x10^21 m-3 in a drift tube. The plasma velocity measured by a time of flight technique and ion Doppler spectrometer was 70 km/s, corresponding to the ion energy of 100 eV for helium. Thus, the ion flux density is 1.4x10^26 m-2s-1. On the other hand, the MCPG is connected to a target chamber for material irradiation experiments. It is important to measure plasma parameters in front of target materials in the target chamber. In particular, a vapor cloud layer in front of the target material produced by the pulsed plasma irradiation has to be characterized in order to understand surface damage of PFMs under ELM-like plasma bombardment. In the conference, preliminary results of application of the He-Ne laser interferometer for the above experiment will be shown.
International Nuclear Information System (INIS)
The purpose of this study was to investigate the feasibility of the autoregressive moving average (ARMA) model for quantification of cerebral blood flow (CBF) with dynamic susceptibility contrast-enhanced magnetic resonance imaging (DSC-MRI) in comparison with deconvolution analysis based on singular value decomposition (DA-SVD). Using computer simulations, we generated a time-dependent concentration of the contrast agent in the volume of interest (VOI) from the arterial input function (AIF) modeled as a gamma-variate function under various CBFs, cerebral blood volumes and signal-to-noise ratios (SNRs) for three different types of residue function (exponential, triangular, and box-shaped). We also considered the effects of delay and dispersion in AIF. The ARMA model and DA-SVD were used to estimate CBF values from the simulated concentration-time curves in the VOI and AIFs, and the estimated values were compared with the assumed values. We found that the CBF value estimated by the ARMA model was more sensitive to the SNR and the delay in AIF than that obtained by DA-SVD. Although the ARMA model considerably overestimated CBF at low SNRs, it estimated the CBF more accurately than did DA-SVD at high SNRs for the exponential or triangular residue function. We believe this study will contribute to an understanding of the usefulness and limitations of the ARMA model when applied to quantification of CBF with DSC-MRI. (author)
Detrapping of hot electrons from magnetic well under ECR heating with parallel HF power launching
International Nuclear Information System (INIS)
The population of hot electrons with the energy of about 100 keV is often generated in magnetic traps under plasma ECRH. The results of an experimental study of this phenomenon at the OGRA-4 facility (baseball-type trap) under a microwave power launch (36 GHz, 200 kW) along the magnetic field are given in this paper. The ECR at the fundamental frequency was used for heating. It has been found out that a hard x-ray radiation gets out mainly of the vacuum chamber wall to which the gyrotron radiation is directed. This confirms the dominant yield of hot electrons towards the microwave propagation. The x-ray radiation was correlated with the gyrotron operation, it instantaneously disappeared, when the gyrotron was switched off. (author) 6 refs., 4 figs
Interlayer Hall effect in double quantum wells subject to in-plane magnetic fields
Czech Academy of Sciences Publication Activity Database
Kolorenč, Jindřich; Smrčka, Ludvík; Středa, Pavel
2002-01-01
Roč. 66, č. 8 (2002), s. 085301-1 - 085301-7. ISSN 0163-1829 R&D Projects: GA ČR GA202/01/0754; GA ČR GA202/01/0764 Institutional research plan: CEZ:AV0Z1010914 Keywords : double-layer two-dimensional electron system * magnetotransport * Hall effect Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.327, year: 2002
Cyclotron resonance in InAs/AlSb quantum wells in magnetic fields up to 45 T
International Nuclear Information System (INIS)
Electron cyclotron resonance in InAs/AlSb heterostructures with quantum wells of various widths in pulsed magnetic fields up to 45 T are investigated. Our experimental cyclotron energies are in satisfactory agreement with the results of theoretical calculations performed using the eight-band kp Hamiltonian. The shift of the cyclotron resonance (CR) line, which corresponds to the transition from the lowest Landau level to the low magnetic-field region, is found upon varying the electron concentration due to the negative persistent photoconductivity effect. It is shown that the observed shift of the CR lines is associated with the finite width of the density of states at the Landau levels
Cyclotron resonance in InAs/AlSb quantum wells in magnetic fields up to 45 T
Energy Technology Data Exchange (ETDEWEB)
Spirin, K. E., E-mail: spirink@ipmras.ru; Krishtopenko, S. S. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Sadofyev, Yu. G. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Drachenko, O. [Laboratoire National des Champs Magn’etiques Intenses (France); Helm, M. [Forschungszentrum Dresden–Rossendorf, Dresden High-Magnetic-Field Laboratory and Institute of Ion-Beam Physics and Materials Research (Germany); Teppe, F.; Knap, W. [GIS-TERALAB Universite Montpellier II, Laboratoire Charles Coulomb UMR CNRS 5221 (L2C) (France); Gavrilenko, V. I. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)
2015-12-15
Electron cyclotron resonance in InAs/AlSb heterostructures with quantum wells of various widths in pulsed magnetic fields up to 45 T are investigated. Our experimental cyclotron energies are in satisfactory agreement with the results of theoretical calculations performed using the eight-band kp Hamiltonian. The shift of the cyclotron resonance (CR) line, which corresponds to the transition from the lowest Landau level to the low magnetic-field region, is found upon varying the electron concentration due to the negative persistent photoconductivity effect. It is shown that the observed shift of the CR lines is associated with the finite width of the density of states at the Landau levels.
Mayer, William; Kanter, Jesse; Vitkalov, Sergey; Bykov, Alexey
The effect of tilted magnetic fields on magnetotransport is studied in GaAs quantum wells with three populated subbands. In perpendicular fields magneto-intersubband oscillations (MISO) are observed. These oscillations obey the relation Δij = (Ei-Ej)=kx9Eωc, where Ei is the energy of the bottom of i-th subband and k is an integer. MISO are periodic in the inverse magnetic field and show three frequencies fij Δij. Due to E1,2pattern with the beat frequency fb = (f13-f23)/2 Δ12. With increasing tilt angle at small magnetic fields, x9EωcΔ12 ,the high frequency beating disappears leaving only HF-MISO with single frequency f =(f13 + f23)/2.It indicates a magnetic breakdown between the lower two subbands. Investigations of the 2D electron system in the regime of the magnetic breakdown are presented. This work was supported by the National Science Foundation (DMR 1104503), the Russian Foundation for Basic Research (Project No.14-02-01158) and the Ministry of Education and Science of the Russian Federation.
Goiriena-Goikoetxea, M.; García-Arribas, A.; Rouco, M.; Svalov, A. V.; Barandiaran, J. M.
2016-04-01
Permalloy disc structures in magnetic vortex state constitute a promising new type of magnetic nanoparticles for biomedical applications. They present high saturation magnetisation and lack of remanence, which ease the remote manipulation of the particles by magnetic fields and avoid the problem of agglomeration, respectively. Importantly, they are also endowed with the capability of low-frequency magneto-mechanical actuation. This effect has already been shown to produce cancer cell destruction using functionalized discs, about 1 μm in diameter, attached to the cell membrane. Here, Permalloy nanodiscs down to 60 nm in diameter are obtained by hole-mask colloidal lithography, which is proved to be a cost-effective method for the uniform patterning of large substrate areas, with a high production yield of nanostructures. The characterisation of the magnetic behaviour of the nanodiscs, complemented with micromagnetic simulations, confirms that they present a very well defined magnetic vortex configuration, unprecedented, to our knowledge, for nanostructures of this size prepared by a high-yield method. The successful detachment of the gold-covered nanodiscs from the substrate is also demonstrated by the use of sacrificial layers.
Enhanced current injection from a quantum well to a quantum dash in magnetic field
Paravicini-Bagliani, Gian L.; Liverini, Valeria; Valmorra, Federico; Scalari, Giacomo; Gramm, Fabian; Faist, Jérôme
2014-08-01
Resonant tunneling injection is a key ingredient in achieving population inversion in a putative quantum dot cascade laser. In a quantum dot based structure, such resonant current requires a matching of the wavefunction shape in k-space between the injector and the quantum dot. We show experimentally that the injection into an excited state of a dash structure can be enhanced tenfold by an in-plane magnetic field that shifts the injector distribution in k-space. These experiments, performed on resonant tunneling diode structures, show unambiguously resonant tunneling into an ensemble of InAs dashes grown between two AlInAs barrier layers. They also show that interface roughness scattering can enhance the tunneling current.
Magnetic Properties of Well-Aligned ZnO Nanorod Arrays Grown by a Simple Hydrothermal Reaction
2014-01-01
Well-aligned ZnO nanorod arrays with room temperature ferromagnetism were prepared on glass substrate through hydrothermal method. The as-prepared nanorod arrays were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), photoluminescence (PL) spectrum, and magnetization measurements. The XRD and SEM results indicated that the ZnO nanorods are with the wurtzite structure and exhibit preferential (002) orientation with c-axis perpen...
Directory of Open Access Journals (Sweden)
Demić Aleksandar
2016-01-01
Full Text Available We present a method for modeling nonparabolicity effects (NPE in quantum nanostructures by using second order perturbation theory. We will analyze application of this model on a quantum well without external electric field and a quantum cascade laser (QCL. This model will allow us to examine the influence of magnetic field on dipole matrix element in QCL structures which will give better insight how NPE can disrupt gain of QCL structures. [Projekat Ministarstva nauke Republike Srbije, br. III45010
Ion Cyclotron Instabilities and the Effect of Microwave Heating in the Phoenix II Magnetic Well
International Nuclear Information System (INIS)
In the PHOENIX II neutral-injection experiment the plasma density is limited by an instability associated with the ion gyrofrequency and its harmonics. The harmonic number increases with density, a given harmonic occurring over only a narrow range. The behaviour has been compared with an infinite-geometry theoretical treatment of the instability driven by the non-Maxwellian nature of the ion velocity distribution resonantly interacting with an electron plasma wave. This gives reasonable agreement with the experimental threshold densities but does not account for more detailed behaviour. A finite geometry treatment has been developed which takes into account the variation of magnetic field along the plasma and the finite length. This accounts for the variation of the instability amplitude with density and the detailed line splitting. Microwave heating at the electron gyrofrequency suppresses instabilities in the higher harmonics of the ion gyrofrequency but introduces an instability at the fundamental which persists over a wide range of density. These results are compared with the expectations of existing theory which suggests the hot electron version of the ion velocity space instability to be the most likely one present. Considerable ion-energy spreading and loss of plasma is associated with these instabilities. Direct measurements of the losses show that these are all accounted for by V‖/v⊥ diffusion, the radial loss being at least an order of magnitude lower. In the heated plasma the loss rate appears to be somewhat less but considerable energy spread nevertheless occurs. The central hot ion density is increased by a factor of two, apparently by additional plasma trapping. (author)
Donor impurity in nanotube with two GaAs/GaAlAs quantum wells: Magnetic field effects
International Nuclear Information System (INIS)
Micro-tubes containing two GaAs/GaAlAs quantum wells (QWs) in a section of the tube layer has been fabricated and optical properties of the embedded QWs has been studied. The ground state binding energy of an off-axis donor in a cylindrical nanotube, containing two GaAs/GaAlAs quantum wells (QWs) in the presence of a uniform magnetic field is calculated as a function of the donor location as well as the density of states. A trial function for describing the asymmetric electron charge distribution is taken as a product of the combination of 1s and 2px,y subband wave functions and an unknown function that depends only on electron-ion separation. We found that the increasing the magnetic field the increasing the binding energy while the impurity is located in the QW1, whereas the opposite occurs when the impurity is located in the QW2. Two peaks in the curves of the binding energy, as a function of the impurity position, are also found as well as in the density of impurity states.
Zitterbewegung of electrons in quantum wells and dots in the presence of an in-plane magnetic field.
Biswas, Tutul; Ghosh, Tarun Kanti
2012-05-01
We study the effect of an in-plane magnetic field on the zitterbewegung (ZB) of electrons in a semiconductor quantum well (QW) and in a quantum dot (QD) with the Rashba and Dresselhaus spin-orbit interactions (SOIs). We obtain a general expression of the time-evolution of the position vector and current of the electron in a semiconductor QW. The amplitude of the oscillatory motion is directly related to the Berry connection in momentum space. We find that in presence of the magnetic field the ZB in a QW does not vanish when the strengths of the Rashba and Dresselhaus SOIs are equal. The in-plane magnetic field helps to sustain the ZB in QWs even at a low value of k(0)d (where d is the width of the Gaussian wavepacket and k(0) is the initial wavevector). The trembling motion of an electron in a semiconductor QW with high Landé g-factor (e.g. InSb) is sustained over a long time, even at a low value of k(0)d. Further, we study the ZB of an electron in QDs within the two sub-band model numerically. The trembling motion persists in time even when the magnetic field is absent as well as when the strengths of the SOI are equal. The ZB in QDs is due to the superposition of oscillatory motions corresponding to all possible differences of the energy eigenvalues of the system. This is an another example of multi-frequency ZB phenomenon. PMID:22481374
Directory of Open Access Journals (Sweden)
Manvir S. Kushwaha
2012-09-01
Full Text Available The most fundamental approach to an understanding of electronic, optical, and transport phenomena which the condensed matter physics (of conventional as well as nonconventional systems offers is generally founded on two experiments: the inelastic electron scattering and the inelastic light scattering. This work embarks on providing a systematic framework for the theory of inelastic electron scattering and of inelastic light scattering from the electronic excitations in GaAs/Ga1−xAlxAs quantum wells. To this end, we start with the Kubo's correlation function to derive the generalized nonlocal, dynamic dielectric function, and the inverse dielectric function within the framework of Bohm-Pines’ random-phase approximation. This is followed by a thorough development of the theory of inelastic electron scattering and of inelastic light scattering. The methodological part is then subjected to the analytical diagnoses which allow us to sense the subtlety of the analytical results and the importance of their applications. The general analytical results, which know no bounds regarding, e.g., the subband occupancy, are then specified so as to make them applicable to practicality. After trying and testing the eigenfunctions, we compute the density of states, the Fermi energy, the full excitation spectrum made up of intrasubband and intersubband – single-particle and collective (plasmon – excitations, the loss functions for all the principal geometries envisioned for the inelastic electron scattering, and the Raman intensity, which provides a measure of the real transitions induced by the (laser probe, for the inelastic light scattering. It is found that the dominant contribution to both the loss peaks and the Raman peaks comes from the collective (plasmon excitations. As to the single-particle peaks, the analysis indicates a long-lasting lack of quantitative comparison between theory and experiments. It is inferred that the inelastic electron
Spin-orbit interaction in magnetic quantum well states of Ni/W(110)
Energy Technology Data Exchange (ETDEWEB)
Nuber, Andreas; Bentmann, Hendrik [Experimentelle Physik VII, Universitaet Wuerzburg (Germany); Reinert, Friedrich [Experimentelle Physik VII, Universitaet Wuerzburg (Germany); Karlsruhe Institute of Technology, 76021 Karlsruhe (Germany)
2011-07-01
Nickel is a model system for ferromagnetism with an exchange splitting of the minority and majority bulk band structure of approximately 0.3 eV. Growing thin films of Nickel on a W(110) substrate results in the formation of quantum well states (QWS) within the film. Due to the non-perfect confinement, the wave function of the QWS extend into the first monolayers of the tungsten substrate leading to an interaction with the large potential gradient of the W atoms. We present a high resolution ARUPS study of the electronic structure of thin Nickel films on W(110) which is influenced by the spin-orbit interaction mediated by the substrate and the exchange interaction of Nickel.
Allain, Hervé; Van Weelderen, Rob; Baudouy, Bertrand; Quintard, Michel; Prat, Marc; Soulaine, Cyprien
2013-01-01
In the field of applied superconductivity, there is a growing need to better understand heat transfers in superconducting accelerator magnets. Depending on the engineering point of view looked at, either 0-D, 1-D, 2D or 3D modeling may be needed. Because of the size of these magnets, alone or coupled together, it is yet, impossible to study this numerically for computational reasons alone without simplification in the description of the geometry and the physics. The main idea of this study...
Yakunin, M. V.; Arapov, Yu. G.; Neverov, V. N.; Podgornyh, S. M.; Shelushinina, N. G.; Harus, G. I.; Zvonkov, B. N.; Uskova, E. A.
Precise scanning of the (B⊥,B‖)-plane while measuring magnetoresistance of the n-InGaAs/GaAs double quantum well (DQW) reveals a number of peculiarities connected with intricate DQW energy spectrum, which are analyzed on the basis of quasiclassical calculations. Magnetic breakdown effects are also considered. Peaks due to the latter mechanism reveal spin-splittings (in spite of lower mobilities as compared with the traditional n-GaAs/AlGaAs DQWs) corresponding to an enhanced effective Lande g-factor.
International Nuclear Information System (INIS)
The principles of stochastic heating are recalled and an experimental measurement method is described. The basic idea of the method is to detect the thresholds of production for some highly charged ions which are linked to the electron energy. The measurements show that the energy increase versus electromagnetic power is given by ΔT = (ΔPsub(RF))sup(α) where α is close to unity. The experimental device is a magnetic well containing an ECR surface where the electron of a plasma are stochastically heated
Energy Technology Data Exchange (ETDEWEB)
Panahi, H., E-mail: t-panahi@guilan.ac.ir [Department of Physics, University of Guilan, 41335-1914 Rasht (Iran, Islamic Republic of); Golshahi, S. [Department of Physics, Rasht Branch, Islamic Azad University, Rasht (Iran, Islamic Republic of); Doostdar, M. [Department of Physics, University of Guilan, 41335-1914 Rasht (Iran, Islamic Republic of)
2013-06-01
In this paper we have calculated variationally the ground state binding energy of a hydrogenic donor impurity in square quantum well and V-shaped quantum well as a function of the well width in the presence of magnetic fields with both constant and position dependent effective mass. The wave function of electrons confined to donor impurity within the quantum well is considered as the two dimensional and three dimensional trial wave functions. It has been found that by increasing the well width, the binding energy decreases smoothly to bulk values while its steepness is sharper in square quantum well in comparison with V-shaped quantum well. Increasing the magnetic field leads to the enhancement of binding energy. At higher magnetic fields, by increasing the well width, binding energy tends to a constant value. The effect of position dependent effective mass on the enhancement of binding energy is more evident in comparison with constant effective mass one.
International Nuclear Information System (INIS)
In this paper we have calculated variationally the ground state binding energy of a hydrogenic donor impurity in square quantum well and V-shaped quantum well as a function of the well width in the presence of magnetic fields with both constant and position dependent effective mass. The wave function of electrons confined to donor impurity within the quantum well is considered as the two dimensional and three dimensional trial wave functions. It has been found that by increasing the well width, the binding energy decreases smoothly to bulk values while its steepness is sharper in square quantum well in comparison with V-shaped quantum well. Increasing the magnetic field leads to the enhancement of binding energy. At higher magnetic fields, by increasing the well width, binding energy tends to a constant value. The effect of position dependent effective mass on the enhancement of binding energy is more evident in comparison with constant effective mass one
Magnetic Properties of Well-Aligned ZnO Nanorod Arrays Grown by a Simple Hydrothermal Reaction
Directory of Open Access Journals (Sweden)
Jiangni Yun
2014-01-01
Full Text Available Well-aligned ZnO nanorod arrays with room temperature ferromagnetism were prepared on glass substrate through hydrothermal method. The as-prepared nanorod arrays were characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, energy dispersive spectroscopy (EDS, photoluminescence (PL spectrum, and magnetization measurements. The XRD and SEM results indicated that the ZnO nanorods are with the wurtzite structure and exhibit preferential (002 orientation with c-axis perpendicular to the substrate surface. The PL results suggested that the possible defect in the as-prepared ZnO nanorod arrays might be VZn, Oi, or OZn. The first-principles calculations reveal that the room temperature ferromagnetism may result from the VZn defects present in the ZnO nanorod and the hybridization of the Zn 3d states with O 2p states is responsible for the half-metallic ferromagnetism in ZnO nanorod.
The D- centre in a quantum well in the presence of parallel electric and strong magnetic fields
International Nuclear Information System (INIS)
An analytical approach to the problem of a negatively charged donor in an infinitely deep quantum well (QW) in the presence of parallel electric and strong magnetic external fields both directed perpendicular to the heteroplanes is developed. The double adiabatic approximation is employed. The dependences of the binding energy on the field strengths, the width of the well and the position of the impurity within the well are derived in explicit form. The effect of the inversion of the electric field is investigated. It is shown that the combined potential acting on the 'outer' electron resembles that of a double QW. When the levels associated with the two effective QWs anticross, a resonant structure arises. The explicit dependence of the resonant splitting on the width of the QW, the strength of the electric field and the position of the impurity are obtained. Using the parameters associated with the GaAs QW, estimates of the inversion shift of the binding energy and the frequency of the emitted resonant radiation induced by the electric field are made
M.V. Yakunin; A. de Visser; G. Galistu; S.M. Podgornykh; Y.G. Sadofyev; N.G. Shelushinina; G.I. Harus
2009-01-01
Development of quantum Hall peculiarities due to mobility gap between spin-split magnetic levels with addition of the parallel magnetic field component B|| is analyzed in double quantum wells (DQW) created in InGaAs/GaAs and InAs/AlSb heterosystems chosen due to their relatively large bulk g-factors
International Nuclear Information System (INIS)
Suppression of neoclassical tearing modes in tokamaks under anomalous transverse transport conditions when the magnetic well effect predominates over the bootstrap drive is studied. Reduced equations of transfer are used in the description. Geodetic effects are considered during the magnetic well calculation. A criterion for the stabilization of neoclassical tearing modes by the compound effect at an arbitrary level of the transverse heat transport by electrons and ions is derived
B. Curé
2011-01-01
The magnet ran smoothly in the last few months until a fast dump occurred on 9th May 2011. Fortunately, this occurred in the afternoon of the first day of the technical stop. The fast dump was due to a valve position controller that caused the sudden closure of a valve. This valve is used to regulate the helium flow on one of the two current leads, which electrically connects the coil at 4.5 K to the busbars at room temperature. With no helium flow on the lead, the voltage drop and the temperatures across the leads increase up to the defined thresholds, triggering a fast dump through the Magnet Safety System (MSS). The automatic reaction triggered by the MSS worked properly. The helium release was limited as the pressure rise was just at the limit of the safety valve opening pressure. The average temperature of the magnet reached 72 K. It took four days to recover the temperature and refill the helium volumes. The faulty valve controller was replaced by a spare one before the magnet ramp-up resumed....
Energy Technology Data Exchange (ETDEWEB)
Onxley, Jennifer D.; Yoo, David S. [Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina (United States); Muradyan, Naira [iCAD Inc., Nashua, New Hampshire (United States); MacFall, James R. [Department of Radiology, Duke University Medical Center, Durham, North Carolina (United States); Brizel, David M. [Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina (United States); Department of Surgery, Duke University Medical Center, Durham, North Carolina (United States); Craciunescu, Oana I., E-mail: Oana.Craciunescu@duke.edu [Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina (United States)
2014-07-01
Purpose: To generate a population-averaged arterial input function (PA-AIF) for quantitative analysis of dynamic contrast-enhanced MRI data in head and neck cancer patients. Methods and Materials: Twenty patients underwent dynamic contrast-enhanced MRI during concurrent chemoradiation therapy. Imaging consisted of 2 baseline scans 1 week apart (B1/B2) and 1 scan after 1 week of chemoradiation therapy (Wk1). Regions of interest (ROIs) in the right and left carotid arteries were drawn on coronal images. Plasma concentration curves of all ROIs were averaged and fit to a biexponential decay function to obtain the final PA-AIF (AvgAll). Right-sided and left-sided ROI plasma concentration curves were averaged separately to obtain side-specific AIFs (AvgRight/AvgLeft). Regions of interest were divided by time point to obtain time-point-specific AIFs (AvgB1/AvgB2/AvgWk1). The vascular transfer constant (K{sub trans}) and the fractional extravascular, extracellular space volume (V{sub e}) for primaries and nodes were calculated using the AvgAll AIF, the appropriate side-specific AIF, and the appropriate time-point-specific AIF. Median K{sub trans} and V{sub e} values derived from AvgAll were compared with those obtained from the side-specific and time-point-specific AIFs. The effect of using individual AIFs was also investigated. Results: The plasma parameters for AvgAll were a{sub 1,2} = 27.11/17.65 kg/L, m{sub 1,2} = 11.75/0.21 min{sup −1}. The coefficients of repeatability (CRs) for AvgAll versus AvgLeft were 0.04 min{sup −1} for K{sub trans} and 0.02 for V{sub e}. For AvgAll versus AvgRight, the CRs were 0.08 min{sup −1} for K{sub trans} and 0.02 for V{sub e}. When AvgAll was compared with AvgB1/AvgB2/AvgWk1, the CRs were slightly higher: 0.32/0.19/0.78 min{sup −1}, respectively, for K{sub trans}; and 0.07/0.08/0.09 for V{sub e}. Use of a PA-AIF was not significantly different from use of individual AIFs. Conclusion: A PA-AIF for head and neck cancer
International Nuclear Information System (INIS)
The principles of resonance averaging as applied to neutron capture reactions are described. Several illustrations of resonance averaging to problems of nuclear structure and the distribution of radiative strength in nuclei are provided. 30 refs., 12 figs
Schulz, R.; Korn, T.; Stich, D.; Wurstbauer, U.; Schuh, D.; Wegscheider, W.; Schüller, C.
2008-04-01
In recent years, ferromagnetic Ga(Mn)As has emerged as a highly interesting material for semiconductor spintronics. One possible application is to use Ga(Mn)As as an injector layer to inject spin-polarized carriers into a non-magnetic semiconductor heterostructure. As Ga(Mn)As layers are typically grown at much lower substrate temperatures than high-mobility GaAs heterostructures, a combination of both requires that the ferromagnetic layer is grown last. We have prepared samples by molecular beam epitaxy which consist of two quantum wells (QWs) of different widths grown at high substrate temperature. The upper QW is separated by a thin barrier (few nm) from a ferromagnetic Ga(Mn)As layer grown at low substrate temperature, while the lower QW is widely separated (more than 100 nm) from the Ga(Mn)As. We observe that the photoluminescence of the upper QW is red-shifted and partially quenched as compared to a control sample without a Ga(Mn)As layer, and time-resolved Faraday rotation measurements reveal that the spin lifetime in the upper QW is up to 50 times longer than the one in the lower QW. We attribute these observations to Mn back-diffusion into the upper QW during sample growth. Both, the PL and the Faraday rotation technique, are highly sensitive to small quantities (below 0.05%) of Mn and allow us to study the effectiveness of different types (e.g., a short-period superlattice) and thicknesses of barrier layers in suppressing Mn diffusion.
Averaging anisotropic cosmologies
International Nuclear Information System (INIS)
We examine the effects of spatial inhomogeneities on irrotational anisotropic cosmologies by looking at the average properties of anisotropic pressure-free models. Adopting the Buchert scheme, we recast the averaged scalar equations in Bianchi-type form and close the standard system by introducing a propagation formula for the average shear magnitude. We then investigate the evolution of anisotropic average vacuum models and those filled with pressureless matter. In the latter case we show that the backreaction effects can modify the familiar Kasner-like singularity and potentially remove Mixmaster-type oscillations. The presence of nonzero average shear in our equations also allows us to examine the constraints that a phase of backreaction-driven accelerated expansion might put on the anisotropy of the averaged domain. We close by assessing the status of these and other attempts to define and calculate 'average' spacetime behaviour in general relativity
International Nuclear Information System (INIS)
We have recently reported that the Haldane spin-chain system, Er2BaNiO5, undergoing antiferromagnetic order below (TN=) 32 K, is characterized by the onset of ferroelectricity near 60 K due to magnetoelectric coupling induced by short-range magnetic-order within spin-chains. We have carried out additional magnetic and dielectric studies to understand the properties well below TN. We emphasize here on the following: (i) A strong frequency dependent behaviors of ac magnetic susceptibility and complex dielectric properties have been observed at much lower temperatures (N. (ii) “Magnetoelectric phase coexistence” is observed at very low temperature (e.g., T = 2 K), where the high-field magnetoelectric phase is partially arrested on returning to zero magnetic field after a cycling through metamagnetic transition.
International Nuclear Information System (INIS)
The goals of the High-Average-Power Laser Program at LLNL are to develop a broad technology base for solid state lasers and to demonstrate high-average-power laser operation with more efficiency and higher beam quality than has been possible with current technology. Major activities are the zig-zag laser testbed and the gas-cooled-slab laser test bed. This section describes these activities as well as discussion of material development; nonlinear optics; laser materials, and applications
Chintzoglou, Georgios; Vourlidas, Angelos
2015-01-01
NOAA Active Region (AR) 11429 was the source of twin super-fast Coronal Mass Ejections (CMEs). The CMEs took place within a hour from each other, with the onset of the first taking place in the beginning of March 7, 2012. This AR fulfills all the requirements for a "super active region"; namely, Hale's law incompatibility and a $\\delta$-spot magnetic configuration. One of the biggest storms of Solar Cycle 24 to date ($D_{st}=-143$ nT) was associated with one of these events. Magnetic Flux Ropes (MFRs) are twisted magnetic structures in the corona, best seen in $\\sim$10 MK hot plasma emission and are often considered the core of erupting structures. However, their "dormant" existence in the solar atmosphere (i.e. prior to eruptions), is an open question. Aided by multi-wavelength observations (SDO/HMI/AIA and STEREO EUVI B) and a Non-Linear Force-Free (NLFFF) model for the coronal magnetic field, our work uncovers two separate, weakly-twisted magnetic flux systems which suggest the existence of pre-eruption MF...
Debus, J.; Ivanov, V. Yu.; Ryabchenko, S. M.; Yakovlev, D. R.; Maksimov, A. A.; Semenov, Yu. G.; Braukmann, D.; Rautert, J.; Löw, U.; Godlewski, M.; Waag, A.; Bayer, M.
2016-05-01
The dynamics of spin-lattice relaxation in the magnetic Mn2 + ion system of (Zn,Mn)Se/(Zn,Be)Se quantum-well structures are studied using optical methods. Pronounced cusps are found in the giant Zeeman shift of the quantum-well exciton photoluminescence at specific magnetic fields below 10 T, when the Mn spin system is heated by photogenerated carriers. The spin-lattice relaxation time of the Mn ions is resonantly accelerated at the cusp magnetic fields. Our theoretical analysis demonstrates that a cusp occurs at a spin-level mixing of single Mn2 + ions and a quick-relaxing cluster of nearest-neighbor Mn ions, which can be described as intrinsic cross-relaxation resonance within the Mn spin system.
Effect of magnetic field on the donor impurity in CdTe/Cd1-xMnxTe quantum well wire
Kalpana, P.; Reuben, A. Merwyn Jasper D.; Nithiananthi, P.; Jayakumar, K.
2016-05-01
The donor impurity binding energy in CdTe / Cd1-xMnxTe QWW with square well confinement along x - direction and parabolic confinement along y - direction under the influence of externally applied magnetic field has been computed using variational principle in the effective mass approximation. The spin polaronic shift has also been computed. The results are presented and discussed.
International Nuclear Information System (INIS)
No-load losses within brakes and clutches based on magnetorheological fluids are unavoidable and represent a major barrier towards their wide-spread commercial adoption. Completely torque free rotation is not yet possible due to persistent fluid contact within the shear gap. In this paper, a novel concept is presented that facilitates the controlled movement of the magnetorheological fluid from an active, torque-transmitting region into an inactive region of the shear gap. This concept enables complete decoupling of the fluid engaging surfaces such that viscous drag torque can be eliminated. In order to achieve the desired effect, motion in the magnetorheological fluid is induced by magnetic forces acting on the fluid, which requires an appropriate magnetic circuit design. In this investigation, we propose a methodology to determine suitable magnetic circuit designs with well-defined fail-safe behavior. The magnetically induced motion of magnetorheological fluids is modeled by the use of the Kelvin body force, and a multi-physics domain simulation is performed to elucidate various transitions between an engaged and disengaged operating mode. The modeling approach is validated by captured high-speed video frames which show the induced motion of the magnetorheological fluid due to the magnetic field. Finally, measurements performed with a prototype actuator prove that the induced viscous drag torque can be reduced significantly by the proposed magnetic fluid control methodology. (paper)
Güth, Dirk; Schamoni, Markus; Maas, Jürgen
2013-09-01
No-load losses within brakes and clutches based on magnetorheological fluids are unavoidable and represent a major barrier towards their wide-spread commercial adoption. Completely torque free rotation is not yet possible due to persistent fluid contact within the shear gap. In this paper, a novel concept is presented that facilitates the controlled movement of the magnetorheological fluid from an active, torque-transmitting region into an inactive region of the shear gap. This concept enables complete decoupling of the fluid engaging surfaces such that viscous drag torque can be eliminated. In order to achieve the desired effect, motion in the magnetorheological fluid is induced by magnetic forces acting on the fluid, which requires an appropriate magnetic circuit design. In this investigation, we propose a methodology to determine suitable magnetic circuit designs with well-defined fail-safe behavior. The magnetically induced motion of magnetorheological fluids is modeled by the use of the Kelvin body force, and a multi-physics domain simulation is performed to elucidate various transitions between an engaged and disengaged operating mode. The modeling approach is validated by captured high-speed video frames which show the induced motion of the magnetorheological fluid due to the magnetic field. Finally, measurements performed with a prototype actuator prove that the induced viscous drag torque can be reduced significantly by the proposed magnetic fluid control methodology.
Benoit Curé
2010-01-01
The magnet worked very well at 3.8 T as expected, despite a technical issue that manifested twice in the cryogenics since June. All the other magnet sub-systems worked without flaw. The issue in the cryogenics was with the cold box: it could be observed that the cold box was getting progressively blocked, due to some residual humidity and air accumulating in the first thermal exchanger and in the adsorber at 65 K. This was later confirmed by the analysis during the regeneration phases. An increase in the temperature difference between the helium inlet and outlet across the heat exchanger and a pressure drop increase on the filter of the adsorber were observed. The consequence was a reduction of the helium flow, first compensated by the automatic opening of the regulation valves. But once they were fully opened, the flow and refrigeration power reduced as a consequence. In such a situation, the liquid helium level in the helium Dewar decreased, eventually causing a ramp down of the magnet current and a field...
Czech Academy of Sciences Publication Activity Database
Kolorenč, Jindřich; Smrčka, Ludvík; Středa, Pavel
2002-01-01
Roč. 12, - (2002), s. 311-314. ISSN 1386-9477 R&D Projects: GA ČR GA202/01/0754; GA ČR GA202/01/0764 Institutional research plan: CEZ:AV0Z1010914 Keywords : double-layer two-dimensional electron system * magnetotransort * Hall effect Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.107, year: 2002
International Nuclear Information System (INIS)
The formula is suggested for the calculation of the transmission coefficient of productive reservoirs at Balakhna-Sabuncha-Ramana deposits. This formula includes values of the efficient porosity derived from nuclear magnetic logging curves and mean values of the open porosity for each studied horizon (obtained from the laboratory analysis data on core samples). This method provides reliable estimates of the porosity of productive horizons in the conditions of their natural bedding
Bouyer, Patricia; Markey, Nicolas; Randour, Mickael; Larsen, Kim G.; Laursen, Simon
2015-01-01
Two-player quantitative zero-sum games provide a natural framework to synthesize controllers with performance guarantees for reactive systems within an uncontrollable environment. Classical settings include mean-payoff games, where the objective is to optimize the long-run average gain per action, and energy games, where the system has to avoid running out of energy. We study average-energy games, where the goal is to optimize the long-run average of the accumulated energy. We show that this ...
Yakunin, M.V.; Visser, de, P.H.B.; Galistu, G.; Podgornykh, S.M.; Sadofyev, Y.G.; Shelushinina, N. G.; Harus, G. I.
2009-01-01
Development of quantum Hall peculiarities due to mobility gap between spin-split magnetic levels with addition of the parallel magnetic field component B|| is analyzed in double quantum wells (DQW) created in InGaAs/GaAs and InAs/AlSb heterosystems chosen due to their relatively large bulk g-factors. In InGaAs/GaAs DQWs, the nonmonotonous behavior of these peculiarities is observed and explained within single-electron approach in terms of competition between enhanced spin splitting and locali...
Excitons in coupled type-II double quantum wells under electric and magnetic fields: InAs/AlSb/GaSb
International Nuclear Information System (INIS)
We calculate the wave functions and the energy levels of an exciton in double quantum wells under electric (F) and magnetic (B) fields along the growth axis. The result is employed to study the energy levels, the binding energy, and the boundary on the F–B plane of the phase between the indirect exciton ground state and the semiconductor ground state for several typical structures of the type-II quasi-two-dimensional quantum wells such as InAs/AlSb/GaSb. The inter-well inter-band radiative transition rates are calculated for exciton creation and recombination. We find that the rates are modulated over several orders of magnitude by the electric and magnetic fields
Benoit Curé
The magnet subsystems resumed operation early this spring. The vacuum pumping was restarted mid March, and the cryogenic power plant was restarted on March 30th. Three and a half weeks later, the magnet was at 4.5 K. The vacuum pumping system is performing well. One of the newly installed vacuum gauges had to be replaced at the end of the cool-down phase, as the values indicated were not coherent with the other pressure measurements. The correction had to be implemented quickly to be sure no helium leak could be at the origin of this anomaly. The pressure measurements have been stable and coherent since the change. The cryogenics worked well, and the cool-down went quite smoothly, without any particular difficulty. The automated start of the turbines had to be fine-tuned to get a smooth transition, as it was observed that the cooling power delivered by the turbines was slightly higher than needed, causing the cold box to stop automatically. This had no consequence as the cold box safety system acts to keep ...
DEFF Research Database (Denmark)
Gramkow, Claus
In this article two common approaches to averaging rotations are compared to a more advanced approach based on a Riemannian metric. Very offten the barycenter of the quaternions or matrices that represent the rotations are used as an estimate of the mean. These methods neglect that rotations belong...... natural approximations to the Riemannian metric, and that the subsequent corrections are inherient in the least squares estimation. Keywords: averaging rotations, Riemannian metric, matrix, quaternion...
Van Essen, H.
2004-01-01
This paper addresses the problem of the separation of rotational and internal motion. It introduces the concept of average angular velocity as the moment of inertia weighted average of particle angular velocities. It extends and elucidates the concept of Jellinek and Li (1989) of separation of the energy of overall rotation in an arbitrary (non-linear) $N$-particle system. It generalizes the so called Koenig's theorem on the two parts of the kinetic energy (center of mass plus internal) to th...
Fibich, Gadi; Gavious, Arieh; Solan, Eilon
2012-01-01
Typically, models with a heterogeneous property are considerably harder to analyze than the corresponding homogeneous models, in which the heterogeneous property is replaced with its average value. In this study we show that any outcome of a heterogeneous model that satisfies the two properties of differentiability and interchangibility is O(\\epsilon^2) equivalent to the outcome of the corresponding homogeneous model, where \\epsilon is the level of heterogeneity. We then use this averaging pr...
DEFF Research Database (Denmark)
Gramkow, Claus
1999-01-01
In this article two common approaches to averaging rotations are compared to a more advanced approach based on a Riemannian metric. Very offten the barycenter of the quaternions or matrices that represent the rotations are used as an estimate of the mean. These methods neglect that rotations belong...... natural approximations to the Riemannian metric, and that the subsequent corrections are inherient in the least squares estimation. Keywords: averaging rotations, Riemannian metric, matrix, quaternion...
Averaged extreme regression quantile
Jureckova, Jana
2015-01-01
Various events in the nature, economics and in other areas force us to combine the study of extremes with regression and other methods. A useful tool for reducing the role of nuisance regression, while we are interested in the shape or tails of the basic distribution, is provided by the averaged regression quantile and namely by the average extreme regression quantile. Both are weighted means of regression quantile components, with weights depending on the regressors. Our primary interest is ...
International Nuclear Information System (INIS)
In the present work, the effects of the intense laser field on total optical absorption coefficient (the linear and third-order nonlinear) and total refractive index change for transition between two lower-lying electronic levels in the step-like GaAs/Ga1−xAlxAs quantum well under external electric and magnetic fields are investigated. The calculations were performed within the compact density-matrix formalism with the use of the effective mass and parabolic band approximations. The obtained results show that both total absorption coefficient and refractive index change are sensitive to the well dimensions and the effects of external fields. By changing the intensities of the electric, magnetic and non-resonant intense laser fields together with the well dimensions, we can obtain the blue or red shift, without the need for the growth of many different samples. - Highlights: • Augmentation of laser-field results in red shift in total AC spectra. • Magnetic field induces a blue-shift in the resonant peak. • Resonant peak position shifts to red with effect of electric field. • Resonant peak of total AC shifts to the higher photon energies with increasing well width
Energy Technology Data Exchange (ETDEWEB)
Kasapoglu, E., E-mail: ekasap@cumhuriyet.edu.tr [Department of Physics, Cumhuriyet University, 58140 Sivas (Turkey); Duque, C.A. [Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia-UdeA, Calle 70 No. 52-21, Medellín (Colombia); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Ave. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Restrepo, R.L. [Department of Physics, Cumhuriyet University, 58140 Sivas (Turkey); Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia-UdeA, Calle 70 No. 52-21, Medellín (Colombia); Escuela de Ingeniería de Antioquia-EIA, Medellín (Colombia); Ungan, F.; Yesilgul, U.; Sari, H. [Department of Physics, Cumhuriyet University, 58140 Sivas (Turkey); Sökmen, I. [Department of Physics, Dokuz Eylül University, 35160 Buca, İzmir (Turkey)
2015-03-15
In the present work, the effects of the intense laser field on total optical absorption coefficient (the linear and third-order nonlinear) and total refractive index change for transition between two lower-lying electronic levels in the step-like GaAs/Ga{sub 1−x}Al{sub x}As quantum well under external electric and magnetic fields are investigated. The calculations were performed within the compact density-matrix formalism with the use of the effective mass and parabolic band approximations. The obtained results show that both total absorption coefficient and refractive index change are sensitive to the well dimensions and the effects of external fields. By changing the intensities of the electric, magnetic and non-resonant intense laser fields together with the well dimensions, we can obtain the blue or red shift, without the need for the growth of many different samples. - Highlights: • Augmentation of laser-field results in red shift in total AC spectra. • Magnetic field induces a blue-shift in the resonant peak. • Resonant peak position shifts to red with effect of electric field. • Resonant peak of total AC shifts to the higher photon energies with increasing well width.
Averaging anisotropic cosmologies
Barrow, J D; Barrow, John D.; Tsagas, Christos G.
2006-01-01
We examine the effects of spatial inhomogeneities on irrotational anisotropic cosmologies by looking at the average properties of pressure-free Bianchi-type models. Adopting the Buchert averaging scheme, we identify the kinematic backreaction effects by focussing on spacetimes with zero or isotropic spatial curvature. This allows us to close the system of the standard scalar formulae with a propagation equation for the shear magnitude. We find no change in the already known conditions for accelerated expansion. The backreaction terms are expressed as algebraic relations between the mean-square fluctuations of the models' irreducible kinematical variables. Based on these we investigate the early evolution of averaged vacuum Bianchi type $I$ universes and those filled with pressureless matter. In the latter case we show that the backreaction effects can modify the familiar Kasner-like singularity and potentially remove Mixmaster-type oscillations. We also discuss the possibility of accelerated expansion due to ...
Essén, H
2003-01-01
This paper addresses the problem of the separation of rotational and internal motion. It introduces the concept of average angular velocity as the moment of inertia weighted average of particle angular velocities. It extends and elucidates the concept of Jellinek and Li (1989) of separation of the energy of overall rotation in an arbitrary (non-linear) $N$-particle system. It generalizes the so called Koenig's theorem on the two parts of the kinetic energy (center of mass plus internal) to three parts: center of mass, rotational, plus the remaining internal energy relative to an optimally translating and rotating frame.
Carrillo, Rafael E; Wiaux, Yves
2013-01-01
Recent developments in Carrillo et al. (2012) and Carrillo et al. (2013) introduced a novel regularization method for compressive imaging in the context of compressed sensing with coherent redundant dictionaries. The approach relies on the observation that natural images exhibit strong average sparsity over multiple coherent frames. The associated reconstruction algorithm, based on an analysis prior and a reweighted $\\ell_1$ scheme, is dubbed Sparsity Averaging Reweighted Analysis (SARA). We review these advances and extend associated simulations establishing the superiority of SARA to regularization methods based on sparsity in a single frame, for a generic spread spectrum acquisition and for a Fourier acquisition of particular interest in radio astronomy.
Energy Technology Data Exchange (ETDEWEB)
Lopez, S.Y. [Grupo de Educacion en Ciencias Experimentales y Matematicas-GECEM, Facultad de Educacion, Universidad de Antioquia, AA 1226 Medellin (Colombia); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Duque, C.A., E-mail: cduque@fisica.udea.edu.c [Instituto de Fisica, Universidad de Antioquia, AA 1226 Medellin (Colombia)
2009-12-15
The photoluminescence energy transitions in GaAs-Ga{sub 1-x}Al{sub x}As coupled double quantum wells are presented by considering the simultaneous effects of applied electric and magnetic fields and hydrostatic pressure. Calculations have been made in the framework of the effective mass and parabolic band approximations and using a variational procedure. The electric field is taken to be oriented along the growth direction of the heterostructure whereas for the magnetic field both in-plane and in-growth directions have been considered. The results show that the hydrostatic pressure and the applied electric field are two useful tools to tune the direct and indirect exciton transitions in such heterostructures. Our results are in good agreement with previous experimental findings in double quantum wells under applied electric field and hydrostatic pressure.
International Nuclear Information System (INIS)
The photoluminescence energy transitions in GaAs-Ga1-xAlxAs coupled double quantum wells are presented by considering the simultaneous effects of applied electric and magnetic fields and hydrostatic pressure. Calculations have been made in the framework of the effective mass and parabolic band approximations and using a variational procedure. The electric field is taken to be oriented along the growth direction of the heterostructure whereas for the magnetic field both in-plane and in-growth directions have been considered. The results show that the hydrostatic pressure and the applied electric field are two useful tools to tune the direct and indirect exciton transitions in such heterostructures. Our results are in good agreement with previous experimental findings in double quantum wells under applied electric field and hydrostatic pressure.
Energy Technology Data Exchange (ETDEWEB)
Platonov, V. V.; Kudasov, Yu. B.; Makarov, I. V.; Maslov, D. A.; Surdin, O. M. [Sarov Physical–Technical Institute—National Research Nuclear University MEPhI (Russian Federation); Zholudev, M. S.; Ikonnikov, A. V.; Gavrilenko, V. I. [Russian Academy of Sciences, Institute of Physics of Microstructures (Russian Federation); Mikhailov, N. N.; Dvoretsky, S. A. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation)
2015-12-15
The magnetoabsorption in magnetic fields as high as 40 T is investigated at T > 77 K in HgTe/CdHgTe quantum-well heterostructures (d{sub QW} ≈ 8 nm). The spectra reveal two lines associated both with intraband transition from the lower Landau level in the conduction band and with interband transition. It is shown that the band structure in these systems changes from inverted to normal with increasing temperature.
DEFF Research Database (Denmark)
Gramkow, Claus
2001-01-01
In this paper two common approaches to averaging rotations are compared to a more advanced approach based on a Riemannian metric. Very often the barycenter of the quaternions or matrices that represent the rotations are used as an estimate of the mean. These methods neglect that rotations belong to...
Vocal attractiveness increases by averaging.
Bruckert, Laetitia; Bestelmeyer, Patricia; Latinus, Marianne; Rouger, Julien; Charest, Ian; Rousselet, Guillaume A; Kawahara, Hideki; Belin, Pascal
2010-01-26
Vocal attractiveness has a profound influence on listeners-a bias known as the "what sounds beautiful is good" vocal attractiveness stereotype [1]-with tangible impact on a voice owner's success at mating, job applications, and/or elections. The prevailing view holds that attractive voices are those that signal desirable attributes in a potential mate [2-4]-e.g., lower pitch in male voices. However, this account does not explain our preferences in more general social contexts in which voices of both genders are evaluated. Here we show that averaging voices via auditory morphing [5] results in more attractive voices, irrespective of the speaker's or listener's gender. Moreover, we show that this phenomenon is largely explained by two independent by-products of averaging: a smoother voice texture (reduced aperiodicities) and a greater similarity in pitch and timbre with the average of all voices (reduced "distance to mean"). These results provide the first evidence for a phenomenon of vocal attractiveness increases by averaging, analogous to a well-established effect of facial averaging [6, 7]. They highlight prototype-based coding [8] as a central feature of voice perception, emphasizing the similarity in the mechanisms of face and voice perception. PMID:20129047
Durnev, M. V.; Tarasenko, S. A.
2015-01-01
We present a theory of the electron structure and the Zeeman effect for the helical edge states emerging in two-dimensional topological insulators based on HgTe/HgCdTe quantum wells with strong natural interface inversion asymmetry. The interface inversion asymmetry, reflecting the real atomistic structure of the quantum well, drastically modifies both bulk and edge states. For the in-plane magnetic field, this asymmetry leads to a strong anisotropy of the edge-state effective $g$-factor whic...
Wan, Caichao; Li, Jian
2015-12-10
With the increasing emphasis on green chemistry, it is becoming more important to develop environmentally friendly matrix materials for the synthesis of nanocomposites. Cellulose aerogels with hierarchical micro/nano-scale three-dimensional network beneficial to control and guide the growth of nanoparticles, are suitable as a class of ideal green nanoparticles hosts to fabricate multifunctional nanocomposites. Herein, a facile oxidative co-precipitation method was carried out to disperse CoFe2O4 nanoparticles in the cellulose aerogels matrixes, and the cellulose aerogels were prepared from the native wheat straw based on a green NaOH/polyethylene glycol solution. The mean diameter of the well-dispersed CoFe2O4 nanoparticles in the hybrid aerogels is 98.5 nm. Besides, the hybrid aerogels exhibit strong magnetic responsiveness, which could be flexibly actuated by a small magnet. And this feature also makes this class of magnetic aerogels possibly useful as recyclable adsorbents and some magnetic devices. Meanwhile, the mild green preparation method could also be extended to fabricate other miscellaneous cellulose-based nanocomposites. PMID:26428110
International Nuclear Information System (INIS)
A study is made of the suppression of neoclassical tearing modes in tokamaks under anomalous transverse transport conditions when the magnetic well effect predominates over the bootstrap drive. It is stressed that the corresponding effect, which is called the compound suppression effect, depends strongly on the profiles of the electron and ion temperature perturbations. Account is taken of the fact that the temperature profile can be established as a result of the competition between anomalous transverse heat transport, on the one hand, and longitudinal collisional heat transport, longitudinal heat convection, longitudinal inertial transport, and transport due to the rotation of magnetic islands, on the other hand. The role of geodesic effects is discussed. The cases of competition just mentioned are described by the model sets of reduced transport equations, which are called, respectively, collisional, convective, inertial, and rotational plasmophysical models. The magnetic well is calculated with allowance for geodesic effects. It is shown that, for strong anomalous heat transport conditions, the contribution of the magnetic well to the generalized Rutherford equation for the island width W is independent of W not only in the collisional model (which has been investigated earlier) but also in the convective and inertial models and depends very weakly (logarithmically) on W in the rotational model. It is this weak dependence that gives rise to the compound effect, which is the subject of the present study. A criterion for the stabilization of neoclassical tearing modes by the compound effect at an arbitrary level of the transverse heat transport by electrons and ions is derived and is analyzed for two cases: when the electron heat transport and ion heat transport are both strong, and when the electron heat transport is strong and the ion heat transport is weak
Covariant approximation averaging
Shintani, Eigo; Blum, Thomas; Izubuchi, Taku; Jung, Chulwoo; Lehner, Christoph
2014-01-01
We present a new class of statistical error reduction techniques for Monte-Carlo simulations. Using covariant symmetries, we show that correlation functions can be constructed from inexpensive approximations without introducing any systematic bias in the final result. We introduce a new class of covariant approximation averaging techniques, known as all-mode averaging (AMA), in which the approximation takes account of contributions of all eigenmodes through the inverse of the Dirac operator computed from the conjugate gradient method with a relaxed stopping condition. In this paper we compare the performance and computational cost of our new method with traditional methods using correlation functions and masses of the pion, nucleon, and vector meson in $N_f=2+1$ lattice QCD using domain-wall fermions. This comparison indicates that AMA significantly reduces statistical errors in Monte-Carlo calculations over conventional methods for the same cost.
Fibich, Gadi; Gavious, Arieh; Solan, Eilon
2012-01-01
Typically, models with a heterogeneous property are considerably harder to analyze than the corresponding homogeneous models, in which the heterogeneous property is replaced with its average value. In this study we show that any outcome of a heterogeneous model that satisfies the two properties of \\emph{differentiability} and \\emph{interchangibility}, is $O(\\epsilon^2)$ equivalent to the outcome of the corresponding homogeneous model, where $\\epsilon$ is the level of heterogeneity. We then us...
International Nuclear Information System (INIS)
Development of quantum Hall peculiarities due to mobility gap between spin-split magnetic levels with addition of the parallel magnetic field component B|| is analyzed in double quantum wells (DQW) created in InGaAs/GaAs and InAs/AlSb heterosystems chosen due to their relatively large bulk g-factors. In InGaAs/GaAs DQWs, the nonmonotonous behavior of these peculiarities is observed and explained within single-electron approach in terms of competition between enhanced spin splitting and localization of electrons in the layers of DQW with increased B||. In InAs/AlSb DQW, the tunneling connection between the layers is very weak due to high barrier, nevertheless the collective odd-numbered peculiarities are revealed that exist due to spontaneous interlayer phase coherence. B|| destroys these states that is manifested, in particular, in the suppression of the peculiarity for filling factor v = 3.
Yakunin, M. V.; de Visser, Anne; Galistu, Gianni; Podgornykh, S. M.; Sadofyev, Yu G.; Shelushinina, N. G.; Harus, G. I.
2009-02-01
Development of quantum Hall peculiarities due to mobility gap between spin-split magnetic levels with addition of the parallel magnetic field component B|| is analyzed in double quantum wells (DQW) created in InGaAs/GaAs and InAs/AlSb heterosystems chosen due to their relatively large bulk g-factors. In InGaAs/GaAs DQWs, the nonmonotonous behavior of these peculiarities is observed and explained within single-electron approach in terms of competition between enhanced spin splitting and localization of electrons in the layers of DQW with increased B||. In InAs/AlSb DQW, the tunneling connection between the layers is very weak due to high barrier, nevertheless the collective odd-numbered peculiarities are revealed that exist due to spontaneous interlayer phase coherence. B|| destroys these states that is manifested, in particular, in the suppression of the peculiarity for filling factor v = 3.
Energy Technology Data Exchange (ETDEWEB)
Yakunin, M V; Podgornykh, S M; Shelushinina, N G; Harus, G I [Institute of Metal Physics, 620041 Ekaterinburg (Russian Federation); Visser, Anne de; Galistu, Gianni [Van der Waals - Zeeman Institute, University of Amsterdam, 1018 XE Amsterdam (Netherlands); Sadofyev, Yu G [Ryazan State Radioengineering University, 390005 Ryazan (Russian Federation)], E-mail: yakunin@imp.uran.ru
2009-02-01
Development of quantum Hall peculiarities due to mobility gap between spin-split magnetic levels with addition of the parallel magnetic field component B{sub ||} is analyzed in double quantum wells (DQW) created in InGaAs/GaAs and InAs/AlSb heterosystems chosen due to their relatively large bulk g-factors. In InGaAs/GaAs DQWs, the nonmonotonous behavior of these peculiarities is observed and explained within single-electron approach in terms of competition between enhanced spin splitting and localization of electrons in the layers of DQW with increased B{sub ||}. In InAs/AlSb DQW, the tunneling connection between the layers is very weak due to high barrier, nevertheless the collective odd-numbered peculiarities are revealed that exist due to spontaneous interlayer phase coherence. B{sub ||} destroys these states that is manifested, in particular, in the suppression of the peculiarity for filling factor v = 3.
Hu, Lun-Hui; Xu, Dong-Hui; Zhang, Fu-Chun; Zhou, Yi
2016-08-01
Motivated by the recent discovery of quantized spin Hall effect in InAs/GaSb quantum wells [Du, Knez, Sullivan, and Du, Phys. Rev. Lett. 114, 096802 (2015), 10.1103/PhysRevLett.114.096802], we theoretically study the effects of in-plane magnetic field and strain effect to the quantization of charge conductance by using Landauer-B ütikker formalism. Our theory predicts a robustness of the conductance quantization against the in-plane magnetic field up to a very high field of 20 T. We use a disordered hopping term to model the strain and show that the strain may help the quantization of the conductance. Relevance to the experiments will be discussed.
Robust Averaging Level Control
Rosander, Peter; Isaksson, Alf; Löfberg, Johan; Forsman, Krister
2011-01-01
Frequent inlet ﬂow changes typically cause problems for averaging level controllers. For a frequently changing inlet ﬂow the upsets do not occur when the system is in steady state and the tank level at its set-point. For this reason the tuning of the level controller gets quite complicated, since not only the size of the upsets but also the time in between them relative to the hold up of the tank have to be considered. One way to obtain optimal ﬂow ﬁltering while directly accounting for futur...
Negative Average Preference Utilitarianism
Directory of Open Access Journals (Sweden)
Roger Chao
2012-03-01
Full Text Available For many philosophers working in the area of Population Ethics, it seems that either they have to confront the Repugnant Conclusion (where they are forced to the conclusion of creating massive amounts of lives barely worth living, or they have to confront the Non-Identity Problem (where no one is seemingly harmed as their existence is dependent on the “harmful” event that took place. To them it seems there is no escape, they either have to face one problem or the other. However, there is a way around this, allowing us to escape the Repugnant Conclusion, by using what I will call Negative Average Preference Utilitarianism (NAPU – which though similar to anti-frustrationism, has some important differences in practice. Current “positive” forms of utilitarianism have struggled to deal with the Repugnant Conclusion, as their theory actually entails this conclusion; however, it seems that a form of Negative Average Preference Utilitarianism (NAPU easily escapes this dilemma (it never even arises within it.
Yakunin, M. V.; Arapov, Yu. G.; Neverov, V. N.; Podgornyh, S. M.; Shelushinina, N. G.; Harus, G. I.; Zvonkov, B. N.; Uskova, E. A.
2007-04-01
Precise scanning of the (B⊥,B∥) plane while measuring magnetoresistance of the n-InGaAs/GaAs double quantum well (DQW) reveals a number of peculiarities connected with intricate DQW energy spectrum, which are analyzed on the basis of quasiclassical calculations. Magnetic breakdown effects are also considered. Peaks due to the latter mechanism reveal spin-splittings (in spite of lower mobilities as compared with the traditional n-GaAs/AlGaAs DQWs) corresponding to an enhanced effective Lande g-factor.
Yesilgul, U.; Al, E. B.; Martínez-Orozco, J. C.; Restrepo, R. L.; Mora-Ramos, M. E.; Duque, C. A.; Ungan, F.; Kasapoglu, E.
2016-08-01
In the present study, the effects of electric and magnetic fields on the linear and third-order nonlinear optical absorption coefficients and relative change of the refractive index in asymmetric GaAs/GaAlAs double quantum wells under intense laser fields are theoretically investigated. The electric field is oriented along the growth direction of the heterostructure while the magnetic field is taken in-plane. The intense laser field is linear polarization along the growth direction. Our calculations are made using the effective-mass approximation and the compact density-matrix approach. Intense laser effects on the system are investigated with the use of the Floquet method with the consequent change in the confinement potential of heterostructures. Our results show that the increase of the electric and magnetic fields blue-shifts the peak positions of the total absorption coefficient and of the total refractive index while the increase of the intense laser field firstly blue-shifts the peak positions and later results in their red-shifting.
Average nuclear surface properties
International Nuclear Information System (INIS)
The definition of the nuclear surface energy is discussed for semi-infinite matter. This definition is extended also for the case that there is a neutron gas instead of vacuum on the one side of the plane surface. The calculations were performed with the Thomas-Fermi Model of Syler and Blanchard. The parameters of the interaction of this model were determined by a least squares fit to experimental masses. The quality of this fit is discussed with respect to nuclear masses and density distributions. The average surface properties were calculated for different particle asymmetry of the nucleon-matter ranging from symmetry beyond the neutron-drip line until the system no longer can maintain the surface boundary and becomes homogeneous. The results of the calculations are incorporated in the nuclear Droplet Model which then was fitted to experimental masses. (orig.)
by B. Curé
2011-01-01
The magnet operation was very satisfactory till the technical stop at the end of the year 2010. The field was ramped down on 5th December 2010, following the successful regeneration test of the turbine filters at full field on 3rd December 2010. This will limit in the future the quantity of magnet cycles, as it is no longer necessary to ramp down the magnet for this type of intervention. This is made possible by the use of the spare liquid Helium volume to cool the magnet while turbines 1 and 2 are stopped, leaving only the third turbine in operation. This obviously requires full availability of the operators to supervise the operation, as it is not automated. The cryogenics was stopped on 6th December 2010 and the magnet was left without cooling until 18th January 2011, when the cryoplant operation resumed. The magnet temperature reached 93 K. The maintenance of the vacuum pumping was done immediately after the magnet stop, when the magnet was still at very low temperature. Only the vacuum pumping of the ma...
Averaging and Captive Wildlife.
DeRosa, Bill; Finch, Patty A.
1985-01-01
Offers a teaching technique that proposes to enliven instruction of statistics for mathematics students. This activity focuses on questions and associated calculations pertaining to wildlife in captivity. Directives for the lesson as well as a complete listing of questions and answers on captive wildlife are included. (ML)
MEASUREMENT AND MODELLING AVERAGE PHOTOSYNTHESIS OF MAIZE
ZS LÕKE
2005-01-01
The photosynthesis of fully developed maize was investigated in the Agrometeorological Research Station Keszthely, in 2000. We used LI-6400 type measurement equipment to locate measurement points where the intensity of photosynthesis mostly nears the average. So later we could obtain average photosynthetic activities featuring the crop, with only one measurement. To check average photosynthesis of maize we used Goudriaan’s simulation model (CMSM) as well to calculate values on cloudless sampl...
Benoit Curé
2010-01-01
Operation of the magnet has gone quite smoothly during the first half of this year. The magnet has been at 4.5K for the full period since January. There was an unplanned short stop due to the CERN-wide power outage on May 28th, which caused a slow dump of the magnet. Since this occurred just before a planned technical stop of the LHC, during which access in the experimental cavern was authorized, it was decided to leave the magnet OFF until 2nd June, when magnet was ramped up again to 3.8T. The magnet system experienced a fault also resulting in a slow dump on April 14th. This was triggered by a thermostat on a filter choke in the 20kA DC power converter. The threshold of this thermostat is 65°C. However, no variation in the water-cooling flow rate or temperature was observed. Vibration may have been the root cause of the fault. All the thermostats have been checked, together with the cables, connectors and the read out card. The tightening of the inductance fixations has also been checked. More tem...
B. Curé
2012-01-01
Following the unexpected magnet stops last August due to sequences of unfortunate events on the services and cryogenics [see CMS internal report], a few more events and initiatives again disrupted the magnet operation. All the magnet parameters stayed at their nominal values during this period without any fault or alarm on the magnet control and safety systems. The magnet was stopped for the September technical stop to allow interventions in the experimental cavern on the detector services. On 1 October, to prepare the transfer of the liquid nitrogen tank on its new location, several control cables had to be removed. One cable was cut mistakenly, causing a digital input card to switch off, resulting in a cold-box (CB) stop. This tank is used for the pre-cooling of the magnet from room temperature down to 80 K, and for this reason it is controlled through the cryogenics control system. Since the connection of the CB was only allowed for a field below 2 T to avoid the risk of triggering a fast d...
B. Curé
2012-01-01
The magnet was energised at the beginning of March 2012 at a low current to check all the MSS safety chains. Then the magnet was ramped up to 3.8 T on 6 March 2012. Unfortunately two days later an unintentional switch OFF of the power converter caused a slow dump. This was due to a misunderstanding of the CCC (CERN Control Centre) concerning the procedure to apply for the CMS converter control according to the beam-mode status at that time. Following this event, the third one since 2009, a discussion was initiated to define possible improvement, not only on software and procedures in the CCC, but also to evaluate the possibility to upgrade the CMS hardware to prevent such discharge from occurring because of incorrect procedure implementations. The magnet operation itself was smooth, and no power cuts took place. As a result, the number of magnetic cycles was reduced to the minimum, with only two full magnetic cycles from 0 T to 3.8 T. Nevertheless the magnet suffered four stops of the cryogeni...
Orbit-averaged Guiding-center Fokker-Planck Operator
Brizard, A J; Decker, J; Duthoit, F -X
2009-01-01
A general orbit-averaged guiding-center Fokker-Planck operator suitable for the numerical analysis of transport processes in axisymmetric magnetized plasmas is presented. The orbit-averaged guiding-center operator describes transport processes in a three-dimensional guiding-center invariant space: the orbit-averaged magnetic-flux invariant $\\ov{\\psi}$, the minimum-B pitch-angle coordinate $\\xi_{0}$, and the momentum magnitude $p$.
Daničić, A.; Radovanović, J.; Milanović, V.; Indjin, D.; Ikonić, Z.
2016-07-01
We consider the influence of additional carrier confinement, achieved by application of strong perpendicular magnetic field, on inter Landau levels electron relaxation rates and the optical gain, of two different GaAs quantum cascade laser structures operating in the terahertz spectral range. Breaking of the in-plane energy dispersion and the formation of discrete energy levels is an efficient mechanism for eventual quenching of optical phonon emission and obtaining very long electronic lifetime in the relevant laser state. We employ our detailed model for calculating the electron relaxation rates (due to interface roughness and electron-longitudinal optical phonon scattering), and solve a full set of rate equations to evaluate the carrier distribution over Landau levels. The numerical simulations are performed for three- and four-well (per period) based structures that operate at 3.9 THz and 1.9 THz, respectively, both implemented in GaAs/Al0.15Ga0.85As. Numerical results are presented for magnetic field values from 1.5 T up to 20 T, while the band nonparabolicity is accounted for.
Labour Turnover Costs and Average Labour Demand
Bertola, Giuseppe
1991-01-01
The effect of labour turnover costs on average employment in a partial equilibrium model of labour demand, depends on the form of the revenue function, on the rates of discount and labour attrition, and on the relative size of hiring and firing costs. If discount and attrition rates are strictly positive, firing costs may well increase average employment even when hiring costs reduce it.
Chen, Chieh-Li; Ishikawa, Hiroshi; Wollstein, Gadi; Bilonick, Richard A.; Kagemann, Larry; Schuman, Joel S.
2016-01-01
Purpose Developing a novel image enhancement method so that nonframe-averaged optical coherence tomography (OCT) images become comparable to active eye-tracking frame-averaged OCT images. Methods Twenty-one eyes of 21 healthy volunteers were scanned with noneye-tracking nonframe-averaged OCT device and active eye-tracking frame-averaged OCT device. Virtual averaging was applied to nonframe-averaged images with voxel resampling and adding amplitude deviation with 15-time repetitions. Signal-to...
Benoit Curé
2010-01-01
The magnet was successfully operated at the end of the year 2009 despite some technical problems on the cryogenics. The magnet was ramped up to 3.8 T at the end of November until December 16th when the shutdown started. The magnet operation met a few unexpected stops. The field was reduced to 3.5 T for about 5 hours on December 3rd due to a faulty pressure sensor on the helium compressor. The following day the CERN CCC stopped unintentionally the power converters of the LHC and the experiments, triggering a ramp down that was stopped at 2.7 T. The magnet was back at 3.8 T about 6 hours after CCC sent the CERN-wide command. Three days later, a slow dump was triggered due to a stop of the pump feeding the power converter water-cooling circuit, during an intervention on the water-cooling plant done after several disturbances on the electrical distribution network. The magnet was back at 3.8 T in the evening the same day. On December 10th a break occurred in one turbine of the cold box producing the liquid ...
B. Curé
2013-01-01
The magnet was operated without any problem until the end of the LHC run in February 2013, apart from a CERN-wide power glitch on 10 January 2013 that affected the CMS refrigerator, causing a ramp down to 2 T in order to reconnect the coldbox. Another CERN-wide power glitch on 15 January 2013 didn’t affect the magnet subsystems, the cryoplant or the power converter. At the end of the magnet run, the reconnection of the coldbox at 2.5 T was tested. The process will be updated, in particular the parameters of some PID valve controllers. The helium flow of the current leads was reduced but only for a few seconds. The exercise will be repeated with the revised parameters to validate the automatic reconnection process of the coldbox. During LS1, the water-cooling services will be reduced and many interventions are planned on the electrical services. Therefore, the magnet cryogenics and subsystems will be stopped for several months, and the magnet cannot be kept cold. In order to avoid unc...
B. Curé
2012-01-01
The magnet and its sub-systems were stopped at the beginning of the winter shutdown on 8th December 2011. The magnet was left without cooling during the cryogenics maintenance until 17th January 2012, when the cryoplant operation resumed. The magnet temperature reached 93 K. The vacuum pumping was maintained during this period. During this shutdown, the yearly maintenance was performed on the cryogenics, the vacuum pumps, the magnet control and safety systems, and the power converter and discharge lines. Several preventive actions led to the replacement of the electrovalve command coils, and the 20A DC power supplies of the magnet control system. The filters were cleaned on the demineralised water circuits. The oil of the diffusion pumps was changed. On the cryogenics, warm nitrogen at 343 K was circulated in the cold box to regenerate the filters and the heat exchangers. The coalescing filters have been replaced at the inlet of both the turbines and the lubricant trapping unit. The active cha...
B. Curé
2011-01-01
The CMS magnet has been running steadily and smoothly since the summer, with no detected flaw. The magnet instrumentation is entirely operational and all the parameters are at their nominal values. Three power cuts on the electrical network affected the magnet run in the past five months, with no impact on the data-taking as the accelerator was also affected at the same time. On 22nd June, a thunderstorm caused a power glitch on the service electrical network. The primary water cooling at Point 5 was stopped. Despite a quick restart of the water cooling, the inlet temperature of the demineralised water on the busbar cooling circuit increased by 5 °C, up to 23.3 °C. It was kept below the threshold of 27 °C by switching off other cooling circuits to avoid the trigger of a slow dump of the magnet. The cold box of the cryogenics also stopped. Part of the spare liquid helium volume was used to maintain the cooling of the magnet at 4.5 K. The operators of the cryogenics quickly restarted ...
B. Curé
2013-01-01
The magnet is fully stopped and at room temperature. The maintenance works and consolidation activities on the magnet sub-systems are progressing. To consolidate the cryogenic installation, two redundant helium compressors will be installed as ‘hot spares’, to avoid the risk of a magnet downtime in case of a major failure of a compressor unit during operation. The screw compressors, their motors, the mechanical couplings and the concrete blocks are already available and stored at P5. The metallic structure used to access the existing compressors in SH5 will be modified to allow the installation of the two redundant ones. The plan is to finish the installation and commissioning of the hot spare compressors before the summer 2014. In the meantime, a bypass on the high-pressure helium piping will be installed for the connection of a helium drier unit later during the Long Shutdown 1, keeping this installation out of the schedule critical path. A proposal is now being prepared for the con...
Benoit Curé.
The magnet operation restarted end of June this year. Quick routine checks of the magnet sub-systems were performed at low current before starting the ramps up to higher field. It appeared clearly that the end of the field ramp down to zero was too long to be compatible with the detector commissioning and operations plans. It was decided to perform an upgrade to keep the ramp down from 3.8T to zero within 4 hours. On July 10th, when a field of 1.5T was reached, small movements were observed in the forward region support table and it was decided to fix this problem before going to higher field. At the end of July the ramps could be resumed. On July 28th, the field was at 3.8T and the summer CRAFT exercise could start. This run in August went smoothly until a general CERN wide power cut took place on August 3rd, due to an insulation fault on the high voltage network outside point 5. It affected the magnet powering electrical circuit, as it caused the opening of the main circuit breakers, resulting in a fast du...
B. Curé
MAGNET During the winter shutdown, the magnet subsystems went through a full maintenance. The magnet was successfully warmed up to room temperature beginning of December 2008. The vacuum was broken later on by injecting nitrogen at a pressure just above one atmosphere inside the vacuum tank. This was necessary both to prevent any accidental humidity ingress, and to allow for a modification of the vacuum gauges on the vacuum tank and maintenance of the diffusion pumps. The vacuum gauges had to be changed, because of erratic variations on the measurements, causing spurious alarms. The new type of vacuum gauges has been used in similar conditions on the other LHC experiments and without problems. They are shielded against the stray field. The lubricants of the primary and diffusion pumps have been changed. Several minor modifications were also carried out on the equipment in the service cavern, with the aim to ease the maintenance and to allow possible intervention during operation. Spare sensors have been bough...
Average luminosity distance in inhomogeneous universes
Kostov, Valentin
2010-01-01
Using numerical ray tracing, the paper studies how the average distance modulus in an inhomogeneous universe differs from its homogeneous counterpart. The averaging is over all directions from a fixed observer not over all possible observers (cosmic), thus it is more directly applicable to our observations. Unlike previous studies, the averaging is exact, non-perturbative, and includes all possible non-linear effects. The inhomogeneous universes are represented by Sweese-cheese models containing random and simple cubic lattices of mass-compensated voids. The Earth observer is in the homogeneous cheese which has an Einstein - de Sitter metric. For the first time, the averaging is widened to include the supernovas inside the voids by assuming the probability for supernova emission from any comoving volume is proportional to the rest mass in it. Despite the well known argument for photon flux conservation, the average distance modulus correction at low redshifts is not zero due to the peculiar velocities. A form...
Self-averaging characteristics of spectral fluctuations
Braun, Petr; Haake, Fritz
2014-01-01
The spectral form factor as well as the two-point correlator of the density of (quasi-)energy levels of individual quantum dynamics are not self-averaging. Only suitable smoothing turns them into useful characteristics of spectra. We present numerical data for a fully chaotic kicked top, employing two types of smoothing: one involves primitives of the spectral correlator, the second a small imaginary part of the quasi-energy. Self-averaging universal (like the CUE average) behavior is found f...
B. Curé
During the winter shutdown, the magnet subsystems went through a full maintenance. The magnet was successfully warmed up to room temperature beginning of December 2008. The vacuum was broken later on by injecting nitrogen at a pressure just above one atmosphere inside the vacuum tank. This was necessary both to prevent any accidental humidity ingress, and to allow for a modification of the vacuum gauges on the vacuum tank and maintenance of the diffusion pumps. The vacuum gauges had to be changed, because of erratic variations on the measurements, causing spurious alarms. The new type of vacuum gauges has been used in similar conditions on the other LHC experiments and without problems. They are shielded against the stray field. The lubricants of the primary and diffusion pumps have been changed. Several minor modifications were also carried out on the equipment in the service cavern, with the aim to ease the maintenance and to allow possible intervention during operation. Spare sensors have been bought. Th...
Basics of averaging of the Maxwell equations
Chipouline, A; Tretyakov, S
2011-01-01
Volume or statistical averaging of the microscopic Maxwell equations (MEs), i.e. transition from microscopic MEs to their macroscopic counterparts, is one of the main steps in electrodynamics of materials. In spite of the fundamental importance of the averaging procedure, it is quite rarely properly discussed in university courses and respective books; up to now there is no established consensus about how the averaging procedure has to be performed. In this paper we show that there are some basic principles for the averaging procedure (irrespective to what type of material is studied) which have to be satisfied. Any homogenization model has to be consistent with the basic principles. In case of absence of this correlation of a particular model with the basic principles the model could not be accepted as a credible one. Another goal of this paper is to establish the averaging procedure for metamaterials, which is rather close to the case of compound materials but should include magnetic response of the inclusi...
Averaging along Uniform Random Integers
Janvresse, Élise
2011-01-01
Motivated by giving a meaning to "The probability that a random integer has initial digit d", we define a URI-set as a random set E of natural integers such that each n>0 belongs to E with probability 1/n, independently of other integers. This enables us to introduce two notions of densities on natural numbers: The URI-density, obtained by averaging along the elements of E, and the local URI-density, which we get by considering the k-th element of E and letting k go to infinity. We prove that the elements of E satisfy Benford's law, both in the sense of URI-density and in the sense of local URI-density. Moreover, if b_1 and b_2 are two multiplicatively independent integers, then the mantissae of a natural number in base b_1 and in base b_2 are independent. Connections of URI-density and local URI-density with other well-known notions of densities are established: Both are stronger than the natural density, and URI-density is equivalent to log-density. We also give a stochastic interpretation, in terms of URI-...
MHD stability of torsatrons using the average method
International Nuclear Information System (INIS)
The stability of torsatrons is studied using the average method, or stellarator expansion. Attention is focused upon the Advanced Toroidal Fusion Device (ATF), an l = 2, 12 field period, moderate aspect ratio configuration which, through a combination of shear and toroidally induced magnetic well, is stable to ideal modes. Using the vertical field (VF) coil system of ATF it is possible to enhance this stability by shaping the plasma to control the rotational transform. The VF coils are also useful tools for exploring the stability boundaries of ATF. By shifting the plasma inward along the major radius, the magnetic well can be removed, leading to three types of long wavelength instabilities: (1) A free boundary ''edge mode'' occurs when the rotational transform at the plasma edge is just less than unity. This mode is stabilized by the placement of a conducting wall at 1.5 times the plasma radius. (2) A free boundary global kink mode is observed at high β. When either β is lowered or a conducting wall is placed at the plasma boundary, the global mode is suppressed, and (3) an interchange mode is observed instead. For this interchange mode, calculations of the second, third, etc., most unstable modes are used to understand the nature of the degeneracy breaking induced by toroidal effects. Thus, the ATF configuration is well chosen for the study of torsatron stability limits
Average Range and Network Synchronizability
International Nuclear Information System (INIS)
The influence of structural properties of a network on the network synchronizability is studied by introducing a new concept of average range of edges. For both small-world and scale-free networks, the effect of average range on the synchronizability of networks with bounded or unbounded synchronization regions is illustrated through numerical simulations. The relations between average range, range distribution, average distance, and maximum betweenness are also explored, revealing the effects of these factors on the network synchronizability of the small-world and scale-free networks, respectively. (general)
Physical Theories with Average Symmetry
Alamino, Roberto C
2013-01-01
This Letter probes the existence of physical laws invariant only in average when subjected to some transformation. The concept of a symmetry transformation is broadened to include corruption by random noise and average symmetry is introduced by considering functions which are invariant only in average under these transformations. It is then shown that actions with average symmetry obey a modified version of Noether's Theorem with dissipative currents. The relation of this with possible violations of physical symmetries, as for instance Lorentz invariance in some quantum gravity theories, is briefly commented.
"Pricing Average Options on Commodities"
Kenichiro Shiraya; Akihiko Takahashi
2010-01-01
This paper proposes a new approximation formula for pricing average options on commodities under a stochastic volatility environment. In particular, it derives an option pricing formula under Heston and an extended lambda-SABR stochastic volatility models (which includes an extended SABR model as a special case). Moreover, numerical examples support the accuracy of the proposed average option pricing formula.
Average-case analysis of numerical problems
2000-01-01
The average-case analysis of numerical problems is the counterpart of the more traditional worst-case approach. The analysis of average error and cost leads to new insight on numerical problems as well as to new algorithms. The book provides a survey of results that were mainly obtained during the last 10 years and also contains new results. The problems under consideration include approximation/optimal recovery and numerical integration of univariate and multivariate functions as well as zero-finding and global optimization. Background material, e.g. on reproducing kernel Hilbert spaces and random fields, is provided.
Benoit Curé
The cooling down to the nominal temperature of 4.5 K was achieved at the beginning of August, in conjunction with the completion of the installation work of the connection between the power lines and the coil current leads. The temperature gradient on the first exchanger of the cold box is now kept within the nominal range. A leak of lubricant on a gasket of the helium compressor station installed at the surface was observed and several corrective actions were necessary to bring the situation back to normal. The compressor had to be refilled with lubricant and a regeneration of the filters and adsorbers was necessary. The coil cool down was resumed successfully, and the cryogenics is running since then with all parameters being nominal. Preliminary tests of the 20kA coil power supply were done earlier at full current through the discharge lines into the dump resistors, and with the powering busbars from USC5 to UXC5 without the magnet connected. On Monday evening August 25th, at 8pm, the final commissionin...
B. Curé
The first phase of the commissioning ended in August by a triggered fast dump at 3T. All parameters were nominal, and the temperature recovery down to 4.5K was carried out in two days by the cryogenics. In September, series of ramps were achieved up to 3 and finally 3.8T, while checking thoroughly the detectors in the forward region, measuring any movement of and around the HF. After the incident of the LHC accelerator on September 19th, corrective actions could be undertaken in the forward region. When all these displacements were fully characterized and repetitive, with no sign of increments in displacement at each field ramp, it was possible to start the CRAFT, Cosmic Run at Four Tesla (which was in fact at 3.8T). The magnet was ramped up to 18.16kA and the 3 week run went smoothly, with only 4 interruptions: due to the VIP visits on 21st October during the LHC inauguration day; a water leak on the cooling demineralized water circuit, about 1 l/min, that triggered a stop of the cooling pumps, and resulte...
Benoit Curé
2013-01-01
Maintenance work and consolidation activities on the magnet cryogenics and its power distribution are progressing according to the schedules. The manufacturing of the two new helium compressor frame units has started. The frame units support the valves, all the sensors and the compressors with their motors. This activity is subcontracted. The final installation and the commissioning at CERN are scheduled for March–April 2014. The overhauls of existing cryogenics equipment (compressors, motors) are in progress. The reassembly of the components shall start in early 2014. The helium drier, to be installed on the high-pressure helium piping, has been ordered and will be delivered in the first trimester of 2014. The power distribution for the helium compressors in SH5 on the 3.3kV network is progressing. The 3.3kV switches, between each compressor and its hot spare compressor, are being installed, together with the power cables for the new compressors. The 3.3kV electrical switchboards in SE5 will ...
Birefringence Determination of Magnetic Moments of Magnetotactic Bacteria
Rosenblatt, Charles; de Araujo, F. Flavio Torres; Frankel, Richard B.
1982-01-01
A birefringence technique is used to determine the average magnetic moments of magnetotactic bacteria in culture. Differences in are noted between live and dead bacteria, as well as between normal density and high density samples of live bacteria.
Power convergence of Abel averages
Kozitsky, Yuri; Shoikhet, David; Zemanek, Jaroslav
2012-01-01
Necessary and sufficient conditions are presented for the Abel averages of discrete and strongly continuous semigroups, $T^k$ and $T_t$, to be power convergent in the operator norm in a complex Banach space. These results cover also the case where $T$ is unbounded and the corresponding Abel average is defined by means of the resolvent of $T$. They complement the classical results by Michael Lin establishing sufficient conditions for the corresponding convergence for a bounded $T$.
Error estimates on averages of correlated data
International Nuclear Information System (INIS)
We describe how the true statistical error on an average of correlated data can be obtained with ease and efficiency by a renormalization group method. The method is illustrated with numerical and analytical examples, having finite as well as infinite range correlations. (orig.)
Self-averaging characteristics of spectral fluctuations
Braun, Petr; Haake, Fritz
2015-04-01
The spectral form factor as well as the two-point correlator of the density of (quasi-)energy levels of individual quantum dynamics are not self-averaging. Only suitable smoothing turns them into useful characteristics of spectra. We present numerical data for a fully chaotic kicked top, employing two types of smoothing: one involves primitives of the spectral correlator, the second, a small imaginary part of the quasi-energy. Self-averaging universal (like the circular unitary ensemble (CUE) average) behavior is found for the smoothed correlator, apart from noise which shrinks like 1/\\sqrt{N} as the dimension N of the quantum Hilbert space grows. There are periodically repeated quasi-energy windows of correlation decay and revival wherein the smoothed correlation remains finite as N\\to ∞ such that the noise is negligible. In between those windows (where the CUE averaged correlator takes on values of the order 1/{{N}2}) the noise becomes dominant and self-averaging is lost. We conclude that the noise forbids distinction of CUE and GUE-type behavior. Surprisingly, the underlying smoothed generating function does not enjoy any self-averaging outside the range of its variables relevant for determining the two-point correlator (and certain higher-order ones). We corroborate our numerical findings for the noise by analytically determining the CUE variance of the smoothed single-matrix correlator.
Well Spacing for Horizontal Wells
Directory of Open Access Journals (Sweden)
C.D.S. Keuengoua
2011-06-01
Full Text Available In the developing phase of a hydrocarbon reservoir and planning for drilling the production wells, it is necessary to drill the wells in an appropriate spacing to achieve maximum economic revenues during the reservoir life span. Well spacing which is the real location and interrelationship between producing oil or gas wells in an oil field is an important parameter. It is determined for the maximum ultimate production of a given reservoir and should be taken in consideration during well planning to avoid drilling of unnecessary wells. This study presents the concept of drainage area on horizontal well and horizontal productivity indices with different equations and their applications. A user friendly Excel Spreadsheet program was developed to calculate the productivity values of horizontal wells using three major available productivity equations. Also, the developed spreadsheet program was used to evaluate the effect of well spacing on the productivities of horizontal wells using productivity index approach and drainage area concept. It also helps to review the comparison between vertical and horizontal wells spacing based on drainage area concept. This program was validated, and then was used to study the effect of horizontal well length on the ratio of horizontal well productivity to vertical well productivity. The results show that higher ratio of horizontal well productivity to vertical well productivity values are obtained with increase length of the horizontal well. It is a very useful tool for making decision about the application of well spacing for horizontal wells.
Sparsity Averaging for Compressive Imaging
Carrillo, Rafael E; Van De Ville, Dimitri; Thiran, Jean-Philippe; Wiaux, Yves
2012-01-01
We propose a novel regularization method for sparse image reconstruction from compressive measurements. The approach relies on the conjecture that natural images exhibit strong average sparsity over multiple coherent frames. The associated reconstruction algorithm, based on an analysis prior and a reweighted $\\ell_1$ scheme, is dubbed Sparsity Averaging Reweighted Analysis (SARA). We test our prior and the associated algorithm through extensive numerical simulations for spread spectrum and Gaussian acquisition schemes suggested by the recent theory of compressed sensing with coherent and redundant dictionaries. Our results show that average sparsity outperforms state-of-the-art priors that promote sparsity in a single orthonormal basis or redundant frame, or that promote gradient sparsity. We also illustrate the performance of SARA in the context of Fourier imaging, for particular applications in astronomy and medicine.
Cranial magnetic resonance imaging
International Nuclear Information System (INIS)
Cranial Magnetic Resonance Imaging is comprehensive, well structured, and well written. The material is current and well referenced. The illustrations are good and complement the text well. The overall quality of publication is above average. The greatest attribute of the book is its readability. The author demonstrates ample skill in making complex subjects, such as MR physics and imaging of cerebral hemorrhage, easy to understand. The book closes with a detailed atlas on the anatomic appearance of the brain on MR images in the axial, coronal, and sagittal planes
On generalized averaged Gaussian formulas
Spalevic, Miodrag M.
2007-09-01
We present a simple numerical method for constructing the optimal (generalized) averaged Gaussian quadrature formulas which are the optimal stratified extensions of Gauss quadrature formulas. These extensions exist in many cases in which real positive Kronrod formulas do not exist. For the Jacobi weight functions w(x)equiv w^{(alpha,beta)}(x)D(1-x)^alpha(1+x)^beta ( alpha,beta>-1 ) we give a necessary and sufficient condition on the parameters alpha and beta such that the optimal averaged Gaussian quadrature formulas are internal.
International Nuclear Information System (INIS)
The T-matrix averaging procedure advocated by Burke, Berrington and Sukumar [1981, J. Phys. B. At. Mol. Phys. 14, 289] is demonstrated to hold in a class of soluble models for two different L2 basis expansions. The convergence rates as the bases are extended to completeness are determined. (author)
Well Spacing for Horizontal Wells
C.D.S. Keuengoua; Amorin, R.
2011-01-01
In the developing phase of a hydrocarbon reservoir and planning for drilling the production wells, it is necessary to drill the wells in an appropriate spacing to achieve maximum economic revenues during the reservoir life span. Well spacing which is the real location and interrelationship between producing oil or gas wells in an oil field is an important parameter. It is determined for the maximum ultimate production of a given reservoir and should be taken in consideration during well plann...
An optimized magnet for magnetic refrigeration
Bjørk, Rasmus; Bahl, Christian Robert Haffenden; Smith, Anders; Christensen, Dennis; Pryds, Nini
2014-01-01
A magnet designed for use in a magnetic refrigeration device is presented. The magnet is designed by applying two general schemes for improving a magnet design to a concentric Halbach cylinder magnet design and dimensioning and segmenting this design in an optimum way followed by the construction of the actual magnet. The final design generates a peak value of 1.24 T, an average flux density of 0.9 T in a volume of 2 L using only 7.3 L of magnet, and has an average low flux density of 0.08 T ...
Stochastic Approximation with Averaging Innovation
Laruelle, Sophie
2010-01-01
The aim of the paper is to establish a convergence theorem for multi-dimensional stochastic approximation in a setting with innovations satisfying some averaging properties and to study some applications. The averaging assumptions allow us to unify the framework where the innovations are generated (to solve problems from Numerical Probability) and the one with exogenous innovations (market data, output of "device" $e.g.$ an Euler scheme) with stationary or ergodic properties. We propose several fields of applications with random innovations or quasi-random numbers. In particular we provide in both setting a rule to tune the step of the algorithm. At last we illustrate our results on five examples notably in Finance.
High average power supercontinuum sources
Indian Academy of Sciences (India)
J C Travers
2010-11-01
The physical mechanisms and basic experimental techniques for the creation of high average spectral power supercontinuum sources is briefly reviewed. We focus on the use of high-power ytterbium-doped fibre lasers as pump sources, and the use of highly nonlinear photonic crystal fibres as the nonlinear medium. The most common experimental arrangements are described, including both continuous wave fibre laser systems with over 100 W pump power, and picosecond mode-locked, master oscillator power fibre amplifier systems, with over 10 kW peak pump power. These systems can produce broadband supercontinua with over 50 and 1 mW/nm average spectral power, respectively. Techniques for numerical modelling of the supercontinuum sources are presented and used to illustrate some supercontinuum dynamics. Some recent experimental results are presented.
On Heroes and Average Moral Human Beings
Kirchgässner, Gebhard
2001-01-01
After discussing various approaches about heroic behaviour in the literature, we first give a definition and classification of moral behaviour, in distinction to intrinsically motivated and ‘prudent' behaviour. Then, we present some arguments on the function of moral behaviour according to ‘minimal' standards of the average individual in a modern democratic society, before we turn to heroic behaviour. We conclude with some remarks on methodological as well as social problems which arise or ma...
International Nuclear Information System (INIS)
The intersubband electron-related nonlinear optical absorption and nonlinear optical rectification in GaAs-Ga1-xAlxAs asymmetric double quantum wells are studied, under the influence of combined or independent applied electric and magnetic fields as well as hydrostatic pressure. The outcome of the density matrix formalism and the effective mass, and parabolic-band approximations have been considered as main theoretical tools for the description. It is obtained that under particular geometrical conditions, with or without electric and/or magnetic field strength, the optical rectification is null and, simultaneously, in such circumstances the optical absorption has a relative maximum. It is also detected that the influence of the hydrostatic pressure leads to increasing or decreasing behaviors of the nonlinear optical absorption in dependence of the particular regime of pressure values considered, with significant distinction of the cases of opposite electric field orientations. - Highlights: → Maxima of the NOA correspond to zero in the NOR. → Electric fields can couple the double quantum wells. → Hydrostatic pressure can couple the double quantum wells. → NOA can increase/decrease with hydrostatic pressure. → Overlap between wave functions depends on the magnetic field.
Energy Technology Data Exchange (ETDEWEB)
Karabulut, I. [Department of Physics, Selcuk University, Konya 42075 (Turkey); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Ave. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Duque, C.A., E-mail: cduque_echeverri@yahoo.e [Instituto de Fisica, Universidad de Antioquia, AA 1226, Medellin (Colombia)
2011-07-15
The intersubband electron-related nonlinear optical absorption and nonlinear optical rectification in GaAs-Ga{sub 1-x}Al{sub x}As asymmetric double quantum wells are studied, under the influence of combined or independent applied electric and magnetic fields as well as hydrostatic pressure. The outcome of the density matrix formalism and the effective mass, and parabolic-band approximations have been considered as main theoretical tools for the description. It is obtained that under particular geometrical conditions, with or without electric and/or magnetic field strength, the optical rectification is null and, simultaneously, in such circumstances the optical absorption has a relative maximum. It is also detected that the influence of the hydrostatic pressure leads to increasing or decreasing behaviors of the nonlinear optical absorption in dependence of the particular regime of pressure values considered, with significant distinction of the cases of opposite electric field orientations. - Highlights: {yields} Maxima of the NOA correspond to zero in the NOR. {yields} Electric fields can couple the double quantum wells. {yields} Hydrostatic pressure can couple the double quantum wells. {yields} NOA can increase/decrease with hydrostatic pressure. {yields} Overlap between wave functions depends on the magnetic field.
Michel Parameters averages and interpretation
International Nuclear Information System (INIS)
The new measurements of Michel parameters in τ decays are combined to world averages. From these measurements model independent limits on non-standard model couplings are derived and interpretations in the framework of specific models are given. A lower limit of 2.5 tan β GeV on the mass of a charged Higgs boson in models with two Higgs doublets can be set and a 229 GeV limit on a right-handed W-boson in left-right symmetric models (95 % c.l.)
... for at-home program. By Beth E. Gibson, PT. (last updated September 2015) Download Brochure Taming Stress (. ... for at-home program. By Beth E. Gibson, PT. (last updated September 2015) Download Brochure Wellness Discussion ...
HIGH AVERAGE POWER OPTICAL FEL AMPLIFIERS
International Nuclear Information System (INIS)
Historically, the first demonstration of the optical FEL was in an amplifier configuration at Stanford University [l]. There were other notable instances of amplifying a seed laser, such as the LLNL PALADIN amplifier [2] and the BNL ATF High-Gain Harmonic Generation FEL [3]. However, for the most part FELs are operated as oscillators or self amplified spontaneous emission devices. Yet, in wavelength regimes where a conventional laser seed can be used, the FEL can be used as an amplifier. One promising application is for very high average power generation, for instance FEL's with average power of 100 kW or more. The high electron beam power, high brightness and high efficiency that can be achieved with photoinjectors and superconducting Energy Recovery Linacs (ERL) combine well with the high-gain FEL amplifier to produce unprecedented average power FELs. This combination has a number of advantages. In particular, we show that for a given FEL power, an FEL amplifier can introduce lower energy spread in the beam as compared to a traditional oscillator. This properly gives the ERL based FEL amplifier a great wall-plug to optical power efficiency advantage. The optics for an amplifier is simple and compact. In addition to the general features of the high average power FEL amplifier, we will look at a 100 kW class FEL amplifier is being designed to operate on the 0.5 ampere Energy Recovery Linac which is under construction at Brookhaven National Laboratory's Collider-Accelerator Department
Flexible time domain averaging technique
Zhao, Ming; Lin, Jing; Lei, Yaguo; Wang, Xiufeng
2013-09-01
Time domain averaging(TDA) is essentially a comb filter, it cannot extract the specified harmonics which may be caused by some faults, such as gear eccentric. Meanwhile, TDA always suffers from period cutting error(PCE) to different extent. Several improved TDA methods have been proposed, however they cannot completely eliminate the waveform reconstruction error caused by PCE. In order to overcome the shortcomings of conventional methods, a flexible time domain averaging(FTDA) technique is established, which adapts to the analyzed signal through adjusting each harmonic of the comb filter. In this technique, the explicit form of FTDA is first constructed by frequency domain sampling. Subsequently, chirp Z-transform(CZT) is employed in the algorithm of FTDA, which can improve the calculating efficiency significantly. Since the signal is reconstructed in the continuous time domain, there is no PCE in the FTDA. To validate the effectiveness of FTDA in the signal de-noising, interpolation and harmonic reconstruction, a simulated multi-components periodic signal that corrupted by noise is processed by FTDA. The simulation results show that the FTDA is capable of recovering the periodic components from the background noise effectively. Moreover, it can improve the signal-to-noise ratio by 7.9 dB compared with conventional ones. Experiments are also carried out on gearbox test rigs with chipped tooth and eccentricity gear, respectively. It is shown that the FTDA can identify the direction and severity of the eccentricity gear, and further enhances the amplitudes of impulses by 35%. The proposed technique not only solves the problem of PCE, but also provides a useful tool for the fault symptom extraction of rotating machinery.
DEFF Research Database (Denmark)
Rozycki, Bartosz
2015-01-01
We live in a world full of rush and a ‘relaxed state of being’ might increasingly play a role in today’s fast paced society to overcome contemporary stress and related illnesses such as burn-outs. The Sleephones concept is a wearable wellness device that aims to support relaxation by combing music...
Qiu, Keping; Menten, Karl M; Liu, Hauyu B; Tang, Ya-Wen
2013-01-01
We report on detection of an ordered magnetic field (B field) threading a massive star-forming clump in the molecular cloud G35.2-0.74, using Submillimeter Array observations of polarized dust emission. Thanks to the sensitive and high-angular-resolution observations, we are able to resolve the morphology of the B field in the plane of sky and detect a great turn of 90 degree in the B field direction: Over the northern part of the clump, where a velocity gradient is evident, the B field is largely aligned with the long axis of the clump, whereas in the southern part, where the velocity field appears relatively uniform, the B field is slightly pinched with its mean direction perpendicular to the clump elongation. We suggest that the clump forms as its parent cloud collapses more along the large scale B field. In this process, the northern part carries over most of the angular momentum, forming a fast rotating system, and pulls the B field into a toroidal configuration. In contrast, the southern part is not sig...
An optimized magnet for magnetic refrigeration
Bjørk, R; Smith, A; Christensen, D V; Pryds, N
2014-01-01
A magnet designed for use in a magnetic refrigeration device is presented. The magnet is designed by applying two general schemes for improving a magnet design to a concentric Halbach cylinder magnet design and dimensioning and segmenting this design in an optimum way followed by the construction of the actual magnet. The final design generates a peak value of 1.24 T, an average flux density of 0.9 T in a volume of 2 L using only 7.3 L of magnet, and has an average low flux density of 0.08 T also in a 2 L volume. The working point of all the permanent magnet blocks in the design is very close to the maximum energy density. The final design is characterized in terms of a performance parameter, and it is shown that it is one of the best performing magnet designs published for magnetic refrigeration.
An optimized magnet for magnetic refrigeration
DEFF Research Database (Denmark)
Bjørk, Rasmus; Bahl, Christian Robert Haffenden; Smith, Anders;
2010-01-01
A magnet designed for use in a magnetic refrigeration device is presented. The magnet is designed by applying two general schemes for improving a magnet design to a concentric Halbach cylinder magnet design and dimensioning and segmenting this design in an optimum way followed by the construction...... of the actual magnet. The final design generates a peak value of 1.24 T, an average flux density of 0.9 T in a volume of 2 L using only 7.3 L of magnet, and has an average low flux density of 0.08 T also in a 2 L volume. The working point of all the permanent magnet blocks in the design is very close...... to the maximum energy density. The final design is characterized in terms of a performance parameter, and it is shown that it is one of the best performing magnet designs published for magnetic refrigeration....
Krchňák, Petr
2016-01-01
Diplomová práce „Wellness centrum'' je zpracována ve formě prováděcí dokumentace obsahující všechny náležitosti dle platných norem a předpisů. Navržený objekt je řešen jako třípodlažní budova. Objekt slouží veřejnosti k rekreaci a sportu. V 1S je umístěno technické zázemí, zázemí pro zaměstnance, šatny a posilovna. V 1 NP se nachází kavárna a wellness. Ve 2NP se nachází kanceláře pro administrativu budovy, masáže, solárium, šatny a fitness sál. Budova je založena na základových patk...
Sparsity averaging for radio-interferometric imaging
Carrillo, Rafael E; Wiaux, Yves
2014-01-01
We propose a novel regularization method for compressive imaging in the context of the compressed sensing (CS) theory with coherent and redundant dictionaries. Natural images are often complicated and several types of structures can be present at once. It is well known that piecewise smooth images exhibit gradient sparsity, and that images with extended structures are better encapsulated in wavelet frames. Therefore, we here conjecture that promoting average sparsity or compressibility over multiple frames rather than single frames is an extremely powerful regularization prior.
Fluctuations of wavefunctions about their classical average
International Nuclear Information System (INIS)
Quantum-classical correspondence for the average shape of eigenfunctions and the local spectral density of states are well-known facts. In this paper, the fluctuations of the quantum wavefunctions around the classical value are discussed. A simple random matrix model leads to a Gaussian distribution of the amplitudes whose width is determined by the classical shape of the eigenfunction. To compare this prediction with numerical calculations in chaotic models of coupled quartic oscillators, we develop a rescaling method for the components. The expectations are broadly confirmed, but deviations due to scars are observed. This effect is much reduced when both Hamiltonians have chaotic dynamics
Average neutron detection efficiency for DEMON detectors
International Nuclear Information System (INIS)
The neutron detection efficiency of a DEMON detector, averaged over the whole volume, was calculated using GEANT and applied to determine neutron multiplicities in an intermediate heavy ion reaction. When a neutron source is set at a distance of about 1 m from the front surface of the detector, the average efficiency, ϵav, is found to be significantly lower (20–30%) than the efficiency measured at the center of the detector, ϵ0. In the GEANT simulation the ratio R=ϵav/ϵ0 was calculated as a function of neutron energy. The experimental central efficiency multiplied by R was then used to determine the average efficiency. The results were applied to a study of the 64Zn+112Sn reaction at 40 A MeV which employed 16 DEMON detectors. The neutron multiplicity was extracted using a moving source fit. The derived multiplicities are compared well with those determined using the neutron ball in the NIMROD detector array in a separate experiment. Both are in good agreement with multiplicities predicted by a transport model calculation using an antisymmetric molecular dynamics (AMD) model code
Bambas, Vratislav
2013-01-01
Novostavba Wellness hotelu. Objekt je částečně podsklepen. Hotel se skládá ze tří částí. Střední trakt je železobetonový skelet a má pět nadzemních podlaží. Tato část slouží jako vstupní hala a hlavní schodiště. Boční trakty mají čtyři nadzemní podlaží a jejich nosný systém je příčný stěnový, zděný, ze systému Porotherm. V suterénu se nachází zázemí hotelu a bazén. Do přízemí je umístěno restaurační zařízení. Ve druhém patře se nacházejí pokoje, posilovna a služby. V posledním patře jsou pouz...
Averaging lifetimes for B hadron species
International Nuclear Information System (INIS)
The measurement of the lifetimes of the individual B species are of great interest. Many of these measurements are well below the 10% level of precision. However, in order to reach the precision necessary to test the current theoretical predictions, the results from different experiments need to be averaged together. Therefore, the relevant systematic uncertainties of each measurement need to be well defined in order to understand the correlations between the results from different experiments. In this paper we discuss the dominant sources of systematic errors which lead to correlations between the different measurements. We point out problems connected with the conventional approach of combining lifetime data and discuss methods which overcome these problems. (orig.)
International Nuclear Information System (INIS)
In this paper, we study the electronic contribution to the elastic constants in strained layer quantum well superlattices of non-parabolic semiconductors with graded structures under strong magnetic quantization and compare the same with that of the constituent materials, by formulating the appropriate dispersion laws. It is found, taking InSb/GaSb quantum well strained superlattices of non-parabolic semiconductors as an example, that the carrier contribution to the second- and third-order elastic constants oscillates both with the electronic concentration and the inverse quantizing magnetic field in different manners together with the fact that the nature of oscillations is totally band structure dependent. We have also suggested an experimental method for determining the electronic contribution to the elastic constants in low-dimensional materials having arbitrary dispersion laws. In addition, the well-known results for bulk specimens of wide-gap stress-free materials have been obtained as special cases from our generalized formulation under certain limiting conditions
Flux-Averaged and Volume-Averaged Concentrations in Continuum Approaches to Solute Transport
Parker, J. C.; van Genuchten, M. Th.
1984-07-01
Transformations between volume-averaged pore fluid concentrations and flux-averaged concentrations are presented which show that both modes of concentration obey convective-dispersive transport equations of identical mathematical form for nonreactive solutes. The pertinent boundary conditions for the two modes, however, do not transform identically. Solutions of the convection-dispersion equation for a semi-infinite system during steady flow subject to a first-type inlet boundary condition is shown to yield flux concentrations, while solutions subject to a third-type boundary condition yield volume-averaged concentrations. These solutions may be applied with reasonable impunity to finite as well as semi-infinite media if back mixing at the exit is precluded. Implications of the distinction between resident and flux concentrations to laboratory and field studies of solute transport are discussed. It is suggested that perceived limitations of the convection-dispersion model for media with large variations in pore water velocities may in certain cases be attributable to a failure to distinguish between volume-averaged and flux-averaged concentrations.
UNEMPLOYMENT BENEFIT, MINIMUM WAGE AND AVERAGE SALARY EARNINGS IN ROMANIA
2012-01-01
The existence of a long-run equilibrium between average salary earnings and labour market public institutions, such as unemployment benefit and minimum wage, is checked using ARDL bounds testing procedure. The results pointed out that long-run causality runs from average salary earnings to labour market public institutions and not vice versa. The short-run dynamics are depicted as well.
Classic hydrodynamic and kinetic formalism as averaging of delta-functional particle images
Kuz'menkov, L S
2014-01-01
Critical analyses of well-known methods of derivation of kinetic and hydrodynamic equations is presented. Another method of derivation of kinetic and hydrodynamic equations from classic mechanics is described. It is shown that equations of classic hydrodynamics can be derived directly from microscopic picture of motion, without using of kinetic equations as an intermediate step. New method of derivation of equation of macroscopic motion includes explicit averaging of microscopic motion on infinitesimally small piece of medium. This averaging leads to presence of electric dipole, magnetic dipole, and higher moments along with the charge density and the current density in hydrodynamic equations. The method under consideration allows to derive equations of evolution for new quantities.
Magnetism and magnetic materials
Coey, J M D
2010-01-01
Covering basic physical concepts, experimental methods, and applications, this book is an indispensable text on the fascinating science of magnetism, and an invaluable source of practical reference data. Accessible, authoritative, and assuming undergraduate familiarity with vectors, electromagnetism and quantum mechanics, this textbook is well suited to graduate courses. Emphasis is placed on practical calculations and numerical magnitudes - from nanoscale to astronomical scale - focussing on modern applications, including permanent magnet structures and spin electronic devices. Each self-contained chapter begins with a summary, and ends with exercises and further reading. The book is thoroughly illustrated with over 600 figures to help convey concepts and clearly explain ideas. Easily digestible tables and data sheets provide a wealth of useful information on magnetic properties. The 38 principal magnetic materials, and many more related compounds, are treated in detail
Bounce averaged trapped electron fluid equations for plasma turbulence
International Nuclear Information System (INIS)
A novel set of nonlinear fluid equations for mirror-trapped electrons is developed which differs from conventional fluid equations in two main respects: (1) the trapped-fluid moments average over only two of three velocity space dimensions, retaining the full pitch angle dependence of the traped electron dynamics, and (2) closure approximations include the effects of collisionless wave-particle resonances with the toroidal precession drift. By speeding up calculations by at least √ mi/me, these bounce averaged fluid equations make possible realistic nonlinear simulations of turbulent particle transport and electron heat transport in tokamaks and other magnetically confined plasmas
Thermodynamic properties of average-atom interatomic potentials for alloys
Nöhring, Wolfram Georg; Curtin, William Arthur
2016-05-01
The atomistic mechanisms of deformation in multicomponent random alloys are challenging to model because of their extensive structural and compositional disorder. For embedded-atom-method interatomic potentials, a formal averaging procedure can generate an average-atom EAM potential and this average-atom potential has recently been shown to accurately predict many zero-temperature properties of the true random alloy. Here, the finite-temperature thermodynamic properties of the average-atom potential are investigated to determine if the average-atom potential can represent the true random alloy Helmholtz free energy as well as important finite-temperature properties. Using a thermodynamic integration approach, the average-atom system is found to have an entropy difference of at most 0.05 k B/atom relative to the true random alloy over a wide temperature range, as demonstrated on FeNiCr and Ni85Al15 model alloys. Lattice constants, and thus thermal expansion, and elastic constants are also well-predicted (within a few percent) by the average-atom potential over a wide temperature range. The largest differences between the average atom and true random alloy are found in the zero temperature properties, which reflect the role of local structural disorder in the true random alloy. Thus, the average-atom potential is a valuable strategy for modeling alloys at finite temperatures.
Averaging in the presence of sliding errors
International Nuclear Information System (INIS)
In many cases the precision with which an experiment can measure a physical quantity depends on the value of that quantity. Not having access to the true value, experimental groups are forced to assign their errors based on their own measured value. Procedures which attempt to derive an improved estimate of the true value by a suitable average of such measurements usually weight each experiment's measurement according to the reported variance. However, one is in a position to derive improved error estimates for each experiment from the average itself, provided an approximate idea of the functional dependence of the error on the central value is known. Failing to do so can lead to substantial biases. Techniques which avoid these biases without loss of precision are proposed and their performance is analyzed with examples. These techniques are quite general and can bring about an improvement even when the behavior of the errors is not well understood. Perhaps the most important application of the technique is in fitting curves to histograms
Beta-energy averaging and beta spectra
International Nuclear Information System (INIS)
A simple yet highly accurate method for approximately calculating spectrum-averaged beta energies and beta spectra for radioactive nuclei is presented. This method should prove useful for users who wish to obtain accurate answers without complicated calculations of Fermi functions, complex gamma functions, and time-consuming numerical integrations as required by the more exact theoretical expressions. Therefore, this method should be a good time-saving alternative for investigators who need to make calculations involving large numbers of nuclei (e.g., fission products) as well as for occasional users interested in restricted number of nuclides. The average beta-energy values calculated by this method differ from those calculated by ''exact'' methods by no more than 1 percent for nuclides with atomic numbers in the 20 to 100 range and which emit betas of energies up to approximately 8 MeV. These include all fission products and the actinides. The beta-energy spectra calculated by the present method are also of the same quality
Optimal estimation of the diffusion coefficient from non-averaged and averaged noisy magnitude data
Kristoffersen, Anders
2007-08-01
The magnitude operation changes the signal distribution in MRI images from Gaussian to Rician. This introduces a bias that must be taken into account when estimating the apparent diffusion coefficient. Several estimators are known in the literature. In the present paper, two novel schemes are proposed. Both are based on simple least squares fitting of the measured signal, either to the median (MD) or to the maximum probability (MP) value of the Probability Density Function (PDF). Fitting to the mean (MN) or a high signal-to-noise ratio approximation to the mean (HS) is also possible. Special attention is paid to the case of averaged magnitude images. The PDF, which cannot be expressed in closed form, is analyzed numerically. A scheme for performing maximum likelihood (ML) estimation from averaged magnitude images is proposed. The performance of several estimators is evaluated by Monte Carlo (MC) simulations. We focus on typical clinical situations, where the number of acquisitions is limited. For non-averaged data the optimal choice is found to be MP or HS, whereas uncorrected schemes and the power image (PI) method should be avoided. For averaged data MD and ML perform equally well, whereas uncorrected schemes and HS are inadequate. MD provides easier implementation and higher computational efficiency than ML. Unbiased estimation of the diffusion coefficient allows high resolution diffusion tensor imaging (DTI) and may therefore help solving the problem of crossing fibers encountered in white matter tractography.
Materials with low DC magnetic susceptibility for sensitive magnetic measurements
Khatiwada, R.; Dennis, L.; Kendrick, R.; Khosravi, M.; Peters, M.; Smith, E.; Snow, W. M.
2016-02-01
Materials with very low DC magnetic susceptibility have many scientific applications. To our knowledge however, relatively little research has been conducted with the goal to produce a totally nonmagnetic material. This phrase in our case means after spatially averaging over macroscopic volumes, it possesses an average zero DC magnetic susceptibility. We report measurements of the DC magnetic susceptibility of three different types of nonmagnetic materials at room temperature: (I) solutions of paramagnetic salts and diamagnetic liquids, (II) liquid gallium-indium alloys and (III) pressed powder mixtures of tungsten and bismuth. The lowest measured magnetic susceptibility among these candidate materials is in the order of 10-9 cgs volume susceptibility units, about two orders of magnitude smaller than distilled water. In all cases, the measured concentration dependence of the magnetic susceptibility is consistent with that expected for the weighted sum of the susceptibilities of the separate components within experimental error. These results verify the well-known Wiedemann additivity law for the magnetic susceptibility of inert mixtures of materials and thereby realize the ability to produce materials with small but tunable magnetic susceptibility. For our particular scientific application, we are also looking for materials with the largest possible number of neutrons and protons per unit volume. The gallium-indium alloys fabricated and measured in this work possess to our knowledge the smallest ratio of volume magnetic susceptibility to nucleon number density per unit volume for a room temperature liquid, and the tungsten-bismuth pressed powder mixtures possess to our knowledge the smallest ratio of volume magnetic susceptibility to nucleon number density per unit volume for a room temperature solid. This ratio is a figure of merit for a certain class of precision experiments that search for possible exotic spin-dependent forces of Nature.
Average transverse momentum quantities approaching the lightfront
Boer, Daniel
2014-01-01
In this contribution to Light Cone 2014, three average transverse momentum quantities are discussed: the Sivers shift, the dijet imbalance, and the $p_T$ broadening. The definitions of these quantities involve integrals over all transverse momenta that are overly sensitive to the region of large transverse momenta, which conveys little information about the transverse momentum distributions of quarks and gluons inside hadrons. TMD factorization naturally suggests alternative definitions of such integrated quantities, using Bessel-weighting and rapidity cut-offs, with the conventional definitions as limiting cases. The regularized quantities are given in terms of integrals over the TMDs of interest that are well-defined and moreover have the advantage of being amenable to lattice evaluations.
Energy Technology Data Exchange (ETDEWEB)
Kehl, Christian
2011-03-28
The main motivation for this thesis was the experimental confirmation of the theoretically predicted magnetic soft mode and the analysis of its dependence on the hole-concentration and external B-field, as well as its disappearance with increasing sample temperature. For that purpose, CdMnTe/CdMgTe QWs (Mn: 0.6%, 1.0%) positioned close to the sample surface (13-19 nm) were investigated in an in-plane applied external magnetic field (up to 4.5 T in Voigt-geometry) via a two-colour experiment i.e. using two light sources. This allows the spin excitation of Mn-ions by simultaneously tuning the hole-concentration towards the ferromagnetic phase transition by photo-generated carriers. Thus, one tuneable laser is responsible for resonant below-barrier excitation as a probe for Multi-SF Raman scattering. The other laser excites photo-generated carriers from above barrier (2.41 eV) for tuning the hole concentration in the QW. Positioning the QW close to the sample surface causes a surface-induced p-doping of the QW (intrinsic hole concentration in the QW) and enables the active tuning of the hole concentration by photo-generated carriers due to different tunnelling behaviour of electrons and holes from the QW to the surface. The Mn-g-factor was decreased by quasi-continuously increasing the above-barrier illumination, while the below-barrier excitation was kept at a constant low power. This results in a Mn-g-factor reduction starting from its atomic value g=2.01 to lowest evaluated Mn-g-factor in this thesis g=1.77. This is a magnetic softening of 12%. Apart from the general magnetic soft mode behaviour at low temperatures, one of the main experimental results in this thesis is the confirmation of the theoretical prediction that the magnetic soft mode behaviour in the external B-field does not only depend on the carrier concentration but also on the B-field strength itself. An additional aspect is the temperature dependence of the magnetic soft mode. The Mn
International Nuclear Information System (INIS)
The main motivation for this thesis was the experimental confirmation of the theoretically predicted magnetic soft mode and the analysis of its dependence on the hole-concentration and external B-field, as well as its disappearance with increasing sample temperature. For that purpose, CdMnTe/CdMgTe QWs (Mn: 0.6%, 1.0%) positioned close to the sample surface (13-19 nm) were investigated in an in-plane applied external magnetic field (up to 4.5 T in Voigt-geometry) via a two-colour experiment i.e. using two light sources. This allows the spin excitation of Mn-ions by simultaneously tuning the hole-concentration towards the ferromagnetic phase transition by photo-generated carriers. Thus, one tuneable laser is responsible for resonant below-barrier excitation as a probe for Multi-SF Raman scattering. The other laser excites photo-generated carriers from above barrier (2.41 eV) for tuning the hole concentration in the QW. Positioning the QW close to the sample surface causes a surface-induced p-doping of the QW (intrinsic hole concentration in the QW) and enables the active tuning of the hole concentration by photo-generated carriers due to different tunnelling behaviour of electrons and holes from the QW to the surface. The Mn-g-factor was decreased by quasi-continuously increasing the above-barrier illumination, while the below-barrier excitation was kept at a constant low power. This results in a Mn-g-factor reduction starting from its atomic value g=2.01 to lowest evaluated Mn-g-factor in this thesis g=1.77. This is a magnetic softening of 12%. Apart from the general magnetic soft mode behaviour at low temperatures, one of the main experimental results in this thesis is the confirmation of the theoretical prediction that the magnetic soft mode behaviour in the external B-field does not only depend on the carrier concentration but also on the B-field strength itself. An additional aspect is the temperature dependence of the magnetic soft mode. The Mn
Magnetic Fluids: Biomedical Applications and Magnetic Fractionation
Rheinländer, Thomas; Kötitz, Róman; Weitschies, Werner; Semmler, Wolfhard
2000-01-01
In addition to engineering applications, magnetic fluids containing magnetic nanoparticles are being increasingly applied to biomedical purposes. Besides the well established use of magnetic particles for biological separation or as contrast agents for magnetic resonance imaging, magnetic particles are also being tested for the inductive heat treatment of tumors or as markers for the quantification of biologically active substances. The properties of magnetic nanoparticles usually exhibit a b...
On averaged force acting on a particle in H.F electromagnetic field
International Nuclear Information System (INIS)
A general expression is obtained for the time averaged force acting on a particle immersed in a magnetic field in the presence of H.F quasiplanar, quasimonochromatic electromagnetic wave. Here, averaging is done over the period of the H.F wave. It is shown that this averaged force is proportional to the time derivative of the squared H.F wave amplitude. The force also includes a term proportional to the gradient of the time constant magnetic field and is connected with the induced magnetic moment in the H.F field. (author). 7 refs
Averages of Values of L-Series
Alkan, Emre; Ono, Ken
2013-01-01
We obtain an exact formula for the average of values of L-series over two independent odd characters. The average of any positive moment of values at s = 1 is then expressed in terms of finite cotangent sums subject to congruence conditions. As consequences, bounds on such cotangent sums, limit points for the average of first moment of L-series at s = 1 and the average size of positive moments of character sums related to the class number are deduced.
Spectral averaging techniques for Jacobi matrices
del Rio, Rafael; Schulz-Baldes, Hermann
2008-01-01
Spectral averaging techniques for one-dimensional discrete Schroedinger operators are revisited and extended. In particular, simultaneous averaging over several parameters is discussed. Special focus is put on proving lower bounds on the density of the averaged spectral measures. These Wegner type estimates are used to analyze stability properties for the spectral types of Jacobi matrices under local perturbations.
Magnetism of uranium/iron multilayers: II. Magnetic properties
Energy Technology Data Exchange (ETDEWEB)
Beesley, A M [Department of Physics, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Zochowski, S W [Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom); Thomas, M F [Department of Physics, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Herring, A D F [Department of Physics, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Langridge, S [ISIS, Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX (United Kingdom); Brown, S D [Department of Physics, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Ward, R C C [Clarendon Laboratory, University of Oxford, Oxford OX1 3PU (United Kingdom); Wells, M R [Clarendon Laboratory, University of Oxford, Oxford OX1 3PU (United Kingdom); Springell, R [Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom); Stirling, W G [Department of Physics, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Lander, G H [European Commission, JRC, Institute for Transuranium Elements, Postfach 2340, Karlsruhe, D-76125 (Germany)
2004-12-01
Well-defined U/Fe multilayers of varying layer thicknesses and bilayer repeat numbers were prepared by a dc magnetron sputtering method. Polarized neutron reflectometry, off-specular neutron diffraction and magnetic moment measurements were used to determine the physical properties of the multilayers leading to an evaluation of the magnetic moments associated with the U and Fe atoms. The multilayers exhibit ferromagnetic behaviour with the easy axis in the plane of the multilayer. The saturation magnetization was found to increase with increasing Fe-layer thickness and the magnetic moment averaged over the structured iron layers was below the bulk value of 2.2 {mu}{sub B}/Fe atom. No anomalies were observed in the magnetization from 4.2 to 375 K in temperature-dependent scans at 0.005 and 0.1 T or in magnetic field scans from 0 to 7 T at 4.2 and 295 K. The hysteresis curves exhibited a small degree of perpendicular magnetic anisotropy. The Curie temperatures for the multilayers were determined from ac susceptibility measurements and were found to be less than the bulk Fe value of 1043 K.
Coupled atomic-molecular condensates in a double-well potential: decaying molecular oscillations
Jing, H; Zhan, M; Gu, Sihong; Jing, Hui; Zhan, Mingsheng
2005-01-01
We present a four-mode model that describes coherent photo-association (PA) in a double-well Bose-Einstein condensate, focusing on the $average$ molecular populations in certain parameters. Our numerical results predict an interesting strong-damping effect of molecular oscillations by controlling the particle tunnellings and PA light strength, which may provide a promising way for creating a stable molecular condensate via coherent PA in a magnetic double-well potential.
Permanent magnet array for the magnetic refrigerator
Lee, S. J.; Kenkel, J. M.; Pecharsky, V. K.; Jiles, D. C.
2002-05-01
Recent research into the development of magnetic refrigeration (MR) operating at room temperature has shown that it can provide a reliable, energy-efficient cooling system. To enhance the cooling power of the magnetic refrigerator, it is required to use a magnetic refrigerant material with large magnetocaloric effect (MCE) at the appropriate temperature. Most advanced magnetic refrigerant materials show largest MCE at high applied magnetic fields generated by a superconducting magnet. For application of MCE to air conditioners or household refrigerators, it is essential to develop a permanent magnet array to form a compact, strong, and energy-efficient magnetic field generator. Generating a magnetic field well above the remanence of a permanent magnet material is hard to achieve through conventional designs. A permanent magnet array based on a hollow cylindrical flux source is found to provide an appropriate geometry and magnetic field strength for MR applications.
The average action for scalar fields near phase transitions
International Nuclear Information System (INIS)
We compute the average action for fields in two, three and four dimensions, including the effects of wave function renormalization. A study of the one loop evolution equations for the scale dependence of the average action gives a unified picture of the qualitatively different behaviour in various dimensions for discrete as well as abelian and nonabelian continuous symmetry. The different phases and the phase transitions can be infered from the evolution equation. (orig.)
Magnetic dissipation Spatial and temporal structure
Nordlund, A A
2002-01-01
A magnetically dominated plasma driven by motions on boundaries at which magnetic field lines are anchored is forced to dissipate the work being done upon it, no matter how small the electrical resistivity. Numerical experiments have clarified that dissipation is achieved through the formation of a hierarchy of electrical current sheets. The probability distribution function of the local winding of magnetic field lines is nearly Gaussian, with a width of the order unity. The dissipation is highly irregular in space and time, but the average level of dissipation is well described by a scaling law that is independent of the electrical resistivity. If the boundary driving is suspended for a period of time the magnetic dissipation rapidly drops to insignificant levels, leaving the magnetic field in a nearly force-free state. Renewed boundary driving leads to a quick return to dissipation levels compatible with the rate of boundary work, with dissipation starting much more rapidly than when starting from idealized...
Average-cost based robust structural control
Hagood, Nesbitt W.
1993-01-01
A method is presented for the synthesis of robust controllers for linear time invariant structural systems with parameterized uncertainty. The method involves minimizing quantities related to the quadratic cost (H2-norm) averaged over a set of systems described by real parameters such as natural frequencies and modal residues. Bounded average cost is shown to imply stability over the set of systems. Approximations for the exact average are derived and proposed as cost functionals. The properties of these approximate average cost functionals are established. The exact average and approximate average cost functionals are used to derive dynamic controllers which can provide stability robustness. The robustness properties of these controllers are demonstrated in illustrative numerical examples and tested in a simple SISO experiment on the MIT multi-point alignment testbed.
Designing a magnet for magnetic refrigeration
Energy Technology Data Exchange (ETDEWEB)
Bjoerk, R.
2010-03-15
This thesis investigates the design and optimization of a permanent magnet assembly for use in a magnetic refrigeration device. The heart of magnetic refrigeration is the adiabatic temperature change in the magnetocaloric material which is caused by the magnetic field. In order to design an ideal magnet assembly the magnetocaloric materials and the refrigeration process itself and their properties and performance as a function of magnetic field are investigated. For the magnetocaloric materials it is the magnetization, specific heat capacity and adiabatic temperature that are investigated as functions of the magnetic field. Following this the process utilized by a magnetic refrigerator to provide cooling is investigated using a publicly available one dimensional numerical model. This process is called active magnetic regeneration (AMR). The aim is to determine the performance of the AMR as a function of the magnetic field in order to learn the properties of the optimal magnet assembly. The performance of the AMR as a function of the synchronization and width of the magnetic field with respect to the AMR cycle, the ramp rate and maximum value of the magnetic field are investigated. Other published magnet designs used in magnetic refrigeration devices are also evaluated, using a figure of merit based on the properties of the investigated magnetocaloric materials, to learn the properties of the best magnet designs to date. Following this investigation the Halbach cylinder, which is a hollow permanent magnet cylinder with a rotating remanent flux density, is investigated in detail as it forms the basis of many magnet designs used in magnetic refrigeration. Here the optimal dimensions of a Halbach cylinder, as well as analytical calculations of the magnetic field for a Halbach cylinder of infinite length, are presented. Once it has been determined which properties are desirable for a magnet used in magnetic refrigeration the design of a new magnet is described. This is
Coherent ensemble averaging techniques for impedance cardiography
Hurwitz, Barry E.; Shyu, Liang-Yu; Reddy, Sridhar P; Schneiderman, Neil; Nagel, Joachim H.
1990-01-01
EKG synchronized ensemble averaging of the impedance cardiogram tends to blur or suppress signal events due to signal jitter or event latency variability. Although ensemble averaging provides some improvement in the stability of the signal and signal to noise ratio under conditions of nonperiodic influences of respiration and motion, coherent averaging techniques were developed to determine whether further enhancement of the impedance cardiogram could be obtained. Physiological signals were o...
Basics of averaging of the Maxwell equations for bulk materials
Chipouline, A; Tretyakov, S
2012-01-01
Volume or statistical averaging of the microscopic Maxwell equations (MEs), i.e. transition from microscopic MEs to their macroscopic counterparts, is one of the main steps in electrodynamics of materials. In spite of the fundamental importance of the averaging procedure, it is quite rarely properly discussed in university courses and respective books; up to now there is no established consensus about how the averaging procedure has to be performed. In this paper we show that there are some basic principles for the averaging procedure (irrespective to what type of material is studied) which have to be satisfied. Any homogenization model has to be consistent with the basic principles. In case of absence of this correlation of a particular model with the basic principles the model could not be accepted as a credible one. Another goal of this paper is to establish the averaging procedure for bulk MM, which is rather close to the case of compound materials but should include magnetic response of the inclusions an...
Industrial Applications of High Average Power FELS
Shinn, Michelle D
2005-01-01
The use of lasers for material processing continues to expand, and the annual sales of such lasers exceeds $1 B (US). Large scale (many m2) processing of materials require the economical production of laser powers of the tens of kilowatts, and therefore are not yet commercial processes, although they have been demonstrated. The development of FELs based on superconducting RF (SRF) linac technology provides a scaleable path to laser outputs above 50 kW in the IR, rendering these applications economically viable, since the cost/photon drops as the output power increases. This approach also enables high average power ~ 1 kW output in the UV spectrum. Such FELs will provide quasi-cw (PRFs in the tens of MHz), of ultrafast (pulsewidth ~ 1 ps) output with very high beam quality. This talk will provide an overview of applications tests by our facility's users such as pulsed laser deposition, laser ablation, and laser surface modification, as well as present plans that will be tested with our upgraded FELs. These upg...
NOAA Average Annual Salinity (3-Zone)
California Department of Resources — The 3-Zone Average Annual Salinity Digital Geography is a digital spatial framework developed using geographic information system (GIS) technology. These salinity...
Improving consensus structure by eliminating averaging artifacts
Directory of Open Access Journals (Sweden)
KC Dukka B
2009-03-01
Full Text Available Abstract Background Common structural biology methods (i.e., NMR and molecular dynamics often produce ensembles of molecular structures. Consequently, averaging of 3D coordinates of molecular structures (proteins and RNA is a frequent approach to obtain a consensus structure that is representative of the ensemble. However, when the structures are averaged, artifacts can result in unrealistic local geometries, including unphysical bond lengths and angles. Results Herein, we describe a method to derive representative structures while limiting the number of artifacts. Our approach is based on a Monte Carlo simulation technique that drives a starting structure (an extended or a 'close-by' structure towards the 'averaged structure' using a harmonic pseudo energy function. To assess the performance of the algorithm, we applied our approach to Cα models of 1364 proteins generated by the TASSER structure prediction algorithm. The average RMSD of the refined model from the native structure for the set becomes worse by a mere 0.08 Å compared to the average RMSD of the averaged structures from the native structure (3.28 Å for refined structures and 3.36 A for the averaged structures. However, the percentage of atoms involved in clashes is greatly reduced (from 63% to 1%; in fact, the majority of the refined proteins had zero clashes. Moreover, a small number (38 of refined structures resulted in lower RMSD to the native protein versus the averaged structure. Finally, compared to PULCHRA 1, our approach produces representative structure of similar RMSD quality, but with much fewer clashes. Conclusion The benchmarking results demonstrate that our approach for removing averaging artifacts can be very beneficial for the structural biology community. Furthermore, the same approach can be applied to almost any problem where averaging of 3D coordinates is performed. Namely, structure averaging is also commonly performed in RNA secondary prediction 2, which
A note on generalized averaged Gaussian formulas
Spalevic, Miodrag
2007-11-01
We have recently proposed a very simple numerical method for constructing the averaged Gaussian quadrature formulas. These formulas exist in many more cases than the real positive Gauss?Kronrod formulas. In this note we try to answer whether the averaged Gaussian formulas are an adequate alternative to the corresponding Gauss?Kronrod quadrature formulas, to estimate the remainder term of a Gaussian rule.
Average Transmission Probability of a Random Stack
Lu, Yin; Miniatura, Christian; Englert, Berthold-Georg
2010-01-01
The transmission through a stack of identical slabs that are separated by gaps with random widths is usually treated by calculating the average of the logarithm of the transmission probability. We show how to calculate the average of the transmission probability itself with the aid of a recurrence relation and derive analytical upper and lower…
40 CFR 76.11 - Emissions averaging.
2010-07-01
... 40 Protection of Environment 16 2010-07-01 2010-07-01 false Emissions averaging. 76.11 Section 76...) ACID RAIN NITROGEN OXIDES EMISSION REDUCTION PROGRAM § 76.11 Emissions averaging. (a) General provisions. In lieu of complying with the applicable emission limitation in § 76.5, 76.6, or 76.7,...
Magnetic Graphene Nanohole Superlattices
Yu, Decai; Lupton, Elizabeth M.; Liu, Miao; Wei LIU; Liu, Feng
2008-01-01
We investigate the magnetic properties of nano-holes (NHs) patterned in graphene using first principles calculations. We show that superlattices consisting of a periodic array of NHs form a new family of 2D crystalline "bulk" magnets whose collective magnetic behavior is governed by inter-NH spin-spin interaction. They exhibit long-range magnetic order well above room temperature. Furthermore, magnetic semiconductors can be made by doping magnetic NHs into semiconducting NH superlattices. Our...
New results on averaging theory and applications
Cândido, Murilo R.; Llibre, Jaume
2016-08-01
The usual averaging theory reduces the computation of some periodic solutions of a system of ordinary differential equations, to find the simple zeros of an associated averaged function. When one of these zeros is not simple, i.e., the Jacobian of the averaged function in it is zero, the classical averaging theory does not provide information about the periodic solution associated to a non-simple zero. Here we provide sufficient conditions in order that the averaging theory can be applied also to non-simple zeros for studying their associated periodic solutions. Additionally, we do two applications of this new result for studying the zero-Hopf bifurcation in the Lorenz system and in the Fitzhugh-Nagumo system.
The Hubble rate in averaged cosmology
International Nuclear Information System (INIS)
The calculation of the averaged Hubble expansion rate in an averaged perturbed Friedmann-Lemaître-Robertson-Walker cosmology leads to small corrections to the background value of the expansion rate, which could be important for measuring the Hubble constant from local observations. It also predicts an intrinsic variance associated with the finite scale of any measurement of H0, the Hubble rate today. Both the mean Hubble rate and its variance depend on both the definition of the Hubble rate and the spatial surface on which the average is performed. We quantitatively study different definitions of the averaged Hubble rate encountered in the literature by consistently calculating the backreaction effect at second order in perturbation theory, and compare the results. We employ for the first time a recently developed gauge-invariant definition of an averaged scalar. We also discuss the variance of the Hubble rate for the different definitions
Short-Term Auditory Memory of Above-Average and Below-Average Grade Three Readers.
Caruk, Joan Marie
To determine if performance on short term auditory memory tasks is influenced by reading ability or sex differences, 62 third grade reading students (16 above average boys, 16 above average girls, 16 below average boys, and 14 below average girls) were administered four memory tests--memory for consonant names, memory for words, memory for…
Time averaging of instantaneous quantities in HYDRA
Energy Technology Data Exchange (ETDEWEB)
McCallen, R.C.
1996-09-01
For turbulent flow the evaluation of direct numerical simulations (DNS) where all scales are resolved and large-eddy simulation (LES) where only large-scales are resolved is difficult because the results are three-dimensional and transient. To simplify the analysis, the instantaneous flow field can be averaged in time for evaluation and comparison to experimental results. The incompressible Navier-Stokes flow code HYDRA has been modified for calculation of time-average quantities for both DNS and LES. This report describes how time averages of instantaneous quantities are generated during program execution (i.e., while generating the instantaneous quantities, instead of as a postprocessing operation). The calculations are performed during program execution to avoid storing values at each time step and thus to reduce storage requirements. The method used in calculating the time-average velocities, turbulent intensities, <{ital u}{sup ``}{sup 2}>, <{ital va}{sup ``}{sup 2}>, and <{ital w}{sup ``}{sup 2}>, and turbulent shear, <{ital u}{sup ``}{ital v}{sup ``}> are outlined. The brackets <> used here represent a time average. the described averaging methods were implemented in the HYDRA code for three-dimensional problem solutions. Also presented is a method for taking the time averages for a number of consecutive intervals and calculating the time average for the sum of the intervals. This method could be used for code restarts or further postprocessing of the timer averages from consecutive intervals. This method was not used in the HYDRA implementation, but is included here for completeness. In HYDRA, the running sums needed fro time averaging are simply written to the restart dump.
Clarifying the Relationship between Average Excesses and Average Effects of Allele Substitutions.
Alvarez-Castro, José M; Yang, Rong-Cai
2012-01-01
Fisher's concepts of average effects and average excesses are at the core of the quantitative genetics theory. Their meaning and relationship have regularly been discussed and clarified. Here we develop a generalized set of one locus two-allele orthogonal contrasts for average excesses and average effects, based on the concept of the effective gene content of alleles. Our developments help understand the average excesses of alleles for the biallelic case. We dissect how average excesses relate to the average effects and to the decomposition of the genetic variance. PMID:22509178
Clarifying the relationship between average excesses and average effects of allele substitutions
Directory of Open Access Journals (Sweden)
Jose M eÁlvarez-Castro
2012-03-01
Full Text Available Fisher’s concepts of average effects and average excesses are at the core of the quantitative genetics theory. Their meaning and relationship have regularly been discussed and clarified. Here we develop a generalized set of one-locus two-allele orthogonal contrasts for average excesses and average effects, based on the concept of the effective gene content of alleles. Our developments help understand the average excesses of alleles for the biallelic case. We dissect how average excesses relate to the average effects and to the decomposition of the genetic variance.
Averaged Lema\\^itre-Tolman-Bondi dynamics
Isidro, Eddy G Chirinos; Piattella, Oliver F; Zimdahl, Winfried
2016-01-01
We consider cosmological backreaction effects in Buchert's averaging formalism on the basis of an explicit solution of the Lema\\^itre-Tolman-Bondi (LTB) dynamics which is linear in the LTB curvature parameter and has an inhomogeneous bang time. The volume Hubble rate is found in terms of the volume scale factor which represents a derivation of the simplest phenomenological solution of Buchert's equations in which the fractional densities corresponding to average curvature and kinematic backreaction are explicitly determined by the parameters of the underlying LTB solution at the boundary of the averaging volume. This configuration represents an exactly solvable toy model but it does not adequately describe our "real" Universe.
Experimental Demonstration of Squeezed State Quantum Averaging
Lassen, Mikael; Sabuncu, Metin; Filip, Radim; Andersen, Ulrik L
2010-01-01
We propose and experimentally demonstrate a universal quantum averaging process implementing the harmonic mean of quadrature variances. The harmonic mean protocol can be used to efficiently stabilize a set of fragile squeezed light sources with statistically fluctuating noise levels. The averaged variances are prepared probabilistically by means of linear optical interference and measurement induced conditioning. We verify that the implemented harmonic mean outperforms the standard arithmetic mean strategy. The effect of quantum averaging is experimentally tested both for uncorrelated and partially correlated noise sources with sub-Poissonian shot noise or super-Poissonian shot noise characteristics.
Average Shape of Transport-Limited Aggregates
Davidovitch, Benny; Choi, Jaehyuk; Bazant, Martin Z.
2005-08-01
We study the relation between stochastic and continuous transport-limited growth models. We derive a nonlinear integro-differential equation for the average shape of stochastic aggregates, whose mean-field approximation is the corresponding continuous equation. Focusing on the advection-diffusion-limited aggregation (ADLA) model, we show that the average shape of the stochastic growth is similar, but not identical, to the corresponding continuous dynamics. Similar results should apply to DLA, thus explaining the known discrepancies between average DLA shapes and viscous fingers in a channel geometry.
Well logging for physical properties
Energy Technology Data Exchange (ETDEWEB)
Hearst, J.R.; Nelson, P.H.
1985-01-01
This book presents the fundamentals of well logging techniques for petroleum and natural gas deposits. Topics considered include the wellbore environment, logging practice; temperature, electrical and magnetic methods; nuclear radiation logging; acoustic logging; borehole gravimetry; ethology; porosity; saturation; permeability; fluid movement; fractures; elemental analysis; cement; directional surveying; dipmeter logging, and some other interesting applications.
Well logging for physical properties
International Nuclear Information System (INIS)
This book presents the fundamentals of well logging techniques for petroleum and natural gas deposits. Topics considered include the wellbore environment, logging practice; temperature, electrical and magnetic methods; nuclear radiation logging; acoustic logging; borehole gravimetry; ethology; porosity; saturation; permeability; fluid movement; fractures; elemental analysis; cement; directional surveying; dipmeter logging, and some other interesting applications
Average Vegetation Growth 1992 - Direct Download
U.S. Geological Survey, Department of the Interior — This map layer is a grid map of 1992 average vegetation growth for Alaska and the conterminous United States. The nominal spatial resolution is 1 kilometer and the...
Average Vegetation Growth 1994 - Direct Download
U.S. Geological Survey, Department of the Interior — This map layer is a grid map of 1994 average vegetation growth for Alaska and the conterminous United States. The nominal spatial resolution is 1 kilometer and the...
Average Vegetation Growth 1991 - Direct Download
U.S. Geological Survey, Department of the Interior — This map layer is a grid map of 1991 average vegetation growth for Alaska and the conterminous United States. The nominal spatial resolution is 1 kilometer and the...
Average Vegetation Growth 1993 - Direct Download
U.S. Geological Survey, Department of the Interior — This map layer is a grid map of 1993 average vegetation growth for Alaska and the conterminous United States. The nominal spatial resolution is 1 kilometer and the...
Average Vegetation Growth 1998 - Direct Download
U.S. Geological Survey, Department of the Interior — This map layer is a grid map of 1998 average vegetation growth for Alaska and the conterminous United States. The nominal spatial resolution is 1 kilometer and the...
Average Vegetation Growth 1999 - Direct Download
U.S. Geological Survey, Department of the Interior — This map layer is a grid map of 1999 average vegetation growth for Alaska and the conterminous United States. The nominal spatial resolution is 1 kilometer and the...
Average Vegetation Growth 1990 - Direct Download
U.S. Geological Survey, Department of the Interior — This map layer is a grid map of 1990 average vegetation growth for Alaska and the conterminous United States. The nominal spatial resolution is 1 kilometer and the...
Average Vegetation Growth 2003 - Direct Download
U.S. Geological Survey, Department of the Interior — This map layer is a grid map of 2003 average vegetation growth for Alaska and the conterminous United States. The nominal spatial resolution is 1 kilometer and the...
A practical guide to averaging functions
Beliakov, Gleb; Calvo Sánchez, Tomasa
2016-01-01
This book offers an easy-to-use and practice-oriented reference guide to mathematical averages. It presents different ways of aggregating input values given on a numerical scale, and of choosing and/or constructing aggregating functions for specific applications. Building on a previous monograph by Beliakov et al. published by Springer in 2007, it outlines new aggregation methods developed in the interim, with a special focus on the topic of averaging aggregation functions. It examines recent advances in the field, such as aggregation on lattices, penalty-based aggregation and weakly monotone averaging, and extends many of the already existing methods, such as: ordered weighted averaging (OWA), fuzzy integrals and mixture functions. A substantial mathematical background is not called for, as all the relevant mathematical notions are explained here and reported on together with a wealth of graphical illustrations of distinct families of aggregation functions. The authors mainly focus on practical applications ...
Sea Surface Temperature Average_SST_Master
National Oceanic and Atmospheric Administration, Department of Commerce — Sea surface temperature collected via satellite imagery from http://www.esrl.noaa.gov/psd/data/gridded/data.noaa.ersst.html and averaged for each region using...
Averaging procedure in variable-G cosmologies
Cardone, Vincenzo F
2008-01-01
Previous work in the literature had built a formalism for spatially averaged equations for the scale factor, giving rise to an averaged Raychaudhuri equation and averaged Hamiltonian constraint, which involve a backreaction source term. The present paper extends these equations to include models with variable Newton parameter and variable cosmological term, motivated by the non-perturbative renormalization program for quantum gravity based upon the Einstein--Hilbert action. The coupling between backreaction and spatially averaged three-dimensional scalar curvature is found to survive, and all equations involving contributions of a variable Newton parameter are worked out in detail. Interestingly, under suitable assumptions, an approximate solution can be found where the universe tends to a FLRW model, while keeping track of the original inhomogeneities through two effective fluids.
MN Temperature Average (1961-1990) - Line
Minnesota Department of Natural Resources — This data set depicts 30-year averages (1961-1990) of monthly and annual temperatures for Minnesota. Isolines and regions were created using kriging and...
Monthly snow/ice averages (ISCCP)
National Aeronautics and Space Administration — September Arctic sea ice is now declining at a rate of 11.5 percent per decade, relative to the 1979 to 2000 average. Data from NASA show that the land ice sheets...
Average Vegetation Growth 1997 - Direct Download
U.S. Geological Survey, Department of the Interior — This map layer is a grid map of 1997 average vegetation growth for Alaska and the conterminous United States. The nominal spatial resolution is 1 kilometer and the...
Average Vegetation Growth 2001 - Direct Download
U.S. Geological Survey, Department of the Interior — This map layer is a grid map of 2001 average vegetation growth for Alaska and the conterminous United States. The nominal spatial resolution is 1 kilometer and the...
MN Temperature Average (1961-1990) - Polygon
Minnesota Department of Natural Resources — This data set depicts 30-year averages (1961-1990) of monthly and annual temperatures for Minnesota. Isolines and regions were created using kriging and...
Average Bandwidth Allocation Model of WFQ
Directory of Open Access Journals (Sweden)
Tomáš Balogh
2012-01-01
Full Text Available We present a new iterative method for the calculation of average bandwidth assignment to traffic flows using a WFQ scheduler in IP based NGN networks. The bandwidth assignment calculation is based on the link speed, assigned weights, arrival rate, and average packet length or input rate of the traffic flows. We prove the model outcome with examples and simulation results using NS2 simulator.
Development of average wages in CR regions
Bejvlová, Jana
2013-01-01
The purpose of this study is to analyse trends in average gross monthly earnings of employees – individuals - in particular regions of the Czech Republic. The analysed time series begin in 2000 as the regions were decisively established on 1st January 2000. Moreover the self-governing competencies were introduced by the Act No. 129/2000 Coll., on Regions (Establishment of Regions). The researched period ends in 2010. Based on model construction of referential sets, the study predicts average ...
Grassmann Averages for Scalable Robust PCA
DEFF Research Database (Denmark)
Hauberg, Søren; Feragen, Aasa; Black, Michael J.
vectors (subspaces) or elements of vectors; we focus on the latter and use a trimmed average. The resulting Trimmed Grassmann Average (TGA) is particularly appropriate for computer vision because it is robust to pixel outliers. The algorithm has low computational complexity and minimal memory requirements......, making it scalable to “big noisy data.” We demonstrate TGA for background modeling, video restoration, and shadow removal. We show scalability by performing robust PCA on the entire Star Wars IV movie....
Hyperplane Arrangements with Large Average Diameter
Deza, Antoine; Xie, Feng
2007-01-01
The largest possible average diameter of a bounded cell of a simple hyperplane arrangement is conjectured to be not greater than the dimension. We prove that this conjecture holds in dimension 2, and is asymptotically tight in fixed dimension. We give the exact value of the largest possible average diameter for all simple arrangements in dimension 2, for arrangements having at most the dimension plus 2 hyperplanes, and for arrangements having 6 hyperplanes in dimension 3. In dimension 3, we g...
The Hubble rate in averaged cosmology
Umeh, Obinna; Larena, Julien; Clarkson, Chris
2010-01-01
The calculation of the averaged Hubble expansion rate in an averaged perturbed Friedmann-Lemaitre-Robertson-Walker cosmology leads to small corrections to the background value of the expansion rate, which could be important for measuring the Hubble constant from local observations. It also predicts an intrinsic variance associated with the finite scale of any measurement of H_0, the Hubble rate today. Both the mean Hubble rate and its variance depend on both the definition of the Hubble rate ...
Nonequilibrium statistical averages and thermo field dynamics
International Nuclear Information System (INIS)
An extension of thermo field dynamics is proposed, which permits the computation of nonequilibrium statistical averages. The Brownian motion of a quantum oscillator is treated as an example. In conclusion it is pointed out that the procedure proposed to computation of time-dependent statistical average gives the correct two-point Green function for the damped oscillator. A simple extension can be used to compute two-point Green functions of free particles
Averaging Problem in Cosmology and Macroscopic Gravity
Zalaletdinov, Roustam
2007-01-01
The Averaging problem in general relativity and cosmology is discussed. The approach of macroscopic gravity to resolve the problem is presented. An exact cosmological solution to the equations of macroscopic gravity is given and its properties are discussed. Contents: 1. Introduction to General Relativity 2. General Relativity -> Relativistic Cosmology 3. Introduction to Relativistic Cosmology 4. Relativistic Cosmology -> Mathematical Cosmology 5. Averaging Problem in Relativistic Cosmology 6...
Method of averaging in Clifford algebras
Shirokov, D. S.
2014-01-01
In this paper we consider different operators acting on Clifford algebras. We consider Reynolds operator of Salingaros' vee group. This operator average" an action of Salingaros' vee group on Clifford algebra. We consider conjugate action on Clifford algebra. We present a relation between these operators and projection operators onto fixed subspaces of Clifford algebras. Using method of averaging we present solutions of system of commutator equations.
Modeling and Instability of Average Current Control
Fang, Chung-Chieh
2012-01-01
Dynamics and stability of average current control of DC-DC converters are analyzed by sampled-data modeling. Orbital stability is studied and it is found unrelated to the ripple size of the orbit. Compared with the averaged modeling, the sampled-data modeling is more accurate and systematic. An unstable range of compensator pole is found by simulations, and is predicted by sampled-data modeling and harmonic balance modeling.
Disk-averaged synthetic spectra of Mars
Tinetti, Giovanna; Meadows, Victoria S.; Crisp, David; Fong, William; Velusamy, Thangasamy; Snively, Heather
2004-01-01
The principal goal of the NASA Terrestrial Planet Finder (TPF) and ESA Darwin mission concepts is to directly detect and characterize extrasolar terrestrial (Earth-sized) planets. This first generation of instruments is expected to provide disk-averaged spectra with modest spectral resolution and signal-to-noise. Here we use a spatially and spectrally resolved model of the planet Mars to study the detectability of a planet's surface and atmospheric properties from disk-averaged spectra as a f...
Magnetic Properties of Erbium Gallium Gallate under High Magnetic Field
Institute of Scientific and Technical Information of China (English)
Zhang Xijuan; Cheng Haiying; Yang Cuihong; Wang Wei
2004-01-01
A theoretical investigation on the magnetic properties of rare-earth Er3+ in Er3 Ga5 O12 was reported. The average magnetic moments(M) for applied magnetic field H parallel to the [001 ], [ 100], [ 110], [ 111 ] direction was studied based on the quantum theory. Temperature dependence of the magnetic properties is analyzed for H applied parallel to the [ 100] and [ 111 ] crystallographic directions. The magnetization decreases with increasing temperature,showing good agreement with thermal effect. A strong anisotropy of the magnetization is found under high magnetic field, but when the magnetic field is small, M and H are proportional.
International Nuclear Information System (INIS)
The 'ingredients' which control a phase transition in well defined systems as well as in random ones (e.q. random magnetic systems) are listed and discussed within a somehow unifying perspective. Among these 'ingredients' the couplings and elements responsible for the cooperative phenomenon, the topological connectivity as well as possible topological incompatibilities, the influence of new degrees of freedom, the order parameter dimensionality, the ground state degeneracy and finally the 'quanticity' of the system are found. The general trends, though illustrated in magnetic systems, essentially hold for all phase transitions, and give a basis for connection of this area with Field theory, Theory of dynamical systems, etc. (Author)
Sun, Shu-Wei; Mei, Jennifer; Tuel, Keelan
2013-01-01
Diffusion tensor imaging (DTI) is achieved by collecting a series of diffusion-weighted images (DWIs). Signal averaging of multiple repetitions can be performed in the k-space (k-avg) or in the image space (m-avg) to improve the image quality. Alternatively, one can treat each acquisition as an independent image and use all of the data to reconstruct the DTI without doing any signal averaging (no-avg). To compare these three approaches, in this study, in vivo DTI data was collected from five ...
Books average previous decade of economic misery.
Directory of Open Access Journals (Sweden)
R Alexander Bentley
Full Text Available For the 20(th century since the Depression, we find a strong correlation between a 'literary misery index' derived from English language books and a moving average of the previous decade of the annual U.S. economic misery index, which is the sum of inflation and unemployment rates. We find a peak in the goodness of fit at 11 years for the moving average. The fit between the two misery indices holds when using different techniques to measure the literary misery index, and this fit is significantly better than other possible correlations with different emotion indices. To check the robustness of the results, we also analysed books written in German language and obtained very similar correlations with the German economic misery index. The results suggest that millions of books published every year average the authors' shared economic experiences over the past decade.
Books average previous decade of economic misery.
Bentley, R Alexander; Acerbi, Alberto; Ormerod, Paul; Lampos, Vasileios
2014-01-01
For the 20(th) century since the Depression, we find a strong correlation between a 'literary misery index' derived from English language books and a moving average of the previous decade of the annual U.S. economic misery index, which is the sum of inflation and unemployment rates. We find a peak in the goodness of fit at 11 years for the moving average. The fit between the two misery indices holds when using different techniques to measure the literary misery index, and this fit is significantly better than other possible correlations with different emotion indices. To check the robustness of the results, we also analysed books written in German language and obtained very similar correlations with the German economic misery index. The results suggest that millions of books published every year average the authors' shared economic experiences over the past decade. PMID:24416159
Cosmic structure, averaging and dark energy
Wiltshire, David L
2013-01-01
These lecture notes review the theoretical problems associated with coarse-graining the observed inhomogeneous structure of the universe at late epochs, of describing average cosmic evolution in the presence of growing inhomogeneity, and of relating average quantities to physical observables. In particular, a detailed discussion of the timescape scenario is presented. In this scenario, dark energy is realized as a misidentification of gravitational energy gradients which result from gradients in the kinetic energy of expansion of space, in the presence of density and spatial curvature gradients that grow large with the growth of structure. The phenomenology and observational tests of the timescape model are discussed in detail, with updated constraints from Planck satellite data. In addition, recent results on the variation of the Hubble expansion on < 100/h Mpc scales are discussed. The spherically averaged Hubble law is significantly more uniform in the rest frame of the Local Group of galaxies than in t...
Average Cycle Period in Asymmetrical Flashing Ratchet
Institute of Scientific and Technical Information of China (English)
WANG Hai-Yan; HE Hou-Sheng; BAO Jing-Dong
2005-01-01
The directed motion of a Brownian particle in a flashing potential with various transition probabilities and waiting times in one of two states is studied. An expression for the average cycle period is proposed and the steady current J of the particle is calculated via Langevin simulation. The results show that the optimal cycle period rm,which takes the maximum of J, is shifted to a small value when the transition probability λ from the potential on to the potential off decreases, the maximalcurrent appears in the case of the average waiting time in the potential on being longer than in the potential off, and the direction of current depends on the ratio of the average times waiting in two states.
Stochastic Averaging and Stochastic Extremum Seeking
Liu, Shu-Jun
2012-01-01
Stochastic Averaging and Stochastic Extremum Seeking develops methods of mathematical analysis inspired by the interest in reverse engineering and analysis of bacterial convergence by chemotaxis and to apply similar stochastic optimization techniques in other environments. The first half of the text presents significant advances in stochastic averaging theory, necessitated by the fact that existing theorems are restricted to systems with linear growth, globally exponentially stable average models, vanishing stochastic perturbations, and prevent analysis over infinite time horizon. The second half of the text introduces stochastic extremum seeking algorithms for model-free optimization of systems in real time using stochastic perturbations for estimation of their gradients. Both gradient- and Newton-based algorithms are presented, offering the user the choice between the simplicity of implementation (gradient) and the ability to achieve a known, arbitrary convergence rate (Newton). The design of algorithms...
Matrix averages relating to Ginibre ensembles
Energy Technology Data Exchange (ETDEWEB)
Forrester, Peter J [Department of Mathematics and Statistics, University of Melbourne, Victoria 3010 (Australia); Rains, Eric M [Department of Mathematics, California Institute of Technology, Pasadena, CA 91125 (United States)], E-mail: p.forrester@ms.unimelb.edu.au
2009-09-25
The theory of zonal polynomials is used to compute the average of a Schur polynomial of argument AX, where A is a fixed matrix and X is from the real Ginibre ensemble. This generalizes a recent result of Sommers and Khoruzhenko (2009 J. Phys. A: Math. Theor. 42 222002), and furthermore allows analogous results to be obtained for the complex and real quaternion Ginibre ensembles. As applications, the positive integer moments of the general variance Ginibre ensembles are computed in terms of generalized hypergeometric functions; these are written in terms of averages over matrices of the same size as the moment to give duality formulas, and the averages of the power sums of the eigenvalues are expressed as finite sums of zonal polynomials.
High Average Power Yb:YAG Laser
Energy Technology Data Exchange (ETDEWEB)
Zapata, L E; Beach, R J; Payne, S A
2001-05-23
We are working on a composite thin-disk laser design that can be scaled as a source of high brightness laser power for tactical engagement and other high average power applications. The key component is a diffusion-bonded composite comprising a thin gain-medium and thicker cladding that is strikingly robust and resolves prior difficulties with high average power pumping/cooling and the rejection of amplified spontaneous emission (ASE). In contrast to high power rods or slabs, the one-dimensional nature of the cooling geometry and the edge-pump geometry scale gracefully to very high average power. The crucial design ideas have been verified experimentally. Progress this last year included: extraction with high beam quality using a telescopic resonator, a heterogeneous thin film coating prescription that meets the unusual requirements demanded by this laser architecture, thermal management with our first generation cooler. Progress was also made in design of a second-generation laser.
The modulated average structure of mullite
Czech Academy of Sciences Publication Activity Database
Birkenstock, J.; Petříček, Václav; Pedersen, B.; Schneider, H.
2015-01-01
Roč. 71, Jun (2015), 358-368. ISSN 0108-7681 R&D Projects: GA ČR(CZ) GA14-03276S Institutional support: RVO:68378271 Keywords : 2:1 mullite * disordered modulated structure * ceramics * neutron diffraction * diffuse Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.184, year: 2014
Books Average Previous Decade of Economic Misery
R Alexander Bentley; Alberto Acerbi; Paul Ormerod; Vasileios Lampos
2014-01-01
For the 20(th) century since the Depression, we find a strong correlation between a 'literary misery index' derived from English language books and a moving average of the previous decade of the annual U.S. economic misery index, which is the sum of inflation and unemployment rates. We find a peak in the goodness of fit at 11 years for the moving average. The fit between the two misery indices holds when using different techniques to measure the literary misery index, and this fit is signific...
On the average pairing energy in nuclei
International Nuclear Information System (INIS)
The macroscopic-microscopic method is applied to calculate the nuclear energies, especially the microscopic shell and pairing corrections. The single-particle levels are obtained with the Yukawa folded mean-field potential. The macroscopic energy is evaluated using the Lublin-Strasbourg Drop model. The shell corrections are obtained using the Strutinsky method with smoothing in nucleon number space. The average nuclear pairing energy is also determined by folding the BCS sums in nucleon number space. The average pairing energy dependence on the nuclear elongation is investigated. (author)
A singularity theorem based on spatial averages
Indian Academy of Sciences (India)
J M M Senovilla
2007-07-01
Inspired by Raychaudhuri's work, and using the equation named after him as a basic ingredient, a new singularity theorem is proved. Open non-rotating Universes, expanding everywhere with a non-vanishing spatial average of the matter variables, show severe geodesic incompletness in the past. Another way of stating the result is that, under the same conditions, any singularity-free model must have a vanishing spatial average of the energy density (and other physical variables). This is very satisfactory and provides a clear decisive difference between singular and non-singular cosmologies.
Changing mortality and average cohort life expectancy
DEFF Research Database (Denmark)
Schoen, Robert; Canudas-Romo, Vladimir
2005-01-01
Period life expectancy varies with changes in mortality, and should not be confused with the life expectancy of those alive during that period. Given past and likely future mortality changes, a recent debate has arisen on the usefulness of the period life expectancy as the leading measure of......, the average cohort life expectancy (ACLE), to provide a precise measure of the average length of life of cohorts alive at a given time. To compare the performance of ACLE with CAL and with period and cohort life expectancy, we first use population models with changing mortality. Then the four...
An improved moving average technical trading rule
Papailias, Fotis; Thomakos, Dimitrios D.
2015-06-01
This paper proposes a modified version of the widely used price and moving average cross-over trading strategies. The suggested approach (presented in its 'long only' version) is a combination of cross-over 'buy' signals and a dynamic threshold value which acts as a dynamic trailing stop. The trading behaviour and performance from this modified strategy are different from the standard approach with results showing that, on average, the proposed modification increases the cumulative return and the Sharpe ratio of the investor while exhibiting smaller maximum drawdown and smaller drawdown duration than the standard strategy.
Simulation of Magnetically Dispersed Arc Plasma
Institute of Scientific and Technical Information of China (English)
白冰; 查俊; 张晓宁; 王城; 夏维东
2012-01-01
Magnetically dispersed arc plasma exhibits typically dispersed uniform arc column as well as diffusive cathode root and diffusive anode root. In this paper magnetically dispersed arc plasma coupled with solid cathode is numerically simulated by the simplified cathode sheath model of LOWKE . The numerical simulation results in argon show that the maximum value of arc root current density on the cathode surface is 3.5×10^7 A/m^2）, and the maximum value of energy flux on the cathode surface is 3× 10^7 J/m^2, both values are less than the average values of a contracted arc, respectively.
Bayesian Model Averaging for Propensity Score Analysis
Kaplan, David; Chen, Jianshen
2013-01-01
The purpose of this study is to explore Bayesian model averaging in the propensity score context. Previous research on Bayesian propensity score analysis does not take into account model uncertainty. In this regard, an internally consistent Bayesian framework for model building and estimation must also account for model uncertainty. The…
Average utility maximization: A preference foundation
A.V. Kothiyal (Amit); V. Spinu (Vitalie); P.P. Wakker (Peter)
2014-01-01
textabstractThis paper provides necessary and sufficient preference conditions for average utility maximization over sequences of variable length. We obtain full generality by using a new algebraic technique that exploits the richness structure naturally provided by the variable length of the sequen
Average beta measurement in EXTRAP T1
International Nuclear Information System (INIS)
Beginning with the ideal MHD pressure balance equation, an expression for the average poloidal beta, ΒΘ, is derived. A method for unobtrusively measuring the quantities used to evaluate ΒΘ in Extrap T1 is described. The results if a series of measurements yielding ΒΘ as a function of externally applied toroidal field are presented. (author)
A Gaussian Average Property for Banach Spaces
Casazza, Peter G.; Nielsen, Niels Jorgen
1996-01-01
In this paper we investigate a Gaussian average property of Banach spaces. This property is weaker than the Gordon Lewis property but closely related to this and other unconditional structures. It is also shown that this property implies that certain Hilbert space valued operators defined on subspaces of the given space can be extended.
Quantum Averaging of Squeezed States of Light
DEFF Research Database (Denmark)
Squeezing has been recognized as the main resource for quantum information processing and an important resource for beating classical detection strategies. It is therefore of high importance to reliably generate stable squeezing over longer periods of time. The averaging procedure for a single...
A Functional Measurement Study on Averaging Numerosity
Tira, Michael D.; Tagliabue, Mariaelena; Vidotto, Giulio
2014-01-01
In two experiments, participants judged the average numerosity between two sequentially presented dot patterns to perform an approximate arithmetic task. In Experiment 1, the response was given on a 0-20 numerical scale (categorical scaling), and in Experiment 2, the response was given by the production of a dot pattern of the desired numerosity…
Reformulation of Ensemble Averages via Coordinate Mapping.
Schultz, Andrew J; Moustafa, Sabry G; Lin, Weisong; Weinstein, Steven J; Kofke, David A
2016-04-12
A general framework is established for reformulation of the ensemble averages commonly encountered in statistical mechanics. This "mapped-averaging" scheme allows approximate theoretical results that have been derived from statistical mechanics to be reintroduced into the underlying formalism, yielding new ensemble averages that represent exactly the error in the theory. The result represents a distinct alternative to perturbation theory for methodically employing tractable systems as a starting point for describing complex systems. Molecular simulation is shown to provide one appealing route to exploit this advance. Calculation of the reformulated averages by molecular simulation can proceed without contamination by noise produced by behavior that has already been captured by the approximate theory. Consequently, accurate and precise values of properties can be obtained while using less computational effort, in favorable cases, many orders of magnitude less. The treatment is demonstrated using three examples: (1) calculation of the heat capacity of an embedded-atom model of iron, (2) calculation of the dielectric constant of the Stockmayer model of dipolar molecules, and (3) calculation of the pressure of a Lennard-Jones fluid. It is observed that improvement in computational efficiency is related to the appropriateness of the underlying theory for the condition being simulated; the accuracy of the result is however not impacted by this. The framework opens many avenues for further development, both as a means to improve simulation methodology and as a new basis to develop theories for thermophysical properties. PMID:26950263
Bootstrapping Density-Weighted Average Derivatives
DEFF Research Database (Denmark)
Cattaneo, Matias D.; Crump, Richard K.; Jansson, Michael
Employing the "small bandwidth" asymptotic framework of Cattaneo, Crump, and Jansson (2009), this paper studies the properties of a variety of bootstrap-based inference procedures associated with the kernel-based density-weighted averaged derivative estimator proposed by Powell, Stock, and Stoker...
A Measure of the Average Intercorrelation
Meyer, Edward P.
1975-01-01
Bounds are obtained for a coefficient proposed by Kaiser as a measure of average correlation and the coefficient is given an interpretation in the context of reliability theory. It is suggested that the root-mean-square intercorrelation may be a more appropriate measure of degree of relationships among a group of variables. (Author)
Full averaging of fuzzy impulsive differential inclusions
Directory of Open Access Journals (Sweden)
Natalia V. Skripnik
2010-09-01
Full Text Available In this paper the substantiation of the method of full averaging for fuzzy impulsive differential inclusions is studied. We extend the similar results for impulsive differential inclusions with Hukuhara derivative (Skripnik, 2007, for fuzzy impulsive differential equations (Plotnikov and Skripnik, 2009, and for fuzzy differential inclusions (Skripnik, 2009.
An approximate analytical approach to resampling averages
DEFF Research Database (Denmark)
Malzahn, Dorthe; Opper, M.
2004-01-01
Using a novel reformulation, we develop a framework to compute approximate resampling data averages analytically. The method avoids multiple retraining of statistical models on the samples. Our approach uses a combination of the replica "trick" of statistical physics and the TAP approach for appr...
Generalized Jackknife Estimators of Weighted Average Derivatives
DEFF Research Database (Denmark)
Cattaneo, Matias D.; Crump, Richard K.; Jansson, Michael
With the aim of improving the quality of asymptotic distributional approximations for nonlinear functionals of nonparametric estimators, this paper revisits the large-sample properties of an important member of that class, namely a kernel-based weighted average derivative estimator. Asymptotic li...
High average-power induction linacs
International Nuclear Information System (INIS)
Induction linear accelerators (LIAs) are inherently capable of accelerating several thousand amperes of /approximately/ 50-ns duration pulses to > 100 MeV. In this paper we report progress and status in the areas of duty factor and stray power management. These technologies are vital if LIAs are to attain high average power operation. 13 figs
Average Equivalent Diameter of A Particulate Material
AL-MAGHRABI, Mohammed-Noor N. H.
2010-01-01
In the field of mineral processing, it is important to determine the size of a particle. A method of defining an average diameter for a collection of particles is presented. The theoretical basis developed for the purpose is verified by a specially designed experimental technique. Key words: mineral processing, particle size, equivalent diameter
An approximate analytical approach to resampling averages
DEFF Research Database (Denmark)
Malzahn, Dorthe; Opper, M.
2004-01-01
Using a novel reformulation, we develop a framework to compute approximate resampling data averages analytically. The method avoids multiple retraining of statistical models on the samples. Our approach uses a combination of the replica "trick" of statistical physics and the TAP approach for...
Ultrafast Magnetization Dynamics
Woodford, S.
2008-01-01
This thesis addresses ultrafast magnetization dynamics from a theoretical perspective. The manipulation of magnetization using the inverse Faraday effect has been studied, as well as magnetic relaxation processes in quantum dots. The inverse Faraday effect – the generation of a magnetic field by nonresonant, circularly polarized light – offers the possibility to control and reverse magnetization on a timescale of a few hundred femtoseconds. This is important both for the technological advant...
Atomic and Magnetic Structure of the Interface in Multilayers
International Nuclear Information System (INIS)
Temperature dependence of the magnetic properties of Fe/Ag vacuum evaporated multilayers was studied in a wide range of layer thickness. For Fe thickness larger than 1 nm continuous magnetic layers can be found, but its hyperfine field is significantly lower than that of pure α-Fe at elevated temperatures. It is attributed to a decrease of the Curie temperature due to Ag impurities in the Fe layer. Below 1 nm Fe thickness magnetic relaxation and the formation of a granular alloy with 35 T average hyperfine field was observed. Magnetoresistance results indicate the presence of Fe clusters in the Ag matrix, as well.
Averaged universe confronted to cosmological observations: a fully covariant approach
Wijenayake, Tharake; Ishak, Mustapha
2016-01-01
One of the outstanding problems in general relativistic cosmology is that of the averaging. That is, how the lumpy universe that we observe at small scales averages out to a smooth Friedmann-Lemaitre-Robertson-Walker (FLRW) model. The root of the problem is that averaging does not commute with the Einstein equations that govern the dynamics of the model. This leads to the well-know question of backreaction in cosmology. In this work, we approach the problem using the covariant framework of Macroscopic Gravity (MG). We use its cosmological solution with a flat FLRW macroscopic background where the result of averaging cosmic inhomogeneities has been encapsulated into a backreaction density parameter denoted $\\Omega_\\mathcal{A}$. We constrain this averaged universe using available cosmological data sets of expansion and growth including, for the first time, a full CMB analysis from Planck temperature anisotropy and polarization data, the supernovae data from Union 2.1, the galaxy power spectrum from WiggleZ, the...
The average baboon brain: MRI templates and tissue probability maps from 89 individuals.
Love, Scott A; Marie, Damien; Roth, Muriel; Lacoste, Romain; Nazarian, Bruno; Bertello, Alice; Coulon, Olivier; Anton, Jean-Luc; Meguerditchian, Adrien
2016-05-15
The baboon (Papio) brain is a remarkable model for investigating the brain. The current work aimed at creating a population-average baboon (Papio anubis) brain template and its left/right hemisphere symmetric version from a large sample of T1-weighted magnetic resonance images collected from 89 individuals. Averaging the prior probability maps output during the segmentation of each individual also produced the first baboon brain tissue probability maps for gray matter, white matter and cerebrospinal fluid. The templates and the tissue probability maps were created using state-of-the-art, freely available software tools and are being made freely and publicly available: http://www.nitrc.org/projects/haiko89/ or http://lpc.univ-amu.fr/spip.php?article589. It is hoped that these images will aid neuroimaging research of the baboon by, for example, providing a modern, high quality normalization target and accompanying standardized coordinate system as well as probabilistic priors that can be used during tissue segmentation. PMID:26975558
Lagrangian-averaged model for magnetohydrodynamic turbulence and the absence of bottlenecks.
Pietarila Graham, Jonathan; Mininni, Pablo D; Pouquet, Annick
2009-07-01
We demonstrate that, for the case of quasiequipartition between the velocity and the magnetic field, the Lagrangian-averaged magnetohydrodynamics (LAMHD) alpha model reproduces well both the large-scale and the small-scale properties of turbulent flows; in particular, it displays no increased (superfilter) bottleneck effect with its ensuing enhanced energy spectrum at the onset of the subfilter scales. This is in contrast to the case of the neutral fluid in which the Lagrangian-averaged Navier-Stokes alpha model is somewhat limited in its applications because of the formation of spatial regions with no internal degrees of freedom and subsequent contamination of superfilter-scale spectral properties. We argue that, as the Lorentz force breaks the conservation of circulation and enables spectrally nonlocal energy transfer (associated with Alfvén waves), it is responsible for the absence of a viscous bottleneck in magnetohydrodynamics (MHD), as compared to the fluid case. As LAMHD preserves Alfvén waves and the circulation properties of MHD, there is also no (superfilter) bottleneck found in LAMHD, making this method capable of large reductions in required numerical degrees of freedom; specifically, we find a reduction factor of approximately 200 when compared to a direct numerical simulation on a large grid of 1536;{3} points at the same Reynolds number. PMID:19658812
Trajectory averaging for stochastic approximation MCMC algorithms
Liang, Faming
2010-01-01
The subject of stochastic approximation was founded by Robbins and Monro [Ann. Math. Statist. 22 (1951) 400--407]. After five decades of continual development, it has developed into an important area in systems control and optimization, and it has also served as a prototype for the development of adaptive algorithms for on-line estimation and control of stochastic systems. Recently, it has been used in statistics with Markov chain Monte Carlo for solving maximum likelihood estimation problems and for general simulation and optimizations. In this paper, we first show that the trajectory averaging estimator is asymptotically efficient for the stochastic approximation MCMC (SAMCMC) algorithm under mild conditions, and then apply this result to the stochastic approximation Monte Carlo algorithm [Liang, Liu and Carroll J. Amer. Statist. Assoc. 102 (2007) 305--320]. The application of the trajectory averaging estimator to other stochastic approximation MCMC algorithms, for example, a stochastic approximation MLE al...
From cellular doses to average lung dose
International Nuclear Information System (INIS)
Sensitive basal and secretory cells receive a wide range of doses in human bronchial and bronchiolar airways. Variations of cellular doses arise from the location of target cells in the bronchial epithelium of a given airway and the asymmetry and variability of airway dimensions of the lung among airways in a given airway generation and among bronchial and bronchiolar airway generations. To derive a single value for the average lung dose which can be related to epidemiologically observed lung cancer risk, appropriate weighting scenarios have to be applied. Potential biological weighting parameters are the relative frequency of target cells, the number of progenitor cells, the contribution of dose enhancement at airway bifurcations, the promotional effect of cigarette smoking and, finally, the application of appropriate regional apportionment factors. Depending on the choice of weighting parameters, detriment-weighted average lung doses can vary by a factor of up to 4 for given radon progeny exposure conditions. (authors)
ANALYSIS OF THE FACTORS AFFECTING THE AVERAGE
Directory of Open Access Journals (Sweden)
Carmen BOGHEAN
2013-12-01
Full Text Available Productivity in agriculture most relevantly and concisely expresses the economic efficiency of using the factors of production. Labour productivity is affected by a considerable number of variables (including the relationship system and interdependence between factors, which differ in each economic sector and influence it, giving rise to a series of technical, economic and organizational idiosyncrasies. The purpose of this paper is to analyse the underlying factors of the average work productivity in agriculture, forestry and fishing. The analysis will take into account the data concerning the economically active population and the gross added value in agriculture, forestry and fishing in Romania during 2008-2011. The distribution of the average work productivity per factors affecting it is conducted by means of the u-substitution method.
Statistics on exponential averaging of periodograms
International Nuclear Information System (INIS)
The algorithm of exponential averaging applied to subsequent periodograms of a stochastic process is used to estimate the power spectral density (PSD). For an independent process, assuming the periodogram estimates to be distributed according to a χ2 distribution with 2 degrees of freedom, the probability density function (PDF) of the PSD estimate is derived. A closed expression is obtained for the moments of the distribution. Surprisingly, the proof of this expression features some new insights into the partitions and Eulers infinite product. For large values of the time constant of the averaging process, examination of the cumulant generating function shows that the PDF approximates the Gaussian distribution. Although restrictions for the statistics are seemingly tight, simulation of a real process indicates a wider applicability of the theory. (orig.)
Endogenous average cost based access pricing
Fjell, Kenneth; Foros, Øystein; Pal, Debashis
2006-01-01
We consider an industry where a downstream competitor requires access to an upstream facility controlled by a vertically integrated and regulated incumbent. The literature on access pricing assumes the access price to be exogenously fixed ex-ante. We analyze an endogenous average cost based access pricing rule, where both firms realize the interdependence among their quantities and the regulated access price. Endogenous access pricing neutralizes the artificial cost advantag...
Extended Bidirectional Texture Function Moving Average Model
Czech Academy of Sciences Publication Activity Database
Havlíček, Michal
Praha: České vysoké učení technické v Praze, 2015 - (Ambrož, P.; Masáková, Z.), s. 1-7 [Doktorandské dny 2015. Praha (CZ), 20.11.2015,27.11.2015] Institutional support: RVO:67985556 Keywords : Bidirectional texture function * moving average random field model Subject RIV: BD - Theory of Information http://library.utia.cas.cz/separaty/2016/RO/havlicek-0455325.pdf
Average Drift Analysis and Population Scalability
He, Jun; Yao, Xin
2013-01-01
This paper aims to study how the population size affects the computation time of evolutionary algorithms in a rigorous way. The computation time of an evolutionary algorithm can be measured by either the expected number of generations (hitting time) or the expected number of fitness evaluations (running time) to find an optimal solution. Population scalability is the ratio of the expected hitting time between a benchmark algorithm and an algorithm using a larger population size. Average drift...
Average Regression-Adjusted Controlled Regenerative Estimates
Lewis, Peter A.W.; Ressler, Richard
1991-01-01
Proceedings of the 1991 Winter Simulation Conference Barry L. Nelson, W. David Kelton, Gordon M. Clark (eds.) One often uses computer simulations of queueing systems to generate estimates of system characteristics along with estimates of their precision. Obtaining precise estimates, espescially for high traffic intensities, can require large amounts of computer time. Average regression-adjusted controlled regenerative estimates result from combining the two techniques ...
Time-dependent angularly averaged inverse transport
Bal, Guillaume; Jollivet, Alexandre
2009-01-01
This paper concerns the reconstruction of the absorption and scattering parameters in a time-dependent linear transport equation from knowledge of angularly averaged measurements performed at the boundary of a domain of interest. We show that the absorption coefficient and the spatial component of the scattering coefficient are uniquely determined by such measurements. We obtain stability results on the reconstruction of the absorption and scattering parameters with respect to the measured al...
Average Light Intensity Inside a Photobioreactor
Directory of Open Access Journals (Sweden)
Herby Jean
2011-01-01
Full Text Available For energy production, microalgae are one of the few alternatives with high potential. Similar to plants, algae require energy acquired from light sources to grow. This project uses calculus to determine the light intensity inside of a photobioreactor filled with algae. Under preset conditions along with estimated values, we applied Lambert-Beer's law to formulate an equation to calculate how much light intensity escapes a photobioreactor and determine the average light intensity that was present inside the reactor.
A Visibility Graph Averaging Aggregation Operator
Chen, Shiyu; Hu, Yong; Mahadevan, Sankaran; Deng, Yong
2013-01-01
The problem of aggregation is considerable importance in many disciplines. In this paper, a new type of operator called visibility graph averaging (VGA) aggregation operator is proposed. This proposed operator is based on the visibility graph which can convert a time series into a graph. The weights are obtained according to the importance of the data in the visibility graph. Finally, the VGA operator is used in the analysis of the TAIEX database to illustrate that it is practical and compare...
Dollar-Cost Averaging: An Investigation
Fang, Wei
2007-01-01
Dollar-cost Averaging (DCA) is a common and useful systematic investment strategy for mutual fund managers, private investors, financial analysts and retirement planners. The issue of performance effectiveness of DCA is greatly controversial among academics and professionals. As a popularly recommended investment strategy, DCA is recognized as a risk reduction strategy; however, the advantage was claimed as the expense of generating higher returns. The dissertation is to intensively inves...
Spatial averaging infiltration model for layered soil
Institute of Scientific and Technical Information of China (English)
HU HePing; YANG ZhiYong; TIAN FuQiang
2009-01-01
To quantify the influences of soil heterogeneity on infiltration, a spatial averaging infiltration model for layered soil (SAI model) is developed by coupling the spatial averaging approach proposed by Chen et al. and the Generalized Green-Ampt model proposed by Jia et al. In the SAI model, the spatial heterogeneity along the horizontal direction is described by a probability distribution function, while that along the vertical direction is represented by the layered soils. The SAI model is tested on a typical soil using Monte Carlo simulations as the base model. The results show that the SAI model can directly incorporate the influence of spatial heterogeneity on infiltration on the macro scale. It is also found that the homogeneous assumption of soil hydraulic conductivity along the horizontal direction will overestimate the infiltration rate, while that along the vertical direction will underestimate the infiltration rate significantly during rainstorm periods. The SAI model is adopted in the spatial averaging hydrological model developed by the authors, and the results prove that it can be applied in the macro-scale hydrological and land surface process modeling in a promising way.
Modern average global sea-surface temperature
Schweitzer, Peter N.
1993-01-01
The data contained in this data set are derived from the NOAA Advanced Very High Resolution Radiometer Multichannel Sea Surface Temperature data (AVHRR MCSST), which are obtainable from the Distributed Active Archive Center at the Jet Propulsion Laboratory (JPL) in Pasadena, Calif. The JPL tapes contain weekly images of SST from October 1981 through December 1990 in nine regions of the world ocean: North Atlantic, Eastern North Atlantic, South Atlantic, Agulhas, Indian, Southeast Pacific, Southwest Pacific, Northeast Pacific, and Northwest Pacific. This data set represents the results of calculations carried out on the NOAA data and also contains the source code of the programs that made the calculations. The objective was to derive the average sea-surface temperature of each month and week throughout the whole 10-year series, meaning, for example, that data from January of each year would be averaged together. The result is 12 monthly and 52 weekly images for each of the oceanic regions. Averaging the images in this way tends to reduce the number of grid cells that lack valid data and to suppress interannual variability.
Unscrambling The "Average User" Of Habbo Hotel
Directory of Open Access Journals (Sweden)
Mikael Johnson
2007-01-01
Full Text Available The “user” is an ambiguous concept in human-computer interaction and information systems. Analyses of users as social actors, participants, or configured users delineate approaches to studying design-use relationships. Here, a developer’s reference to a figure of speech, termed the “average user,” is contrasted with design guidelines. The aim is to create an understanding about categorization practices in design through a case study about the virtual community, Habbo Hotel. A qualitative analysis highlighted not only the meaning of the “average user,” but also the work that both the developer and the category contribute to this meaning. The average user a represents the unknown, b influences the boundaries of the target user groups, c legitimizes the designer to disregard marginal user feedback, and d keeps the design space open, thus allowing for creativity. The analysis shows how design and use are intertwined and highlights the developers’ role in governing different users’ interests.
On Backus average for generally anisotropic layers
Bos, Len; Slawinski, Michael A; Stanoev, Theodore
2016-01-01
In this paper, following the Backus (1962) approach, we examine expressions for elasticity parameters of a homogeneous generally anisotropic medium that is long-wave-equivalent to a stack of thin generally anisotropic layers. These expressions reduce to the results of Backus (1962) for the case of isotropic and transversely isotropic layers. In over half-a-century since the publications of Backus (1962) there have been numerous publications applying and extending that formulation. However, neither George Backus nor the authors of the present paper are aware of further examinations of mathematical underpinnings of the original formulation; hence, this paper. We prove that---within the long-wave approximation---if the thin layers obey stability conditions then so does the equivalent medium. We examine---within the Backus-average context---the approximation of the average of a product as the product of averages, and express it as a proposition in terms of an upper bound. In the presented examination we use the e...
Disk-averaged synthetic spectra of Mars
Tinetti, G; Fong, W; Meadows, V S; Snively, H; Velusamy, T; Crisp, David; Fong, William; Meadows, Victoria S.; Snively, Heather; Tinetti, Giovanna; Velusamy, Thangasamy
2004-01-01
The principal goal of the NASA Terrestrial Planet Finder (TPF) and ESA Darwin mission concepts is to directly detect and characterize extrasolar terrestrial (Earth-sized) planets. This first generation of instruments is expected to provide disk-averaged spectra with modest spectral resolution and signal-to-noise. Here we use a spatially and spectrally resolved model of the planet Mars to study the detectability of a planet's surface and atmospheric properties from disk-averaged spectra as a function of spectral resolution and wavelength range, for both the proposed visible coronograph (TPF-C) and mid-infrared interferometer (TPF-I/Darwin) architectures. At the core of our model is a spectrum-resolving (line-by-line) atmospheric/surface radiative transfer model which uses observational data as input to generate a database of spatially-resolved synthetic spectra for a range of illumination conditions (phase angles) and viewing geometries. Results presented here include disk averaged synthetic spectra, light-cur...
New approximative orientation averaging of the water molecule interacting with the thermal neutron
International Nuclear Information System (INIS)
Orientation averaging is performed by exact orientation averaging (EOA→) and four approximate methods (two ell known and two new) and expression for the microscopic scattering kernel of thermal neutrons on water molecules are developed. Two well known approximate orientation averagings are Krieger-Nelkin's (KN) and Kappel-Young;s (KY). The results obtained by one pf the two newly proposed approximate orientation averaging methods agree best with the corresponding results obtained by EOA→. The biggest discrepancies between the EOA→ results and results of the approximate methods are obtained using well known KN approximate orientation averaging. (author)
Average resonance parameters of germanium and selenium nuclei
International Nuclear Information System (INIS)
Full sets of average resonance parameters S0, S1, R0', R1', S1,3/2 for germanium and selenium nuclei with natural isotope content are determined. Parameters are received from the analysis of experimental neutron elastic scattering cross sections at energy region up to 440 keV with the help of the method developed by the authors. The analysis of recommended parameters and some literature data is fulfilled as well.
Mueller, Fred M.; Bronisz, Lawrence; Grube, Holger; Nelson, David C.; Mace, Jonathan L.
2006-11-14
A magnetic infrasound sensor is produced by constraining a permanent magnet inside a magnetic potential well above the surface of superconducting material. The magnetic infrasound sensor measures the position or movement of the permanent magnet within the magnetic potential well, and interprets the measurements. Infrasound sources can be located and characterized by combining the measurements from one or more infrasound sensors. The magnetic infrasound sensor can be tuned to match infrasound source types, resulting in better signal-to-noise ratio. The present invention can operate in frequency modulation mode to improve sensitivity and signal-to-noise ratio. In an alternate construction, the superconductor can be levitated over a magnet or magnets. The system can also be driven, so that time resolved perturbations are sensed, resulting in a frequency modulation version with improved sensitivity and signal-to-noise ratio.
Magnetized vortex tubes in the solar wind plasma
International Nuclear Information System (INIS)
We make new applications of our previously proposed method for estimating the strain-rate tensor and vorticity vector in plasmas (concerning the local deformation and self rotation of the plasma fluid elements, respectively) solely from magnetic field time series. Here we use solar wind measurements of Ulysses spacecraft made in the outer heliosphere, on and off the ecliptic plane, during the period 1990-1998. The application results imply that the solar wind plasma is, to a good approximation, weakly incompressible, being nearly incompressible on the local magnetic field-normal plane, while expanding at maximum strain rate in the magnetic field direction. This property is theoretically expected, at least for low and intermediate beta plasmas, and supports previous arguments for two-dimensional MHD turbulence in the solar wind. In the magnetic induction equation the vorticity term is favoured, being at least an order of magnitude larger than the strain-rate term, thus explaining the magnetic field alignment of the minimum magnetic field variance and the random wandering of the magnetic field's vector tip on a sphere, both being well known, general features of the heliospheric magnetic field fluctuations. Further, the solar wind is found dominated by magnetized vortex sheet structures (MVS), on the tangential plane of which lie the, (not generally aligned) average vectors of magnetic field, vorticity and plasma velocity in the solar-corotating frame of reference. These coplanarity properties are shown to be consistent with a theoretically predicted force-free state, minimizing the total energy while conserving a generalized helicity function. The theory additionally implies that the (not directly measured by Ulysses) electric current density also lies on the MVS tangential plane, hence the MVS also constitute current sheets. The MVS spatial orientation implies that the MVS are wrapped in the form of magnetized vortex tubes with axes aligned to the average magnetic
Parents' Reactions to Finding Out That Their Children Have Average or above Average IQ Scores.
Dirks, Jean; And Others
1983-01-01
Parents of 41 children who had been given an individually-administered intelligence test were contacted 19 months after testing. Parents of average IQ children were less accurate in their memory of test results. Children with above average IQ experienced extremely low frequencies of sibling rivalry, conceit or pressure. (Author/HLM)
Strong constraints on magnetized white dwarfs surpassing the Chandrasekhar mass limit
Nityananda, Rajaram
2013-01-01
We show that recently proposed white dwarf models with masses well in excess of the Chandrasekhar limit, based on modifying the equation of state by a super-strong magnetic field in the centre, are very far from equilibrium because of the neglect of Lorentz forces. An upper bound on the central magnetic fields, from a spherically averaged hydrostatic equation, appears to be much smaller than the values assumed. Robust estimates of the Lorentz forces are also made without assuming spherical averaging. These again bear out the results obtained from a spherically averaged model. In our assessment, these rule out the possibility that magnetic tension could change the situation in favour of larger magnetic fields. We conclude that such super-Chandrasekhar models are unphysical and exploration of their astrophysical consequences is premature.
The Role of the Harmonic Vector Average in Motion Integration
Directory of Open Access Journals (Sweden)
Alan eJohnston
2013-10-01
Full Text Available The local speeds of object contours vary systematically with the cosine of the angle between the normal component of the local velocity and the global object motion direction. An array of Gabor elements whose speed changes with local spatial orientation in accordance with this pattern can appear to move as a single surface. The apparent direction of motion of plaids and Gabor arrays has variously been proposed to result from feature tracking, vector addition and vector averaging in addition to the geometrically correct global velocity as indicated by the intersection of constraints (IOC solution. Here a new combination rule, the harmonic vector average (HVA, is introduced, as well as a new algorithm for computing the IOC solution. The vector sum can be discounted as an integration strategy as it increases with the number of elements. The vector average over local vectors that vary in direction always provides an underestimate of the true global speed. The harmonic vector average however provides the correct global speed and direction for an unbiased sample of local velocities with respect to the global motion direction, as is the case for a simple closed contour. The HVA over biased samples provides an aggregate velocity estimate that can still be combined through an IOC computation to give an accurate estimate of the global velocity, which is not true of the vector average. Psychophysical results for type II Gabor arrays show perceived direction and speed falls close to the intersection of constraints direction for Gabor arrays having a wide range of orientations but the IOC prediction fails as the mean orientation shifts away from the global motion direction and the orientation range narrows. In this case perceived velocity generally defaults to the harmonic vector average.
Masir, M. Ramezani; Vasilopoulos, P.; Matulis, A.; Peeters, F. M.
2010-01-01
We evaluate the transmission through magnetic barriers in graphene-based nanostructures. Several particular cases are considered: a magnetic step, single and double barriers, δ -function barriers as well as barrier structures with inhomogeneous magnetic field profiles but with average magnetic field equal to zero. The transmission exhibits a strong dependence on the direction of the incident wave vector. In general the resonant structure of the transmission is significantly more pronounced for (Dirac) electrons with linear spectrum compared to that for electrons with a parabolic one.
The average free volume model for liquids
Yu, Yang
2014-01-01
In this work, the molar volume thermal expansion coefficient of 59 room temperature ionic liquids is compared with their van der Waals volume Vw. Regular correlation can be discerned between the two quantities. An average free volume model, that considers the particles as hard core with attractive force, is proposed to explain the correlation in this study. A combination between free volume and Lennard-Jones potential is applied to explain the physical phenomena of liquids. Some typical simple liquids (inorganic, organic, metallic and salt) are introduced to verify this hypothesis. Good agreement from the theory prediction and experimental data can be obtained.
Phase-averaged transport for quasiperiodic Hamiltonians
Bellissard, J; Schulz-Baldes, H
2002-01-01
For a class of discrete quasi-periodic Schroedinger operators defined by covariant re- presentations of the rotation algebra, a lower bound on phase-averaged transport in terms of the multifractal dimensions of the density of states is proven. This result is established under a Diophantine condition on the incommensuration parameter. The relevant class of operators is distinguished by invariance with respect to symmetry automorphisms of the rotation algebra. It includes the critical Harper (almost-Mathieu) operator. As a by-product, a new solution of the frame problem associated with Weyl-Heisenberg-Gabor lattices of coherent states is given.
Independence, Odd Girth, and Average Degree
DEFF Research Database (Denmark)
Löwenstein, Christian; Pedersen, Anders Sune; Rautenbach, Dieter;
2011-01-01
We prove several tight lower bounds in terms of the order and the average degree for the independence number of graphs that are connected and/or satisfy some odd girth condition. Our main result is the extension of a lower bound for the independence number of triangle-free graphs of maximum...... degree at most three due to Heckman and Thomas [Discrete Math 233 (2001), 233–237] to arbitrary triangle-free graphs. For connected triangle-free graphs of order n and size m, our result implies the existence of an independent set of order at least (4n−m−1) / 7. ...
PROFILE OF HIRED FARMWORKERS, 1998 ANNUAL AVERAGES
Runyan, Jack L.
2000-01-01
An average of 875,000 persons 15 years of age and older did hired farmwork each week as their primary job in 1998. An additional 63,000 people did hired farmwork each week as their secondary job. Hired farmworkers were more likely than the typical U.S. wage and salary worker to be male, Hispanic, younger, less educated, never married, and not U.S. citizens. The West (42 percent) and South (31.4 percent) census regions accounted for almost three-fourths of the hired farmworkers. The rate of un...
Time-dependent angularly averaged inverse transport
International Nuclear Information System (INIS)
This paper concerns the reconstruction of the absorption and scattering parameters in a time-dependent linear transport equation from knowledge of angularly averaged measurements performed at the boundary of a domain of interest. Such measurement settings find applications in medical and geophysical imaging. We show that the absorption coefficient and the spatial component of the scattering coefficient are uniquely determined by such measurements. We obtain stability results on the reconstruction of the absorption and scattering parameters with respect to the measured albedo operator. The stability results are obtained by a precise decomposition of the measurements into components with different singular behavior in the time domain
Time-dependent angularly averaged inverse transport
Bal, Guillaume
2009-01-01
This paper concerns the reconstruction of the absorption and scattering parameters in a time-dependent linear transport equation from knowledge of angularly averaged measurements performed at the boundary of a domain of interest. We show that the absorption coefficient and the spatial component of the scattering coefficient are uniquely determined by such measurements. We obtain stability results on the reconstruction of the absorption and scattering parameters with respect to the measured albedo operator. The stability results are obtained by a precise decomposition of the measurements into components with different singular behavior in the time domain.
High average power laser for EUV lithography
Energy Technology Data Exchange (ETDEWEB)
Kania, D.R.; Gaines, D.P.; Hermann, M.; Honig, J.; Hostetler, R.; Levesque, R.; Sommargren, G.E.; Spitzer, R.C.; Vernon, S.P.
1995-01-19
We have demonstrated the operation of a high average power, all solid state laser and target system for EUV lithography. The laser operates at 1.06 {mu}m with a pulse repetition rate of 200 Hz. Each pulse contains up to 400 mJ of energy and is less than 10 ns in duration. The ELTV conversion efficiency measured with the laser is independent of the laser repetition rate. Operating at 200 Hz, the laser has been used for lithography using a 3 bounce Kohler illuminator.
Some averaging functions in image reduction
Czech Academy of Sciences Publication Activity Database
Paternain, D.; Bustince, H.; Fernández, J.; Beliakov, G.; Mesiar, Radko
Berlin: Springer, 2010 - (García-Pedrajas, N.; Herrera, F.; Benítez, J.), s. 399-408. (Lecture Notes in Artificial Intelligence . 6098). ISBN 978-3-642-13032-8. ISSN 0302-9743. [IEA/AIE 2010. Cordoba (ES), 01.06.2010-04.06.2010] Institutional research plan: CEZ:AV0Z10750506 Keywords : image reduction * local reduction operators * aggregation functions Subject RIV: BA - General Mathematics http://library.utia.cas.cz/separaty/2010/E/mesiar-some averaging functions in image reduction.pdf
The effect of cosmic inhomogeneities on the average cosmological dynamics
Singh, T P
2011-01-01
It is generally assumed that on sufficiently large scales the Universe is well-described as a homogeneous, isotropic FRW cosmology with a dark energy. Does the formation of nonlinear cosmic inhomogeneities produce a significant effect on the average large-scale FLRW dynamics? As an answer, we suggest that if the length scale at which homogeneity sets in is much smaller than the Hubble length scale, the back-reaction due to averaging over inhomogeneities is negligible. This result is supported by more than one approach to study of averaging in cosmology. Even if no single approach is sufficiently rigorous and compelling, they are all in agreement that the effect of averaging in the real Universe is small. On the other hand, it is perhaps fair to say that there is no definitive observational evidence yet that there indeed is a homogeneity scale which is much smaller than the Hubble scale, or for that matter, if today's Universe is indeed homogeneous on large scales. If the Copernican principle can be observatio...
Fuel optimum low-thrust elliptic transfer using numerical averaging
Tarzi, Zahi; Speyer, Jason; Wirz, Richard
2013-05-01
Low-thrust electric propulsion is increasingly being used for spacecraft missions primarily due to its high propellant efficiency. As a result, a simple and fast method for low-thrust trajectory optimization is of great value for preliminary mission planning. However, few low-thrust trajectory tools are appropriate for preliminary mission design studies. The method presented in this paper provides quick and accurate solutions for a wide range of transfers by using numerical orbital averaging to improve solution convergence and include orbital perturbations. Thus, preliminary trajectories can be obtained for transfers which involve many revolutions about the primary body. This method considers minimum fuel transfers using first-order averaging to obtain the fuel optimum rates of change of the equinoctial orbital elements in terms of each other and the Lagrange multipliers. Constraints on thrust and power, as well as minimum periapsis, are implemented and the equations are averaged numerically using a Gausian quadrature. The use of numerical averaging allows for more complex orbital perturbations to be added in the future without great difficulty. The effects of zonal gravity harmonics, solar radiation pressure, and thrust limitations due to shadowing are included in this study. The solution to a transfer which minimizes the square of the thrust magnitude is used as a preliminary guess for the minimum fuel problem, thus allowing for faster convergence to a wider range of problems. Results from this model are shown to provide a reduction in propellant mass required over previous minimum fuel solutions.
Rademacher averages on noncommutative symmetric spaces
Merdy, Christian Le
2008-01-01
Let E be a separable (or the dual of a separable) symmetric function space, let M be a semifinite von Neumann algebra and let E(M) be the associated noncommutative function space. Let $(\\epsilon_k)_k$ be a Rademacher sequence, on some probability space $\\Omega$. For finite sequences $(x_k)_k of E(M), we consider the Rademacher averages $\\sum_k \\epsilon_k\\otimes x_k$ as elements of the noncommutative function space $E(L^\\infty(\\Omega)\\otimes M)$ and study estimates for their norms $\\Vert \\sum_k \\epsilon_k \\otimes x_k\\Vert_E$ calculated in that space. We establish general Khintchine type inequalities in this context. Then we show that if E is 2-concave, the latter norm is equivalent to the infimum of $\\Vert (\\sum y_k^*y_k)^{{1/2}}\\Vert + \\Vert (\\sum z_k z_k^*)^{{1/2}}\\Vert$ over all $y_k,z_k$ in E(M) such that $x_k=y_k+z_k$ for any k. Dual estimates are given when E is 2-convex and has a non trivial upper Boyd index. We also study Rademacher averages for doubly indexed families of E(M).
Trajectory averaging for stochastic approximation MCMC algorithms
Liang, Faming
2010-10-01
The subject of stochastic approximation was founded by Robbins and Monro [Ann. Math. Statist. 22 (1951) 400-407]. After five decades of continual development, it has developed into an important area in systems control and optimization, and it has also served as a prototype for the development of adaptive algorithms for on-line estimation and control of stochastic systems. Recently, it has been used in statistics with Markov chain Monte Carlo for solving maximum likelihood estimation problems and for general simulation and optimizations. In this paper, we first show that the trajectory averaging estimator is asymptotically efficient for the stochastic approximation MCMC (SAMCMC) algorithm under mild conditions, and then apply this result to the stochastic approximation Monte Carlo algorithm [Liang, Liu and Carroll J. Amer. Statist. Assoc. 102 (2007) 305-320]. The application of the trajectory averaging estimator to other stochastic approximationMCMC algorithms, for example, a stochastic approximation MLE algorithm for missing data problems, is also considered in the paper. © Institute of Mathematical Statistics, 2010.
Microfluidic magnetic separator using an array of soft magnetic elements
DEFF Research Database (Denmark)
Smistrup, Kristian; Lund-Olesen, Torsten; Hansen, Mikkel Fougt;
2006-01-01
We present the design, fabrication, characterization, and demonstration of a new passive magnetic bead separator. The device operates in an effective state when magnetized by an external magnetic field of only 50 mT, which is available from a tabletop electromagnet. We demonstrate the complete...... capture of 1.0 mu m fluorescent magnetic beads from a 7.5 mu L sample volume traveling at an average linear fluid velocity of 5 mm/s....
Microfluidic magnetic separator using an array of soft magnetic elements
Smistrup, Kristian; Lund-Olesen, Torsten; Hansen, Mikkel Fougt; Tang, Peter Torben
2006-01-01
We present the design, fabrication, characterization, and demonstration of a new passive magnetic bead separator. The device operates in an effective state when magnetized by an external magnetic field of only 50 mT, which is available from a tabletop electromagnet. We demonstrate the complete capture of 1.0 mu m fluorescent magnetic beads from a 7.5 mu L sample volume traveling at an average linear fluid velocity of 5 mm/s.
Detect Adjacent Well by Analyzing Geomagnetic Anomalies
Directory of Open Access Journals (Sweden)
Su Zhang
2014-03-01
Full Text Available This study describes a method of determining the position of adjacent well by analyzing geomagnetic anomalies in the drilling. In the experiment, put a casing in the geomagnetic field respectively to simulate 3 conditions, which are vertical well, deviated well and horizontal well. Study the interference of regional geomagnetic caused by casing, summary the law of the regional geomagnetic field anomalies caused by the adjacent casing. Experimental results show that: magnetic intensity distortion caused by deviated well is similar to that caused by horizontal well, but the distortion is different from vertical well. The scope and amplitude of N and E component magnetic intensity distortion will increase with the increase of casing inclination, meanwhile the scope and amplitude of V component distortion will decrease and the distortion value changes from negative to positive to the southwest of adjacent well. Through the analysis of geomagnetic anomalies, the position of the adjacent wells could be determined.
A Moving Average Bidirectional Texture Function Model
Czech Academy of Sciences Publication Activity Database
Havlíček, Michal; Haindl, Michal
Vol. II. Heidelberg: Springer, 2013 - (Wilson, R.; Bors, A.; Hancock, E.; Smith, W.), s. 338-345. (Lecture Notes in Computer Science. 8048). ISBN 978-3-642-40245-6. ISSN 0302-9743. [International Conference on Computer Analysis of Images and Patterns (CAIP 2013) /15./. York (GB), 27.08.2013-29.08.2013] R&D Projects: GA ČR GA102/08/0593; GA ČR GAP103/11/0335 Institutional support: RVO:67985556 Keywords : BTF * texture analysis * texture synthesis * data compression Subject RIV: BD - Theory of Information http://library.utia.cas.cz/separaty/2013/RO/havlicek-a moving average bidirectional texture function model.pdf
The Lang-Trotter Conjecture on Average
Baier, Stephan
2006-01-01
For an elliptic curve $E$ over $\\ratq$ and an integer $r$ let $\\pi_E^r(x)$ be the number of primes $p\\le x$ of good reduction such that the trace of the Frobenius morphism of $E/\\fie_p$ equals $r$. We consider the quantity $\\pi_E^r(x)$ on average over certain sets of elliptic curves. More in particular, we establish the following: If $A,B>x^{1/2+\\epsilon}$ and $AB>x^{3/2+\\epsilon}$, then the arithmetic mean of $\\pi_E^r(x)$ over all elliptic curves $E$ : $y^2=x^3+ax+b$ with $a,b\\in \\intz$, $|a...
Electromagnetic modes induced by averaged geodesic curvature
International Nuclear Information System (INIS)
Full text: Kinetic theory of geodesic acoustic and related modes is developed with emphasis on the electromagnetic effects due to electron parallel motion, higher order dispersion and drift effects. In general, dispersion of GAM is determined by the ion sound Larmor radius, ion Larmor radius, and electron inertia. Relative contribution of these effects depends on the particular regime and mode localization. It is shown that there are exist new type of electromagnetic (Alfven) modes induced by averaged geodesic curvature. It is shown that the fluid limit of the kinetic dispersion relation is exactly recovered by the extended MHD (Grad hydrodynamics) exactly recovers the kinetic dispersion relation for geodesic acoustic modes (GAMs). The coupling of modes of different polarization is investigated within the extended MHD and kinetic models. The role of drift effects, in particular, electron temperature gradient on GAMs and related modes is investigated. (author)
Average prime-pair counting formula
Korevaar, Jaap; Riele, Herman Te
2010-04-01
Taking r>0 , let π_{2r}(x) denote the number of prime pairs (p, p+2r) with p≤ x . The prime-pair conjecture of Hardy and Littlewood (1923) asserts that π_{2r}(x)˜ 2C_{2r} {li}_2(x) with an explicit constant C_{2r}>0 . There seems to be no good conjecture for the remainders ω_{2r}(x)=π_{2r}(x)- 2C_{2r} {li}_2(x) that corresponds to Riemann's formula for π(x)-{li}(x) . However, there is a heuristic approximate formula for averages of the remainders ω_{2r}(x) which is supported by numerical results.
The balanced survivor average causal effect.
Greene, Tom; Joffe, Marshall; Hu, Bo; Li, Liang; Boucher, Ken
2013-01-01
Statistical analysis of longitudinal outcomes is often complicated by the absence of observable values in patients who die prior to their scheduled measurement. In such cases, the longitudinal data are said to be "truncated by death" to emphasize that the longitudinal measurements are not simply missing, but are undefined after death. Recently, the truncation by death problem has been investigated using the framework of principal stratification to define the target estimand as the survivor average causal effect (SACE), which in the context of a two-group randomized clinical trial is the mean difference in the longitudinal outcome between the treatment and control groups for the principal stratum of always-survivors. The SACE is not identified without untestable assumptions. These assumptions have often been formulated in terms of a monotonicity constraint requiring that the treatment does not reduce survival in any patient, in conjunction with assumed values for mean differences in the longitudinal outcome between certain principal strata. In this paper, we introduce an alternative estimand, the balanced-SACE, which is defined as the average causal effect on the longitudinal outcome in a particular subset of the always-survivors that is balanced with respect to the potential survival times under the treatment and control. We propose a simple estimator of the balanced-SACE that compares the longitudinal outcomes between equivalent fractions of the longest surviving patients between the treatment and control groups and does not require a monotonicity assumption. We provide expressions for the large sample bias of the estimator, along with sensitivity analyses and strategies to minimize this bias. We consider statistical inference under a bootstrap resampling procedure. PMID:23658214
SEASONAL AVERAGE FLOW IN RÂUL NEGRU HYDROGRAPHIC BASIN
Directory of Open Access Journals (Sweden)
VIGH MELINDA
2015-03-01
Full Text Available The Râul Negru hydrographic basin is a well individualised physical-geographical unit inside the Braşov Depression. The flow is controlled by six hydrometric stations placed on the main river and on two important tributaries. The data base for seasonal flow analysis contains the discharges from 1950-2012. The results of data analysis show that there significant space-time differences between multiannual seasonal averages. Some interesting conclusions can be obtained by comparing abundant and scarce periods. Flow analysis was made using seasonal charts Q = f(T. The similarities come from the basin’s relative homogeneity, and the differences from flow’s evolution and trend. Flow variation is analysed using variation coefficient. In some cases appear significant Cv values differences. Also, Cv values trends are analysed according to basins’ average altitude.
The Vela X-1 pulse-averaged spectrum as observed by BeppoSAX
Orlandini, M; Frontera, F; Cusumano, G; Del Sordo, S; Giarrusso, S; Piraino, S; Segreto, A; Guainazzi, M; Piro, L
1997-01-01
We report on the 20 ksec observation of Vela X-1 performed by BeppoSAX on 1996 July 14 during its Science Verification Phase. We observed the source in two intensity states, characterized by a change in luminosity of a factor ~ 2, and a change in absorption of a factor ~ 10. The single Narrow Field Instrument pulse-averaged spectra are well fit by a power law with significantly different indices. This is in agreement with the observed changes of slope in the wide-band spectrum: a first change of slope at ~ 10 keV, and a second one at ~ 35 keV. To mimic this behaviour we used a double power law modified by an exponential cutoff --- the so-called NPEX model --- to fit the whole 2-100 keV continuum. This functional is able to adequately describe the data, expecially the low intensity state. We found an absorption-like feature at ~ 57 keV, very well visible in the ratio performed with the Crab spectrum. We interpreted this feature as a cyclotron resonance, corresponding to a neutron star surface magnetic strength...
Industry-grade high average power femtosecond light source
Heckl, O. H.; Weiler, S.; Fleischhaker, R.; Gebs, R.; Budnicki, A.; Wolf, M.; Kleinbauer, J.; Russ, S.; Kumkar, M.; Sutter, D. H.
2014-03-01
Ultrashort pulses are capable of processing practically any material with negligible heat affected zone. Typical pulse durations for industrial applications are situated in the low picosecond-regime. Pulse durations of 5 ps or below are a well established compromise between the electron-phonon interaction time of most materials and the need for pulses long enough to suppress detrimental effects such as nonlinear interaction with the ablated plasma plume. However, sub-picosecond pulses can further increase the ablation efficiency for certain materials, depending on the available average power, pulse energy and peak fluence. Based on the well established TruMicro 5000 platform (first release in 2007, third generation in 2011) an Yb:YAG disk amplifier in combination with a broadband seed laser was used to scale the output power for industrial femtosecond-light sources: We report on a subpicosecond amplifier that delivers a maximum of 160 W of average output power at pulse durations of 750 fs. Optimizing the system for maximum peak power allowed for pulse energies of 850 μJ at pulse durations of 650 fs. Based on this study and the approved design of the TruMicro 5000 product-series, industrygrade, high average power femtosecond-light sources are now available for 24/7 operation. Since their release in May 2013 we were able to increase the average output power of the TruMicro 5000 FemtoEdition from 40 W to 80 W while maintaining pulse durations around 800 fs. First studies on metals reveal a drastic increase of processing speed for some micro processing applications.
Bounce-averaged Fokker-Planck solver in non-axisymmetric toroidal geometry
Energy Technology Data Exchange (ETDEWEB)
Ju, M.; Basiuk, V.; Peysson, Y
2001-02-01
It is expected that magnetic ripples can have significant effects on the usual trajectories of particles. This leads to the diffusive losses of particle and energy due to magnetic ripples. For the consistent estimation of these losses on Tore Supra, the Fokker-Planck equation bounce-averaged in the axisymmetric toroidal geometry should be bounce-averaged in the non-axisymmetric toroidal geometry including magnetic ripple effects. The bounce averaged coefficients in the Fokker-Planck equation can be represented by the multiplication with the constants such as {lambda}, S{sup *} and ({delta}){sub {tau}{sub B}}. Therefore, in this work, the new explicit expressions for these constants are developed in nonaxisymmetric toroidal geometry for the circulating particles and trapped particles in the usual banana orbits. From the results, it is found out that for circulating particles, the effects of magnetic ripples on the bounce averaged coefficients are negligible while, for banana trapped particles, those effects can be non-negligible. (authors)
Initial vector magnetic anomaly map from Magsat
Langel, R. A.; Schnetzler, C. C.; Phillips, J. D.; Horner, R. J.
1982-01-01
Global magnetic component anomaly field maps have been derived from the Magsat vector magnetometer data obtained from November 1979 through May 1980. The amplitude of variations of the components over the maps are between 10 and 15 nT, well above the noise in the data. Averaged data, in 2-by-2 deg blocks, exhibit standard errors of the mean of about 1 nT over most of the X and Z maps, and about 2 nT over most of the Y maps. Errors rise to about twice these amounts near the auroral belts. Most of the anomalies in the component data are consistent with a crustal magnetization model which incorporates dipoles aligned only in the direction of the main field. However, there appear to be some regions which require dipoles aligned in some other direction i.e., remanent magnetization.
Metallic Magnetic Nanoparticles
A Hernando; P. Crespo; M. A. García
2005-01-01
In this paper, we reviewed some relevant aspects of the magnetic properties of metallic nanoparticles with small size (below 4 nm), covering the size effects in nanoparticles of magnetic materials, as well as the appearance of magnetism at the nanoscale in materials that are nonferromagnetic in bulk. These results are distributed along the text that has been organized around three important items: fundamental magnetic properties, different fabrication procedures, and characterization techniqu...
Preparation of high viscosity average molecular mass poly-L-lactide
Institute of Scientific and Technical Information of China (English)
ZHOU Zhi-hua; RUAN Jian-ming; ZOU Jian-peng; ZHOU Zhong-cheng; SHEN Xiong-jun
2006-01-01
Poly-L-lactide(PLLA) was synthesized by ring-opening polymerization from high purity L-lactide with tin octoate as initiator, and characterized by means of infrared, and 1H-nuclear magnetic resonance. The influences of initiator concentration,polymerization temperature and polymerization time on the viscosity average molecular mass of PLLA were investigated. The effects of different purification methods on the concentration of initiator and viscosity average molecular mass were also studied. PLLA with a viscosity average molecular mass of about 50.5×104 was obtained when polymerization was conducted for 24 h at 140 ℃ with the molar ratio of monomer to purification initator being 12 000. After purification, the concentration of tin octoate decreases; however,the effect of different purification methods on the viscosity average molecular mass of PLLA is different, and the obtained PLLA is a typical amorphous polymeric material. The crystallinity of PLLA decreases with the increase of viscosity average molecular mass.
Uniform excitations in magnetic nanoparticles
DEFF Research Database (Denmark)
Mørup, Steen; Frandsen, Cathrine; Hansen, Mikkel Fougt
2010-01-01
We present a short review of the magnetic excitations in nanoparticles below the superparamagnetic blocking temperature. In this temperature regime, the magnetic dynamics in nanoparticles is dominated by uniform excitations, and this leads to a linear temperature dependence of the magnetization...... and the magnetic hyperfine field, in contrast to the Bloch T3/2 law in bulk materials. The temperature dependence of the average magnetization is conveniently studied by Mössbauer spectroscopy. The energy of the uniform excitations of magnetic nanoparticles can be studied by inelastic neutron scattering....
Uniform excitations in magnetic nanoparticles
Directory of Open Access Journals (Sweden)
Steen Mørup
2010-11-01
Full Text Available We present a short review of the magnetic excitations in nanoparticles below the superparamagnetic blocking temperature. In this temperature regime, the magnetic dynamics in nanoparticles is dominated by uniform excitations, and this leads to a linear temperature dependence of the magnetization and the magnetic hyperfine field, in contrast to the Bloch T3/2 law in bulk materials. The temperature dependence of the average magnetization is conveniently studied by Mössbauer spectroscopy. The energy of the uniform excitations of magnetic nanoparticles can be studied by inelastic neutron scattering.
Leading and following sunspots: their magnetic properties and ultra-violet emission above them
Zagainova, Iu. S.; Fainshtein, V. G.; Obridko, V. N.
2015-01-01
Using SDO/HMI and SDO/AIA data for sunspot groups of the 24th solar cycle, we analyzed magnetic properties and He II 304 emission in leading and following sunspots separately. Simultaneous examination of umbral magnetic properties and atmospheric characteristics above the umbrae draws on average differences in He II 304 contrast over the umbrae of leading and following spots we discovered earlier for solar cycle 23 sunspot groups based on SOHO data as well as on the hypothetical relationship ...
Recent Activities in Magnetic Separation in Sweden
Wang, Yanmin; Forssberg, Eric
1995-01-01
This paper describes some industrial applications of magnetic separation in Swedish mineral industry. Recent studies on magnetic treatment of minerals in Sweden are also presented. These studies involve selectivity of wet magnetic separation, wet magnetic recovery of mineral fines and ultrafines, sulphide processing by magnetic means, as well as dry magnetic purification of industrial minerals.
Dynamic speckle texture processing using averaged dimensions
Rabal, Héctor; Arizaga, Ricardo; Cap, Nelly; Trivi, Marcelo; Mavilio Nuñez, Adriana; Fernandez Limia, Margarita
2006-08-01
Dynamic speckle or biospeckle is a phenomenon generated by laser light scattering in biological tissues. It is also present in some industrial processes where the surfaces exhibit some kind of activity. There are several methods to characterize the dynamic speckle pattern activity. For quantitative measurements, the Inertia Moment of the co occurrence matrix of the temporal history of the speckle pattern (THSP) is usually used. In this work we propose the use of average dimensions (AD) for quantitative classifications of textures of THSP images corresponding to different stages of the sample. The AD method was tested in an experiment with the drying of paint, a non biological phenomenon that we usually use as dynamic speckle initial test. We have chosen this phenomenon because its activity can be followed in a relatively simple way by gravimetric measures and because its behaviour is rather predictable. Also, the AD was applied to numerically simulated THSP images and the performance was compared with other quantitative method. Experiments with biological samples are currently under development.
Average path length for Sierpinski pentagon
Peng, Junhao
2011-01-01
In this paper,we investigate diameter and average path length(APL) of Sierpinski pentagon based on its recursive construction and self-similar structure.We find that the diameter of Sierpinski pentagon is just the shortest path lengths between two nodes of generation 0. Deriving and solving the linear homogenous recurrence relation the diameter satisfies, we obtain rigorous solution for the diameter. We also obtain approximate solution for APL of Sierpinski pentagon, both diameter and APL grow approximately as a power-law function of network order $N(t)$, with the exponent equals $\\frac{\\ln(1+\\sqrt{3})}{\\ln(5)}$. Although the solution for APL is approximate,it is trusted because we have calculated all items of APL accurately except for the compensation($\\Delta_{t}$) of total distances between non-adjacent branches($\\Lambda_t^{1,3}$), which is obtained approximately by least-squares curve fitting. The compensation($\\Delta_{t}$) is only a small part of total distances between non-adjacent branches($\\Lambda_t^{1...
Calculating Free Energies Using Average Force
Darve, Eric; Pohorille, Andrew; DeVincenzi, Donald L. (Technical Monitor)
2001-01-01
A new, general formula that connects the derivatives of the free energy along the selected, generalized coordinates of the system with the instantaneous force acting on these coordinates is derived. The instantaneous force is defined as the force acting on the coordinate of interest so that when it is subtracted from the equations of motion the acceleration along this coordinate is zero. The formula applies to simulations in which the selected coordinates are either unconstrained or constrained to fixed values. It is shown that in the latter case the formula reduces to the expression previously derived by den Otter and Briels. If simulations are carried out without constraining the coordinates of interest, the formula leads to a new method for calculating the free energy changes along these coordinates. This method is tested in two examples - rotation around the C-C bond of 1,2-dichloroethane immersed in water and transfer of fluoromethane across the water-hexane interface. The calculated free energies are compared with those obtained by two commonly used methods. One of them relies on determining the probability density function of finding the system at different values of the selected coordinate and the other requires calculating the average force at discrete locations along this coordinate in a series of constrained simulations. The free energies calculated by these three methods are in excellent agreement. The relative advantages of each method are discussed.
High-average-power solid state lasers
International Nuclear Information System (INIS)
In 1987, a broad-based, aggressive R ampersand D program aimed at developing the technologies necessary to make possible the use of solid state lasers that are capable of delivering medium- to high-average power in new and demanding applications. Efforts were focused along the following major lines: development of laser and nonlinear optical materials, and of coatings for parasitic suppression and evanescent wave control; development of computational design tools; verification of computational models on thoroughly instrumented test beds; and applications of selected aspects of this technology to specific missions. In the laser materials areas, efforts were directed towards producing strong, low-loss laser glasses and large, high quality garnet crystals. The crystal program consisted of computational and experimental efforts aimed at understanding the physics, thermodynamics, and chemistry of large garnet crystal growth. The laser experimental efforts were directed at understanding thermally induced wave front aberrations in zig-zag slabs, understanding fluid mechanics, heat transfer, and optical interactions in gas-cooled slabs, and conducting critical test-bed experiments with various electro-optic switch geometries. 113 refs., 99 figs., 18 tabs
A new approach for Bayesian model averaging
Institute of Scientific and Technical Information of China (English)
TIAN XiangJun; XIE ZhengHui; WANG AiHui; YANG XiaoChun
2012-01-01
Bayesian model averaging (BMA) is a recently proposed statistical method for calibrating forecast ensembles from numerical weather models.However,successful implementation of BMA requires accurate estimates of the weights and variances of the individual competing models in the ensemble.Two methods,namely the Expectation-Maximization (EM) and the Markov Chain Monte Carlo (MCMC) algorithms,are widely used for BMA model training.Both methods have their own respective strengths and weaknesses.In this paper,we first modify the BMA log-likelihood function with the aim of removing the additional limitation that requires that the BMA weights add to one,and then use a limited memory quasi-Newtonian algorithm for solving the nonlinear optimization problem,thereby formulating a new approach for BMA (referred to as BMA-BFGS).Several groups of multi-model soil moisture simulation experiments from three land surface models show that the performance of BMA-BFGS is similar to the MCMC method in terms of simulation accuracy,and that both are superior to the EM algorithm.On the other hand,the computational cost of the BMA-BFGS algorithm is substantially less than for MCMC and is almost equivalent to that for EM.
Magnetization profiles in Fe/SmCo Spring Magnets with Graded Interfaces
Liu, Y. H.; Jiang, J. S.; Te Velthuis, S. G. E.; Ambaye, H.; Parizzi, A.
2010-03-01
To understand the improved effectiveness of the exchange coupling in Fe/SmCo spring magnets with a graded interface, we have determined the magnetic structure with Polarized Neutron Reflectometry (PNR). PNR confirms that the Fe/SmCo interface is greatly intermixed. Magnetic hysteresis curves show well-separated coercive fields for the soft phase HC^S and the hard phase HC^H. Large spin-flip (SF) scattering reveals a twisted magnetic structure at HC^S. SF scattering initially decreases slightly when H increases, then drops dramatically when H> HC^H. This suggests that the twisted region first becomes more narrow and then suddenly diminishes once the SmCo layer switches. Combining 1D micro-magnetic simulations and PNR, we find that the SmCo layer has a much lower average in-plane anisotropy than the bulk. The scattering along the recoil loops strongly depends on the starting field, but in all cases a collinear magnetic structure is indicated at low fields. Overall, the magnetization reversal is mostly reversible rotation for H HC^H.
Jackknife model averaging of the current account determinants
Directory of Open Access Journals (Sweden)
Urošević Branko
2012-01-01
Full Text Available This paper investigates the short to medium-term empirical relationships between the current account balances and a broad set of macroeconomic determinants in Serbia and selected CEE countries. Using novel model averaging techniques we focus the analysis to individual country’s data only. The results suggest that the model tracks the current account movements over the past decade quite well and captures its relative volatility. Signs and magnitudes of different coefficients indicate significant heterogeneity among countries providing empirical support for the country-level analysis.
Effect of random edge failure on the average path length
International Nuclear Information System (INIS)
We study the effect of random removal of edges on the average path length (APL) in a large class of uncorrelated random networks in which vertices are characterized by hidden variables controlling the attachment of edges between pairs of vertices. A formula for approximating the APL of networks suffering random edge removal is derived first. Then, the formula is confirmed by simulations for classical ER (Erdoes and Renyi) random graphs, BA (Barabasi and Albert) networks, networks with exponential degree distributions as well as random networks with asymptotic power-law degree distributions with exponent α > 2. (paper)
RELATIONSHIP BETWEEN J-INTEGRAL AND FRACTURE SURFACE AVERAGE PROFILE
Institute of Scientific and Technical Information of China (English)
Y.G. Cao; S.F. Xue; K.Tanaka
2007-01-01
To investigate the causes that led to the formation of cracks in materials, a novel method that only considered the fracture surfaces for determining the fracture toughness parameters of J-integral for plain strain was proposed. The principle of the fracture-surface topography analysis (FRASTA) was used. In FRASTA, the fracture surfaces were scanned by laser microscope and the elevation data was recorded for analysis. The relationship between J-integral and fracture surface average profile for plain strain was deduced. It was also verified that the J-integral determined by the novel method and by the compliance method matches each other well.
Analysis of nonlinear systems using ARMA [autoregressive moving average] models
International Nuclear Information System (INIS)
While many vibration systems exhibit primarily linear behavior, a significant percentage of the systems encountered in vibration and model testing are mildly to severely nonlinear. Analysis methods for such nonlinear systems are not yet well developed and the response of such systems is not accurately predicted by linear models. Nonlinear ARMA (autoregressive moving average) models are one method for the analysis and response prediction of nonlinear vibratory systems. In this paper we review the background of linear and nonlinear ARMA models, and illustrate the application of these models to nonlinear vibration systems. We conclude by summarizing the advantages and disadvantages of ARMA models and emphasizing prospects for future development. 14 refs., 11 figs
Visualizing motion in potential wells
Jolly, Pratibha; Zollman, Dean; Rebello, N. Sanjay; Dimitrova, Albena
1998-01-01
The concept of potential-energy diagrams is of fundamental importance in the study of quantum physics. Yet, students are rarely exposed to this powerful alternative description in introductory classes and thus have difficulty comprehending its significance when they encounter it in beginning-level quantum courses. We describe a learning unit that incorporates a sequence of computer-interfaced experiments using dynamics or air-track systems. This unit is designed to make the learning of potential-energy diagrams less abstract. Students begin by constructing the harmonic or square-well potential diagrams using either the velocity data and assuming conservation of energy or the force-displacement graph for the elastic interaction of an object constrained by springs or bouncing off springy blocks. Then, they investigate the motion of a rider magnet interacting with a configuration of field magnets and plot directly the potential-energy diagrams using a magnetic field sensor. The ease of measurement allows exploring the motion in a large variety of potential shapes in a short duration class.
Marković, Suzana; Raspor, Sanja; Komšić, Jelena
2015-01-01
Although wellness is becoming an increasingly popular concept in practice, academic research regarding wellness services, in general, and tourists as wellness customers, in particular, is lacking. Thus, the purpose of this study is to identify the main characteristics of wellness customers in hotel wellness settings. The study was conducted in hotel wellness centres in the Opatija Riviera (Croatia). The empirical research was organized in two steps, using two different instruments for collect...
A New CFAR Detector Based on Automatic Censoring Cell Averaging and Cell Averaging
Directory of Open Access Journals (Sweden)
Yuhua Qin
2013-06-01
Full Text Available In order to improve the interference immunity of the detector, a new CFAR detector (ACGCA-CFAR based on automatic censoring cell averaging (ACCA and cell averaging (CA is presented in this paper. It takes the greatest value of ACCA and CA local estimation as the noise power estimation. Under swerling II assumption, the analytic expressions of in homogeneous background are derived. In contrast to other detectors, the ACGCA-CFAR detector has higher detection performance both in homogeneous and nonhomogeneous backgrounds, while the sample sorting time of ACGCA is only quarter that of OS and ACCA.
Global Average Brightness Temperature for April 2003
2003-01-01
[figure removed for brevity, see original site] Figure 1 This image shows average temperatures in April, 2003, observed by AIRS at an infrared wavelength that senses either the Earth's surface or any intervening cloud. Similar to a photograph of the planet taken with the camera shutter held open for a month, stationary features are captured while those obscured by moving clouds are blurred. Many continental features stand out boldly, such as our planet's vast deserts, and India, now at the end of its long, clear dry season. Also obvious are the high, cold Tibetan plateau to the north of India, and the mountains of North America. The band of yellow encircling the planet's equator is the Intertropical Convergence Zone (ITCZ), a region of persistent thunderstorms and associated high, cold clouds. The ITCZ merges with the monsoon systems of Africa and South America. Higher latitudes are increasingly obscured by clouds, though some features like the Great Lakes, the British Isles and Korea are apparent. The highest latitudes of Europe and Eurasia are completely obscured by clouds, while Antarctica stands out cold and clear at the bottom of the image. The Atmospheric Infrared Sounder Experiment, with its visible, infrared, and microwave detectors, provides a three-dimensional look at Earth's weather. Working in tandem, the three instruments can make simultaneous observations all the way down to the Earth's surface, even in the presence of heavy clouds. With more than 2,000 channels sensing different regions of the atmosphere, the system creates a global, 3-D map of atmospheric temperature and humidity and provides information on clouds, greenhouse gases, and many other atmospheric phenomena. The AIRS Infrared Sounder Experiment flies onboard NASA's Aqua spacecraft and is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., under contract to NASA. JPL is a division of the California Institute of Technology in Pasadena.
Magnetic Properties as Indicators of Cu and Zn Contamination in Soils
Institute of Scientific and Technical Information of China (English)
LU Sheng-Gao; BAI Shi-Qiang; FU Li-Xia
2008-01-01
Concentrations of copper (Cu) and zinc (Zn) and various magnetic parameters in contaminated urban roadside soils were investigated using chemical analysis and magnetic measurements. The results revealed highly elevated Cu and Zn concentrations as well as magnetic susceptibility in the roadside soils. The mean concentrations of Cu and Zn in these roadside soils were almost twice those in average Chincsc soils, with the mean magnetic susceptibility of the roadside soils reaching about 179×10-8m3 kg-1. This enhanced magnetic susceptibility was attributed to the presence of anthro-pogcnic soft ferrimagnetic particles. A low frequency-dependent susceptibility (2.5%±1.0%) observed in the roadside soils indicated the coarse multidomain (MD) fcrrimagnetic grains to be the dominant contributor to magnetic susceptibility.The Cu and Zn concentration of the soils had highly significant linear correlations with magnetic susceptibility (P≤0.01),anhysterctic remanent magnetization (P≤0.01), and saturation isothermal remanent magnetization (P≤0.01). This suggested that heavy metals were associated with ferrimagnetic particles in soils, which were attributed to input of traffic emissions and industrial activities. Scanning electron microscopy and energy dispersive X-ray spectra of magnetic extracts of the roadside soils further suggested the link between the magnetic signal and concentrations of heavy metals. Thus, the magnetic parameters could provide a proxy measure for the level of heavy metal contamination and could be a potential tool for the detection and mapping of contaminated soils.
The role of the harmonic vector average in motion integration.
Johnston, Alan; Scarfe, Peter
2013-01-01
The local speeds of object contours vary systematically with the cosine of the angle between the normal component of the local velocity and the global object motion direction. An array of Gabor elements whose speed changes with local spatial orientation in accordance with this pattern can appear to move as a single surface. The apparent direction of motion of plaids and Gabor arrays has variously been proposed to result from feature tracking, vector addition and vector averaging in addition to the geometrically correct global velocity as indicated by the intersection of constraints (IOC) solution. Here a new combination rule, the harmonic vector average (HVA), is introduced, as well as a new algorithm for computing the IOC solution. The vector sum can be discounted as an integration strategy as it increases with the number of elements. The vector average over local vectors that vary in direction always provides an underestimate of the true global speed. The HVA, however, provides the correct global speed and direction for an unbiased sample of local velocities with respect to the global motion direction, as is the case for a simple closed contour. The HVA over biased samples provides an aggregate velocity estimate that can still be combined through an IOC computation to give an accurate estimate of the global velocity, which is not true of the vector average. Psychophysical results for type II Gabor arrays show perceived direction and speed falls close to the IOC direction for Gabor arrays having a wide range of orientations but the IOC prediction fails as the mean orientation shifts away from the global motion direction and the orientation range narrows. In this case perceived velocity generally defaults to the HVA. PMID:24155716
Characterizing individual painDETECT symptoms by average pain severity
Sadosky, Alesia; Koduru, Vijaya; Bienen, E Jay; Cappelleri, Joseph C
2016-01-01
Background painDETECT is a screening measure for neuropathic pain. The nine-item version consists of seven sensory items (burning, tingling/prickling, light touching, sudden pain attacks/electric shock-type pain, cold/heat, numbness, and slight pressure), a pain course pattern item, and a pain radiation item. The seven-item version consists only of the sensory items. Total scores of both versions discriminate average pain-severity levels (mild, moderate, and severe), but their ability to discriminate individual item severity has not been evaluated. Methods Data were from a cross-sectional, observational study of six neuropathic pain conditions (N=624). Average pain severity was evaluated using the Brief Pain Inventory-Short Form, with severity levels defined using established cut points for distinguishing mild, moderate, and severe pain. The Wilcoxon rank sum test was followed by ridit analysis to represent the probability that a randomly selected subject from one average pain-severity level had a more favorable outcome on the specific painDETECT item relative to a randomly selected subject from a comparator severity level. Results A probability >50% for a better outcome (less severe pain) was significantly observed for each pain symptom item. The lowest probability was 56.3% (on numbness for mild vs moderate pain) and highest probability was 76.4% (on cold/heat for mild vs severe pain). The pain radiation item was significant (P<0.05) and consistent with pain symptoms, as well as with total scores for both painDETECT versions; only the pain course item did not differ. Conclusion painDETECT differentiates severity such that the ability to discriminate average pain also distinguishes individual pain item severity in an interpretable manner. Pain-severity levels can serve as proxies to determine treatment effects, thus indicating probabilities for more favorable outcomes on pain symptoms.
Targeted Cancer Screening in Average-Risk Individuals.
Marcus, Pamela M; Freedman, Andrew N; Khoury, Muin J
2015-11-01
Targeted cancer screening refers to use of disease risk information to identify those most likely to benefit from screening. Researchers have begun to explore the possibility of refining screening regimens for average-risk individuals using genetic and non-genetic risk factors and previous screening experience. Average-risk individuals are those not known to be at substantially elevated risk, including those without known inherited predisposition, without comorbidities known to increase cancer risk, and without previous diagnosis of cancer or pre-cancer. In this paper, we describe the goals of targeted cancer screening in average-risk individuals, present factors on which cancer screening has been targeted, discuss inclusion of targeting in screening guidelines issued by major U.S. professional organizations, and present evidence to support or question such inclusion. Screening guidelines for average-risk individuals currently target age; smoking (lung cancer only); and, in some instances, race; family history of cancer; and previous negative screening history (cervical cancer only). No guidelines include common genomic polymorphisms. RCTs suggest that targeting certain ages and smoking histories reduces disease-specific cancer mortality, although some guidelines extend ages and smoking histories based on statistical modeling. Guidelines that are based on modestly elevated disease risk typically have either no or little evidence of an ability to affect a mortality benefit. In time, targeted cancer screening is likely to include genetic factors and past screening experience as well as non-genetic factors other than age, smoking, and race, but it is of utmost importance that clinical implementation be evidence-based. PMID:26165196
Magnetic susceptibility from electron holes
Directory of Open Access Journals (Sweden)
R. A. Treumann
2013-07-01
Full Text Available A recent theory of magnetic field amplification in electron holes is extended to derive the magnetic susceptibility of an electron-hole gas propagating in a magnetic flux tube along the ambient magnetic field. It is shown that the hole gas behaves diamagnetic adding some small amount to the well-known Landau susceptibility in the hole-carrying volume.
Homodyne measurement of average photon number
Webb, J G; Huntington, E H
2005-01-01
We describe a new scheme for the measurement of mean photon flux at an arbitrary optical sideband frequency using homodyne detection. Experimental implementation of the technique requires an AOM in addition to the homodyne detector, and does not require phase locking. The technique exhibits polarisation, frequency and spatial mode selectivity, as well as much improved speed, resolution and dynamic range when compared to linear photodetectors and avalanche photo diodes (APDs), with potential application to quantum state tomography and information encoding using an optical frequency basis. Experimental data also directly confirms the Quantum Mechanical description of vacuum noise.
Grassmann Averages for Scalable Robust PCA
DEFF Research Database (Denmark)
Hauberg, Søren; Feragen, Aasa; Black, Michael J.
2014-01-01
As the collection of large datasets becomes increasingly automated, the occurrence of outliers will increase—“big data” implies “big outliers”. While principal component analysis (PCA) is often used to reduce the size of data, and scalable solutions exist, it is well-known that outliers can arbit......, making it scalable to “big noisy data.” We demonstrate TGA for background modeling, video restoration, and shadow removal. We show scalability by performing robust PCA on the entire Star Wars IV movie....
Hearing Office Average Processing Time Ranking Report, April 2016
Social Security Administration — A ranking of ODAR hearing offices by the average number of hearings dispositions per ALJ per day. The average shown will be a combined average for all ALJs working...
Hearing Office Average Processing Time Ranking Report, February 2016
Social Security Administration — A ranking of ODAR hearing offices by the average number of hearings dispositions per ALJ per day. The average shown will be a combined average for all ALJs working...
Benkler, Erik; Sterr, Uwe
2015-01-01
The power spectral density in Fourier frequency domain, and the different variants of the Allan deviation (ADEV) in dependence on the averaging time are well established tools to analyse the fluctuation properties and frequency instability of an oscillatory signal. It is often supposed that the statistical uncertainty of a measured average frequency is given by the ADEV at a well considered averaging time. However, this approach requires further mathematical justification and refinement, which has already been done regarding the original ADEV for certain noise types. Here we provide the necessary background to use the modified Allan deviation (modADEV) and other two-sample deviations to determine the uncertainty of weighted frequency averages. The type of two-sample deviation used to determine the uncertainty depends on the method used for determination of the average. We find that the modADEV, which is connected with $\\Lambda$-weighted averaging, and the two sample deviation associated to a linear phase regr...
DEFF Research Database (Denmark)
Fallesen, Peter
2013-01-01
Individuals who spent time in foster care as children fare on average worse than non-placed peers in early adult life. Recent research on the effect of foster care placement on early adult life outcomes provides mixed evidence. Some studies suggest negative effects of foster care placement on early...... care on income and labor market participation....
Energy Technology Data Exchange (ETDEWEB)
Decker, J.; Peysson, Y
2004-12-01
A new original code for solving the 3-D relativistic and bounce-averaged electron drift kinetic equation is presented. It designed for the current drive problem in tokamak with an arbitrary magnetic equilibrium. This tool allows self-consistent calculations of the bootstrap current in presence of other external current sources. RF current drive for arbitrary type of waves may be used. Several moments of the electron distribution function are determined, like the exact and effective fractions of trapped electrons, the plasma current, absorbed RF power, runaway and magnetic ripple loss rates and non-thermal Bremsstrahlung. Advanced numerical techniques have been used to make it the first fully implicit (reverse time) 3-D solver, particularly well designed for implementation in a chain of code for realistic current drive calculations in high {beta}{sub p} plasmas. All the details of the physics background and the numerical scheme are presented, as well a some examples to illustrate main code capabilities. Several important numerical points are addressed concerning code stability and potential numerical and physical limitations. (authors)
International Nuclear Information System (INIS)
A new original code for solving the 3-D relativistic and bounce-averaged electron drift kinetic equation is presented. It designed for the current drive problem in tokamak with an arbitrary magnetic equilibrium. This tool allows self-consistent calculations of the bootstrap current in presence of other external current sources. RF current drive for arbitrary type of waves may be used. Several moments of the electron distribution function are determined, like the exact and effective fractions of trapped electrons, the plasma current, absorbed RF power, runaway and magnetic ripple loss rates and non-thermal Bremsstrahlung. Advanced numerical techniques have been used to make it the first fully implicit (reverse time) 3-D solver, particularly well designed for implementation in a chain of code for realistic current drive calculations in high βp plasmas. All the details of the physics background and the numerical scheme are presented, as well a some examples to illustrate main code capabilities. Several important numerical points are addressed concerning code stability and potential numerical and physical limitations. (authors)
Equivalent magnetization over the World Ocean
Dyment, J.; Hamoudi, M.; Choi, Y.; Thebault, E.; Quesnel, Y.; Roest, W. R.; Lesur, V.
2012-12-01
In another presentation (Hamoudi et al., this meeting), we present the construction of a new candidate for the World Digital Magnetic Anomaly Map (WDMAM) over oceanic areas. This map is based on: (a) a more realistic forward modeling of the marine magnetic anomalies which includes remanent magnetization vectors taking into account the age and motion of the oceanic lithosphere; (b) evaluation of the equivalent magnetization by comparison of the synthetic and observed anomalies along ship tracks; and (c) adjustment of the synthetic anomaly maps using this equivalent magnetization prior to merging with the observed anomalies. A by-product of this approach is a global distribution of equivalent magnetization over the World's Ocean. Note that, because no global basement map exists for the oceanic areas, we assume a uniform, 5 km-deep and 1 km-thick magnetized layer for the forward model. The resulting equivalent magnetization is therefore relative to this over-simplistic magnetic source. A first observation is that, within the hypotheses of the forward model, the average equivalent magnetization is about 3 A/m, a value which compares well with the Natural Remanent Magnetization (NRM) measured on ancient basalt samples. As expected, the mid-ocean ridges are marked by stronger equivalent magnetizations, an observation which reflects both the stronger NRM measured at ridge axes and their shallower bathymetry (not taken into account in our forward model). More interesting is the observation of significant along-axis variations. In the North Atlantic Ocean, the Kolbeinsey and Reykjanes ridges around Iceland are marked by a very strong equivalent magnetization and the Azores Plateau by a strong one as well.. Again this may reflect the combined effect of shallower seafloor, thicker and/or more magnetized basaltic layer at hotspots. In contrast, the areas between 45 and 55°N and between 0 and 10°N (Equatorial FZ) correspond to a weak equivalent magnetization. Further south
Repulsion of Single-well Fundamental Edge Magnetoplasmons in Double Quantum Wells
Balev, O. G.; Vasilopoulos, P.
1998-01-01
A {\\it microscopic} treatment of fundamental edge magnetoplasmons (EMPs) along the edge of a double quantum well (DQW) is presented for strong magnetic fields, low temperatures, and total filling factor \
The effect of temperature on the average volume of Barkhausen jump on Q235 carbon steel
Guo, Lei; Shu, Di; Yin, Liang; Chen, Juan; Qi, Xin
2016-06-01
On the basis of the average volume of Barkhausen jump (AVBJ) vbar generated by irreversible displacement of magnetic domain wall under the effect of the incentive magnetic field on ferromagnetic materials, the functional relationship between saturation magnetization Ms and temperature T is employed in this paper to deduce the explicit mathematical expression among AVBJ vbar, stress σ, incentive magnetic field H and temperature T. Then the change law between AVBJ vbar and temperature T is researched according to the mathematical expression. Moreover, the tensile and compressive stress experiments are carried out on Q235 carbon steel specimens at different temperature to verify our theories. This paper offers a series of theoretical bases to solve the temperature compensation problem of Barkhausen testing method.
Average thermospheric wind patterns over the polar regions, as observed by CHAMP
Directory of Open Access Journals (Sweden)
H. Lühr
2007-06-01
Full Text Available Measurements of the CHAMP accelerometer are utilized to investigate the average thermospheric wind distribution in the polar regions at altitudes around 400 km. This study puts special emphasis on the seasonal differences in the wind patterns. For this purpose 131 days centered on the June solstice of 2003 are considered. Within that period CHAMP's orbit is precessing once through all local times. The cross-track wind estimates of all 2030 passes are used to construct mean wind vectors for 918 equal-area cells. These bin averages are presented in corrected geomagnetic coordinates. Both hemispheres are considered simultaneously providing summer and winter responses for the same prevailing geophysical conditions. The period under study is characterized by high magnetic activity (K_{p}=4− but moderate solar flux level (F10.7=124. Our analysis reveals clear wind features in the summer (Northern Hemisphere. Over the polar cap there is a fast day-to-night flow with mean speeds surpassing 600 m/s in the dawn sector. At auroral latitudes we find strong westward zonal winds on the dawn side. On the dusk side, however, an anti-cyclonic vortex is forming. The dawn/dusk asymmetry is attributed to the combined action of Coriolis and centrifugal forces. Along the auroral oval the sunward streaming plasma causes a stagnation of the day-to-night wind. This effect is particularly clear on the dusk side. On the dawn side it is evident only from midnight to 06:00 MLT. The winter (Southern Hemisphere reveals similar wind features, but they are less well ordered. The mean day-to-night wind over the polar cap is weaker by about 35%. Otherwise, the seasonal differences are mainly confined to the dayside (06:00–18:00 MLT. In addition, the larger offset between geographic and geomagnetic pole in the south also causes hemispheric differences of the thermospheric wind distribution.
Average thermospheric wind patterns over the polar regions, as observed by CHAMP
Lühr, H.; Rentz, S.; Ritter, P.; Liu, H.; Häusler, K.
2007-06-01
Measurements of the CHAMP accelerometer are utilized to investigate the average thermospheric wind distribution in the polar regions at altitudes around 400 km. This study puts special emphasis on the seasonal differences in the wind patterns. For this purpose 131 days centered on the June solstice of 2003 are considered. Within that period CHAMP's orbit is precessing once through all local times. The cross-track wind estimates of all 2030 passes are used to construct mean wind vectors for 918 equal-area cells. These bin averages are presented in corrected geomagnetic coordinates. Both hemispheres are considered simultaneously providing summer and winter responses for the same prevailing geophysical conditions. The period under study is characterized by high magnetic activity (Kp=4-) but moderate solar flux level (F10.7=124). Our analysis reveals clear wind features in the summer (Northern) Hemisphere. Over the polar cap there is a fast day-to-night flow with mean speeds surpassing 600 m/s in the dawn sector. At auroral latitudes we find strong westward zonal winds on the dawn side. On the dusk side, however, an anti-cyclonic vortex is forming. The dawn/dusk asymmetry is attributed to the combined action of Coriolis and centrifugal forces. Along the auroral oval the sunward streaming plasma causes a stagnation of the day-to-night wind. This effect is particularly clear on the dusk side. On the dawn side it is evident only from midnight to 06:00 MLT. The winter (Southern) Hemisphere reveals similar wind features, but they are less well ordered. The mean day-to-night wind over the polar cap is weaker by about 35%. Otherwise, the seasonal differences are mainly confined to the dayside (06:00-18:00 MLT). In addition, the larger offset between geographic and geomagnetic pole in the south also causes hemispheric differences of the thermospheric wind distribution.
International Nuclear Information System (INIS)
A pulsed magnetic field magnetic force microscope (PMF-MFM) is developed for evaluation of the magnetic properties of nano-scale materials and devices, as well as the characteristics of MFM tips. We present the setup of the PMF-MFM system, and focus on the evaluation of a FeCo soft magnetic tip by PMF-MFM. We find a new theoretical method to calculate tip magnetization curves (M-H curves) using MFM phase signals. We measure the MFM phase and amplitude signals for the FeCo tip during the presence of the pulsed magnetic fields oriented parallel and antiparallel to the initial tip magnetization direction, and acquire the tip coercivity H c ∼ 1.1 kOe. The tip M-H curves are also calculated using the MFM phase signals data. We obtain the basic features of the tip magnetic properties from the tip M-H curves. (paper)
Magnetic Graphene Nanohole Superlattices
Yu, Decai; Liu, Miao; Liu, Wei; Liu, Feng
2008-01-01
We investigate the magnetic properties of nano-holes (NHs) patterned in graphene using first principles calculations. We show that superlattices consisting of a periodic array of NHs form a new family of 2D crystalline "bulk" magnets whose collective magnetic behavior is governed by inter-NH spin-spin interaction. They exhibit long-range magnetic order well above room temperature. Furthermore, magnetic semiconductors can be made by doping magnetic NHs into semiconducting NH superlattices. Our findings offer a new material system for fundamental studies of spin-spin interaction and magnetic ordering in low dimensions, and open up the exciting opportunities of making engineered magnetic materials for storage media and spintronics applications.
Highly efficient magnetic separation using five-aligned superconducting bulk magnet
International Nuclear Information System (INIS)
We have constructed the highly efficient magnetic separation system using five-aligned superconducting bulk magnets, which has ten usable magnetic poles on both sides in open space. We applied the bulk magnet system to the magnetic separation of ferromagnetic particles (magnetite; Fe3O4) and paramagnetic ones (α-hematite; Fe2O3) dispersed in water for various average particle diameters d, flow speeds VF and initial concentrations C0 of the particles. The multi-bulk magnet system has been confirmed to be effective for the magnetic separation and the efficiency of the magnetic separation per one magnetic pole has been estimated using the theoretical relation.
Highly efficient magnetic separation using five-aligned superconducting bulk magnet
Fujishiro, Hiroyuki; Miura, Takashi; Naito, Tomoyuki; Hayashi, Hidemi
2010-06-01
We have constructed the highly efficient magnetic separation system using five-aligned superconducting bulk magnets, which has ten usable magnetic poles on both sides in open space. We applied the bulk magnet system to the magnetic separation of ferromagnetic particles (magnetite; Fe3O4) and paramagnetic ones (α-hematite Fe2O3) dispersed in water for various average particle diameters d, flow speeds VF and initial concentrations C0 of the particles. The multi-bulk magnet system has been confirmed to be effective for the magnetic separation and the efficiency of the magnetic separation per one magnetic pole has been estimated using the theoretical relation.
Thermomagnetic determination of Fe3O4 magnetic nanoparticle diameters for biomedical applications
International Nuclear Information System (INIS)
The utility and promise of magnetic nanoparticles (MagNPs) for biomedicine rely heavily on accurate determination of the particle diameter attributes. While the average functional size and size distribution of the magnetic nanoparticles directly impact the implementation and optimization of nanobiotechnology applications in which they are employed, the determination of these attributes using electron microscopy techniques can be time-consuming and misrepresentative of the full nanoparticle population. In this work the average particle diameter and distribution of an ensemble of Fe3O4 ferrimagnetic nanoparticles are determined solely from temperature-dependent magnetization measurements; the results compare favorably to those obtained from extensive electron microscopy observations. The attributes of a population of biocompatible Fe3O4 nanoparticles synthesized by a thermal decomposition method are obtained from quantitative evaluation of a model that incorporates the distribution of superparamagnetic blocking temperatures represented through thermomagnetization data. The average size and size distributions are determined from magnetization data via temperature-dependent zero-field-cooled magnetization. The current work is unique from existing approaches based on magnetic measurement for the characterization of a nanoparticle ensemble as it provides both the average particle size as well as the particle size distribution. - Highlights: → Size distribution of nanoparticles determined via thermomagnetic response. → Calculated distribution exhibited reasonable agreement with electron microscopy. → Effective anisotropy constant determined is by scaling of distribution function. → Minimizes need for particle sizing using electron microscopy. → Facile alternative to conventional size determination techniques.
Statistical properties of the gyro-averaged standard map
da Fonseca, Julio D.; Sokolov, Igor M.; Del-Castillo-Negrete, Diego; Caldas, Ibere L.
2015-11-01
A statistical study of the gyro-averaged standard map (GSM) is presented. The GSM is an area preserving map model proposed in as a simplified description of finite Larmor radius (FLR) effects on ExB chaotic transport in magnetized plasmas with zonal flows perturbed by drift waves. The GSM's effective perturbation parameter, gamma, is proportional to the zero-order Bessel function of the particle's Larmor radius. In the limit of zero Larmor radius, the GSM reduces to the standard, Chirikov-Taylor map. We consider plasmas in thermal equilibrium and assume a Larmor radius' probability density function (pdf) resulting from a Maxwell-Boltzmann distribution. Since the particles have in general different Larmor radii, each orbit is computed using a different perturbation parameter, gamma. We present analytical and numerical computations of the pdf of gamma for a Maxwellian distribution. We also compute the pdf of global chaos, which gives the probability that a particle with a given Larmor radius exhibits global chaos, i.e. the probability that Kolmogorov-Arnold-Moser (KAM) transport barriers do not exist.
A deeper look into magnetic nanostructures using advanced scattering methods
Indian Academy of Sciences (India)
T H Brückel; E Kentzinger; S Mattauch; A Paul; U Rücker; J Voigt
2008-11-01
Magnetic thin film systems and laterally patterned magnetic media are the basis of spintronic devices for information technology. In this contribution, we will show that neutron scattering under grazing incidence with polarization analysis is able to provide unique depth resolved information on magnetization, magnetic correlations and magne-tization dynamics relevant for basic and applied research on nanostructured magnetic materials. It is well established that specular neutron reflectivity with polarization analysis from thin film systems and multilayers provides layer-resolved information on interface rough-ness and on the laterally averaged magnetization. Off-specular diffuse scattering with polarization analysis gives access to lateral correlations, i.e. the detailed interface morphology, the magnetic order of nanoscale objects (stripes or islands), the magnetic fluctuations or domain structure. Depending on the scattering geometry – reflectometry or grazing incidence small angle neutron scattering (GISANS) – correlations on lateral length scales from the nanometer up to the 100 micrometer range become accessible. Close to total reflection, kinematical scattering theory breaks down and dynamical effects have to be taken into account. Simulations in the distorted wave Born approximation (DWBA) allow one to extract quantitative parameters for a statistical model description. On several examples we will demonstrate the power of the method – from the magnetic fluctuations in remanent sputtered films via the magnetic structure of rare earth multilayers with competing interactions to the remagnetization process of exchange bias systems or the domain structures of laterally patterned giant magnetoresistance multilayers. Finally we will give an outlook on what will be possible on next generation instruments such as the magnetism reflectometer MARIA of the Juelich Centre for Neutron Science (JCNS) at FRM-II.
Bootstrap current due to shear of magnetic field stochasticity
International Nuclear Information System (INIS)
The 'bootstrap' current is a fundamental effect in toroidal magnetic confinement. It is shown that the electron current in stochastic magnetic field causes not only anomalous electron heat transport, but also novel currents, termed 'anomalous bootstrap' in order to bring up the analogy with the well-known effect in the neoclassical theory. Due to the magnetic fluctuations an additional bootstrap current appears. Its value is proportional to the derivative of square of the magnetic fluctuations, the radial electric field and ratio of streaming velocity to thermal one for collisionless case. The obtained bootstrap current can be comparable with the Ohmic current. In the collisional case, in contrast to the collisionless case, the value of bootstrap current does not depend on the magnitude of the averaged velocity, but its direction is determined by the streaming velocity sign. (J.P.N.)
International Nuclear Information System (INIS)
The nuclear structure of even-even nuclei in ground state band and other excited bands with non zero band head is collectively built. The level energy in medium mass region deviates below the ideal rotor energy formula EI = AI(I+1). The average scaling coefficient with asymmetric parameter and bAV rises for Er-Os nuclei when N increases from 88 to 104
Tae-Hwy Lee; Yundong Tu; Aman Ullah
2014-01-01
The equity premium, return on equity minus return on risk-free asset, is expected to be positive. We consider imposing such positivity constraint in local historical average (LHA) in nonparametric kernel regression framework. It is also extended to the semiparametric single index model when multiple predictors are used. We construct the constrained LHA estimator via an indicator function which operates as `model-selection' between the unconstrained LHA and the bound of the constraint (zero fo...
DEFF Research Database (Denmark)
Mik-Meyer, Nanna
2015-01-01
Klumme. Wellness er blevet et syndrom, og dets symptomer er angst, selvbebrejdelser og skyldfølelse. Kommentar med udgangspunkt i: Carl Cederström & Andre Spicer, "The Wellness Syndrome" (Polity Books, 2015. 200 p.).......Klumme. Wellness er blevet et syndrom, og dets symptomer er angst, selvbebrejdelser og skyldfølelse. Kommentar med udgangspunkt i: Carl Cederström & Andre Spicer, "The Wellness Syndrome" (Polity Books, 2015. 200 p.)....
Demonstration of a 10 kW average power 94 GHz gyroklystron amplifier
Blank, M.; Danly, B. G.; Levush, B.; Calame, J. P.; Nguyen, K.; Pershing, D.; Petillo, J.; Hargreaves, T. A.; True, R. B.; Theiss, A. J.; Good, G. R.; Felch, K.; James, B. G.; Borchard, P.; Cahalan, P.; Chu, T. S.; Jory, H.; Lawson, W. G.; Antonsen, T. M.
1999-12-01
The experimental demonstration of a high average power W-band (75-110 GHz) gyroklystron amplifier is reported. The gyroklystron has produced 118 AW peak output power and 29.5% electronic efficiency in the TE011 mode using a 66.7 kV, 6 A electron beam at 0.2% rf duty factor. At this operating point, the instantaneous full width at half-maximum (FWHM) bandwidth is 600 MHz. At 11% rf duty factor, the gyroklystron has produced up to 10.1 kW average power at 33% electronic efficiency with a 66 kV, 4.15 A electron beam. This represents world record performance for an amplifier at this frequency. At the 10.1 kW average power operating point, the FWHM bandwidth is 420 MHz. At higher magnetic fields and lower beam voltages, larger bandwidths can be achieved at the expense of peak and average output power.
DEFF Research Database (Denmark)
Finbow, Arthur; Frendrup, Allan; Vestergaard, Preben D.
cardinality then G is a total well dominated graph. In this paper we study composition and decomposition of total well dominated trees. By a reversible process we prove that any total well dominated tree can both be reduced to and constructed from a family of three small trees....
Magnetic moment distributions in α-Fe nanowire array
Institute of Scientific and Technical Information of China (English)
LI; Fashen; (李发伸); REN; Liyuan; (任立元); NIU; Ziping; (牛紫平); WANG; Haixin; (王海新); WANG; Tao; (王涛)
2003-01-01
α-Fe nanowire array has been electrodeposited into anodic aluminum oxide template. The magnetic moment distributions, in the interior and near the extremities of α-Fe nanowire with 60 nm in diameter, have been studied by means of transmission Mossbauer spectroscopy (MS), conversion electron Mossbauer spectroscopy (CEMS) and micromagnetic simulation. Transmission Mossbauer spectrum (MS) shows that the magnetic moments, inside the α-Fe nanowire array, are well parallel to nanowire, while conversion electron Mossbauer spectrum (CEMS) reveals that the magnetic moments, near the extremities of nanowire, diverge from the long axis of wire, and the average diverging angle calculated by the intensity ratio ofthe 2,5 peaks is about 24.0°. Moreover, the magnetic moment distributions of different depths to the top of wire are counted using micromagnetic simulation, which indicates that, the interior magnetic moments are strictly parallel to nanowire, and the closer the magnetic moment to the top of wire, the larger the diverging angle. Magnetic measurement shows that this α-Fe nanowire array represents a strong magnetic anisotropy.
Permanent magnet system of alpha magnetic spectrometer
Institute of Scientific and Technical Information of China (English)
陈和生
2000-01-01
Alpha magnetic spectrometer (AMS) is the first large magnetic spectrometer in space. Its precursor flight was completed successfully in June 1998. The key part of AMS is the permanent magnet system, which was built by the Institute of Electric Engineering, the Institute of High Energy Physics and the Chinese Academy of Launch Vehicle Technology. This system includes a permanent magnet made of high grade NdFeB and a support structure. The unique design of the permanent magnet based on the magic ring fulfills the severe requirements on the magnetic field leakage and the dipole moment for space experiments. The permanent magnet weighs about 2 tons, and provides a geometric acceptance of 0.6 m2·sr and an analyzing power BL2 of 0.135 T·m2. It works up to 40℃ without demagnetization. The main structure is a thin double shell, which undergoes the strong magnetic force and torque of the permanent magnet, as well as the large load during launching and landing. The permanent magnet system fulfills the requirem
Permanent magnet system of alpha magnetic spectrometer
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
Alpha magnetic spectrometer (AMS) is the first large magnetic spectrometer in space. Its precursor flight was completed successfully in June 1998. The key part of AMS is the permanent magnet system, which was built by the Institute of Electric Engineering, the Institute of High Energy Physics and the Chinese Academy of Launch Vehicle Technology. This system includes a permanent magnet made of high grade NdFeB and a support structure. The unique design of the permanent magnet based on the magic ring fulfills the severe requirements on the magnetic field leakage and the dipole moment for space experiments. The permanent magnet weighs about 2 tons, and provides a geometric acceptance of 0.6 m2 ·sr and an analyzing power BL2 of 0.135 T·m2. It works up to 40℃ without demagnetization. The main structure is a thin double shell, which undergoes the strong magnetic force and torque of the permanent magnet, as well as the large load during launching and landing. The permanent magnet system fulfills the requirements from AMS, and satisfies the strict safety standards of NASA.
40 CFR 1033.710 - Averaging emission credits.
2010-07-01
... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Averaging emission credits. 1033.710... Averaging emission credits. (a) Averaging is the exchange of emission credits among your engine families. You may average emission credits only as allowed by § 1033.740. (b) You may certify one or more...
The effect of three-dimensional fields on bounce averaged particle drifts in a tokamak
International Nuclear Information System (INIS)
The impact of applied 3D magnetic fields on the bounce-averaged precessional drifts in a tokamak plasma are calculated. Local 3D MHD equilibrium theory is used to construct solutions to the equilibrium equations in the vicinity of a magnetic surface for a large aspect ratio circular tokamak perturbed by applied 3D fields. Due to modulations of the local shear caused by near-resonant Pfirsch-Schlüter currents, relatively weak applied 3D fields can have a large effect on trapped particle precessional drifts
Large reversible magnetocaloric effect in a Ni-Co-Mn-In magnetic shape memory alloy
Huang, L.; Cong, D. Y.; Ma, L.; Nie, Z. H.; Wang, Z. L.; Suo, H. L.; Ren, Y.; Wang, Y. D.
2016-01-01
Reversibility of the magnetocaloric effect in materials with first-order magnetostructural transformation is of vital significance for practical magnetic refrigeration applications. Here, we report a large reversible magnetocaloric effect in a Ni49.8Co1.2Mn33.5In15.5 magnetic shape memory alloy. A large reversible magnetic entropy change of 14.6 J/(kg K) and a broad operating temperature window of 18 K under 5 T were simultaneously achieved, correlated with the low thermal hysteresis (˜8 K) and large magnetic-field-induced shift of transformation temperatures (4.9 K/T) that lead to a narrow magnetic hysteresis (1.1 T) and small average magnetic hysteresis loss (48.4 J/kg under 5 T) as well. Furthermore, a large reversible effective refrigeration capacity (76.6 J/kg under 5 T) was obtained, as a result of the large reversible magnetic entropy change, broad operating temperature window, and small magnetic hysteresis loss. The large reversible magnetic entropy change and large reversible effective refrigeration capacity are important for improving the magnetocaloric performance, and the small magnetic hysteresis loss is beneficial to reducing energy dissipation during magnetic field cycle in potential applications.
Resonance averaged channel radiative neutron capture cross sections
International Nuclear Information System (INIS)
In order to apply Lane amd Lynn's channel capture model in calculations with a realistic optical model potential, we have derived an approximate wave function for the entrance channel in the neutron-nucleus reaction, based on the intermediate interaction model. It is valid in the exterior region as well as the region near the nuclear surface, ans is expressed in terms of the wave function and reactance matrix of the optical model and of the near-resonance parameters. With this formalism the averaged channel radiative neutron capture cross section in the resonance region is written as the sum of three terms. The first two terms correspond to contribution of the optical model real and imaginary parts respectively, and together can be regarded as the radiative capture of the shape elastic wave. The third term is a fluctuation term, corresponding to the radiative capture of the compound elastic wave in the exterior region. On applying this theory in the resonance region, we obtain an expression for the average valence radiative width similar to that of Lane and Mughabghab. We have investigated the magnitude and energy dependence of the three terms as a function of the neutron incident energy. Calculated results for 98Mo and 55Mn show that the averaged channel radiative capture cross section in the giant resonance region of the neutron strength function may account for a considerable fraction of the total (n, γ) cross section; at lower neutron energies a large part of this channel capture arises from the fluctuation term. We have also calculated the partial capture cross section in 98Mo and 55Mn at 2.4 keV and 24 keV, respectively, and compared the 98Mo results with the experimental data. (orig.)
Magnetic properties of Fe nanoclusters on Cu(111) studied with X-ray magnetic circular dichroism
Energy Technology Data Exchange (ETDEWEB)
Fauth, Kai [Physikalisches Institut, Universitaet Wuerzburg (Germany); MPI for Metals Research, Stuttgart (Germany); Ballentine, Greg E. [MPI for Metals Research, Stuttgart (Germany); Praetorius, Christian [Physikalisches Institut, Universitaet Wuerzburg (Germany); Kleibert, Armin; Wilken, Norman; Voitkans, Andris; Meiwes-Broer, Karl-Heinz [Institute of Physics, University of Rostock (Germany)
2010-05-15
The magnetisation and magnetic response of Fe nanoclusters are studied by temperature and density dependent in situ X-ray magnetic circular dichroism after deposition onto Cu(111). The nanoclusters possess enhanced spin magnetic moments at low temperature, whereas no enhancement is found for the orbital moments. The analysis of magnetisation curves and the temperature dependent remnant magnetisation reveals that the individual magnetic anisotropy energies are distributed over a wide range of values, ranging from below to far above the value of bulk {alpha}-Fe. As a result, ferromagnetic response is obtained at ambient temperature, even though the nanocluster densities range well below percolation threshold. At higher cluster densities agglomeration and substrate mediated interaction increase the mean blocking temperature in the particle ensemble. The observed macroscopic magnetic in-plane anisotropy derives from the average dipolar interactions between the nanoclusters. Single particle properties, substrate mediated coupling and dipolar interactions thus independently contribute to magnetic characteristics on equal footing. (Abstract Copyright [2010], Wiley Periodicals, Inc.)
DEFF Research Database (Denmark)
Enemark, Søren; Santos, Ilmar
2014-01-01
Passive magnetic bearings are known due to the excellent characteristics in terms of friction and no requirement of additional energy sources to work. However, passive magnetic bearings do not provide damping, are not stable and, depending on their design, may also introduce magnetic eccentricity....... Such magnetic eccentricities are generated by discrepancies in magnet fabrication. In this framework the main focus of the work is the theoretical as well as experimental investigation of the nonlinear dynamics of a rotor-bearing system with strong emphasis on the magnetic eccentricities and non......-linear stiffness. In this investigation passive magnetic bearings using axially- aligned neodymium cylinder magnets are investigated. The cylinder magnets are axially magnetised for rotor as well as bearings. Compared to bearings with radial magnetisation, the magnetic stiffness of axially-aligned bearings is...
Magnetism in heterogeneous thin film systems: Resonant X-ray scattering studies
Kortright, J B; Bader, S D; Hellwig, O; Marguiles, D T; Fullerton, E E
2003-01-01
Magnetic and chemical heterogeneity are common in a broad range of magnetic thin film systems. Emerging resonant soft X-ray scattering techniques are well suited to resolve such heterogeneity at relevant length scales. Resonant X-ray magneto-optical Kerr effect measurements laterally average over heterogeneity but can provide depth resolution in different ways, as illustrated in measurements resolving reversible and irreversible changes in different layers of exchange-spring heterostructures. Resonant small-angle scattering measures in-plane heterogeneity and can resolve magnetic and chemical scattering sources in different ways, as illustrated in measurements of granular alloy recording media.
ANALYTIC EXPRESSION OF MAGNETIC FIELD DISTRIBUTION OF RECTANGULAR PERMANENT MAGNETS
Institute of Scientific and Technical Information of China (English)
苟晓凡; 杨勇; 郑晓静
2004-01-01
From the molecular current viewpoint,an analytic expression exactly describing magnetic field distribution of rectangular permanent magnets magnetized sufficiently in one direction was derived from the Biot-Savart's law. This expression is useful not only for the case of one rectangular permanent magnet bulk, but also for that of several rectangular permanent magnet bulks. By using this expression,the relations between magnetic field distribution and the size of rectangular permanent magnets as well as the magnitude of magnetic field and the distance from the point in the space to the top (or bottom) surface of rectangular permanent magnets were discussed in detail. All the calculating results are consistent with experimental ones. For transverse magnetic field which is a main magnetic field of rectangular permanent magnets,in order to describe its distribution,two quantities,one is the uniformity in magnitude and the other is the uniformity in distribution of magnetic field,were defined. Furthermore, the relations between them and the geometric size of the magnet as well as the distance from the surface of permanent magnets were investigated by these formulas. The numerical results show that the geometric size and the distance have a visible influence on the uniformity in magnitude and the uniformity in distribution of the magnetic field.
A Cause of Falsely High Noise Level in Signal Averaged Electrocardiogram Recordings
Donoiu, I.; Mustafa, Roxana Edmee; Ionescu, D.D.
2011-01-01
Signal averaged electrocardiogram (SAECG) is a well-established noninvasive method of exploration in patients at risk for sudden cardiac death. The time-domain SAECG analysis has a set of well-defined standards, including the value of accepted noise level. In very rare instances, the final noise level appears to remain unacceptably high even after carefully preparing the skin of the patient and averaging a great number of QRS complexes. We encountered three such cases in patients who had a SA...
Organizational Wellness Modeling
Constantin OPREAN; Alina Mihaela VANU; Amelia BUCUR
2009-01-01
The aim of the present paper is to establish certain mathematical models for organizational wellness as well as to create some wellness optimization problems applicable to any type of organization (including universities) that might be mathematically solved resorting to aspects of operational research of mathematical analysis. The results obtained associated with a mathematical apparatus enable one to perform analyses, comparisons, interpretations, predictions. All of us have, consciously or ...
... health trends related to the following: Overall mood Mood disorder symptoms Lifestyle (including sleep, exercise, etc.) Medication and side effects Physical health Using the DBSA Wellness Tracker can ...
Improved germanium well detectors
International Nuclear Information System (INIS)
Germanium well detectors with metal surface barrier contact are comparable for general use with conventional germanium coaxial detectors. They offer very high sensitivity, the highest presently available
New challenges? Well, certainly!
DEFF Research Database (Denmark)
Lauridsen, Karen M.
New challenges? Well, certainly! With the internationalization of European higher education, teaching and learning through the medium of a foreign language has become more and more widespread in recent years. This requires, of course, that lecturers as well as students have the necessary language...... proficiency, but research as well as experience on the ground tells us that this is not enough. Everyone must learn to navigate in the multilingual and multicultural learning space because lecturers as well as students may come from different countries and cultures and therefore have different first languages...
Vibrationally averaged dipole moments of methane and benzene isotopologues
Arapiraca, A. F. C.; Mohallem, J. R.
2016-04-01
DFT-B3LYP post-Born-Oppenheimer (finite-nuclear-mass-correction (FNMC)) calculations of vibrationally averaged isotopic dipole moments of methane and benzene, which compare well with experimental values, are reported. For methane, in addition to the principal vibrational contribution to the molecular asymmetry, FNMC accounts for the surprisingly large Born-Oppenheimer error of about 34% to the dipole moments. This unexpected result is explained in terms of concurrent electronic and vibrational contributions. The calculated dipole moment of C6H3D3 is about twice as large as the measured dipole moment of C6H5D. Computational progress is advanced concerning applications to larger systems and the choice of appropriate basis sets. The simpler procedure of performing vibrational averaging on the Born-Oppenheimer level and then adding the FNMC contribution evaluated at the equilibrium distance is shown to be appropriate. Also, the basis set choice is made by heuristic analysis of the physical behavior of the systems, instead of by comparison with experiments.
Prompt fission neutron spectra and average prompt neutron multiplicities
International Nuclear Information System (INIS)
We present a new method for calculating the prompt fission neutron spectrum N(E) and average prompt neutron multiplicity anti nu/sub p/ as functions of the fissioning nucleus and its excitation energy. The method is based on standard nuclear evaporation theory and takes into account (1) the motion of the fission fragments, (2) the distribution of fission-fragment residual nuclear temperature, (3) the energy dependence of the cross section sigma/sub c/ for the inverse process of compound-nucleus formation, and (4) the possibility of multiple-chance fission. We use a triangular distribution in residual nuclear temperature based on the Fermi-gas model. This leads to closed expressions for N(E) and anti nu/sub p/ when sigma/sub c/ is assumed constant and readily computed quadratures when the energy dependence of sigma/sub c/ is determined from an optical model. Neutron spectra and average multiplicities calculated with an energy-dependent cross section agree well with experimental data for the neutron-induced fission of 235U and the spontaneous fission of 252Cf. For the latter case, there are some significant inconsistencies between the experimental spectra that need to be resolved. 29 references
Large interface simulation in an averaged two-fluid code
International Nuclear Information System (INIS)
Different ranges of size of interfaces and eddies are involved in multiphase flow phenomena. Classical formalisms focus on a specific range of size. This study presents a Large Interface Simulation (LIS) two-fluid compressible formalism taking into account different sizes of interfaces. As in the single-phase Large Eddy Simulation, a filtering process is used to point out Large Interface (LI) simulation and Small interface (SI) modelization. The LI surface tension force is modelled adapting the well-known CSF method. The modelling of SI transfer terms is done calling for classical closure laws of the averaged approach. To simulate accurately LI transfer terms, we develop a LI recognition algorithm based on a dimensionless criterion. The LIS model is applied in a classical averaged two-fluid code. The LI transfer terms modelling and the LI recognition are validated on analytical and experimental tests. A square base basin excited by a horizontal periodic movement is studied with the LIS model. The capability of the model is also shown on the case of the break-up of a bubble in a turbulent liquid flow. The break-up of a large bubble at a grid impact performed regime transition between two different scales of interface from LI to SI and from PI to LI. (author)
Comparison of seasonal and yearly average indoor radon levels using CR-39 detectors
International Nuclear Information System (INIS)
In order to assess the effect of long term exposure, CR-39 based radon dosimeters were exposed to indoor radon in the drawing rooms (living room) of 200 selected houses of the districts of Swabi, Mardan and Charsadda in the North West Frontier Province (NWFP) as well as in the Mohmand and Bajuar Agencies of the federally administered tribal areas (FATA), Pakistan. Dosimeters were exposed to the indoor radon during each season as well as throughout the year. From the measured indoor radon data it was observed that seasonal yearly average value were higher than that of the 12 months average indoor radon concentration values. The overall seasonal average was found to be 13% higher than that of the 12 months exposed CR-39 based dosimeters. However after the removal of the worst differences, seasonal average remains only 8 % higher than the 12 months averaged value.
Comparison of seasonal and yearly average indoor radon levels using CR-39 detectors
Energy Technology Data Exchange (ETDEWEB)
Rahman, Said [Space Applications Division, SPAS Dte, Sparcent, SUPARCO, Karachi-75270 (Pakistan); Matiullah, E-mail: matiullah@pinstech.org.p [Physics Division, PINSTECH, Nilore, Islamabad (Pakistan); Ghauri, B.M. [Space Applications Division, SPAS Dte, Sparcent, SUPARCO, Karachi-75270 (Pakistan)
2010-02-15
In order to assess the effect of long term exposure, CR-39 based radon dosimeters were exposed to indoor radon in the drawing rooms (living room) of 200 selected houses of the districts of Swabi, Mardan and Charsadda in the North West Frontier Province (NWFP) as well as in the Mohmand and Bajuar Agencies of the federally administered tribal areas (FATA), Pakistan. Dosimeters were exposed to the indoor radon during each season as well as throughout the year. From the measured indoor radon data it was observed that seasonal yearly average value were higher than that of the 12 months average indoor radon concentration values. The overall seasonal average was found to be 13% higher than that of the 12 months exposed CR-39 based dosimeters. However after the removal of the worst differences, seasonal average remains only 8 % higher than the 12 months averaged value.
International Nuclear Information System (INIS)
The 820 GeV HERA proton storage ring, presently under construction at DESY, will be equipped with about 650 superconducting main magnets (dipoles and quadrupoles) and approximately the same number of superconducting correction elements (dipoles, quadrupoles and sextupoles). These magnets will form a continuous cold string through the 6.3 km long HERA tunnel interrupted only by warm sections around the interaction regions. The magnet system is cooled with one phase helium supplied by a 3 block central refrigeration system of 20 kW refrigeration power at 4.3 K. Two phase helium is returned through the magnets for temperature control. Prototypes of all types of superconducting magnets have been built and tested at liquid helium temperatures. The tested magnets have good field quality and good quench behaviour, which proves that these magnets are well suited for HERA
Magnetism in lanthanide superlattices
DEFF Research Database (Denmark)
Goff, J.P.; Sarthour, R.S.; McMorrow, D.F.; Yakhou, F.; Stunault, A.; Ward, R.C.C.; Wells, M.R.
Neutron diffraction studies of heavy rare-earth superlattices have revealed the stabilization of novel magnetic phases chat are not present in bulk materials. The most striking result is the propagation of the magnetic ordering through nonmagnetic spacer materials. Here we describe some recent X......-ray magnetic resonant scattering studies of light rare-earth superlattices, which illuminate the mechanism of interlayer coupling, and provide access to different areas of Physics. such as the interplay between superconductivity and magnetism. Magnetic X-ray diffraction is found to be particularly well suited...... to the study of the modulated magnetic structures in superlattices, and provides unique information on the conduction-electron spin-density wave responsible for the propagation of magnetic order. (C) 2000 Elsevier Science B.V. All rights reserved....
Magnetism in lanthanide superlattices
DEFF Research Database (Denmark)
Goff, J.P.; Sarthour, R.S.; McMorrow, D.F.;
2000-01-01
Neutron diffraction studies of heavy rare-earth superlattices have revealed the stabilization of novel magnetic phases chat are not present in bulk materials. The most striking result is the propagation of the magnetic ordering through nonmagnetic spacer materials. Here we describe some recent X......-ray magnetic resonant scattering studies of light rare-earth superlattices, which illuminate the mechanism of interlayer coupling, and provide access to different areas of Physics. such as the interplay between superconductivity and magnetism. Magnetic X-ray diffraction is found to be particularly well suited...... to the study of the modulated magnetic structures in superlattices, and provides unique information on the conduction-electron spin-density wave responsible for the propagation of magnetic order. (C) 2000 Elsevier Science B.V. All rights reserved....
Quantum gravity unification via transfinite arithmetic and geometrical averaging
International Nuclear Information System (INIS)
In E-Infinity theory, we have not only infinitely many dimensions but also infinitely many fundamental forces. However, due to the hierarchical structure of ε(∞) spacetime we have a finite expectation number for its dimensionality and likewise a finite expectation number for the corresponding interactions. Starting from the preceding fundamental principles and using the experimental findings as well as the theoretical value of the coupling constants of the electroweak and the strong forces we present an extremely simple averaging procedure for determining the quantum gravity unification coupling constant with and without super symmetry. The work draws heavily on previous results, in particular a paper, by the Slovian Prof. Marek-Crnjac [Marek-Crnjac L. On the unification of all fundamental forces in a fundamentally fuzzy Cantorian ε(∞) manifold and high energy physics. Chaos, Solitons and Fractals 2004;4:657-68
On the physical effects of consistent cosmological averaging
Brown, Iain A; Herman, D Leigh; Latta, Joey
2013-01-01
We use cosmological perturbation theory to study the backreaction effects of a self-consistent and well-defined cosmological averaging on the dynamics and the evolution of the Universe. Working with a perturbed Friedman-Lemaitre-Robertson-Walker Einstein-de Sitter cosmological solution in a comoving volume-preserving gauge, we compute the expressions for the expansion scalar and deceleration parameter to second order, which we use to characterize the backreaction. We find that the fractional shift in the Hubble parameter with respect to the input background cosmological model is Delta~10^{-5}, which leads to an effective energy density of the order of a few times 10^{-5}. In addition, we find that an appropriate measure of the fractional shift in the deceleration parameter Q is very large.
Characterizing individual painDETECT symptoms by average pain severity
Directory of Open Access Journals (Sweden)
Sadosky A
2016-07-01
Full Text Available Alesia Sadosky,1 Vijaya Koduru,2 E Jay Bienen,3 Joseph C Cappelleri4 1Pfizer Inc, New York, NY, 2Eliassen Group, New London, CT, 3Outcomes Research Consultant, New York, NY, 4Pfizer Inc, Groton, CT, USA Background: painDETECT is a screening measure for neuropathic pain. The nine-item version consists of seven sensory items (burning, tingling/prickling, light touching, sudden pain attacks/electric shock-type pain, cold/heat, numbness, and slight pressure, a pain course pattern item, and a pain radiation item. The seven-item version consists only of the sensory items. Total scores of both versions discriminate average pain-severity levels (mild, moderate, and severe, but their ability to discriminate individual item severity has not been evaluated.Methods: Data were from a cross-sectional, observational study of six neuropathic pain conditions (N=624. Average pain severity was evaluated using the Brief Pain Inventory-Short Form, with severity levels defined using established cut points for distinguishing mild, moderate, and severe pain. The Wilcoxon rank sum test was followed by ridit analysis to represent the probability that a randomly selected subject from one average pain-severity level had a more favorable outcome on the specific painDETECT item relative to a randomly selected subject from a comparator severity level.Results: A probability >50% for a better outcome (less severe pain was significantly observed for each pain symptom item. The lowest probability was 56.3% (on numbness for mild vs moderate pain and highest probability was 76.4% (on cold/heat for mild vs severe pain. The pain radiation item was significant (P<0.05 and consistent with pain symptoms, as well as with total scores for both painDETECT versions; only the pain course item did not differ.Conclusion: painDETECT differentiates severity such that the ability to discriminate average pain also distinguishes individual pain item severity in an interpretable manner. Pain
Control of average spacing of OMCVD grown gold nanoparticles
Rezaee, Asad
Metallic nanostructures and their applications is a rapidly expanding field. Nobel metals such as silver and gold have historically been used to demonstrate plasmon effects due to their strong resonances, which occur in the visible part of the electromagnetic spectrum. Localized surface plasmon resonance (LSPR) produces an enhanced electromagnetic field at the interface between a gold nanoparticle (Au NP) and the surrounding dielectric. This enhanced field can be used for metal-dielectric interfacesensitive optical interactions that form a powerful basis for optical sensing. In addition to the surrounding material, the LSPR spectral position and width depend on the size, shape, and average spacing between these particles. Au NP LSPR based sensors depict their highest sensitivity with optimized parameters and usually operate by investigating absorption peak: shifts. The absorption peak: of randomly deposited Au NPs on surfaces is mostly broad. As a result, the absorption peak: shifts, upon binding of a material onto Au NPs might not be very clear for further analysis. Therefore, novel methods based on three well-known techniques, self-assembly, ion irradiation, and organo-meta1lic chemical vapour deposition (OMCVD) are introduced to control the average-spacing between Au NPs. In addition to covalently binding and other advantages of OMCVD grown Au NPs, interesting optical features due to their non-spherical shapes are presented. The first step towards the average-spacing control is to uniformly form self-assembled monolayers (SAMs) of octadecyltrichlorosilane (OTS) as resists for OMCVD Au NPs. The formation and optimization of the OTS SAMs are extensively studied. The optimized resist SAMs are ion-irradiated by a focused ion beam (Fill) and ions generated by a Tandem accelerator. The irradiated areas are refilled with 3-mercaptopropyl-trimethoxysilane (MPTS) to provide nucleation sites for the OMCVD Au NP growth. Each step during sample preparation is monitored by
Water Treatment Technology - Wells.
Ross-Harrington, Melinda; Kincaid, G. David
One of twelve water treatment technology units, this student manual on wells provides instructional materials for five competencies. (The twelve units are designed for a continuing education training course for public water supply operators.) The competencies focus on the following areas: dug, driven, and chilled wells, aquifer types, deep well…
Purging of wells with bailers has been a standard practice in the underground storage tank program as well as other groundwater regulatory programs for many years. Several studies in the Northeast and the West have shown that, under certain circumstances, samples collected witho...
Analytic continuation by averaging Padé approximants
Schött, Johan; Locht, Inka L. M.; Lundin, Elin; Grânäs, Oscar; Eriksson, Olle; Di Marco, Igor
2016-02-01
The ill-posed analytic continuation problem for Green's functions and self-energies is investigated by revisiting the Padé approximants technique. We propose to remedy the well-known problems of the Padé approximants by performing an average of several continuations, obtained by varying the number of fitted input points and Padé coefficients independently. The suggested approach is then applied to several test cases, including Sm and Pr atomic self-energies, the Green's functions of the Hubbard model for a Bethe lattice and of the Haldane model for a nanoribbon, as well as two special test functions. The sensitivity to numerical noise and the dependence on the precision of the numerical libraries are analyzed in detail. The present approach is compared to a number of other techniques, i.e., the nonnegative least-squares method, the nonnegative Tikhonov method, and the maximum entropy method, and is shown to perform well for the chosen test cases. This conclusion holds even when the noise on the input data is increased to reach values typical for quantum Monte Carlo simulations. The ability of the algorithm to resolve fine structures is finally illustrated for two relevant test functions.
Synchrotron radiation techniques. Extension to magnetism research
International Nuclear Information System (INIS)
Recently developed techniques using synchrotron radiation for the study of magnetism are reviewed. These techniques are based on X-ray absorption spectroscopy (XAS), and they exhibit significant advantages in element specificity. This is very important since the most attractive magnetic materials contain many magnetic elements, and those with small magnetic moments often play an essential role in the magnetic properties. Circularly polarized X-rays emitted from bending magnets or helical undulators allow us to perform magnetic circular dichroism measurements to reveal microscopic magnetic properties of various kinds of magnetic materials. X-ray absorption magnetic circular dichroism (XMCD) is discussed in detail. This technique provides unique information on orbital magnetic moments as well as spin magnetic moments, which are useful for the study of magnetic anisotropy. X-ray magnetic linear dichroism (XMLD) and X-ray resonant magnetic reflectometry (XRMR) techniques are also described. (author)
On the Individual Expectations of Non-Average Investors
Lucia Del Chicca; Gerhard Larcher
2011-01-01
An “average investor” is an investor who has “average risk aversion”, “average expectations” on the market returns and should invest in the “market portfolio” (this is, according to the Capital Asset Pricing Model, the best possible portfolio for such an investor). He is compared with a “non-average investor”. This - in our setting - is an investor who has the same “average risk aversion” but invests in other investment strategies, for example options. Such a “`non-average investor” must cons...
Hershkowitz, N.; Forest, C.; Wang, E. Y.; Intrator, T.
1987-01-01
Nonmonotonic plasma potential structures are a common feature of many double layers and sheaths. Steady state plasma potential wells separating regions having different plasma potentials are often found in laboratory experiments. In order to exist, such structures all must find a solution to a common problem. Ions created by charge exchange or ionization in the region of the potential well are electrostatically confined and tend to accumulate and fill up the potential well. The increase in positive charge should eliminate the well. Nevertheless, steady state structures are found in which the wells do not fill up. This means that it is important to take into account processes which 'pump' ions from the well. As examples of ion pumping of plasma wells, potential dips in front of a positively biased electro collecting anode in a relatively cold, low density multidipole plasma is considered. Pumping is provided by ion leaks from the edges of the potential dip or by oscillating the applied potential. In the former case the two dimensional character of the problem is shown to be important.
International Nuclear Information System (INIS)
A plurality of blowing ports with introduction units are disposed to a plurality of ducts in a dry well, and a cooling unit comprising a cooler, a blower and an isolating valve is disposed outside of the dry well. Cooling air and the atmosphere in the dry well are mixed to form a cooling gas and blown into the dry well to control the temperature. Since the cooling unit is disposed outside of the dry well, the maintenance of the cooling unit can be performed even during the plant operation. In addition, since dampers opened/closed depending on the temperature of the atmosphere are disposed to the introduction units for controlling the temperature of the cooling gas, the temperature of the atmosphere in the dry well can be set to a predetermined level rapidly. Since an axial flow blower is used as the blower of the cooling unit, it can be contained in a ventilation cylinder. Then, the atmosphere in the dry well flowing in the ventilation cylinder can be prevented from leaking to the outside. (N.H.)
Mohammedi, N
2016-01-01
We study the quantum behaviour of a particle moving in a one-dimensional double well potential. This double well is obtained by gluing together, at the origin, two shifted harmonic oscillator potentials. The Schr\\"odinger equation is exactly solvable. The requirement that discontinuities, in the wavefunction and its first derivative, are absent at the origin, leads to the quantisation of the energy eigenvalues. We also show that oscillations in time take place between two nearby single harmonic oscillator ground states. Finally, the double well potential is augmented by a Dirac delta-function potentials at the origin and the corresponding Schr\\"odinger equation is solved.
International Nuclear Information System (INIS)
This paper describes the development and application of a comprehensive oil or gas well performance model. The model contains six distinct sections: stimulation design, tubing and/or casing flow, reservoir and near-wellbore calculations, production forecasting, wellbore heat transmission, and economics. These calculations may be performed separately or in an integrated fashion with data and results shared among the different sections. The model analysis allows evaluation of all aspects of well completion design, including the effects on future production and overall well economics
Hoyos, M; Moore, L R; McCloskey, K E; Margel, S; Zuberi, M; Chalmers, J J; Zborowski, M
2000-12-01
Advantages of the continuous magnetic flow sorting for biomedical applications over current, batch-wise magnetic separations include high throughput and a potential for scale-up operations. A continuous magnetic sorting process has been developed based on the quadrupole magnetic field centered on an annular flow channel. The performance of the sorter has been described using the conceptual framework of split-flow thin (SPLITT) fractionation, a derivative of field-flow fractionation (FFF). To eliminate the variability inherent in working with a heterogenous cell population, we developed a set of monodisperse magnetic microspheres of a characteristic magnetization, and a magnetophoretic mobility, similar to those of the cells labeled with a magnetic colloid. The theory of the magnetic sorting process has been tested by injecting a suspension of the magnetic beads into the carrier fluid flowing through the sorter and by comparing the theoretical and experimental recovery versus total flow-rate profiles. The position of the recovery maxima along the total flow-rate axis was a function of the average bead magnetophoretic mobility and the magnetic field intensity. The theory has correctly predicted the position of the peak maxima on the total flow-rate axis and the dependence on the bead mobility and the field intensity, but has not correctly predicted the peak heights. The differences between the calculated and the measured peak heights were a function of the total flow-rate through the system, indicating a fluid-mechanical origin of the deviations from the theory (such as expected of the lift force effects in the system). The well-controlled elution studies using the monodisperse magnetic beads, and the SPLITT theory, provided us with a firm basis for the future sorter evaluation using cell mixtures. PMID:11153960
Li, Zhiyong; Zheng, Jianping; Zeng, Qingli; Liu, Qingsheng; Griffin, W. L.
2014-02-01
Studies of the petrology, mineral chemistry, and rock magnetic properties of nine pyroxenite xenoliths from Hannuoba basalts, northern North China Craton, have been made to determine the magnetization signature of the continental lower crust. These pyroxenites are weakly magnetic with low average susceptibility (χ) and saturation isothermal remanent magnetization (Mrs) of 39.59 × 10-8 m3 kg-1 and 12.05 × 10-3 Am2 kg-1, respectively. The magnetic minerals are mainly magnetite, pyrrhotite, and Fe-rich spinel, which significantly contribute to χ and natural remanent magnetization. Magnetite occurs as interstitial microcrystals together with zeolite aggregates, indicating a secondary origin in a supergene environment. In contrast, pyrrhotite and Fe-rich spinel were formed prior to the xenoliths' ascent to the surface, as evidenced by their dominant occurrence as tiny inclusions and thin exsolution lamellae in pyroxene. The Fe-rich spinel has ~ 50% mole fraction of Fe3O4 and corresponds to the strongest magnetization, and its coexistence with Mg-rich spinel implies a reheating event due to the underplating of basaltic magma. Besides, armalcolite and ilmenite were found in the reaction rims between xenoliths and the basalt, but they contribute little to the whole rock magnetization. However, these pyroxenite xenoliths would be nonmagnetic at in situ depths, as well as peridotite and mafic granulite xenoliths derived from the crust-mantle transition zone (~ 32-42 km). Therefore, we suggest the limiting depth of magnetization at the boundary between weakly magnetic deep-seated (lower crust and upper mantle) xenoliths and strongly magnetic Archean granulite facies rocks (~ 32 km) in Hannuoba, northern North China Craton.
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Agricultural Drainage Well Intakes
Iowa State University GIS Support and Research Facility — Locations of surface intakes for registered agriculture drainage wells according to the database maintained by IDALS. Surface intakes were located from their...
Seasonal Sea Surface Temperature Averages, 1985-2001 - Direct Download
U.S. Geological Survey, Department of the Interior — This data set consists of four images showing seasonal sea surface temperature (SST) averages for the entire earth. Data for the years 1985-2001 are averaged to...
Cost averaging techniques for robust control of flexible structural systems
Hagood, Nesbitt W.; Crawley, Edward F.
1991-01-01
Viewgraphs on cost averaging techniques for robust control of flexible structural systems are presented. Topics covered include: modeling of parameterized systems; average cost analysis; reduction of parameterized systems; and static and dynamic controller synthesis.
Average annual runoff in the United States, 1951-80
U.S. Geological Survey, Department of the Interior — This is a line coverage of average annual runoff in the conterminous United States, 1951-1980. Surface runoff Average runoff Surface waters United States
Nuclear Spin Dynamics in Parabolic Quantum Wells
Tifrea, I.; Flatte, Michael E.
2003-01-01
We present a detailed analytical and numerical analysis of the nuclear spin dynamics in parabolic quantum wells. The shallow potential of parabolic quantum wells permits substantial modification of the electronic wave function in small electric fields. The nuclear spin relaxation via the hyperfine interaction depends on the electronic local density of states, therefore the local nuclear relaxation time depends sensitively on the electric field. For an inhomogeneous nuclear magnetization, such...
The SU(N) Wilson Loop Average in 2 Dimensions
Karjalainen, Esa
1993-01-01
We solve explicitly a closed, linear loop equation for the SU(2) Wilson loop average on a two-dimensional plane and generalize the solution to the case of the SU(N) Wilson loop average with an arbitrary closed contour. Furthermore, the flat space solution is generalized to any two-dimensional manifold for the SU(2) Wilson loop average and to any two-dimensional manifold of genus 0 for the SU(N) Wilson loop average.
International Nuclear Information System (INIS)
We review the fundamental physics of magnetic reconnection in laboratory and space plasmas, by discussing results from theory, numerical simulations, observations from space satellites, and the recent results from laboratory plasma experiments. After a brief review of the well-known early work, we discuss representative recent experimental and theoretical work and attempt to interpret the essence of significant modern findings. In the area of local reconnection physics, many significant findings have been made with regard to two-fluid physics and are related to the cause of fast reconnection. Profiles of the neutral sheet, Hall currents, and the effects of guide field, collisions, and micro-turbulence are discussed to understand the fundamental processes in a local reconnection layer both in space and laboratory plasmas. While the understanding of the global reconnection dynamics is less developed, notable findings have been made on this issue through detailed documentation of magnetic self-organization phenomena in fusion plasmas. Application of magnetic reconnection physics to astrophysical plasmas is also briefly discussed.
Energy Technology Data Exchange (ETDEWEB)
Masaaki Yamada, Russell Kulsrud and Hantao Ji
2009-09-17
We review the fundamental physics of magnetic reconnection in laboratory and space plasmas, by discussing results from theory, numerical simulations, observations from space satellites, and the recent results from laboratory plasma experiments. After a brief review of the well-known early work, we discuss representative recent experimental and theoretical work and attempt to interpret the essence of significant modern findings. In the area of local reconnection physics, many significant findings have been made with regard to two- uid physics and are related to the cause of fast reconnection. Profiles of the neutral sheet, Hall currents, and the effects of guide field, collisions, and micro-turbulence are discussed to understand the fundamental processes in a local reconnection layer both in space and laboratory plasmas. While the understanding of the global reconnection dynamics is less developed, notable findings have been made on this issue through detailed documentation of magnetic self-organization phenomena in fusion plasmas. Application of magnetic reconnection physics to astrophysical plasmas is also brie y discussed.
Remanent magnetization model for the broken ridge satellite magnetic anomaly
Johnson, B. D.
1983-01-01
A crustal model for the interpretation of the Broken Ridge satellite magnetic anomaly was constructed from bathymetric data assuming an Airy-type isostatic compensation. An average crustal magnetization of 6 A.m is required to account for the observed anomaly amplitudes provided that the whole crust is homogeneously magnetized. In contrast, a model representing only the topographic expression of the Broken Ridge, above the surrounding sea floor, requires a magnetization of the order of 40 A.m-1. Since this latter figure is much higher than is to be expected from studies of magnetic properties of oceanic rocks, it is concluded that the majority of the crustal volume of Broken Ridge is magnetized relatively uniformly. The direction of the source magnetization is consistent with an inclination shallower than the present geomagnetic field and close to that of an axial dipole. Since a more northerly source location for Broken Ridge is contrary to the paleolatitude data it is though that the magnetization represents a magnetization obtained by averaging the geomagnetic field direction over a sufficient time to remove secular variation effects. This pattern is indicative of viscous magnetization.
Spectral averaging techniques for Jacobi matrices with matrix entries
Sadel, Christian
2009-01-01
A Jacobi matrix with matrix entries is a self-adjoint block tridiagonal matrix with invertible blocks on the off-diagonals. Averaging over boundary conditions leads to explicit formulas for the averaged spectral measure which can potentially be useful for spectral analysis. Furthermore another variant of spectral averaging over coupling constants for these operators is presented.
40 CFR 1042.710 - Averaging emission credits.
2010-07-01
... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Averaging emission credits. 1042.710..., Banking, and Trading for Certification § 1042.710 Averaging emission credits. (a) Averaging is the exchange of emission credits among your engine families. (b) You may certify one or more engine families...
Sample Size Bias in Judgments of Perceptual Averages
Price, Paul C.; Kimura, Nicole M.; Smith, Andrew R.; Marshall, Lindsay D.
2014-01-01
Previous research has shown that people exhibit a sample size bias when judging the average of a set of stimuli on a single dimension. The more stimuli there are in the set, the greater people judge the average to be. This effect has been demonstrated reliably for judgments of the average likelihood that groups of people will experience negative,…
Averaging in SU(2) open quantum random walk
Clement, Ampadu
2014-03-01
We study the average position and the symmetry of the distribution in the SU(2) open quantum random walk (OQRW). We show that the average position in the central limit theorem (CLT) is non-uniform compared with the average position in the non-CLT. The symmetry of distribution is shown to be even in the CLT.
Averaging in SU(2) open quantum random walk
International Nuclear Information System (INIS)
We study the average position and the symmetry of the distribution in the SU(2) open quantum random walk (OQRW). We show that the average position in the central limit theorem (CLT) is non-uniform compared with the average position in the non-CLT. The symmetry of distribution is shown to be even in the CLT
Evaluation of the average ion approximation for a tokamak plasma
International Nuclear Information System (INIS)
The average ion approximation, sometimes used to calculated atomic processes in plasmas, is assessed by computing deviations in various rates over a set of conditions representative of tokamak edge plasmas. Conditions are identified under which the rates are primarily a function of the average ion charge and plasma parameters, as assumed in the average ion approximation. (Author) 19 refs., tab., 5 figs
Plan averaging for multicriteria navigation of sliding window IMRT and VMAT
International Nuclear Information System (INIS)
Purpose: To describe a method for combining sliding window plans [intensity modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT)] for use in treatment plan averaging, which is needed for Pareto surface navigation based multicriteria treatment planning. Methods: The authors show that by taking an appropriately defined average of leaf trajectories of sliding window plans, the authors obtain a sliding window plan whose fluence map is the exact average of the fluence maps corresponding to the initial plans. In the case of static-beam IMRT, this also implies that the dose distribution of the averaged plan is the exact dosimetric average of the initial plans. In VMAT delivery, the dose distribution of the averaged plan is a close approximation of the dosimetric average of the initial plans. Results: The authors demonstrate the method on three Pareto optimal VMAT plans created for a demanding paraspinal case, where the tumor surrounds the spinal cord. The results show that the leaf averaged plans yield dose distributions that approximate the dosimetric averages of the precomputed Pareto optimal plans well. Conclusions: The proposed method enables the navigation of deliverable Pareto optimal plans directly, i.e., interactive multicriteria exploration of deliverable sliding window IMRT and VMAT plans, eliminating the need for a sequencing step after navigation and hence the dose degradation that is caused by such a sequencing step
Plan averaging for multicriteria navigation of sliding window IMRT and VMAT
Energy Technology Data Exchange (ETDEWEB)
Craft, David, E-mail: dcraft@partners.org; Papp, Dávid; Unkelbach, Jan [Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114 (United States)
2014-02-15
Purpose: To describe a method for combining sliding window plans [intensity modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT)] for use in treatment plan averaging, which is needed for Pareto surface navigation based multicriteria treatment planning. Methods: The authors show that by taking an appropriately defined average of leaf trajectories of sliding window plans, the authors obtain a sliding window plan whose fluence map is the exact average of the fluence maps corresponding to the initial plans. In the case of static-beam IMRT, this also implies that the dose distribution of the averaged plan is the exact dosimetric average of the initial plans. In VMAT delivery, the dose distribution of the averaged plan is a close approximation of the dosimetric average of the initial plans. Results: The authors demonstrate the method on three Pareto optimal VMAT plans created for a demanding paraspinal case, where the tumor surrounds the spinal cord. The results show that the leaf averaged plans yield dose distributions that approximate the dosimetric averages of the precomputed Pareto optimal plans well. Conclusions: The proposed method enables the navigation of deliverable Pareto optimal plans directly, i.e., interactive multicriteria exploration of deliverable sliding window IMRT and VMAT plans, eliminating the need for a sequencing step after navigation and hence the dose degradation that is caused by such a sequencing step.
Using Bayes Model Averaging for Wind Power Forecasts
Preede Revheim, Pål; Beyer, Hans Georg
2014-05-01
For operational purposes predictions of the forecasts of the lumped output of groups of wind farms spread over larger geographic areas will often be of interest. A naive approach is to make forecasts for each individual site and sum them up to get the group forecast. It is however well documented that a better choice is to use a model that also takes advantage of spatial smoothing effects. It might however be the case that some sites tends to more accurately reflect the total output of the region, either in general or for certain wind directions. It will then be of interest giving these a greater influence over the group forecast. Bayesian model averaging (BMA) is a statistical post-processing method for producing probabilistic forecasts from ensembles. Raftery et al. [1] show how BMA can be used for statistical post processing of forecast ensembles, producing PDFs of future weather quantities. The BMA predictive PDF of a future weather quantity is a weighted average of the ensemble members' PDFs, where the weights can be interpreted as posterior probabilities and reflect the ensemble members' contribution to overall forecasting skill over a training period. In Revheim and Beyer [2] the BMA procedure used in Sloughter, Gneiting and Raftery [3] were found to produce fairly accurate PDFs for the future mean wind speed of a group of sites from the single sites wind speeds. However, when the procedure was attempted applied to wind power it resulted in either problems with the estimation of the parameters (mainly caused by longer consecutive periods of no power production) or severe underestimation (mainly caused by problems with reflecting the power curve). In this paper the problems that arose when applying BMA to wind power forecasting is met through two strategies. First, the BMA procedure is run with a combination of single site wind speeds and single site wind power production as input. This solves the problem with longer consecutive periods where the input data
Real-time fluid transport characterization through direct acquisition of the averaged propagator
Kittler, Wilfred; Hunter, Mark; Galvosas, Petrik
2015-08-01
Brownian motion (diffusion) and coherent flow are fundamental for many natural and artificial processes. Therefore, its accurate measurement and description is highly desirable in many areas of science, engineering, and technology. Currently available methods commonly involve multiple experiments and substantial processing of acquired data. This contribution proposes a theoretical and experimental framework that enables one to directly examine the dynamics of fluid matter subject to diffusion and flow through the acquisition of the so-called averaged propagator. This statistical function holds all information on particle mobility due to flow and diffusion averaged over the observed fluid. The proposed method is based on a single instantaneous nuclear magnetic resonance measurement event. It also removes the need for data postprocessing by capturing the averaged propagator directly as the acquired signal, which enables the monitoring of diffusion and flow in real time.
International Nuclear Information System (INIS)
Short-pulse accelerator technology developed during time period from the early 60's through the late 80's is now being extended to high average power systems capable of being used in industrial and environmental applications. Processes requiring high dose levels and/or high volume throughput may require systems with beam power levels from several hundreds of kilowatts to megawatts. Processes may include chemical waste mitigation, flue gas cleanup, food pasteurization, and new forms of materials preparation and treatment. This paper will address the present status of high average power systems now in operation that use combinations of semiconductor and saturable core magnetic switches with inductive voltage adders to achieve MeV beams of electrons or x-rays over areas of 10,000 cm2 or more. Similar high average power technology is also being used below 1 MeV to drive repetitive ion beam sources for treatment of material surfaces
Energy Technology Data Exchange (ETDEWEB)
Campbell, D. A.; Morris, C. W.; Sinclair, A. R.; Hanold, R. J.; Vetter, O. J.
1981-03-01
The stimulation of geothermal wells presents some new and challenging problems. Formation temperatures in the 300-600 F range can be expected. The behavior of stimulation fluids, frac proppants, and equipment at these temperatures in a hostile brine environment must be carefully evaluated before performance expectations can be determined. In order to avoid possible damage to the producing horizon of the formation, high temperature chemical compatibility between the in situ materials and the stimulation materials must be verified. Perhaps most significant of all, in geothermal wells the required techniques must be capable of bringing about the production of very large amounts of fluid. This necessity for high flow rates represents a significant departure from conventional petroleum well stimulation and demands the creation of very high near-wellbore permeability and/or fractures with very high flow conductivity.
Amirov, Elnur
2016-04-01
Sperry-Sun (Sperry Drilling Services) is the leader in MWD/LWD reliability, has developed the industry's first LWD NMR/MRIL-WD (nuclear magnetic resonance) tool. The MRIL-WD (magnetic resonance imaging logging-while-drilling) service directly measures the T1 component of hydrogen in subsurface rock units while drilling to obtain total reservoir porosity and to dissect the observed total porosity into its respective components of free fluid and bound fluid porosity. These T1 data are used to secure accurate total, free-fluid, capillary-bound water, and clay-bound water porosity of the reservoir sections which can be drilled in the several Runs. Over the last decade, results from Magnetic Resonance Imaging logs (NMR) have added significant value to petrophysical analysis and understanding by providing total, free-fluid and bound-fluid porosities, combined with fluid typing capabilities. With MRIL-WD very valuable Real-Time or Recorded Memory data/information is now available during or shortly after the drilling operation (formation properties measurement can be taken right after a drill bit penetration), while trip in and trip out as well. A key point in utilizing MRIL in an LWD environment is motion-tolerant measurements. Recent MRIL-WD logging runs from the Shah Deniz wells located in the Khazarian-Caspian Sea of the Azerbaijan Republic helped to delineate and assess hydrocarbon bearing zones. Acquired results demonstrate how MRIL data can be acquired while-drilling and provide reliable/high quality measurements. Magnetic Resonance Imaging logs at some developments wells have become a cornerstone in formation evaluation and petrophysical understanding. By providing total, free-fluid, and bound-fluid porosities together with fluid typing, MRIL results have significantly added to the assessment of reservoirs. In order to reduce NPT (Non-Productive Time) and save the rig operations time, there is always the desire to obtain logging results as soon as possible
Magnetic Flux Density in the Heliosphere through Several Solar Cycles
Erdős, G.; Balogh, A.
2014-01-01
We studied the magnetic flux density carried by solar wind to various locations in the heliosphere, covering a heliospheric distance range of 0.3-5.4 AU and a heliolatitudinal range from 80° south to 80° north. Distributions of the radial component of the magnetic field, BR , were determined over long intervals from the Helios, ACE, STEREO, and Ulysses missions, as well as from using the 1 AU OMNI data set. We show that at larger distances from the Sun, the fluctuations of the magnetic field around the average Parker field line distort the distribution of BR to such an extent that the determination of the unsigned, open solar magnetic flux density from the average lang|BR |rang is no longer justified. We analyze in detail two methods for reducing the effect of fluctuations. The two methods are tested using magnetic field and plasma velocity measurements in the OMNI database and in the Ulysses observations, normalized to 1 AU. It is shown that without such corrections for the fluctuations, the magnetic flux density measured by Ulysses around the aphelion phase of the orbit is significantly overestimated. However, the matching between the in-ecliptic magnetic flux density at 1 AU (OMNI data) and the off-ecliptic, more distant, normalized flux density by Ulysses is remarkably good if corrections are made for the fluctuations using either method. The main finding of the analysis is that the magnetic flux density in the heliosphere is fairly uniform, with no significant variations having been observed either in heliocentric distance or heliographic latitude.
Magnetic flux density in the heliosphere through several solar cycles
Energy Technology Data Exchange (ETDEWEB)
Erdős, G. [Wigner Research Centre for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary); Balogh, A., E-mail: erdos.geza@wigner.mta.hu [The Blackett Laboratory, Imperial College London, London SW7 2BZ (United Kingdom)
2014-01-20
We studied the magnetic flux density carried by solar wind to various locations in the heliosphere, covering a heliospheric distance range of 0.3-5.4 AU and a heliolatitudinal range from 80° south to 80° north. Distributions of the radial component of the magnetic field, B{sub R} , were determined over long intervals from the Helios, ACE, STEREO, and Ulysses missions, as well as from using the 1 AU OMNI data set. We show that at larger distances from the Sun, the fluctuations of the magnetic field around the average Parker field line distort the distribution of B{sub R} to such an extent that the determination of the unsigned, open solar magnetic flux density from the average (|B{sub R} |) is no longer justified. We analyze in detail two methods for reducing the effect of fluctuations. The two methods are tested using magnetic field and plasma velocity measurements in the OMNI database and in the Ulysses observations, normalized to 1 AU. It is shown that without such corrections for the fluctuations, the magnetic flux density measured by Ulysses around the aphelion phase of the orbit is significantly overestimated. However, the matching between the in-ecliptic magnetic flux density at 1 AU (OMNI data) and the off-ecliptic, more distant, normalized flux density by Ulysses is remarkably good if corrections are made for the fluctuations using either method. The main finding of the analysis is that the magnetic flux density in the heliosphere is fairly uniform, with no significant variations having been observed either in heliocentric distance or heliographic latitude.
Well production practical handbook
Energy Technology Data Exchange (ETDEWEB)
Cholet, H.
2000-07-01
This new Handbook is designed to give a complete, comprehensive overview of field development and well production, providing a wealth of practical information. It is intended as a reference guide for petroleum engineers and oil field operators, yet also provides readily-available solutions to practical problems. The user will find the guidelines, recommendations, formulas and charts currently in use, as it covers most of the cases encountered in the field. Even when a problem has been contracted out to a service company, reference to this handbook will help the oil field manager to better monitor out-sourced work and current operations. The handbook also introduces the new techniques of well production (horizontal and multilateral wells, heavy oil production, etc.). Many examples are given throughout to facilitate the use of the formulas. Also, measurements are frequently expressed in both metric and U.S. units. The symbols used for these units conform to the recommendations of the SPE Board of Directors. This publication will therefore serve both as a guide and as a handbook, in which the operator will find answers to his questions, along with quick and easy solutions to most of the problems that occur in field development. Contents: General data. Casing and tubing. Coiled tubing. Packers. Pressure losses. Fundamentals of petroleum reservoirs. Well productivity. Formation damage control. Sand control. Stimulation. Horizontal and multilateral wells. Water management. Heavy ail production, Enhanced oil recovery. Artificial lift. Beam pumping and other reciprocating rod pumps. Gas lift. Electric submersible pumps. Progressing cavity pumps. Hydraulic pumping. Multiphase pumping and metering. Deposit treatment. Well servicing. Cased hole logging and imaging. Financial formulas for investment decisions. List of standards for petroleum production. Glossary. (author)
Physician health and wellness.
McClafferty, Hilary; Brown, Oscar W
2014-10-01
Physician health and wellness is a critical issue gaining national attention because of the high prevalence of physician burnout. Pediatricians and pediatric trainees experience burnout at levels equivalent to other medical specialties, highlighting a need for more effective efforts to promote health and well-being in the pediatric community. This report will provide an overview of physician burnout, an update on work in the field of preventive physician health and wellness, and a discussion of emerging initiatives that have potential to promote health at all levels of pediatric training. Pediatricians are uniquely positioned to lead this movement nationally, in part because of the emphasis placed on wellness in the Pediatric Milestone Project, a joint collaboration between the Accreditation Council for Graduate Medical Education and the American Board of Pediatrics. Updated core competencies calling for a balanced approach to health, including focus on nutrition, exercise, mindfulness, and effective stress management, signal a paradigm shift and send the message that it is time for pediatricians to cultivate a culture of wellness better aligned with their responsibilities as role models and congruent with advances in pediatric training. Rather than reviewing programs in place to address substance abuse and other serious conditions in distressed physicians, this article focuses on forward progress in the field, with an emphasis on the need for prevention and anticipation of predictable stressors related to burnout in medical training and practice. Examples of positive progress and several programs designed to promote physician health and wellness are reviewed. Areas where more research is needed are highlighted. PMID:25266440
Materials with low DC magnetic susceptibility for sensitive magnetic measurements
Khatiwada, Rakshya; Kendrick, Rachel; Khosravi, Marjan; Peters, Michael; Smith, Erick; Snow, Mike
2015-01-01
Materials with very low DC magnetic susceptibility have many scientific applications. To our knowledge however, relatively little research has been conducted with the goal to produce a totally nonmagnetic material. This phrase in our case means after spatially averaging over macroscopic volumes, it possesses an average zero DC magnetic susceptibility. We report measurements of the DC magnetic susceptibility of three different types of nonmagnetic materials at room temperature: (I) solutions of paramagnetic salts and diamagnetic liquids, (II) liquid gallium-indium alloys and (III) pressed powder mixtures of tungsten and bismuth. The lowest measured magnetic susceptibility among these candidate materials is in the order of 10^-9 cgs volume susceptibility units, about two orders of magnitude smaller than distilled water. In all cases, the measured concentration dependence of the magnetic susceptibility is consistent with that expected for the weighted sum of the susceptibilities of the separate components within...
International Nuclear Information System (INIS)
It is well known that reversed (negative)magnetic shear is favorable for the stability of ballooning mode in tokamak, and hence for the achievement of high β, large bootstrap current. In several recent experiment it has been seen that negative magnetic shear strongly enhanced plasma performance. Based on MHD ballooning model stability theory and Hirshman's expression for the flux surface averaged parallel bootstrap current density, marginal stability regions of plasma ballooning mode and bootstrap current density profile in negative magnetic shear configuration are calculated. The results shows negative magnetic shear configuration permit larger β value and produced larger bootstrap current fraction. If parameter q2R/Lp is nearly equivalent, when shear value between +-0.2--+-0.5, negative magnetic shear permit two times larger β than positive magnetic shear and corresponding bootstrap current fraction ≥70%. The results provide a reference for the feasible research of hybrid reactor core
Ondrušová, Denisa
2012-01-01
Předmětem bakalářské práce je návrh firemního wellness – „Hubnu v dubnu“ pro zvolenou firmu. Tato práce obsahuje všechny potřebné informace, které jsou nutné k vytvoření konkrétní nabídky firemního wellness. Finální návrh bude připraven pro zařazení do portfolia CESA VUT v Brně.
International Nuclear Information System (INIS)
The single well technique method includes measurement of parameters of groundwater flow in saturated rock. For determination of filtration velocity the dilution of radioactive tracer is measured, for direction logging the collimeter is rotated in the probe linked with the compass. The limiting factor for measurement of high filtration velocities is the occurrence of turbulent flow. The single well technique is used in civil engineering projects, water works and subsurface drainage of liquid waste from disposal sites. The radioactive tracer method for logging the vertical fluid movement in bore-holes is broadly used in groundwater survey and exploitation. (author)
Magnetic Field Measurements in Beam Guiding Magnets
Henrichsen, K N
1998-01-01
Electromagnets used as beam guiding elements in particle accelerators and colliders require very tight tole-rances on their magnetic fields and on their alignment along the particle path. This article describes the methods and equipment used for magnetic measurements in beam transport magnets. Descriptions are given of magnetic resonance techniques, various induction coil methods, Hall generator measurements, the fluxgate magnetometer as well as the recently developed method of beam based alignment. References of historical nature as well as citations of recent work are given. The present commercial availability of the different sensors and asso-ciated equipment is indicated. Finally we shall try to analyze possible future needs for developments in those fields.
Indian Academy of Sciences (India)
D Bahadur; Jyotsnendu Giri
2003-06-01
Magnetism plays an important role in different applications of health care. Magnetite (Fe34) is biocompatible and therefore is one of the most extensively used biomaterials for different applications ranging from cell separation and drug delivery to hyperthermia. Other than this, a large number of magnetic materials in bulk as well as in the form of nano particles have been exploited for a variety of medical applications. In this review, we summarize the salient features of clinical applications, where magnetic biomaterials are used. Magnetic intracellular hyperthermia for cancer therapy is discussed in detail.
Ultrafast green laser exceeding 400 W of average power
Gronloh, Bastian; Russbueldt, Peter; Jungbluth, Bernd; Hoffmann, Hans-Dieter
2014-05-01
We present the world's first laser at 515 nm with sub-picosecond pulses and an average power of 445 W. To realize this beam source we utilize an Yb:YAG-based infrared laser consisting of a fiber MOPA system as a seed source, a rod-type pre-amplifier and two Innoslab power amplifier stages. The infrared system delivers up to 930 W of average power at repetition rates between 10 and 50 MHz and with pulse durations around 800 fs. The beam quality in the infrared is M2 = 1.1 and 1.5 in fast and slow axis. As a frequency doubler we chose a Type-I critically phase-matched Lithium Triborate (LBO) crystal in a single-pass configuration. To preserve the infrared beam quality and pulse duration, the conversion was carefully modeled using numerical calculations. These take dispersion-related and thermal effects into account, thus enabling us to provide precise predictions of the properties of the frequency-doubled beam. To be able to model the influence of thermal dephasing correctly and to choose appropriate crystals accordingly, we performed extensive absorption measurements of all crystals used for conversion experiments. These measurements provide the input data for the thermal FEM analysis and calculation. We used a Photothermal Commonpath Interferometer (PCI) to obtain space-resolved absorption data in the bulk and at the surfaces of the LBO crystals. The absorption was measured at 1030 nm as well as at 515 nm in order to take into account the different absorption behavior at both occurring wavelengths.
The imprint of stratospheric transport on column-averaged methane
Directory of Open Access Journals (Sweden)
A. Ostler
2015-07-01
Full Text Available Model simulations of column-averaged methane mixing ratios (XCH4 are extensively used for inverse estimates of methane (CH4 emissions from atmospheric measurements. Our study shows that virtually all chemical transport models (CTM used for this purpose are affected by stratospheric model-transport errors. We quantify the impact of such model transport errors on the simulation of stratospheric CH4 concentrations via an a posteriori correction method. This approach compares measurements of the mean age of air with modeled age and expresses the difference in terms of a correction to modeled stratospheric CH4 mixing ratios. We find age differences up to ~ 3 years yield to a bias in simulated CH4 of up to 250 parts per billion (ppb. Comparisons between model simulations and ground-based XCH4 observations from the Total Carbon Column Network (TCCON reveal that stratospheric model-transport errors cause biases in XCH4 of ~ 20 ppb in the midlatitudes and ~ 27 ppb in the arctic region. Improved overall as well as seasonal model-observation agreement in XCH4 suggests that the proposed, age-of-air-based stratospheric correction is reasonable. The latitudinal model bias in XCH4 is supposed to reduce the accuracy of inverse estimates using satellite-derived XCH4 data. Therefore, we provide an estimate of the impact of stratospheric model-transport errors in terms of CH4 flux errors. Using a one-box approximation, we show that average model errors in stratospheric transport correspond to an overestimation of CH4 emissions by ~ 40 % (~ 7 Tg yr−1 for the arctic, ~ 5 % (~ 7 Tg yr−1 for the northern, and ~ 60 % (~ 7 Tg yr−1 for the southern hemispheric mid-latitude region. We conclude that an improved modeling of stratospheric transport is highly desirable for the joint use with atmospheric XCH4 observations in atmospheric inversions.
Estimation of the average correlation coefficient for stratified bivariate data.
Rubenstein, L M; Davis, C S
1999-03-15
If the relationship between two ordered categorical variables X and Y is influenced by a third categorical variable with K levels, the Cochran-Mantel-Haenszel (CMH) correlation statistic QC is a useful stratum-adjusted summary statistic for testing the null hypothesis of no association between X and Y. Although motivated by and developed for the case of K I x J contingency tables, the correlation statistic QC is also applicable when X and Y are continuous variables. In this paper we derive a corresponding estimator of the average correlation coefficient for K I x J tables. We also study two estimates of the variance of the average correlation coefficient. The first is a restricted variance based on the variances of the observed cell frequencies under the null hypothesis of no association. The second is an unrestricted variance based on an asymptotic variance derived by Brown and Benedetti. The estimator of the average correlation coefficient works well in tables with balanced and unbalanced margins, for equal and unequal stratum-specific sample sizes, when correlation coefficients are constant over strata, and when correlation coefficients vary across strata. When the correlation coefficients are zero, close to zero, or the cell frequencies are small, the confidence intervals based on the restricted variance are preferred. For larger correlations and larger cell frequencies, the unrestricted confidence intervals give superior performance. We also apply the CMH statistic and proposed estimators to continuous non-normal data sampled from bivariate gamma distributions. We compare our methods to statistics for data sampled from normal distributions. The size and power of the CMH and normal theory statistics are comparable. When the stratum-specific sample sizes are small and the distributions are skewed, the proposed estimator is superior to the normal theory estimator. When the correlation coefficient is zero or close to zero, the restricted confidence intervals
SMARTer for magnetic structure studies
Indian Academy of Sciences (India)
E G R Putra; A Ikram; J Kohlbrecher
2008-11-01
SMARTer, a 36-meter small angle neutron scattering (SANS) spectrometer was installed at the Neutron Scattering Laboratory (NSL), National Nuclear Energy Agency of Indonesia – BATAN in Serpong, Indonesia and has performed the experiment for studying the magnetic structures of Cu(NiFe), CuCo and FeSiBNbCu metal alloys. The experiments were conducted at room temperature and up to 1 T (10 kOe) of external magnetic field. At zero fields, isotropic scattering identified as nuclear scattering is dominant. When a magnetic field is applied in a horizontal direction perpendicular to the neutron beam, the response of the magnetic scattering permits extraction of the field-induced re-arrangement of the magnetic moment. With increasing field the distortion is more pronounced and the magnetic scattering dominates the intensity and affects the peak position. Radial and angular averaging from experimental data are given to show the details of magnetic structures.