Multi Configuration Research Articles

The role of viscoelastic contrast in orientation selection of block copolymer lamellar phases under oscillatory shear

The mesoscale rheology of a lamellar phase of a block copolymer is modeled as a structured fluid of uniaxial symmetry. The model predicts a viscoelastic response that depends on the angle between the local lamellar planes and velocity gradients. We focus on the stability under oscillatory shear of a two layer configuration comprising a parallel and a perpendicularly oriented domain, so that the two layers have a different viscoelastic modulus G*(ω). A long wave, low Reynolds number expansion is introduced to analytically obtain the region of stability. When the response of the two layers is purely viscous, we recover earlier results according to which the interface is unstable for non-zero Reynolds number flows when the thinner layer is more viscous. On the other hand, when viscoelasticity is included, we find that the interface can become unstable even for zero Reynolds number. The interfacial instability is argued to dynamically favor perpendicular relative to parallel orientation, and hence we suggest that the perpendicular orientation would be selected in a multi domain configuration in the range of frequency ω in which viscoelastic contrast among orientations is appreciable.

Constructal multi scale cylinders with rotation cooled by natural convection

This paper investigated the thermal behaviour of an assembly of multi scale cylinders in a staggered counter-rotating configuration cooled by natural convection with the objective of maximizing the heat transfer density rate (heat transfer rate per unit volume). A numerical model was used to solve the governing equations that describe the temperature and flow fields and a mathematical optimisation algorithm was used to find the optimal structure for flow configurations with two degrees of freedom. The multi scale structure of the cylinder assembly was optimized for each flow regime (Rayleigh number) and cylinder rotation speed for two degrees of freedom. Smaller cylinders were placed at the entrance to the assembly, in the wedge-shaped flow regions occupied by fluid that had not yet been used for heat transfer, to create additional length scales to the flow configuration.It was found that there was almost no effect of cylinder rotation on the maximum heat transfer density rate, when compared to stationary cylinders, at each Rayleigh number; with the exception of high cylinder rotation speeds, which served to suppress the heat transfer density rate. It was, however, found that the optimized spacing decreased as the cylinder rotation speed was increased at each Rayleigh number. Results further show that the maximum heat transfer density rate for a multi scale configuration (without cylinder rotation) was higher than a single scale configuration (with rotating cylinders) with an exception at very low Rayleigh numbers.

Higher order resonant intershell electronic recombination for highly charged ions

Intershell tri-electronic recombination (TR) is reported for highly charged ions of Ar, Fe and Kr, where simultaneously to the K-shell excitation an additional L electron is excited due to resonant recombination of a free electron. Clear evidence on quadru-electronic recombination (QR) is found too, with two additional L electrons being excited at once. The experimental results on first and higher order recombination processes are discussed and compared with multi configuration Dirac-Fock calculations.

Film Cooling Adiabatic Effectiveness for Cylindrical Holes Embedded in Multi Trench Configuration

In this study, computational simulations were made using ANSYS CFX to predict the improvements in film cooling performance with multi trench. Multi-trench configuration consists of two trenches together, one wider trench and the other is narrow trench that extruded from the wider one. Several blowing ratios in the range (0.5, 1, 2 and 3) were investigated. By using the multi trench configuration, the coolant jet impacted the trench wall two times allowing increasing the spreading of coolant laterally in the trench, reducing jet velocity and jet completely covered on the surface. The results indicate that this configuration increased adiabatic effectiveness as blowing ratio increased. The multi trench configuration increased adiabatic effectiveness up to 100% near the hole, 43% at X/D = 40 and 31% at downstream X/D = 137 for blowing ratio of 3 and no observed film blow-off at this blowing ratio. The adiabatic film effectiveness of multi trench configuration outperformed the narrow trench at different blowing ratios

Quantum-dynamics study of the ${\rm H}_5^+$H5+ cluster: Full dimensional benchmark results on its vibrational states

A full-dimensional quantum dynamics study is carried out for the highly fluxional H(5)(+) cation on a recent reference potential energy surface by using the multi configuration time-dependent Hartree method. With five equivalent light atoms and shallow barriers between various low-lying stationary points on the surface, the spectroscopic characterization of H(5)(+) represents a huge challenge for accurate quantum dynamics simulations. The present calculation is the first such a study on this cation, which together with its isotope analogies are of primary importance in the interstellar chemistry. The vibrational ground state properties and several vibrationally excited states corresponding to low vibrational frequency motions, not yet directly observable by the experiment, are presented and analyzed.

Multi-Metric Based Face Identification with Multi Configuration LBP Descriptor

This paper deals with the performance improvement of a mono modal face identification. A statistical study of various structures of the LBPs (Local Binary Patterns) features associated to two metrics is performed to find out those committing errors on different subjects. Then, during the identification stage, these optimal variants are used, and a simple score level fusion is adopted. The score fusion is done after min-max normalization. The main contribution of this paper consists in the association of multiple LBP schemes with different metrics using simple fusion operation. The overall identification rating up to 99% using AT&T database is achieved.

A quantum-classical simulation of a multi-surface multi-mode nuclear dynamics on $ {\rm C_{6}H}_{6}^{+} $ incorporating degeneracy among electronic states

We have performed a nuclear dynamics simulation to calculate photoelectron spectra and population profiles of benzene radical cation (C6H\(_6^+\)) employing the parallelized Time Dependent Discrete Variable Representation (TDDVR) approach. For this purpose, we have considered two multi-state multi-mode model Hamiltonians of C6H\(_6^+\) with degeneracy among the eectronic states: (a) One consists of three states and eight modes, which in turn leads to a five state thirteen mode Hamiltonian (X 2E1g -B 2E2g -C 2A2u ) due to the degeneracy; and (b) The other is constituted of three states and thirteen modes which is basically a five state twenty mode Hamiltonian (B 2E2g -D 2E1u -E 2B2u ) for the same reason. Since these electronic states are interconnected by several conical intersections in the vicinity of the Franck Condon region, it will be challenging to pursue such large dynamical calculation in the presence of nonadiabaticity among the electronic states. The spectral as well as population profiles calculated with the advent of TDDVR approach show reasonably good agreement with the results obtained by the Multi Configuration Time Dependent Hartree (MCTDH) methodology. The photoelectron spectra of benzene is quantum - classically simulated using parallelized time dependent discrete variable representation (TDDVR) method, where the degeneracy among different states is considered in the realistic model Hamiltonian of corresponding system.

Optimizing receiver and transmitter layout in optical wireless multi spot configuration access link

The study of indoor optical wireless (OW) environment is complicated by the difficulty of obtaining accurate impulse response for a large number of transmitter/receiver locations. An accurate impulse response for a given receiver location requires not only direct path, but also reflections up to nth order. The impulse response obtained is only valid for a specific location and for specific receiver parameters. If a receiver moves, the impulse response has to be recalculated. In this paper, we utilize an efficient approach for calculating optical wireless channel to study the optimal region of transmitters and receivers in a multi spot diffusing configuration. This paper takes advantage of an efficient calculation technique to study the optimal layout of receiver locations and transmitter locations in multi spot diffusing environment. Received power and delay spread are used as metrics to optimize receiver and transmitter layouts.

Multi beam observations of cosmic radio noise using a VHF radar with beam forming by a Butler matrix

Abstract. The Leibniz-Institute of Atmospheric Physics (IAP) in Kühlungsborn started to install a new MST radar on the North-Norwegian island Andøya (69.30° N, 16.04° E) in 2009. The new Middle Atmosphere Alomar Radar System (MAARSY) replaces the previous ALWIN radar which has been successfully operated for more than 10 years. The MAARSY radar provides increased temporal and spatial resolution combined with a flexible sequential point-to-point steering of the radar beam. To increase the spatiotemporal resolution of the observations a 16-port Butler matrix has been built and implemented to the radar. In conjunction with 64 Yagi antennas of the former ALWIN antenna array the Butler matrix simultaneously provides 16 individual beams. The beam forming capability of the Butler matrix arrangement has been verified observing the galactic cosmic radio noise of the supernova remnant Cassiopeia A. Furthermore, this multi beam configuration has been used in passive experiments to estimate the cosmic noise absorption at 53.5 MHz during events of enhanced solar and geomagnetic activity as indicators for enhanced ionization at altitudes below 90 km. These observations are well correlated with simultaneous observations of corresponding beams of the co-located imaging riometer AIRIS (69.14° N, 16.02° E) at 38.2 MHz. In addition, enhanced cosmic noise absorption goes along with enhanced electron densities at altitudes below about 90 km as observed with the co-located Saura MF radar using differential absorption and differential phase measurements.

Full-dimensional multi configuration time dependent Hartree calculations of the ground and vibrationally excited states of He2,3Br2 clusters

Quantum dynamics calculations are reported for the tetra-, and penta-atomic van der Waals He(N)Br(2) complexes using the multiconfiguration time-dependent Hartree (MCTDH) method. The computations are carried out in satellite coordinates, and the kinetic energy operator in this set of coordinates is given. A scheme for the representation of the potential energy surface based on the sum of the three-body HeBr(2) interactions at CSSD(T) level plus the He-He interaction is employed. The potential surfaces show multiple close lying minima, and a quantum description of such highly floppy multiminima systems is presented. Benchmark, full-dimensional converged results on ground vibrational/zero-point energies are reported and compared with recent experimental data available for all these complexes, as well as with previous variational quantum calculations for the smaller HeBr(2) and He(2)Br(2) complexes on the same surface. Some low-lying vibrationally excited eigenstates are also computed by block improved relaxation calculations. The binding energies and the corresponding vibrationally averaged structures are determined for different conformers of these complexes. Their relative stability is discussed, and contributes to evaluate the importance of the multiple-minima topology of the underlying potential surface.

Stereocontrol of attosecond time-scale electron dynamics in ABCU using ultrafast laser pulses: a computational study

The attosecond time-scale electronic dynamics induced by an ultrashort laser pulse is computed using a multi configuration time dependent approach in ABCU (C(10)H(19)N), a medium size polyatomic molecule with a rigid cage geometry. The coupling between the electronic states induced by the strong pulse is included in the many electron Hamiltonian used to compute the electron dynamics. We show that it is possible to implement control of the electron density stereodynamics in this medium size molecule by varying the characteristics of the laser pulse, for example by polarizing the electric field either along the N-C axis of the cage, or in the plane perpendicular to it. The excitation produces an oscillatory, non-stationary, electronic state that exhibits localization of the electron density in different parts of the molecule both during and after the pulse. The coherent oscillations of the non-stationary electronic state are also demonstrated through the alternation of the dipole moment of the molecule.

Multi stage high rate biomethanation of poultry litter with self mixed anaerobic digester

A multi stage high rate biomethanation process with novel self mixed anaerobic digester (SMAD) was developed in the present study to reduce the hydraulic residence time (HRT), increase the volatile solids (VS) loading rate, improve the VS destruction efficiency and enhance the methane yield. Specific design features of SMAD were useful in mixing the digester contents without consuming power and de-alienated the problem of scum formation. In the first phase, poultry litter having 10% total solids (TS) was subjected to high rate biomethanation in multi stage configuration (SMAD-I and II in series with UASB reactor). It was observed that gross VS reduction of 58%, gross methane yield of 0.16 m3 kg(-1) (VS reduced) and VS loading rate of 3.5 kg VS m(-3) day(-1) at HRT of 13 days was obtained. In the second phase SMAD-II was bypassed from the process scheme keeping the other parameters same as in the first phase. The results obtained were not as encouraging as in the first phase. The study showed that multi stage configuration with SMAD design improved the anaerobic digestion process efficiency of poultry litter.

Generalized Møller-Plesset Partitioning in Multiconfiguration Perturbation Theory.

Two perturbation (PT) theories are developed starting from a multiconfiguration (MC) zero-order function. To span the configuration space, the theories employ biorthogonal vector sets introduced in the MCPT framework. At odds with previous formulations, the present construction operates with the full Fockian corresponding to a principal determinant, giving rise to a nondiagonal matrix of the zero-order resolvent. The theories provide a simple, generalized Møller-Plesset (MP) second-order correction to improve any reference function, corresponding either to a complete or incomplete model space. Computational demand of the procedure is determined by the iterative inversion of the Fockian, similarly to the single reference MP theory calculated in a localized basis. Relation of the theory to existing multireference (MR) PT formalisms is discussed. The performance of the present theories is assessed by adopting the antisymmetric product of strongly orthogonal geminal (APSG) wave functions as the reference function.

On the line intensity ratios of prominent Si II, Si III, and Si IV multiplets

Line intensities of singly, doubly and triply ionized silicon (Si II, Si III, and Si IV, respectively) belonging to the prominent higher multiplets, are of interest in laboratory and astrophysical plasma diagnostics. We measured these line intensities in the emission spectra of pulsed helium discharge. The Si II line intensity ratios in the 3 s3 p 22 D–3 s 24 p 2 P o , 3 s 23 d 2 D–3 s 24 f 2 F o , and 3 s 24 p 2 P o –3 s 24 d 2 D transitions, the Si III line intensity ratios in the 3 s3 d 3 D–3 s4 p 3 P o , 3 s4 p 3 P o –3 s4 d 3 D, 3 s4 p 3 P o –3 s5 s 3 S, 3 s4 s 3 S–3 s4 p 3 P o , and 3 s4 f 3 F o –3 s5 g 3 G transitions, and the Si IV line intensity ratios in the 4 p 2 P o –4 d 2 D and 4 p 2 P o –5 s 2 S transitions were obtained in a helium plasma at an electron temperature of about 17,000 ± 2000 K. Line shapes were recorded using a spectrograph and an ICCD camera as a highly-sensitive detection system. The silicon atoms were evaporated from a Pyrex discharge tube designed for the purpose. They represent impurities in the optically thin helium plasma at the silicon ionic wavelengths investigated. The line intensity ratios obtained were compared with those available in the literature, and with values calculated on the basis of available transition probabilities. The experimental data corresponded well with line intensity ratios calculated using the transition probabilities obtained from a Multi Configuration Hartree–Fock approximation for Si III and Si IV spectra. We recommend corrections of some Si II transition probabilities.

Formation of the ion-pair in electron recombination with H+3

We present a two-dimensional theoretical study of the formation of the ion-pair, H+2 + H−, in electron recombination with H+3 in its ground electronic and vibrational state. The relevant potential energy surfaces, electronic couplings and autoionization widths are calculated by combining electron scattering calculations with quantum chemistry calculations. The nuclear dynamics on six coupled electronic states is studied by propagating wave packets using the MCTDH (Multi Configuration Time-Dependent Hartree) method. Also the cross section for ion-pair formation in electron recombination with D+3 is calculated.

Calculation of Temperature Distribution in Eccentric Multi Core Diode Pumped Fiber Lasers by Green Function Method

In this paper, the temperature distribution in fiber lasers pumped by multi diode bars located in out-of-fiber axis has been investigated semi-analytically. For this reason, we consider heat deposition in fiber lasers due to pump and the nonhomogeneous heat conduction equation has been solved by using Green function method in a cylindrical coordinate system. Our model has been used for single, double and multi pumped configuration and, for a typical fiber lasers, the results have been plotted and discussed.

Indirect effects of membrane configuration on MBR sludge filterability

During a combined pilot-scale study, operating conditions were fixed for three different membrane configurations a multi tube, a hollow fibre and a flat sheet membrane type. Changes in activated sludge filterability were quantified depending on the membrane chambers, the permeate flux of extraction and the membrane chamber aeration. The aim of this study was to provide a better understanding of the interactions between MBR activated sludges and hydraulic circumstances depending on membrane configurations. Two mechanisms can be distinguished from this study: Due to practical arrangements, hydraulic conditions in each membrane unit are different, leading to different total suspended solids concentrations (TSS). These margins in TSS contents cause differences in filtration behaviour. The multi tube configuration did not affect the activated sludge filterability. The activated sludge filterability remained the same in spite of flux and air-lift velocity changes. The fl at sheet and the hollow fibre configuration did affect the sludge filterability. The filterability improved significantly at high flux and at low air-lift velocity (from 20% to 90% of improvement). The TSS concentration phenomenon is likely to be responsible for the activated sludge filterability improvement. It might be due to floc structure modifications resulting in a better cake layer porosity. No correlations were found between SMP and filterability.

Changes in cerebral blood flow after acetazolamide: an experimental study comparing near‐infrared spectroscopy and SPECT

It is important to find a reliable and bedside method, which can estimate the cerebral blood flow (CBF) of patients in clinical settings. Estimation of CBF by calculating a blood flow index (BFI) using continuous wave near-infrared spectroscopy (CW-NIRS) and indocyanine green (ICG) as an i.v. tracer has been proposed to be a feasible and promising method. To validate if the BFI method can detect relative changes in CBF we compared data with the established method (133)Xenon single photon emission computer tomography ((133)Xe-SPECT). Ten healthy subjects were investigated before and after a bolus of acetazolamide. NIRS data were obtained using a multi source detector separation configuration in order to assess a corrected BFI (BFI(corr)) value, which attempts to eliminate contamination of skin blood flow. Data obtained showed no significant correlation between CBF changes measured by (133)Xe-SPECT and BFI(corr) (0.133, P = 0.732). After acetazolamide, a 49% increase in CBF was detected using the (133)Xe-SPECT method, whereas no changes in any ICG variables were observed after acetazolamide. The study shows that it is not possible to obtain reliable BFI data, which reflect changes in CBF after acetazolamide infusion, using the CW-NIRS and ICG method.

The grasp2K relativistic atomic structure package

This paper describes grasp2K, a general-purpose relativistic atomic structure package. It is a modification and extension of the GRASP92 package by [F.A. Parpia, C. Froese Fischer, I.P. Grant, Comput. Phys. Comm. 94 (1996) 249]. For the sake of continuity, two versions are included. Version 1 retains the GRASP92 formats for wave functions and expansion coefficients, but no longer requires preprocessing and more default options have been introduced. Modifications have eliminated some errors, improved the stability, and simplified interactive use. The transition code has been extended to cases where the initial and final states have different orbital sets. Several utility programs have been added. Whereas Version 1 constructs a single interaction matrix for all the J's and parities, Version 2 treats each J and parity as a separate matrix. This block structure results in a reduction of memory use and considerably shorter eigenvectors. Additional tools have been developed for this format. The CPU intensive parts of Version 2 have been parallelized using MPI. The package includes a “make” facility that relies on environment variables. These make it easier to port the application to different platforms. The present version supports the 32-bit Linux and ibmSP environments where the former is compatible with many Unix systems. Descriptions of the features and the program/data flow of the package will be given in some detail in this report.

Multidimensional wave packet dynamics in polypeptides: Coupled amide-exciton chain-vibrational motion in an α-helix

Wave packet dynamics in eight dimensions and for eight coupled “diabatic” states are discussed in using the multi configuration time-dependent Hartree method. For this purpose a reduced dimensionality model for an α-helical polypeptide is used which combines intra amide unit high frequency vibrations with the low frequency longitudinal vibrations of the units along a single chain of hydrogen bonds. The model comprises the possibility to form delocalized vibrational Frenkel exciton states as well as to localize them by an appropriate chain compression. As it has been already shown [D.V. Tsivlin, H.-D. Meyer, V. May, J. Chem. Phys. 124 (2006) 134907; D.V. Tsivlin, V. May, J. Chem. Phys. 125 (2006) 224902] the used model is also ready to give a satisfactory reproduction of infrared transient absorption spectra taken either in the absorption range of CO amide vibrations or NH amide vibrations. Wave packet dynamics following special initial states are discussed based on the reduced single chain coordinate probability distribution as well as on the expectation values of the chain coordinates themselves. The high frequency excitation energy transfer through the chain is found to be anisotropic due to the intrinsic asymmetry of the exciton chain vibrational coupling. It is accompanied by a displacement impulse of the amide units.