Calculation Of Response Functions Research Articles

Transverse (e,e′) Response Functions for 4He

This poster presentation is intended to show preliminary results from calculations of the inclusive (e,e′) transverse response functions of 4He. Up to now we have only included the E1 and M1 multipoles and therefore no comparison with experiment is shown. That will be done once all relevant multipoles have been calculated. Details of the calculation are summarized in the text below.

Development of neutron spectrum unfolding method for advanced nuclear emulsion

In order to realize neutron spectroscopy in high-intensity gamma ray fields such as those present in spent nuclear fuel storage facilities using an advanced nuclear emulsion based on a non-sensitized OPERA film with AgBr grain sizes of 60 nm, a new neutron spectrum unfolding method has been developed. The response functions were evaluated in the neutron energy range between 0.1 and 4.5 MeV by Monte Carlo calculations. To realize a highly reliable unfolding method that does not require an initial guess spectrum, an algorithm was formulized based on the maximum entropy principle and the maximum likelihood method, and the new unfolding code MEALU was developed. The code performance was checked by analyses of mock-up data. As an example, the neutron spectrum from fresh fuel of the experimental fast reactor Joyo was calculated and track lengths were simulated using the calculated response function and the estimated spectrum. Comparison between the original neutron spectrum and the unfolded one confirmed the effectiveness of the proposed method.

A method of neutron-energy evaluation based on the position distribution of recoil protons

A method of neutron-energy evaluation, which was recently proposed by the author’s group, has been applied to the investigation of an Am-Be source in order to confirm the validity of this novel approach; the method is based on the position distribution measurement of recoil protons by an imaging plate (IP) combined with a cone-like converter. The observed position distribution of recoil protons apparently involved neutron-energy information. An unfolding of the position distribution was plainly attempted with the response functions calculated by a simplified Monte Carlo method; the evaluated neutron spectra indicated the energy characteristics of an Am-Be source. When a full Monte Carlo Code, PHITS, was used to calculate the position distributions of recoil protons in order to obtain more correct response functions, the result of neutron-spectra evaluation has been much improved. The evaluation of neutron-energy spectrum by the present method will be further improved by the more accurate calculation of response functions with taking account of the complicated response of IP to low energy protons carefully, as well as by the application of more reliable unfolding algorithms and more appropriate position sensitive detectors.

A study of beam loss pattern and dose distribution around the TPS LINAC during beam commissioning

Beam loss estimation is very important for accelerator shielding design and accurate dose evaluation. The 150-MeV LINAC system of the Taiwan Photon Source (TPS) was assembled and installed in a temporary bunker for acceptance test. Gamma-ray and neutron dose rates around the area were repeatedly measured during beam commissioning. Monitoring results indicated that the beam loss pattern could change drastically over time, especially during the first few weeks of the test, which has caused radiation safety concerns in the area. To facilitate shielding analysis and beam loss diagnosis, FLUKA was used to estimate dose distributions around the area resulting from a series of ideal point beam losses. A full-scale geometry model including main components of the accelerator, structure of the bunker, and additional local shielding has been established to make the simulations as realistic as possible. The resultant dose distributions could be regarded as useful response functions in evaluating combined beam loss scenarios. Taking the beam test on September 23, 2011 as an example, this study has demonstrated that a reasonable beam loss pattern and a detailed dose distribution could be obtained through a synthetic analysis of the calculated response functions and on-site dose rate measurements.

Elastic modulus and thermal properties of InN in the rocksalt phase

Elastic constants, vibration modes and thermodynamic properties of InN in the rocksalt phase are presented by means of ab initio calculations in the framework of plane-wave pseudopotential implementation of the density functional theory with the local density approximation and response-function calculations. The pressure dependence of the elastic constants and phonon frequencies was investigated. Moreover, the influence of temperature on the entropy and heat capacity is also discussed. The computed values are in good agreement with the data available in the literature.

The Seismic Frequency Response Function Calculation of Multi-Span Simply Supported Girder Bridge

In order to simplify the analysis and calculation of multi-span simply supported girder bridge, the seismic frequency response function equation of longitudinal vibration for single-span simply supported girder bridge is established, based on the Fourier transform of the motion equations of multi-degree-of-freedom system. The calculation method of the seismic frequency response for the vertical moment and displacement of multi-span simply supported beam bridge is proposed according to the transfer matrix principle. Taking a bridge of Qinghai-Tibet Railway as an example, the maximum displacement and moment are solved. The result shows that: the displacement of the control section of the side spans is smaller than that of the middle of the bridge, while the moment is opposite. The corresponding Fourier amplitude spectrums under the pulse loads are given finally.

WE-G-103-02: DQE of CsI Microcolumnar X-Ray Detectors Using Hybridmantis and Lubberts' Formulation

Purpose: We describe a method to study the detective quantum efficiency (DQE) performance of CsI microcolumnar CsI x-ray detectors using hybridmantis, an approach for Monte Carlo simulations that maximizes utilization of CPUs and GPUs within modern workstations. Methods: We use hybridmantis, which is a modified version of penelope that outputs coordinates and energy deposited during x-ray and electron interactions occurring within the scintillator which are then used as source for optical showers using fastdetect2. We make use of the Lubberts description of the scintillator as a stack of thin layers and calculate the transfer of noise and signal as the weighted summation of the contribution of each layer. Results: We show results in terms of the Lubberts fraction and then report DQE by introducing the Swank factor and the x-ray interaction efficiency calculated from the Monte Carlo output. We report DQE results calculated using our methods for 4 screen models previously studied by our group. Conclusion: This method relies on the calculation of point response functions at each depth and proper weighting of the contribution of each layer to signal and noise transfer. This methodology can be used to guide optimization approaches for maximizing DQE of microcolumnar CsI x-ray detectors.

An optimized semiclassical approximation for vibrational response functions

The observables of multidimensional infrared spectroscopy may be calculated from nonlinear vibrational response functions. Fully quantum dynamical calculations of vibrational response functions are generally impractical, while completely classical calculations are qualitatively incorrect at long times. These challenges motivate the development of semiclassical approximations to quantum mechanics, which use classical mechanical information to reconstruct quantum effects. The mean-trajectory (MT) approximation is a semiclassical approach to quantum vibrational response functions employing classical trajectories linked by deterministic transitions representing the effects of the radiation-matter interaction. Previous application of the MT approximation to the third-order response function R(3)(t3, t2, t1) demonstrated that the method quantitatively describes the coherence dynamics of the t3 and t1 evolution times, but is qualitatively incorrect for the waiting-time t2 period. Here we develop an optimized version of the MT approximation by elucidating the connection between this semiclassical approach and the double-sided Feynman diagrams (2FD) that represent the quantum response. Establishing the direct connection between 2FD and semiclassical paths motivates a systematic derivation of an optimized MT approximation (OMT). The OMT uses classical mechanical inputs to accurately reproduce quantum dynamics associated with all three propagation times of the third-order vibrational response function.

A Study on the Propulsion Performance of KCS in Still Water and Regular Wave

Since most merchant vessels are mainly influenced by the added resistance in an actual sea, they could be navigated more efficiently if this added resistance could be precisely predicted and then effectively reduced. In this paper, we have computed the effective horsepower based on the resistance performance in still water and then calculated the added resistance in regular wave in order to estimate a ship's propulsion performance on a voyage. Firstly, we have performed experiments using a model of KCS in a circulating water channel to estimate the flow characteristics around a container ship and the ship's resistance in still water. Then we have calculated the motion response function in regular wave as well as the values for the increase in resistance, and evaluated the ship's motion performance in waves according to the calculated response function. It was found that the resistance in waves increased because the ship's motion response value became larger as the ship's speed increased in the case of head sea. The effect of the added resistance could be reduced by maneuvering the ship to the encounter angle of <TEX>$120^{\circ}$</TEX> in areas of long wavelengths and to head sea in areas of short wavelengths.

A band Lanczos approach for calculation of vibrational coupled cluster response functions: simultaneous calculation of IR and Raman anharmonic spectra for the complex of pyridine and a silver cation

We describe new methods for the calculation of IR and Raman spectra using vibrational response theory. Using damped linear response functions that incorporate a Lorentzian line-shape function from the outset, it is shown how the calculation of Raman spectra can be carried out through the calculation of a set of vibrational response functions in the same manner as described previously for IR spectra. The necessary set of response functions can be calculated for both vibrational coupled cluster (VCC) and vibrational configuration interaction (VCI) anharmonic vibrational wave-functions. For the efficient and simultaneous calculation of the full set of necessary response functions, a non-hermitian band Lanczos algorithm is implemented for VCC, and a hermitian band Lanczos algorithm is implemented for VCI. It is shown that the simultaneous calculation of several response functions is often advantageous. Sample calculations are presented for pyridine and the complex between pyridine and the silver cation.

Response function calculations of Ba3Si6O12N2 and Ba3Si6O9N4 for the understanding of the optical properties of the Eu-doped phosphors

Vibrational and elastic properties of Ba3Si6O12N2 and Ba3Si6O9N4 are investigated to aiming at the understanding the difference in luminescence and thermal quenching behaviour of Ba3Si6O12N2:Eu (green luminescence with weak thermal quenching) and Ba3Si6O9N4:Eu (blue–green luminescence with strong thermal quenching). Computed results indicate no significant differences between Ba3Si6O12N2 and Ba3Si6O9N4, suggesting that the difference in thermal quenching may be explained by auto-ionization model rather than configurational coordinate diagram.

Full density-matrix numerical renormalization group calculation of impurity susceptibility and specific heat of the Anderson impurity model

Recent developments in the numerical renormalization group (NRG) allow the construction of the full density matrix (FDM) of quantum impurity models (see A. Weichselbaum and J. von Delft) by using the completeness of the eliminated states introduced by F. B. Anders and A. Schiller (2005). While these developments prove particularly useful in the calculation of transient response and finite temperature Green's functions of quantum impurity models, they may also be used to calculate thermodynamic properties. In this paper, we assess the FDM approach to thermodynamic properties by applying it to the Anderson impurity model. We compare the results for the susceptibility and specific heat to both the conventional approach within NRG and to exact Bethe ansatz results. We also point out a subtlety in the calculation of the susceptibility (in a uniform field) within the FDM approach. Finally, we show numerically that for the Anderson model, the susceptibilities in response to a local and a uniform magnetic field coincide in the wide-band limit, in accordance with the Clogston-Anderson compensation theorem.

Drought sensitivity of three co-occurring conifers within a dry inner Alpine environment

We applied dendroclimatological techniques to determine long-term stationarity of climate-growth relationships and recent growth trends of three widespread coniferous tree species of the central Austrian Alps, which grow intermixed at dry-mesic sites within a dry inner Alpine environment (750 m asl). Time series of annual increments were developed from > 120 mature trees of Picea abies, Larix decidua and Pinus sylvestris. Calculation of response functions for the period 1911 - 2009 revealed significant differences among species in response to climate variables. While precipitation in May - June favoured radial growth of Picea abies and Larix decidua, Pinus sylvestris growth mainly depended on April - May precipitation. P. abies growth was most sensitive to May - June temperature (inverse relationship). Moving response function coefficients indicated increasing drought sensitivity of all species in recent decades, which is related to a decline in soil moisture availability due to increasing stand density and tree size and higher evapotranspiration rates in a warmer climate. While recent trend in basal area increment (BAI) of L. decidua distinctly declined implying high vulnerability to drought stress, moderately shade-tolerant P. abies showed steadily increasing BAI and quite constant BAI was maintained in drought adapted P. sylvestris, although at lowest level of all species. We conclude that synergistic effects of stand dynamics and climate warming increased drought sensitivity, which changed competitive strength of co-occurring conifers due to differences in inherent adaptive capacity.

Monte-Carlo Simulation of Response Functions for Natural Gamma-Rays in LaBr3 Detector System with Complex Borehole Configurations

Usually, there are several methods, e.g. experiment, interpolation experiment-based, analytic function, and Monte-Carlo simulation, to calculate the response functions in LaBr3(Ce) detectors. In logging applications, the experiment-based methods cannot be adopted because of their limitations. Analytic function has the advantage of fast calculating speed, but it is very difficult to take into account many effects that occur in practical applications. On the contrary, Monte-Carlo simulation can deal with physical and geometric configurations very tactfully. It has a distinct advantage for calculating the functions with complex configurations in borehole. A new application of LaBr3(Ce) detector is in natural gamma-rays borehole spectrometer for uranium well logging. Calculation of response functions must consider a series of physical and geometric factors under complex logging conditions, including earth formations and its relevant parameters, different energies, material and thickness of the casings, the fluid between the two tubes, and relative position of the LaBr3(Ce) crystal to steel ingot at the front of logging tube. The present work establishes Monte-Carlo simulation models for the above-mentioned situations, and then performs calculations for main gamma-rays from natural radio-elements series. The response functions can offer experimental directions for the design of borehole detection system, and provide technique basis and basic data for spectral analysis of natural gamma-rays, and for sourceless calibration in uranium quantitative interpretation.

Maximum-Likelihood Deconvolution in the Spatial and Spatial-Energy Domain for Events With Any Number of Interactions

In previous works, maximum-likelihood expectation-maximization deconvolution for two-interaction events within a single CdZnTe detector with dimensions of was implemented. This deconvolution method is capable of estimating the source image for each energy range as well as the incident spectrum for each direction around the detector. To improve the detection efficiency and the image resolution, we have built a four-detector array system; each detector has dimensions of . Using this detector-array system, from a Co-60 measurement, 41.5% of recorded events in the energy window from 1100 keV to 1200 keV are two-interaction events. The goal of this work is to increase the efficiency of this deconvolution algorithm by extending the calculation of the system response functions to events with other number of interactions. We first analytically extend the system response function calculation to three-interaction events by deriving the probability density function, considering the measurement noise, and integrating over the digitization and pixelation volume. The system response function is then simplified, modularized, and extrapolated to events with other numbers of interactions from an array system. By including events with any number of interactions in the system model, imaging makes use of all recorded events, and the angular resolution is improved. This deconvolution algorithm is applicable to any gamma-ray detector system that has the capability of recording 3D interaction location and energy deposition for each interaction.

Anisotropy in the flexural response of the Indian Shield

We seek to determine the strain field which has accumulated in the Indian Shield due to the continental drift of Gondwanaland. We have used a method which involves the calculation of the 2D isostatic coherence response function between Bouguer gravity and topography as a function of azimuth by way of multispectrogram analysis. The average coherence is maximum consistently in the Indian Shield in a direction, which is at an angle of 45° to the major trend of suture zones within the shield, a result which is in good agreement with the strain inferred from absolute plate motion (APM) in a hot spot reference frame. This directionality of mechanical plate weakness suggests that all paleostress fields were erased due to the movement of the Indian plate during the Himalayan orogeny.

Measurement and simulation of neutron response function of organic liquid scintillator detector

Response functions of monoenergetic neutrons at various energies, corresponding to a measured neutron energy spectrum have been extracted. The experimental response functions for neutron energies in the range of ∼ 2 – 20 MeV have been compared with the respective GEANT4 predictions. It has been found that, there is some discrepancy between the experimental and the GEANT4 simulated neutron response functions at lower pulse height regions, which increases with the increase of neutron energy. This might be due to the incompleteness of the physics processes used in the present GEANT4 simulations. In particular, higher order reaction processes which become more significant at higher energies should be properly taken into account in the calculation of response function.

Time-dependent Gutzwiller theory for multi-band Hubbard models

We formulate a multi-band generalization of the time-dependent Gutzwiller theory. This approach allows for the calculation of general two-particle response functions, which are crucial for an understanding of various experiments in solid-state physics. As a first application, we study the momentum- and frequency-resolved magnetic susceptibility in a two-band Hubbard model. As in the case of underlying ground-state approaches, we find significant differences between the results of our method and those from a time-dependent Hartree–Fock approximation.

Vibrational contributions to cubic response functions from vibrational configuration interaction response theory

In continuation of our recent paper on vibrational quadratic response functions for vibrational configuration interaction wave functions, we present in this paper a derivation and implementation of the pure vibrational cubic response function for vibrational configuration interaction wave functions. In addition, we present combined electronic and vibrational cubic response functions derived from sum-over-states expressions in the Born-Oppenheimer framework and a discussion of complicating issues. The implementation enables analytic calculation of the pure vibrational cubic response function via response theory, which constitutes a part of the vibronic cubic response function.

Technical Note: A novel approach to estimation of time-variable surface sources and sinks of carbon dioxide using empirical orthogonal functions and the Kalman filter

Abstract. In this work we propose an approach to solving a source estimation problem based on representation of carbon dioxide surface emissions as a linear combination of a finite number of pre-computed empirical orthogonal functions (EOFs). We used National Institute for Environmental Studies (NIES) transport model for computing response functions and Kalman filter for estimating carbon dioxide emissions. Our approach produces results similar to these of other models participating in the TransCom3 experiment. Using the EOFs we can estimate surface fluxes at higher spatial resolution, while keeping the dimensionality of the problem comparable with that in the regions approach. This also allows us to avoid potentially artificial sharp gradients in the fluxes in between pre-defined regions. EOF results generally match observations more closely given the same error structure as the traditional method. Additionally, the proposed approach does not require additional effort of defining independent self-contained emission regions.