Adaptive staircase techniques in psychoacoustics: a comparison of human data and a mathematical model

Data from a simple tone-in-noise simultaneous masking task were used to evaluate each of two common adaptive staircase rules (a "1 up 2 down" rule and a "1 up 3 down" rule) and the parameter estimation by sequential testing (PEST) technique in combination with each of two psychophysical procedures [a two-alternative forced-choice (2AFC) and a three-alternative forced-choice (3AFC) procedure]. These human data were compared to predictions generated by a mathematical model based on Markov theory. The model predicts that threshold estimates obtained with the adaptive techniques should be equal to those derived with equivalent "fixed signal level" techniques. However, the human data indicate that the adaptive techniques tend to yield lower thresholds. The model predicts that the standard error of a threshold estimate obtained from an adaptive technique will decrease and approach zero as the number of trials used to compute the estimate increases. The human data show greater variability than predicted and approach a nonzero value as the number of trials increases. The predictions of the model suggest that the commonly used combination of the 2AFC procedure and the 1 up 2 down rule is the least efficient method of estimating a threshold and that the 3AFC procedure in combination with the 1 up 3 down rule is the most efficient method. The human data are less consistent, but generally show the combination of the 2AFC procedure and the 1 up 2 down rule to be one of the least efficient methods. Possible explanations for the differences between the model's predictions and the human data, as well as suggestions for laboratory practice, are discussed.     

MtsslWizard: In Silico Spin-Labeling and Generation of Distance Distributions in PyMOL

MtsslWizard is a computer program, which operates as a plugin for the PyMOL molecular graphics system. MtsslWizard estimates distances between spin labels on proteins quickly with user-configurable options through a simple graphical interface. In default mode, the program searches for ensembles of possible MTSSL conformations that do not clash with a static model of the protein. Once conformations are assigned, distance distributions between two or more ensembles are calculated, displayed, and can be exported to other software. The program’s use is evaluated in a number of challenging test cases and its strengths and weaknesses evaluated. The benefits of the program are its accuracy and simplicity.     

Achievable accuracy of parameter estimation for multidimensional NMR experiments

A fundamental issue in NMR spectroscopy is the estimation of parameters such as the Larmor frequencies of nuclei, J coupling constants, and relaxation rates. The Cramer-Rao lower bound provides a method to assess the best achievable accuracy of parameter estimates resulting from an unbiased estimation procedure. We show how the Cramer-Rao lower bound can be calculated for data obtained from multidimensional NMR experiments. The Cramer-Rao lower bound is compared to the variance of parameter estimates for simulated data using a least-squares estimation procedure. It is also shown how our results on the Cramer-Rao lower bound can be used to analyze whether an experimental design can be improved to provide experimental data which can result in parameter estimates with higher accuracy. The concept of nonuniform averaging in the indirect dimension is introduced and studied in connection with nonuniform sampling of the data.     

基于生成函数方法的现实网络座键渗流建模

基于生成函数方法针对现实网络构建座键渗流模型, 并应用于4种有代表性的具体网络, 检验其对关键渗流指标估计的精确程度, 讨论模型估计误差成因, 同时给出其简单应用。所得现实网络渗流模型可应用于估计各类现实网络承受点边打击之后的连通状态, 也可以用来评估现实网络的整体抗毁程度。该模型处理过程简单, 预测结果精度与信息传播算法的结果精度相比可以被接受, 其计算用时则远低于信息传播算法, 具备很好的应用潜力。     

Auditory-nerve first-spike latency and auditory absolute threshold: a computer model

A computer model of the auditory periphery was used to address the question of what constitutes the physiological substrate of absolute auditory threshold. The model was first evaluated to show that it is consistent with experimental findings that auditory-nerve fiber spikes can be predicted to occur when the running integral of stimulus pressure reaches some critical value [P. Heil and H. Neubauer, J. Neurosci. 15, 7404-7415 (2001)]. It was then modified to examine two ways in which the accumulation and clearance of receptor presynaptic calcium might explain this effect. Both methods gave results that matched the animal data. It was also shown how the rate of clearance of presynaptic calcium could be used to explain the origin of differences between low and high spontaneous-rate fiber types. When spiking activity is aggregated across a number of similar high spontaneous-rate fibers and used as the input to a model of a cochlear nucleus coincidence neuron, its response can be used to judge whether or not a stimulus is present. A simulated psychophysical experiment then demonstrated that this simple decision procedure can reproduce measurements of absolute auditory threshold for tones in quiet where the threshold is a joint function of both time and level.     

Full Automation of Quantitation of in Vivo NMR by LPSVD(CR) and EPLPSVD

A full automatic and reliable method for NMR quantification is proposed. It is based on the linear prediction singular-value decomposition with continuous regularization [LPSVD(CR)] and on the enhancement procedure (EP) followed by LPSVD (EPLPSVD). Advantages of both methods have been considered. LPSVD(CR) has been used to find a good estimate for the number of spectral components. A significance test allows refining this number, which is then used in the EPLPSVD method. A Monte Carlo study has proved that EPLPSVD is a maximum-likelihood estimator. This new algorithm leads to reliable estimates for the spectral parameters even for signals with a low signal-to-noise ratio. No a priori knowledge is needed.     

Analysis of Connection Availability in an All-Optical Mesh Network

This paper presents the method of an availability performance analysis that can be used for all-optical networks. We compare different schemes of protection and restoration in a fully connected mesh network based on optical cross-connects, optical fibers, and fiber amplifiers. Specifically treated is an optical mesh network physically mapped onto a Scandinavian backbone. In order to compare different survivability strategies, we selected two nodes located roughly 420 km apart. The goal of this work is to point out possible ways to improve connection availability. A number of survivability schemes are compared, for which the availability model of logical connection is derived and a calculation procedure is described. Our results show that unprotected schemes cannot ascertain reasonably high requirements on connection availability in the backbone network. Thus, if a redundant structure of logical connection is considered, the particular survivability scheme should be evaluated in order to maximize connection availability.     

Operator product expansions in the massless Schwinger model

The known operator solution of the massless Schwinger model is used to calculate exactly, in three operator product expansions, the coefficient functions of the first few operators of low dimension which contribute when vacuum matrix elements are to be taken. A comparison of the results provides a test of the procedure used by M. A. Shifman, A. I. Vainshtein, and V. I. Zakharov [Nucl. Phys. B147 (1979), 385–447] in their study of QCD. It is found that the shift in vacua does not affect the calculation of coefficient functions. The vacuum insertion approximation yields somewhat misleading estimates of vacuum expectation values of some composite operators; however, the standard method used to estimate the errors of vacuum insertion indicates that the approximation is unreliable in this model.     

How accurately can the parameters from a model of anisotropic 3He gas diffusion in lung acinar airways be estimated? Bayesian view

In the framework of a recently proposed method for in vivo lung morphometry, acinar lung airways are considered as a set of randomly oriented cylinders covered by alveolar sleeves. Diffusion of (3)He in each airway is anisotropic and can be described by distinct longitudinal and transverse diffusion coefficients. This macroscopically isotropic but microscopically anisotropic model allows estimation of these diffusion coefficients from multi b-value MR experiments despite the airways being too small to be resolved by direct imaging. Herein a Bayesian approach is used for analyzing the uncertainties in the model parameter estimates. The approach allows evaluation of relative errors of the parameter estimates as functions of the "true" values of the parameters, the signal-to-noise ratio, the maximum b-value and the total number of b-values used in the experiment. For a given set of the "true" diffusion parameters, the uncertainty in the estimated diffusion coefficients has a minimum as a function of maximum b-value and total number of data points. Choosing the MR pulse sequence parameters corresponding to this minimum optimizes the diffusion MR experiment and gives the best possible estimates of the diffusion coefficients. The mathematical approach presented can be generalized for models containing arbitrary numbers of estimated parameters.     

Further assessment of forward pressure level for in situ calibration

Quantifying ear-canal sound level in forward pressure has been suggested as a more accurate and practical alternative to sound pressure level (SPL) calibrations used in clinical settings. The mathematical isolation of forward (and reverse) pressure requires defining the The?venin-equivalent impedance and pressure of the sound source and characteristic impedance of the load; however, the extent to which inaccuracies in characterizing the source and/or load impact forward pressure level (FPL) calibrations has not been specifically evaluated. This study examined how commercially available probe tips and estimates of characteristic impedance impact the calculation of forward and reverse pressure in a number of test cavities with dimensions chosen to reflect human ear-canal dimensions. Results demonstrate that FPL calibration, which has already been shown to be more accurate than in situ SPL calibration, can be improved particularly around standing-wave null frequencies by refining estimates of characteristic impedance. Better estimates allow FPL to be accurately calculated at least through 10 kHz using a variety of probe tips in test cavities of different sizes, suggesting that FPL calibration can be performed in ear canals of all sizes. Additionally, FPL calibration appears a reasonable option when quantifying the levels of extended high-frequency (10-18 kHz) stimuli.     

Prediction of speech intelligibility for public address systems in traffic tunnels

Traffic tunnels are generally hostile acoustic environments, both in terms of reverberation and ambient noise levels. Public address (PA) systems used to convey spoken warnings must meet stringent design requirements in order to produce sufficiently intelligible speech. To be able to predict PA system performance at tunnel design time, two different speech transmission index (STI) calculation procedures were implemented. The first procedure predicts the STI based on ray-tracing simulations. Comparison with measured STI data showed that this simulation approach yields accurate intelligibility estimates. However, the procedure is time-consuming and too complex to be used by non-specialists. For this reason, a second (simpler and more efficient) procedure was developed, based on fixed non-linear regression, statistically deriving prediction functions from measured data and ray-tracing results. This procedure was compared to the approach based on ray tracing, and found to yield STI predictions closely matching those of the ray-tracing model.     

A bag model study ofD mesons

An investigation of the newly discovered charmed mesonsD 0 andD +, particularly their non-leptonic decay modes, is carried out in the framework of the MIT bag model. The amplitude for a number of two-body final state decays are explicitly evaluated and compared with other available estimates.     

Sequentially Estimating the Approximate Conditional Mean Using Extreme Learning Machines

This study examined the extreme learning machine (ELM) applied to the Wald test statistic for the model specification of the conditional mean, which we call the WELM testing procedure. The omnibus test statistics available in the literature weakly converge to a Gaussian stochastic process under the null that the model is correct, and this makes their application inconvenient. By contrast, the WELM testing procedure is straightforwardly applicable when detecting model misspecification. We applied the WELM testing procedure to the sequential testing procedure formed by a set of polynomial models and estimate an approximate conditional expectation. We then conducted extensive Monte Carlo experiments to evaluate the performance of the sequential WELM testing procedure and verify that it consistently estimates the most parsimonious conditional mean when the set of polynomial models contains a correctly specified model. Otherwise, it consistently rejects all the models in the set.     

Monte carlo estimates of domain-deformation sensitivities

It is shown that, when a Monte Carlo algorithm is used for estimation of any physical quantity A, a simple and fast additional procedure can be implemented that simultaneously estimates the sensitivity of A to any problem parameter. The proposed approach is general and systematic in the sense that: (i) it includes domain-deformation sensitivities, i.e., cases where a change in the parameter modifies the domain over which the sampled random variables are defined and (ii) a simple generic procedure is presented to address all remaining free choices in terms of variance minimization.     

Multivariate analysis of multiple impedance spectra

A one-step method for evaluation of multiple impedance measurements in a multivariate analysis is presented. Usually two steps are necessary to extract model parameters like activation energy from impedance measurements at two or more temperatures. First, each measurement is analyzed with CNLS (complex nonlinear least squares) software using the same equivalent circuit. Second, activation energy is obtained in a NLS fit of conductivity data. This two-step procedure could lead to doubtful results as fit errors because of noise in the first step could prevent reliable results in the second step. Error estimates of model parameters are only based on the second step, ignoring the quality of the first step. Using a one-step method, model parameters are directly obtained from multiple impedance measurements, often resulting in more reliable results and meaningful error estimates than for the two-step procedure. Similar approaches to the one proposed have been reported in literature. Although some approaches are reported to be implemented in a software package, none of these are available to the community. The aim of this paper is to clearly point out the mathematics used and the benefits of a simultaneous analysis of impedance spectra.     

基于帧间预测的红外焦平面阵列非均匀校正算法

提出了一种基于帧间预测的非均匀校正算法,它可以通过场景配准从当前已校正图像中估计出下一帧未校正图像的真值,然后将所得的场景估计与相应的噪音图像用于线性拟合,其拟合参量即可用来进行非均匀校正.该方法的主要优点在于抗噪音能力强,预测准确度高,且能够实时处理.详细阐述了算法的基本原理及其流程,并用真实红外数据对算法性能进行验证,取得了较好的效果.     

Comparative analysis of Reaction-Diffusion Manifold based reduced models for Head-On- and Side-Wall-Quenching flames

In this study, multi-dimensional molecular transport phenomena during Flame-Wall-Interactions (FWI) and their effects on model reduction strategies are investigated. In order to access the problem, the standard configurations of a two-dimensional Side-Wall Quenching (SWQ) flame and a one-dimensional Head-On Quenching (HOQ) flame are used and compared. In the case of the SWQ configuration it is shown that the gradients of the species scatter significantly both in the physical space and in the state space. Moreover, the gradient vector of the specific enthalpy describing energy losses towards the wall is not aligned with the gradient vectors of the species, which can be considered as a typical case while a flame in application might approach to the wall at any arbitrary transversal direction. This observation motivates to take the gradients’ scattering and multi-dimensional transport phenomena into account during model reduction to describe reliably the quenching process.The Reaction-Diffusion Manifold (REDIM) method is applied in this work. The method allows to take into account multi-dimensional transport in a very generic way. In order to generate the REDIM, gradient estimates are approximated by using a Singular-Value Decomposition (SVD) of SWQ detailed gradients fields. Two-dimensional REDIMs for both cases are constructed and compared to each other. Different transport (diffusion) models are implemented to compare quantitatively the manifolds with HOQ and SOQ gradients estimates. The comparison shows that the differences between reduced models with varying transport models is significantly larger than the differences for varying configurations (multidimensional gradient estimates). This justifies the use of a relatively simple REDIM for more complicated geometries and configurations. This simplifies the treatment and model reduction procedure significantly for such complicated transient phenomena.     

Measurements and calculations on the simple up-down adaptive procedure for speech-in-noise tests

The simple up-down adaptive procedure is a common method for measuring speech reception thresholds. It is used by the Dutch speech-in-noise telephone screening test [National Hearing test; Smits and Houtgast Ear Hear. 26, 89-95 (2005)]. The test uses digit triplets to measure the speech reception threshold in noise by telephone (SRTT(n)). About 66 000 people took this test within four months of its introduction and details were stored of all individual measurements. Analyses of this large volume of data have revealed that the standard deviation of SRTT(n) estimates increases with hearing loss. This paper presents a calculation model which--using an intelligibility function as input--can determine the standard deviation of SRTT(n) estimates and the bias for the simple up-down procedure. The effects of variations in the slope of the intelligibility function, the guess rate, the starting level, the heterogeneity of the speech material, and the possibilities of optimizing SRTT(n) measurements were all explored with this model. The predicted decrease in the standard deviation of SRTT(n) estimates as a result of optimizing the speech material was confirmed by measurements in 244 listeners. The paper concludes by discussing possibilities for optimizing the development of comparable tests.     

Applicability of the multi-reference double-excitation CI (MRD-CI) method to the calculation of electronic wavefunctions and comparison with related techniques

Implementation of a multi-reference double-excitation CI (MRD-CI) method is discussed and its results are compared with those of related techniques. This approach employs a configuration selection procedure to order the various generated species according to their energy-lowering capability and then uses an energy extrapolation procedure based on perturbation theory to obtain suitably accurate estimates of the eigenvalues of the entire MRD-CI space. By employing this selection procedure it is possible to test from 2000 to 4000 symmetry-adapted functions (SAF's) per second of CPU time on an IBM 370–168 system, thereby allowing one to apply the energy extrapolation quite conveniently to CI spaces consisting of several hundred thousand species. By systematically increasing the number of reference configurations in the MRD-CI it is clear that the limit of a full CI can be approached and as a result such a computational procedure appears to be generally valid for any type of electronic state and for any nuclear geometry as well as being quite practical. Applications to a number of molecular systems are considered and comparison is made with the results of other theoretical techniques presently available, from which studies it is concluded that the MRD-CI can account for roughly 95 per cent of the total valence-shell correlation attainable with a given AO basis while still employing a relatively small number of reference configurations to generate the associated CI space.     

DETERMINATION OF ELASTIC CONSTANTS OF ANISOTROPIC LAMINATED PLATES USING ELASTIC WAVES AND A PROGRESSIVE NEURAL NETWORK

In this paper, a procedure is suggested to inversely determine the elastic constants of anisotropic laminated plates using a progressive neural network (NN). The surface displacement responses are used as the inputs for the NN model. The outputs of the NN are the elastic constants of anisotropic laminated plates. The hybrid numerical method (HNM) is used to calculate the displacement responses of laminated plates to an incident wave for given elastic constants. The NN model is trained using the results from the HNM. A modified back-propagation learning algorithm with a dynamically adjusted learning rate and an additional jump factor is developed to tackle the possible saturation of the sigmoid function and to speed up the training process for the NN model. The concept of orthogonal array was adopted to generate the representative combinations of elastic constants, which reduces significantly the number of training data while maintaining its data completeness. Once trained, the NN model can be used for on-line determination of the elastic constants if the dynamic displacement responses on the surface of the laminated plate can be obtained. The determined elastic constants are then used in the HNM to calculate the displacement responses. The NN model would go through a progressive retraining process until the calculated displacement responses using the determined results are sufficiently close to the actual responses. This procedure is examined for an actual glass/epoxy laminated plate. It is found that the present procedure is very robust and efficient for determining the elastic constants of anisotropic laminated plates.