Bayesian Inference Approach to Particle Size Distribution Estimation in Ferrofluids

We present an effective direct extraction method for particle size distribution based on Bayesian inference theory with a free-form model. We give an example of the application to the particle size distribution analysis in ferrofluid consisting of cobalt particles in toluene. The method gives a unique solution to the distribution without assuming the shape of the distribution of the particle size     

Imaging and 3D elemental characterization of intact bacterial spores by high-resolution secondary ion mass spectrometry

We present a quantitative, imaging technique based on nanometer-scale secondary ion mass spectrometry for mapping the 3D elemental distribution present in an individual micrometer-sized Bacillus spore. We use depth profile analysis to access the 3D compositional information of an intact spore without the additional sample preparation steps (fixation, embedding, and sectioning) typically used to access substructural information in biological samples. The method is designed to ensure sample integrity for forensic characterization of Bacillus spores. The minimal sample preparation/alteration required in this methodology helps to preserve sample integrity. Furthermore, the technique affords elemental distribution information at the individual spore level with nanometer-scale spatial resolution and high (microg/g) analytical sensitivity. We use the technique to map the 3D elemental distribution present within Bacillus thuringiensis israelensis spores.     

An Approach for Cost-Efficient Grid Integration of Distributed Renewable Energy Sources

We describe a specific approach to capacity man a ge ment for distribution grids. Based on simulations, it has been found that by curtailing a maximum of 5% of the yearly energy production on a per-generator basis, distribution grid connection capacity can be doubled. We also present the setting and fi rst results of a fi eld test for validating the approach in a rural distribution grid in northern Germany.     

Fracture statistics in the three-dimensional random fuse model

We present numerical simulations for the fracture of the three dimensional random fuse model. The damage accumulated prior to fracture follows a Gaussian distribution, suggesting the absence of long-range correlations. The strength distribution is found to be Lognormal with a logarithmic size effect for the average strength. We relate this result with the distribution of damage clusters.     

Optical encryption by using a synthesized mutual intensity function

We present an optical encryption method for handling time-varying information by means of properly designing a four-dimensional mutual intensity function distribution. We present the theory and validate the basic concept with numerical simulations and experimental results.     

Optimal processors for images with an arbitrary number of gray levels

We present a new group of processors, optimal in a maximum-likelihood sense, for target location in images with a discrete number of gray levels. The discrete gray-level distribution can be of any arbitrary form. We compare the performance of the processor derived for five discrete levels with the performance of a processor derived for a continuous Gaussian distribution and show that there are cases when only the processor derived for discrete levels will exhibit satisfactory performance. We give an explanation of this difference based on moment analysis and show how the correlation orders are related to statistical moments of the input scene.     

Information distribution at the output of angle encoders

We present analytic expressions for the density distribution for the information at the output of digital angle encoders. We show how the error in reproduction of quantization levels affects the basic information density distribution. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 18–19, May, 1995.     

Near-field intensity correlations of scattered light

We show that the two-point correlation function in the near field of scattered light is simply related to the scattered intensity distribution. We present a new, to our knowledge, optical scheme to measure the correlation function in the near field, and we describe a processing technique that permits the subtraction of stray light on a statistical basis. We present experimental data for solutions of latex spheres, and we show that this novel technique is a powerful alternative to static light scattering.     

Combining forecasts in short term load forecasting: Empirical analysis and identification of robust forecaster

We present an empirical analysis to show that combination of short term load forecasts leads to better accuracy. We also discuss other aspects of combination, i.e., distribution of weights, effect of variation in the historical window and distribution of forecast errors. The distribution of forecast errors is analyzed in order to get a robust forecast. We define a robust forecaster as one which has consistency in forecast accuracy, lesser shocks (outliers) and lower standard deviation in the distribution of forecast errors. We propose a composite ranking (CRank) scheme based on a composite score which considers three performance measures—standard deviation, kurtosis of distribution of forecast errors and accuracy of forecasts. The CRank helps in identification of a robust forecasts given a choice of individual and combined forecaster. The empirical analysis has been done with the real life data sets of two distribution companies in India.     

Process capability indices for Weibull distributions and upper specification limits

We consider a previously proposed class of capability indices that are useful when the quality characteristic of interest has a skewed, zero‐bound distribution with a long tail towards large values and there is an upper specification with a pre‐specified target value, T=0. We investigate this class of process capability indices when the underlying distribution is a Weibull distribution and focus on the situation when the Weibull distribution is highly skewed. We propose an estimator of the index in the studied class, based on the maximum likelihood estimators of the parameters in the Weibull distribution, and derive an asymptotic distribution for this estimator. Furthermore, we suggest a decision rule based on the estimated index and its asymptotic distribution and present a power comparison between the proposed estimator and a previously studied estimator. A simulation study is also performed to investigate the true significance level when the sample size is small or moderate. An example from a Swedish industry is presented. Copyright © 2008 John Wiley & Sons, Ltd.     

Frequency domain modeling of reradiation in highly scattering media

We present a straightforward procedure for frequency domain modeling of reradiation in a highly scattering medium with an arbitrary, finite three-dimensional geometry. We use a finite difference numerical solver to determine the fluence distribution at the excitation wavelength, which is then coupled to the emission wavelength with an array of equivalent reradiating sources. We then calculate the fluence distribution at the emission wavelength with a second, independent numerical simulation with new optical parameters appropriate to the emission wavelength, using the distributed reradiating sources as the excitation. We compare three-dimensional simulations of a fluorophore distributed in a scattering medium with experimental data. We also compare simulations of the Raman reradiation of small diamonds in a scattering medium with experiment.     

Efficient mode transformations of degenerate Laguerre-Gaussian beams

We present an approach for efficient conversion of a single-high-order-mode distribution from a laser to a nearly Gaussian distribution and vice versa. It is based on dividing the high-order mode distribution into equal parts that are then combined together coherently. We implement our approach with several optical arrangements that include a combination of discrete elements and some with single interferometric elements. These arrangements are analyzed and experimentally evaluated for converting the TEM01 mode distribution with Mx(2) = 3 to a nearly Gaussian beam with Mx(2) = 1.045 or Mx(2) = 1.15. The basic principle, design, and experimental results obtained with several conversion arrangements are presented. The results reveal that conversion efficiency is typically greater than 90%, compared with theoretical ones. In addition, some arrangement is exploited for converting the fundamental Gaussian-beam distribution into the TEM01 mode distribution.     

The multiple lot sizing problem with rigid demand and interrupted geometric yield

We study the multiple lot sizing problem with interrupted geometric yield distribution. Compared to the binomial and discrete uniform yields, the lot sizing problem with interrupted geometric distribution is less studied. We present results characterizing the behavior of the cost function and optimal lot sizes. These results help us understand the imperfect processes described by the interrupted geometric distribution. We also develop bounds which lead to an efficient numerical procedure with an approximately linear computation time for large problems.     

The propagation of radiation in capillary-porous colloidal bodies

We present a solution for the problem of the distribution of spectral radiation fluxes through the thickness of a layer and the quantity of radiant energy absorbed by the elementary layers at a specific depth in capillary-porous colloidal bodies. We have demonstrated that the solution is found to be in good agreement with experiment.     

Quantifying Uncertainty in Lumber Grading and Strength Prediction: A Bayesian Approach

This article presents a joint distribution for the strength of a randomly selected piece of structural lumber and its observable characteristics. In the process of lumber strength testing, these characteristics are ascertained under strict grading protocols, as they have the potential to be strength reducing. However, for practical reasons, only a few such selected characteristics among the many present, are recorded. We present a data-generating mechanism that reflects the uncertainties resulting from the grading protocol. A Bayesian approach is then adopted for model fitting and construction of a predictive distribution for strength that accounts for the unrecorded characteristics. The method is validated on simulated examples, and then applied on a sample of specimens tested for bending and tensile strength. Use of the predictive distribution is demonstrated, and insights gained into the grading process are described. Details of the lumber testing experiments can be found in the online supplementary materials.     

Application of a forward-angle-scattering transmissometer for simultaneous measurements of particle size and number density in an optically dense medium

We consider the multiple-scattering and forward-scattering corrections to the transmission measurements in the case of a detector with a variable field of view. The transmission functions for predicting the angular distribution of forward-scattering transmittance are proposed. We present results of measurements of transmission functions for polystyrene spheres. Numerical estimations of the forward-multiple-scattering corrections are in good agreement with the experimental results.     

Photon Correlation Measurement of Ion Oscillation Frequencies in a Combined Trap

Abstract

We present experimental verification of the oscillation frequencies of magnesium ions in a combined trap for a wide range of a.c. voltages and magnetic fields. We employ a new technique to measure these trap resonances using the distribution of time intervals between consecutively detected fluorescence photons.     

Determination of particle size by using the angular distribution of backscattered light as measured with low-coherence interferometry

We employ a novel interferometer to measure the angular distribution of light backscattered by a turbid medium. Through comparison of the measured data with the predictions of Mie theory, we are able to determine the size of the scatterers comprising the medium with subwavelength precision. As the technique is based on low-coherence interferometry, we are able to examine the evolution of the angular distribution of scattered light as it propagates into the medium. The effects of multiple scattering as a function of penetration depth in the medium are analyzed. We also present various considerations for extending this technique to determining structural information in biological tissues, such as the effects of a distribution of particle sizes and the need to average out speckle contributions.     

Profiling of micrometer-sized laser beams in restricted volumes

We present a method for determining the three-dimensional intensity distribution of directed laser radiation with micrometer resolution in restricted volumes. Our method is based on the incoupling and guiding properties of optical fibers, with the current version requiring only a few hundred micrometers across the measuring volume. We characterize the performance of the method and experimentally demonstrate profiling of micrometer-sized laser beams. We discuss the limiting factors and routes toward a further increase of the resolution and beam profiling in even more restricted volumes. Finally, as an application example, we present profiling of laser beams inside a micro ion trap with integrated optical fibers.     

Reverse phase contrast: an experimental demonstration

We present experimental results showing that the reverse phase contrast (RPC) technique is a viable method for the generation of a binary phase distribution from a spatially varying amplitude pattern using Fourier plane filtering techniques. Experimental results are shown for the generation of a binary 0-pi phase only distribution using either an amplitude mask or a spatial light modulator to provide the input and the results are shown to be in agreement with theoretical predictions for the RPC technique.