Maximum-likelihood estimation of circle parameters via convolution.

The accurate fitting of a circle to noisy measurements of circumferential points is a much studied problem in the literature. In this paper, we present an interpretation of the maximum-likelihood estimator (MLE) and the Delogne-K?sa estimator (DKE) for circle-center and radius estimation in terms of convolution on an image which is ideal in a certain sense. We use our convolution-based MLE approach to find good estimates for the parameters of a circle in digital images. In digital images, it is then possible to treat these estimates as preliminary estimates into various other numerical techniques which further refine them to achieve subpixel accuracy. We also investigate the relationship between the convolution of an ideal image with a "phase-coded kernel" (PCK) and the MLE. This is related to the "phase-coded annulus" which was introduced by Atherton and Kerbyson who proposed it as one of a number of new convolution kernels for estimating circle center and radius. We show that the PCK is an approximate MLE (AMLE). We compare our AMLE method to the MLE and the DKE as well as the Cramér-Rao Lower Bound in ideal images and in both real and synthetic digital images.     

3D Generative Model Latent Disentanglement via Local Eigenprojection

Designing realistic digital humans is extremely complex. Most data-driven generative models used to simplify the creation of their underlying geometric shape do not offer control over the generation of local shape attributes. In this paper, we overcome this limitation by introducing a novel loss function grounded in spectral geometry and applicable to different neural-network-based generative models of 3D head and body meshes. Encouraging the latent variables of mesh variational autoencoders (VAEs) or generative adversarial networks (GANs) to follow the local eigenprojections of identity attributes, we improve latent disentanglement and properly decouple the attribute creation. Experimental results show that our local eigenprojection disentangled (LED) models not only offer improved disentanglement with respect to the state-of-the-art, but also maintain good generation capabilities with training times comparable to the vanilla implementations of the models. Our code and pre-trained models are available at github.com/simofoti/LocalEigenprojDisentangled .     

Enhancing Prony’s method by nuclear norm penalization and extension to missing data

Prony’s method is a widely used method for modelling signals using a finite sum of exponential terms. It has innumerable applications in weather modelling, finance, medical signal analysis, image compression, time series analysis, power grids, etc. Prony’s method has, however, the reputation of being unstable with respect to noise perturbations. The goal of the present paper is to assess the potential improvements of a nuclear-norm-penalized regularization of Prony’s method. The nuclear norm regularization is a standard technique for improving the performance when processing noisy signals with low-rank underlying structure such as in matrix completion, matrix compressed sensing, hidden variable models. We consider both the standard setting and the case of missing data. We provide a fast estimation algorithm for the nuclear-norm-penalized least-squares minimization. Monte Carlo experiments show that regularization can significantly enhance the performance of Prony’s method with and without missing data.     

Process models in design and development

Many models of the design and development process have been published over the years, representing it for different purposes and from different points of view. This article contributes an organising framework that clarifies the topology of the literature on these models and thereby relates the main perspectives that have been developed. The main categories of model are introduced. Their contexts, advantages, and limitations are considered through discussion of selected examples. It is demonstrated that the framework integrates coverage of earlier reviews and as such provides a new perspective on the literature. Finally, key characteristics of design and development process models are discussed considering their applications in practice, and opportunities for further research are suggested. Overall, the article should aid researchers in positioning new models and new modelling approaches in relation to state-of-the-art. It may also be of interest to practitioners and educators seeking an overview of developments in this area.     

Estimation receiver operating characteristic curve and ideal observers for combined detection/estimation tasks

The localization receiver operating characteristic (LROC) curve is a standard method to quantify performance for the task of detecting and locating a signal. This curve is generalized to arbitrary detection/estimation tasks to give the estimation ROC (EROC) curve. For a two-alternative forced-choice study, where the observer must decide which of a pair of images has the signal and then estimate parameters pertaining to the signal, it is shown that the average value of the utility on those image pairs where the observer chooses the correct image is an estimate of the area under the EROC curve (AEROC). The ideal LROC observer is generalized to the ideal EROC observer, whose EROC curve lies above those of all other observers for the given detection/estimation task. When the utility function is nonnegative, the ideal EROC observer is shown to share many mathematical properties with the ideal observer for the pure detection task. When the utility function is concave, the ideal EROC observer makes use of the posterior mean estimator. Other estimators that arise as special cases include maximum a posteriori estimators and maximum-likelihood estimators.     

A wavelet-based method of measuring fluctuating harmonics for determining the filter time constant of IEC standard harmonic analyzers

Harmonic analyzers are used to test the fluctuating harmonic emissions of electrical appliances to international regulations. This paper describes a wavelet-based method of measuring level-changing harmonics (bursts) for use in the calibration of these analyzers. The method is shown to be reliable for measuring various mixtures of harmonics. The importance of calibrating harmonic analyzers under conditions of fluctuating harmonics is discussed.     

Objective comparison of quantitative imaging modalities without the use of a gold standard

Imaging is often used for the purpose of estimating the value of some parameter of interest. For example, a cardiologist may measure the ejection fraction (EF) of the heart in order to know how much blood is being pumped out of the heart on each stroke. In clinical practice, however, it is difficult to evaluate an estimation method because the gold standard is not known, e.g., a cardiologist does not know the true EF of a patient. Thus, researchers have often evaluated an estimation method by plotting its results against the results of another (more accepted) estimation method, which amounts to using one set of estimates as the pseudogold standard. In this paper, we present a maximum-likelihood approach for evaluating and comparing different estimation methods without the use of a gold standard with specific emphasis on the problem of evaluating EF estimation methods. Results of numerous simulation studies will be presented and indicate that the method can precisely and accurately estimate the parameters of a regression line without a gold standard, i.e., without the x axis.     

ResultMaps: Visualization for Search Interfaces

Hierarchical representations are common in digital repositories, yet are not always fully leveraged in their onlinesearch interfaces. This work describes ResultMaps, which use hierarchical treemap representations with query string-driven digital library search engines. We describe two lab experiments, which find that ResultsMap users yield significantly better results over a control condition on some subjective measures, and we find evidence that ResultMaps have ancillary benefits via increased understanding of some aspects of repository content. The ResultMap system and experiments contribute an understanding of the benefits—direct and indirect—of the ResultMap approach to repository search visualization.     

Topology/shape optimisation of axisymmetric continuum structures – a metamorphic development approach

A novel topology/shape optimisation method for axisymmetric elastic solids, based on solid modeling and FE analysis, is presented. Optimal profiles of minimum-mass axisymmetric structures are sought by growing and degenerating simple initial structures subject to response constraints. The rates of the growth and degeneration are controlled based on the current objective and constraint functions of the optimisation problem under consideration. The optimal structures are developed metamorphically in specified infinite design domains using both quadrilateral and triangular axisymmetric finite elements that are ideally suited for modeling continua involving curved boundaries.The robustness of this fully automatic method is studied and validated with the first example of seeking the optimal shape of a centrally suspended axisymmetric object with minimum strain energy caused by self-weight. Then the method is applied to a practical industrial design problem: the design of a turbine disk. The variations of load and boundary conditions caused by shape change in these problems, including the gravitational and centrifugal loads, and temperature distribution are accommodated in the optimisation procedures. Thus, the design model closely resembles the real design problem. The results demonstrate the success of the method in generating optimal but realistic solutions to practical design problems.     

Evaluation of a fluorescent derivative of AMD3100 and its interaction with the CXCR4 chemokine receptor

AMD3100 is a potent and selective antagonist of the CXCR4 receptor; it has been shown to block the route of entry of HIV into host T-cells. This compound and its analogues have since been found to act as haematopoietic stem cell mobilisation agents and, more recently, as anti-cancer agents. Here, we have examined a fluorescent derivative of AMD3100, L(1), which offered the potential to assess the behaviour of AMD3100 at the cell surface by using optical imaging modalities. The binuclear Zn(II) , Cu(II) and Ni(II) complexes of L(1) have also been investigated as these metals have been previously shown to enhance the binding properties of AMD3100. Furthermore, Zn(II) and Cu(II) are known to enhance and quench, respectively, the fluorescence of similar anthracenyl-based ligands. Whilst L(1) demonstrates an ability to inhibit the binding of the anti-CXCR4 monoclonal antibody 12G5 (IC(50) =0.25-0.9 μM), the incorporation of an anthracenyl moiety resulted in a significantly reduced affinity for CXCR4 compared to AMD3100 (IC(50) =10 nM). We observed no significant increase in fluorescence intensity following incubation with murine pre-B cells overexpressing CXCR4 compared to a control cell line. This limits the usefulness of L(1) as a fluorescent imaging probe. Interestingly, the Zn(II) complex, which carries an overall +4 charge, revealed marginally higher specificity and reduced toxicity in vitro compared to the free ligand, albeit with reduced affinity for CXCR4 (IC(50) =1.8-5 μM). We suggest that the incorporation of an anthracenyl group contributes to the lipophilic character of the free ligand, thereby resulting in transport across the plasma membrane. This effect is seemingly diminished when the ligand is complexed to charged metal ions.