On the robustness of parameter estimation of superimposed signalsby dynamic programming

We analyze a recently proposed dynamic programming algorithm (REDP) for maximum likelihood (ML) parameter estimation of superimposed signals in noise. We show that it degrades gracefully with deviations from the key assumption of a limited interaction signal model (LISMO), providing exact estimates when the LISMO assumption holds exactly. In particular, we show that the deviations of the REDP estimates from the exact ML are continuous in the deviation of the signal model from the LISMO assumption. These deviations of the REDP estimates from the MLE are further quantified by a comparison to an ML algorithm with an exhaustive multidimensional search on a lattice in parameter space. We derive an explicit expression for the lattice spacing for which the two algorithms have equivalent optimization performance, which can be used to assess the robustness of REDP to deviations from the LISMO assumption. The values of this equivalent lattice spacing are found to be small for a classical example of superimposed complex exponentials in noise, confirming the robustness of REDP for this application     

A mixed-mode crack analysis of rectilinear anisotropic solids using conservation laws of elasticity

A very simple and convenient method of analysis for studying two-dimensional mixed-mode crack problems in rectilinear anisotropic solids is presented. The analysis is formulated on the basis of conservation laws of anisotropic elasticity and of fundamental relationships in anisotropic fracture mechanics. The problem is reduced to a system of linear algebraic equations in mixed-mode stress intensity factors. One of the salient features of the present approach is that it can determine directly the mixed-mode stress intensity solutions from the conservation integrals evaluated along a path removed from the crack-tip region without the need of solving the corresponding complex near-field boundary value problem. Several examples with solutions available in the literature are solved to ensure the accuracy of the current analysis. This method is further demonstrated to be superior to other approaches in its numerical simplicity and computational efficiency. Solutions of more complicated and practical engineering problems dealing with the crack emanating from a circular hole in composites are presented also to illustrate the capacity of this method.

---

Résumé On présente une méthode d'analyse simple et bien adaptée à l'étude de problèmes de fissuration bidimensionnelle de mode mixte dans des solides rectilinéaires anisotropes. L'analyse est formulée sur la base des lois de conservation de l'élasticité anisotrope et sur les relations fondamentales dans la mécanique de rupture anisotrope. Le problème est ramené à un système d'équations algébriques linéaires exprimant les facteurs d'intensité d'entaille pour un mode mixte. L'un des faits saillants de l'approche envisagée est qu'elle peut déterminer directement les solutions d'intensité de contrainte suivant un mode mixte à partir des intégrales de conservation évaluées le long d'un parcours éloigné par rapport à l'extrémité de la fissure, sans qu'il soit nécessaire de résoudre le problème correspondant de la valeur du champ proche complexe. Divers exemples, ainsi que des solutions disponibles dans la littérature, sont résolus et confrontés en vue de tester la fiabilité de l'analyse réalisée. La méthode s'avère supérieure aux autres approches de par sa simplicité numérique et son efficacité de calcul. Des solutions à des problèmes plus compliqués et pratiques rencontrés en ingénièrie où une fissure émane d'un trou circulaire dans des matières composites sont également présentées, en vue d'illustrer les capacités de cette méthode.

     

Derivation of optimal processing parameters of polypropylene foam thermoforming by an artificial neural network

The effects of processing parameters on the thermoforming of polymeric foam sheets are highly nonlinear and fully coupled. The complex interconnection of these dominant processing parameters makes the process design a difficult task. In this study, the optimal processing parameters of polypropylene foam thermoforming are obtained by the use of an artificial neural network. Data from tests carried out on a lab‐scale thermoforming machine were used to train an artificial neural network, which serves as an inverse model of the process. The inverse model has the desired product dimensions as inputs and the corresponding processing parameters as outputs. The structure, together with the training methods, of the artificial neural network is also investigated. The feasibility of the proposed method is demonstrated by experimental manufacturing of cups with optimal geometry derived from the finite element method. Except the dimension deviation at one location, which amounts to 17.14%, deviations of the other locations are all below 3.5%. POLYM. ENG. SCI., 45:375–384, 2005. © 2005 Society of Plastics Engineers     

Thermomagnetic nernst effect in an electrolytic system

A phenomenological theory for thermomagnetic effect in an electrolyte system is worked out. A sinusoidal variation of the induced emf is observed perpendicular to the heat flow when an external magnetic field is applied to the system, across the flow with varying angles. The experimental results are found in good agreement with the presented theory in HNO₃ (900 × 10^?4 M). Planar Nernst effect is therefore measured and the coefficient γ is estimated.     

Arterial elastin synthesis in the young chick

In the growing chick a marked stimulation in soluble and mature arterial elastin synthesis occurs 2 and 5 weeks after hatching. Measurement of [3H]valine and [3H]proline incorporation into arterial soluble protein during this period indicated that most of the label is found in a 70 000 dalton protein subunit. The labeled soluble subunit had the characteristics of native soluble elastin or tropoelastin. During the period in which the greatest percentage increase in mature elastin occurs, the highest specific activities of soluble [3H]valine-labeled protein were observed. These changes were striking and suggest a developmental period for the growing chick in which factors related to elastin metabolism may be more easily studied.     

Ego impairment in schizophrenia as reflected in the Object Sorting Test.

Matched groups of schizophrenics and neurotics (a group which also included personality disorders), were compared on their performance on the Object Sorting Test. The schizophrenics could be significantly differentiated from the neurotics (and personality disorders) by virtue of their conceptualizations involving open-private ideas (à la McGaughran and Moran, 1956), inappropriate sorting, peculiar verbalizations, and perseverative thinking. The results are related to ego impairment in schizophrenia, and add to the capacity of this test of conceptual thinking to distinguish the thinking activity of schizophrenics from that of most other psychiatric patients. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluating the effectiveness of a participatory ergonomics approach in reducing the risk and severity of injuries from manual handling

Manual handling is the greatest contributor to non-fatal injury and disease in the workplace, commonly accounting for one-third of national injury counts. Interventional strategies that have focused on selecting or modifying the worker have been ineffective in reducing injury risk. In recent times, participatory ergonomics has been widely adopted as a process to reduce the risk of injury from manual handling but it is not well validated as an intervention. This study evaluated the effectiveness of a participatory ergonomics risk assessment approach in reducing the rate and severity of injuries from manual and non-manual handling sustained by a cohort of 137 cleaners within a hospital setting. The date of injury and the workers' compensation claim cost and hours lost from work were obtained for each injury incurred during the 4-year pre-intervention and 3-year intervention period. The age, gender and hours worked were ascertained for every cleaner whether injured or not. Using generalized linear mixed modelling analysis, reductions of rate of injury by two-thirds, workers' compensation claim costs by 62% and hours lost by 35% for manual handling injuries were found to be associated with the intervention period. Although the cleaners experienced a significant intervention period reduction in non-manual handling injury rate, the corresponding changes in severity of injury were not significant. The success of the intervention supports the adoption of a participatory ergonomics approach in reducing the rate and consequence of injuries in the workplace.