Analysis and Regularization of the Thin-Wire Integral Equation With Reduced Kernel

For the straight wire, modeled as a hollow tube, we establish a conditional equivalence relation between the integral equations with exact and reduced kernel. This relation allows us to examine the existence and uniqueness conditions for the integral equation with reduced kernel, based on a local argument. Further, we characterize the ill-posedness of integral equation with reduced kernel and we propose a regularization and filtering procedure to extend the range of this integral equation     

On the consistency of individual classification using short scales.

Short tests containing at most 15 items are used in clinical and health psychology, medicine, and psychiatry for making decisions about patients. Because short tests have large measurement error, the authors ask whether they are reliable enough for classifying patients into a treatment and a nontreatment group. For a given certainty level, proportions of correct classifications were computed for varying test length, cut-scores, item scoring, and choices of item parameters. Short tests were found to classify at most 50% of a group consistently. Results were much better for tests containing 20 or 40 items. Small differences were found between dichotomous and polytomous (5 ordered scores) items. It is recommended that short tests for high-stakes decision making be used in combination with other information so as to increase reliability and classification consistency. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A bumpy train ride: A field experiment on insult, honor, and emotional reactions.

The present research examined the relationship between adherence to honor norms and emotional reactions after an insult. Participants were 42 Dutch male train travelers, half of whom were insulted by a confederate who bumped into the participant and made a degrading remark. Compared with insulted participants with a weak adherence to honor norms, insulted participants with a strong adherence to honor norms were (a) more angry, (b) less joyful, (c) less fearful, and (d) less resigned. Moreover, insulted participants with a strong adherence to honor norms perceived more anger in subsequent stimuli than not-insulted participants with a strong adherence to these norms. The present findings support a direct relationship among insult, adherence to honor norms, and emotional reactions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An efficient computation scheme for the free space Green's function of a two-dimensional semiinfinite phased array

A simple scheme is developed to compute the Green's function of a periodic semiinfinite array in free space. It is based on the spectral representation of the fields radiated by an infinite linear array of dipoles. Results related to successive linear arrays are added in the space domain. This summation can be accelerated tremendously by using an elementary extrapolation technique. The resulting formulation converges everywhere in the plane containing the array, and the number of terms required to achieve a given precision increases slowly away from this plane.     

Iterative determination of permittivity and conductivity profiles of a dielectric slab in the time domain

A numerical method is presented to compute one unknown constitutive parameter of an inhomogeoeous lossy dielectric slab from the reflected field in the time domain. The method is based upon a space-time discretization of the integral equation for the reflected field. In the inversion, especially those space-time points where the numerical computation of the electric-field strength in the slab is most accurate are taken into account. This is achieved by computing the unknown parameter iteratively. Alternately solving equations for an approximate direct-scattering problem and an approximate inverse-scattering problem yields successive approximations for the electric field in the slab and the unknown constitutive coefficient. Both problems lead to an infinite system of linear equations from which a finite subsystem is selected. General criteria for this selection are presented. Various profiles have been reconstructed numerically from the reflected field due to a sine-squared incident pulse.     

Quality of life in relation to overweight and body fat distribution

OBJECTIVES: This study quantified the impairment of quality of life attributable to body fatness by using the standardized SF-36 Health Survey. METHODS: Tertiles of waist circumference and body mass index (BMI) in 1885 men and 2156 women aged 20 to 59 years in the Netherlands in 1995 were compared. RESULTS: The odds ratios and 95% confidence intervals of subjects with the largest waist circumferences, compared with those in the lowest tertile, were 1.8 (1.3, 2.4) in men and 2.2 (1.7, 2.9) in women with difficulties in bending, kneeling, or stooping; 2.2 (1.4, 3.7) in men and 1.7 (1.2, 2.6) in women with difficulties in walking 500 m; and 1.3 (1.0, 1.9) in men and 1.5 (1.1, 1.9) in women with difficulties in lifting or carrying groceries. Anthropometric measures were less strongly associated with social functioning, role limitations due to physical or emotional problems, mental health, vitality, pain, or health change in 1 year. The relationship between quality of life measures and BMI were similar to those between quality of life measures and waist circumference. CONCLUSIONS: Large waist circumferences and high BMIs are more likely to be associated with impaired quality of life and disability affecting basic activities of daily living.     

Yield stress distribution in injection‐moulded glassy polymers

A methodology for structural analysis simulations is presented that incorporates the distribution of mechanical properties along the geometrical dimensions of injection‐moulded amorphous polymer products. It is based on a previously developed modelling approach, where the thermomechanical history experienced during processing was used to determine the yield stress at the end of an injection‐moulding cycle. Comparison between experimental data and simulation results showed an excellent quantitative agreement, both for short‐term tensile tests as well as long‐term creep experiments over a range of strain rates, applied stresses, and testing temperatures. Changes in mould temperature and component wall thickness, which directly affect the cooling profiles and, hence, the mechanical properties, were well captured by the methodology presented. Furthermore, it turns out that the distribution of the yield stress along a tensile bar is one of the triggers for the onset of the (strong) localization generally observed in experiments. © 2015 Society of Chemical Industry     

Theoretical and computational aspects of 2-D inverse profiling

The authors discuss two techniques for solving two-dimensional (2D) inverse scattering problems by parameterizing the scattering configuration, and determining the optimum value of the parameters by minimizing a cost function involving the known scattered-field data. The computation of the fields in each estimated configuration is considered as an auxiliary problem. To improve the efficiency of these computations, the CGFFT iterative scheme is combined with a special extrapolation procedure that is valid for problems with a varying physical parameter such as frequency, angle of incidence, or contrast. Further, they analyze the dynamic range and the resolution of linearized schemes. To obtain an acceptable resolution for an object with a large contrast with respect to the surrounding medium, multiple-frequency information is used. Finally, the availability of a fast-forward solver was an incentive to consider nonlinear optimization. In particular, the authors use a quasi-Newton algorithm at only twice the computational cost of the distorted-wave Born iterative scheme     

Global, Local, and Graphical Person-Fit Analysis Using Person-Response Functions.

Person-fit statistics test whether the likelihood of a respondent's complete vector of item scores on a test is low given the hypothesized item response theory model. This binary information may be insufficient for diagnosing the cause of a misfitting item-score vector. The authors propose a comprehensive methodology for person-fit analysis in the context of nonparametric item response theory. The methodology (a) includes H. Van der Flier's (1982) global person-fit statistic U3 to make the binary decision about fit or misfit of a person's item-score vector, (b) uses kernel smoothing (J. O. Ramsay, 1991) to estimate the person-response function for the misfitting item-score vectors, and (c) evaluates unexpected trends in the person-response function using a new local person-fit statistic (W. H. M. Emons, 2003). An empirical data example shows how to use the methodology for practical person-fit analysis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

3D Viscoelastic analysis of a polymer solution in a complex flow

A mixed low-order finite element technique based on the Discrete Elastic Viscous Stress Splitting (DEVSS)/Discontinuous Galerkin (DG) method has been developed for the analysis of three-dimensional viscoelastic flows in the presence of multiple relaxation times. In order to evaluate the predictive capabilities of some established nonlinear constitutive relations like the Giesekus and the Phan-Thien–Tanner (PTT) model results of 3D calculations are compared with experimental results in a cross-slot flow geometry. Moreover, the performance of a new viscoelastic constitutive equation that provides enhanced independent control of the shear and elongational properties is investigated. Steady shear flows and a combined shear/elongational flow are analyzed for a polyisobutylene solution. A general method is introduced to compare calculated stresses along the depth of the flow with birefringence measurements using the stress optical rule. In particular at and downstream of the stagnation point in the cross-slot flow geometry, the numerical/experimental evaluation shows that the multi-mode Giesekus and the PTT model are unable to describe the stress-related experimental observations. The new viscoelastic constitutive relation proves to perform significantly better for this stagnation flow.