Deep penetration analysis with dynamic cylindrical cavitation fields

Dynamic cylindrical cavitation fields are studied for a family of plastic orthotropic solids with arbitrary strain hardening response. Analysis is within the framework of plane-strain, steady state flow theory of associated plasticity. New formulae for cavitation pressure are validated against accurate numerical analysis and contact is made with existing studies. A uniform procedure is presented for estimating penetration depth of rigid axisymmetric projectiles at normal impact. Comparison with available experimental data reveals a very good agreement for both spherical and cylindrical dynamic cavitation models. Quasi-static cavitation pressure formulae can predict penetration depth with an appropriate scaling of the yield stress. The scaling factors appear to be independent of material properties but reflect the shape of head profile.     

Nonlinearizable single-input control systems do not admit stationary symmetries

The main result of the paper states that almost any analytic single-input control system, which is truly nonlinear, that is not feedback linearizable, with controllable linearization at an equilibrium point, does not admit any symmetry preserving that point. By almost any system, we mean that we exclude a small class of odd systems, that admit just one nontrivial symmetry conjugated to minus identity. The obtained results are based on a recent classification of nonlinear single-input systems under formal feedback. We also describe symmetries of feedback linearizable systems.     

Diagnostic value of tissue polypeptide-specific antigen (TPS) in neuroblastoma and Wilms' tumour

Although tissue polypeptide-specific antigen (TPS) has been described as a potentially useful serum marker of tumour activity in adult epithelial tumours, few data are available for childhood malignancies. Neuroblastomas and Wilms' tumours are the commonest types of solid malignancies found in the retroperitoneum of children. At this time, a widely used marker for Wilms' tumour is not available. Using an enzyme-linked immunosorbent assay (ELISA) kit, serum TPS levels in 23 children with neuroblastomas, nine with Wilms' tumours and 22 with benign tumours were evaluated to test the usefulness of the marker in identifying malignancies. Compared with healthy children (n = 110), the preoperative least-square means (LSM) of serum TPS were considerably elevated in both neuroblastoma (LSM = 209 U l(-1)) and Wilms' tumour (LSM = 235 U l(-1)), whereas values in benign tumours were only slightly elevated. Although the Wilms' tumours were associated with higher preoperative serum TPS levels, there was no statistically significant difference compared with neuroblastomas. Receiver operating characteristic analysis (ROC curves) showed a high sensitivity and specificity for both malignancies. Successful treatment resulted in decrease in TPS serum values. Serum TPS measurements in children presenting with abdominal masses can help in diagnosing the two commonest extracranial solid malignancies of childhood. Furthermore, TPS could acquire a pivotal role in monitoring therapy.     

Illumination of light vectors modulated in 3-D photoelastic media

Summary The dependency of the illumination of a light vector that is subjected to modulation along its path in a three-dimensional photoelastic medium, on the rotation of the principal directions (RPD) of stresses is investigated. The consistency and characteristics of the interaction of the light intensity and the RPD for three different photoelastic materials are explored. The deviation of the rotation of the optical axes from those of the principal ones, in 3-D birefringent material, is illustrated. Furthermore, the interrelation of this deviation and the magnitude of the RPD is studied. The experimentally obtained results are shown in four diagrams.With 7 Figures     

High numerical aperture in multimode microstructured optical fibers

Microstructured or "air-clad" fibers, with air holes surrounding a large core, have recently demonstrated much wider light-acceptance angles than conventional fibers. An original and accurate method is presented for determining the numerical aperture of such fibers using leaky modes. The dependence on length, wavelength, and various microstructure dimensions are evaluated for the first time for a class of fibers that exhibit exceptionally high numerical apertures. These results show excellent agreement with published measurements on similar fibers and verify that bridge thicknesses much smaller than the wavelength are required for high numerical apertures.     

Specific interactions study in complexes of poly(mono-n-alkyl itaconates) with tertiary polyamides

This paper reports an FT-IR study of blends of poly(mono-n-alkyl itaconates) with poly(N,N-dimethylacrylamide) (PDMA) and poly(ethyloxazoline) (PEOX). Strong hydrogen bonding has been found, and both polybases have shown similar acceptor strengths. Derivative techniques show asymmetric profiles for the free carbonyl band of the polybases, resulting in shifted band locations. The extent of the interassociation has been estimated by spectral curve fitting of the polybase carbonyl band. The results show that the interaction degree in blends with PEOX does not depend on the length of the poly(monoalkyl itaconate) side group, while an inter-associating ability loss is observed in blends with PDMA as the side-group size of the polyacid increases. This different behavior is attributed to the greater interspacing between vicinal carbonyl groups in PEOX. This band shows conformational sensitivity and reflects the conformational changes that occur as the steric hindrances present in the medium (due to the bulky side groups of the polyacids) increase.     

Strict feedforward control systems,linearisability, and convergent normal forms

This article discusses the feedback equivalence of multi-inputs feedforward control systems via smooth (resp. analytic) feedback transformations. We first address the state (resp. feedback) linearisation problem, and provide easily computable algorithms that yield explicit state (resp. feedback) linearising coordinates for systems in strict feedforward form. The application of the algorithms does not require checking the commutativity (resp. involutivity) of the distributions associated with the system, and the algorithms fail after few steps if the system is not linearisable. In the latter case, the algorithms are extended to provide coordinate systems bringing the system into a normal form which is a smooth (resp. analytic) counterpart of Kang's formal normal form. Illustrative examples for both the linearisation and convergent normal form include the vertical take off and landing aircraft, the multi-vehicle wireless testbed among others.     

Impact of Multimedia-Based Instruction on Learning and Retention

Studies measuring and evaluating the impact of the same multimedia-based education on learners in universities and high schools are a relatively new phenomenon. This study provides a summary of the results from research on the effects of multimedia-based safety education conducted by the M. E. Rinker Sr. School of Building Construction at the University of Florida. The findings are presented along with their related statistical test results. The findings indicate multimedia-based, self-paced learning offers very distinct advantages over traditional, instructor-led classroom learning. Overall, both the high-school and university student groups involved in the study exhibited superior retention rates when learning from the multimedia-based materials. Higher scoring students in the classroom showed little difference in either media, while students who tended to score at the low end of the grading scale uniformly scored higher on multimedia-based materials. The reduced variation in student performance based on test scores in the CD-ROM instruction indicates the positive effects of multimedia-based instruction.     

Parametric Estimation of Affine Transformations: An Exact Linear Solution

We consider the problem of estimating the geometric deformation of an object, with respect to some reference observation on it. Existing solutions, set in the standard coordinate system imposed by the measurement system, lead to high-dimensional, non-convex optimization problems. We propose a novel framework that employs a set of non-linear functionals to replace this originally high dimensional problem by an equivalent problem that is linear in the unknown transformation parameters. The proposed solution includes the case where the deformation relating the observed signature of the object and the reference template is composed both of the geometric deformation due to the affine transformation of the coordinate system and a constant amplitude gain. The proposed solution is unique and exact and is applicable to any affine transformation regardless of its magnitude.