Correlating low energy impact damage with changes in modal parameters: a preliminary study on composite beams

This paper is an experimental study of the effects of multi-site damage on the vibration response of a composite beam damaged by low energy impact. The variation of the modal parameters with different levels of impact energy and density of impact is studied. Specimens are impacted symmetrically in order to induce a global rate of damage. A damage detection tool Damage Index is introduced in order to verify the estimation of damping ratios. Design of Experiments is used to establish the sensitivity of both energy of impact and density of damage. The DOE analysis results (using natural frequency only) indicate that impact energy for 2nd, 3rd and 4th bending modes is the most significant factor contributing to the changes in the modal parameters for this kind of symmetrical dynamic test

Presynchronization of estrous cycles in dairy cows before ovsynch + CIDR and resynchronization of repeat estrus using the CIDR

Postpartum anestrus is one of the major limitations to achieving acceptable pregnancy rates. The Ovsynch protocol is an excellent tool to improve reproductive efficiency of dairy cows because it can induce estrous cycles in anestrous cows. In the first experiment, administering two PGF2 injections to lactating dairy cows 14 days apart with the second injection given 12 days before the Ovsynch protocol increased (P\u3c0.05) pregnancy rate by 10 percentage points in cycling and noncycling cows. Inserting a progesterone-releasing insert (CIDR) for 7 days during the Ovsynch protocol did not further increase pregnancy rates. In a second experiment, a resynchronization treatment consisting of a used CIDR inserted for 7 days from days 13 to 20 after insemination increased (P\u3c0.05) embryo survival from day 30 to 58 by 11 percentage points but failed to increase overall rate of return to estrus and conception rate at the second AI (first eligible estrus after first AI).; Dairy Day, 2001, Kansas State University, Manhattan, KS, 2001

Robust Henderson III estimators of variance components in the nested error model

Common methods for estimating variance components in Linear Mixed Models include Maximum Likelihood (ML) and Restricted Maximum Likelihood (REML). These methods are based on the strong assumption of multivariate normal distribution and it is well know that they are very sensitive to outlying observations with respect to any of the random components. Several robust altematives of these methods have been proposed (e.g. Fellner 1986, Richardson and Welsh 1995). In this work we present several robust alternatives based on the Henderson method III which do not rely on the normality assumption and provide explicit solutions for the variance components estimators. These estimators can later be used to derive robust estimators of regression coefficients. Finally, we describe an application of this procedure to small area estimation, in which the main target is the estimation of the means of areas or domains when the within-area sample sizes are small

Some combinatorial identities related to commuting varieties and Hilbert schemes

In this article we explore some of the combinatorial consequences of recent results relating the isospectral commuting variety and the Hilbert scheme of points in the plane

Hierarchical Gaussian process mixtures for regression

As a result of their good performance in practice and their desirable analytical properties, Gaussian process regression models are becoming increasingly of interest in statistics, engineering and other fields. However, two major problems arise when the model is applied to a large data-set with repeated measurements. One stems from the systematic heterogeneity among the different replications, and the other is the requirement to invert a covariance matrix which is involved in the implementation of the model. The dimension of this matrix equals the sample size of the training data-set. In this paper, a Gaussian process mixture model for regression is proposed for dealing with the above two problems, and a hybrid Markov chain Monte Carlo (MCMC) algorithm is used for its implementation. Application to a real data-set is reported

Cratering Experiments on the Self Armoring of Coarse-Grained Granular Targets

Recently published crater statistics on the small asteroids 25143 Itokawa and 433 Eros show a significant depletion of craters below approx. 100 m in diameter. Possible mechanisms that were brought up to explain this lack of craters were seismic crater erasure and self armoring of a coarse, boulder covered asteroid surface. While seismic shaking has been studied in this context, the concept of armoring lacks a deeper inspection and an experimental ground truth. We therefore present cratering experiments of glass bead projectiles impacting into granular glass bead targets, where the grain sizes of projectile and target are in a similar range. The impact velocities are in the range of 200 to 300 m/s. We find that craters become fainter and irregular shaped as soon as the target grains are larger than the projectile sizes and that granular craters rarely form when the size ratio between projectile and target grain is around 1:10 or smaller. In that case, we observe a formation of a strength determined crater in the first struck target grain instead. We present a simple model based on the transfer of momentum from the projectile to this first target grain, which is capable to explain our results with only a single free parameter, which is moreover well determined by previous experiments. Based on estimates of typical projectile size and boulder size on Itokawa and Eros, given that our results are representative also for km/s impact velocities, armoring should play an important role for their evolution.Comment: accepted for publication in Icaur

Low loss, tightly coilable, hollow core photonic bandgap fibers for mid-IR applications

We describe low loss (50dB/km at 3.3µm) and low bend sensitivity mid-IR hollow core-photonic bandgap fiber. Gas sensing applications are highlighted by a methane spectrum recorded in our fiber

Association of HLA types A1-B8-DR3 and B27 with rapid and slow progression of HIV disease

We examined how HLA types A1-B8-DR3 and B27 were related to progression of clinical disease and rate of loss of CD4 lymphocytes in the Edinburgh City Hospital cohort of HIV-positive patients, mainly injection drug users. Patients (n = 692) were prospectively followed from 1985 through March 1994. Accurately estimated seroconversion times were determined retrospectively for a subgroup of 313 (45%). Of 262 patients (39%) who were fully or partially HLA typed, 155 (50%) had known seroconversions. Of 34 patients typed positive for A1-B8-DR3, 29 progressed to CDC stage IV, 22 to AIDS and 20 died. Twelve patients were typed positive for B27; six of these progressed to CDC stage IV, one to AIDS and none died. In a proportional hazards analysis of the 313 patients with known seroconversions, A1-B8-DR3 was significantly associated with covariate-adjusted relative risks of 3.7 (95% CI 1.9-7.2), 3.1 (1.6-6.0) and 1.9 (1.1-3.2) for progression from seroconversion to death, AIDS and CDC stage IV, respectively. Events for B27 were too rare to include B27 in analyses to death and AIDS, but B27 was significantly associated with slower progression to CDC stage IV (0.3, CI 0.1-0.9). Random effects growth curve models were used to estimate individual rates of loss of square root CD4 count and loss of CD4 percentage, for 603 and 617 patients, respectively. A1-B8-DR3 was associated with rapid loss of both markers (p=0.02 and p = 0.01, respectively); B27 was associated with slow loss of both markers (p=0.04 and p<0.005

Hollow core photonic bandgap fibers for mid-IR applications

We review our fabrication of low loss (50dB/km at 3.3µm) and low bend sensitivity HC-PBGFs for mid-IR operation. Gas sensing applications are highlighted by a high resolution methane spectrum recorded in 1.26m of gas-filled fibe

Extreme short wavelength operation (1.65 - 1.7 µm) of silica-based thulium-doped fiber amplifier

We report the first demonstration of silica-based thulium-doped fiber amplifier (TDFA) working in the 1.65 - 1.7 µm waveband. Up to 29 dB small signal gain and noise figure as low as 6.5 dB are achieved