Active vibration control (AVC) of a satellite boom structure using optimally positioned stacked piezoelectric actuators

In this paper, results for active vibration control predicted from experimental measurements on a lightweight structure are compared with purely computational predictions. The structure studied is a 4.5m long satellite boom consisting of 10 identical bays with equilateral triangular cross sections. First, the results from a Fortran code that is based on a receptance analysis are validated against the experimental forced response of the boom structure. Exhaustive searches are then carried out to find the optimum positions for one and two actuators. Finally, a genetic algorithm is employed to find high-quality positions for three actuators on the structure that will achieve the greatest reductions in vibration transmission. Having found these actuator positions, experiments are then carried out to verify the quality of the theoretical predictions. It was found that the attenuation achievable in practice for one, two and three actuators were, respectively, 15.1, 26.1 and 33.5 dB

Active vibration control (AVC) of a satellite boom structure using optimally positioned stacked piezoelectric actuators

In this paper, results for active vibration control predicted from experimental measurements on a lightweight structure are compared with purely computational predictions. The structure studied is a 4.5m long satellite boom consisting of 10 identical bays with equilateral triangular cross sections. First, the results from a Fortran code that is based on a receptance analysis are validated against the experimental forced response of the boom structure. Exhaustive searches are then carried out to find the optimum positions for one and two actuators. Finally, a genetic algorithm is employed to find high-quality positions for three actuators on the structure that will achieve the greatest reductions in vibration transmission. Having found these actuator positions, experiments are then carried out to verify the quality of the theoretical predictions. It was found that the attenuation achievable in practice for one, two and three actuators were, respectively, 15.1, 26.1 and 33.5 dB

Ices in Star-Forming Regions: First Results from VLT-ISAAC

The first results from a VLT-ISAAC program on L- and M-band infrared spectroscopy of deeply-embedded young stellar objects are presented. The advent of 8-m class telescopes allows high S/N spectra of low-luminosity sources to be obtained. In our first observing run, low- and medium-resolution spectra have been measured toward a dozen objects, mostly in the Vela and Chamaeleon molecular clouds. The spectra show strong absorption of H2O and CO ice, as well as weak features at `3.47' and 4.62 mu. No significant solid CH3OH feature at 3.54 mu is found, indicating that the CH3OH/H2O ice abundance is lower than toward some massive protostars. Various evolutionary diagnostics are investigated for a set of sources in Vela.Comment: 8 pages, 4 figures, to appear in The Origins of Stars and Planets: the VLT View, eds. J. Alves, M. McCaughrean (Springer Verlag

Determination of optimal ultrasound planes for the initialisation of image registration during endoscopic ultrasound-guided procedures

Purpose Navigation of endoscopic ultrasound (EUS)-guided procedures of the upper gastrointestinal (GI) system can be technically challenging due to the small fields-of-view of ultrasound and optical devices, as well as the anatomical variability and limited number of orienting landmarks during navigation. Co-registration of an EUS device and a pre-procedure 3D image can enhance the ability to navigate. However, the fidelity of this contextual information depends on the accuracy of registration. The purpose of this study was to develop and test the feasibility of a simulation-based planning method for pre-selecting patient-specific EUS-visible anatomical landmark locations to maximise the accuracy and robustness of a feature-based multimodality registration method. Methods A registration approach was adopted in which landmarks are registered to anatomical structures segmented from the pre-procedure volume. The predicted target registration errors (TREs) of EUS-CT registration were estimated using simulated visible anatomical landmarks and a Monte Carlo simulation of landmark localisation error. The optimal planes were selected based on the 90th percentile of TREs, which provide a robust and more accurate EUS-CT registration initialisation. The method was evaluated by comparing the accuracy and robustness of registrations initialised using optimised planes versus non-optimised planes using manually segmented CT images and simulated (n=9) or retrospective clinical (n=1) EUS landmarks. Results The results show a lower 90th percentile TRE when registration is initialised using the optimised planes compared with a non-optimised initialisation approach (p value <0.01). Conclusions The proposed simulation-based method to find optimised EUS planes and landmarks for EUS-guided procedures may have the potential to improve registration accuracy. Further work will investigate applying the technique in a clinical setting

Bayesian evaluation of budgets for endemic disease control: an example using management changes to reduce milksomatic cell count early in the first lactation of Irish dairy cows

The aim of this research was to determine budgets for specific management interventions to control heifer mastitis in Irish dairy herds as an example of evidence synthesis and 1-step Bayesian micro-simulation in a veterinary context. Budgets were determined for different decision makers based on their willingness to pay. Reducing the prevalence of heifers with a high milk somatic cell count (SCC) early in the first lactation could be achieved through herd level management interventions for pre- and peri-partum heifers, however the cost effectiveness of these interventions is unknown. A synthesis of multiple sources of evidence, accounting for variability and uncertainty in the available data is invaluable to inform decision makers around likely economic outcomes of investing in disease control measures. One analytical approach to this is Bayesian micro-simulation, where the trajectory of different individuals undergoing specific interventions is simulated. The classic micro-simulation framework was extended to encompass synthesis of evidence from 2 separate statistical models and previous research, with the outcome for an individual cow or herd assessed in terms of changes in lifetime milk yield, disposal risk, and likely financial returns conditional on the interventions being simultaneously applied. The 3 interventions tested were storage of bedding inside, decreasing transition yard stocking density, and spreading of bedding evenly in the calving area. Budgets for the interventions were determined based on the minimum expected return on investment, and the probability of the desired outcome. Budgets for interventions to control heifer mastitis were highly dependent on the decision maker's willingness to pay, and hence minimum expected return on investment. Understanding the requirements of decision makers and their rational spending limits would be useful for the development of specific interventions for particular farms to control heifer mastitis, and other endemic diseases. Keywords Bayesian; Micro-simulation; Dairy heifer; Mastitis control; Cost-effectiveness; Decision makin

Minimal muscle damage after a marathon and no influence of beetroot juice on inflammation and recovery

This study examined whether beetroot juice (BTJ) would attenuate inflammation and muscle damage following a marathon. Using a double blind, independent group’s design, 34 runners (~16 previous marathons completed) consumed either BTJ or an isocaloric placebo (PLA) for 3 days following a marathon. Maximal isometric voluntary contractions (MIVC), countermovement jumps (CMJ), muscle soreness, serum cytokines, leucocytosis, creatine kinase (CK), high sensitivity C-reactive protein (hs-CRP) and aspartate aminotransferase (AST) were measured pre, post, and on the 2 days after the marathon. CMJ and MIVC were reduced after the marathon (P0.05). Muscle soreness was increased in the day after the marathon (BTJ; 45±48 vs. PLA; 46±39 mm) and had returned to baseline by day 2, irrespective of supplementation (P=0.694). Cytokines (Interleukin-6; IL-6, interleukin-8, tumour necrosis factor-α) were increased immediately post-marathon but apart from IL-6 had returned to baseline values by day 1 post. No interaction effects were evident for IL-6 (P=0.213). Leucocytes increased 1.7 fold after the race and remained elevated 2 days post, irrespective of supplement (P<0.0001). CK peaked at 1 day post marathon (BTJ: 965±967 & PLA: 1141±979 IU·L-1) and like AST and hs-CRP, was still elevated 2 days after the marathon (P<0.05); however, no group differences were present for these variables. Beetroot juice did not attenuate inflammation or reduce muscle damage following a marathon, possibly because most of these indices were not markedly different from baseline values in the days after the marathon

The First Magnetic Fields

We review current ideas on the origin of galactic and extragalactic magnetic fields. We begin by summarizing observations of magnetic fields at cosmological redshifts and on cosmological scales. These observations translate into constraints on the strength and scale magnetic fields must have during the early stages of galaxy formation in order to seed the galactic dynamo. We examine mechanisms for the generation of magnetic fields that operate prior during inflation and during subsequent phase transitions such as electroweak symmetry breaking and the quark-hadron phase transition. The implications of strong primordial magnetic fields for the reionization epoch as well as the first generation of stars is discussed in detail. The exotic, early-Universe mechanisms are contrasted with astrophysical processes that generate fields after recombination. For example, a Biermann-type battery can operate in a proto-galaxy during the early stages of structure formation. Moreover, magnetic fields in either an early generation of stars or active galactic nuclei can be dispersed into the intergalactic medium.Comment: Accepted for publication in Space Science Reviews. Pdf can be also downloaded from http://canopus.cnu.ac.kr/ryu/cosmic-mag1.pd