Piezoceramics-based Devices for Active Balancing of Flexible Shafts

This paper focuses on vibration control of flexible shafts by means of rotorfixed piezoelectric materials. The target is to realize compact solutions for the suppression of problematic resonant vibration at so-called flexural critical speeds. For analysis, parametric finite element models of flexible rotors with piezoceramic sheets and strain or displacement sensors are developed, where the number of degrees of freedom is kept low. Several mechanisms which can destabilize flexible rotors are quantisized, such as rotor material damping, dissipation of currents induced in rotor-fixed piezoceramics and active feedback control proportional to rotor strain rates. The effectiveness of low frequency feedback and feedforward control for the suppression of the unbalance response is demonstrated using analytic and experimental results. Emphasis is on the interaction between the dynamics of the rotor and that of the connected electronic circuits. The experimental setup which is used for validation is a flexible shaft equipped with piezoceramic sheets and strain sensors. A slipring assembly is used to simplify measurements with, and control of, the sensors and actuators on the shaft and to facilitate the development of compact drive electronics

Development of temporal and spatial bimanual coordination during childhood

Developmental changes in bimanual coordination were examined in four age groups: 6/7, 10/11, 14/15 years, and young adults. Temporal coupling was assessed through the stabilizing contributions of interlimb interactions related to planning, error correction, and reflexes during rhythmic wrist movements, by comparing various unimanual and bimanual tasks involving passive and active movements. Spatial coupling was assessed via bimanual line-circle drawing. With increasing age, temporal stability improved. Relative contributions of planning and reflex interactions to the achieved stability did not change, whereas error correction improved. In-phase and antiphase coordination developed at similar rates; implications of this result were discussed in terms of mirror-activity inhibition. Overall spatial drawing performance (circularity, variability, smoothness) improved with age, and spatial interference was smaller in adults than children. Whereas temporal coupling increased from 6/7 years to adulthood, spatial coupling changed mainly after 14/15 years. This difference in the development of temporal and spatial coupling corresponds to the anterior-posterior direction of corpus callosum myelination as reported in the literature

An Internet-Based Course And The Application Of Employment-Based Methods In Civil Engineering Projects

The paper addresses the question of how educational activities in civil engineering in the Netherlands can contribute to the application of employment-based programs in developing countries. National policy makers and international donor representatives acknowledge the various advantages of employment-based programs. However, for a number of reasons the implementation of such programs generally forms a severe bottleneck. Because of the limited number of implemented programs the employment-based methods have not been sufficiently tested and improved, which in turn inhibits reaching the full potential of the employmentbased policies. The University of Twente (UT) has developed a modest program to assist interested governmental and private organisations to enhance the scope and quality of implementation of projects. Based on the existing body of knowledge - to which in particular ILO, WORK and IHE have contributed - a course has been established that can be followed via the Internet. This course offers the basic principles of employment-based civil engineering as well as a framework to develop and implement project proposals. Each of the three modules consists of course material (texts, pictures and films) and an individual assignment that the student submits to the lecturer. Next, the University's internship and traineeship programs provide interested candidates an opportunity to render practical assistance at the spot while at the same time collecting and processing data. After their preparation at the UT the students normally spend 3 to 4 months abroad, frequently in outlying areas. The preparation and execution are carried out under supervision of University staff, while the University also provides financial support by paying for the international travel. Besides their direct contribution to development activities, the students' experiences and reports form the input for improvements in implementation and policy making. So far over 20 students have executed such assignments, mainly in South Africa. The oral presentation of the paper includes a demonstration of the Internet-based course and a discussion with participants on concrete project ideas

Real-time quantification and display of skin radiation during coronary angiography and intervention

BACKGROUND: Radiographically guided investigations may be associated with excessive radiation exposure, which may cause skin injuries. The purpose of this study was to develop and test a system that measures in real time the dose applied to each 1-cm(2) area of skin, taking into account the movement of the x-ray source and changes in the beam characteristics. The goal of such a system is to help prevent high doses that might cause skin injury. METHODS AND RESULTS: The entrance point, beam size, and dose at the skin of the patient were calculated by use of the geometrical settings of gantry, investigation table, and x-ray beam and an ionization chamber. The data are displayed graphically. Three hundred twenty-two sequential cardiac investigations in adult patients were analyzed. The mean peak entrance dose per investigation was 0.475 Gy to a mean skin area of 8.2 cm(2). The cumulative KERMA-area product per investigation was 52.2 Gy/cm(2) (25.4 to 99.2 Gy/cm(2)), and the mean entrance beam size at the skin was 49.2 cm(2). Twenty-eight percent of the patients (90/322) received a maximum dose of 2 Gy. CONCLUSIONS: Monitoring of the dose distribution at the skin will alert the operator to the development of high-dose areas; by use of other gantry settings with nonoverlapping entrance fields, different generator settings, and extra collimation, skin lesion can be avoided

Severity of Diabetes Mellitus and Total Hip or Knee Replacement: A Population-Based Case-Control Study

Contains fulltext : 171491.pdf (publisher's version ) (Open Access)It is generally thought that people with diabetes mellitus (DM) are more likely to suffer from osteoarthritis (OA) due to an increased body mass index (BMI), resulting in mechanical destruction of cartilage. However, previous studies have suggested a coexisting metabolic causality.To evaluate the risk of hip or knee replacement, as a proxy for severe OA, in patients with DM. We additionally evaluated the risk of total joint replacement (TJR) with various proxies for increased DM severity.A population-based case-control study was performed, using the Clinical Practice Research Datalink (CPRD). Cases (n = 94,609) were defined as patients >18 years who had undergone TJR between 2000 and 2012. Controls were matched by age, gender, and general practice. Conditional logistic regression was used to estimate the risk of total knee (TKR) and total hip replacement (THR) surgery associated with use of antidiabetic drugs (ADs). We additionally stratified current AD users by proxies for DM severity.Current AD use was significantly associated with a lower risk of TKR (OR = 0.86 (95% CI = 0.78-0.94)) and THR (OR = 0.90 (95% CI = 0.82-0.99)) compared to patients not using ADs. Moreover, risk of TKR and THR was decreased with increasing HbA1c.This study does not support the theory that DM patients are more likely to suffer from severe OA as compared to patients without diabetes. Moreover, risk of severe OA necessitating TJR decreases with increasing DM severity. This is possibly due to dissimilarities in methodology, a decrease in eligibility for surgery, or variability of OA phenotypes

Estimate of the Collins fragmentation function in a chiral invariant approach

We predict the features of the Collins function, which describes the fragmentation of a transversely polarized quark into an unpolarized hadron, by modeling the fragmentation process at a low energy scale. We use the chiral invariant approach of Manohar and Georgi, where constituent quarks and Goldstone bosons are considered as effective degrees of freedom in the non-perturbative regime of QCD. To test the approach we calculate the unpolarized fragmentation function and the transverse momentum distribution of a produced hadron, both of which are described reasonably well. In the case of semi-inclusive deep-inelastic scattering, our estimate of the Collins function in connection with the transversity distribution gives rise to a transverse single spin asymmetry of the order of 10%, supporting the idea of measuring the transversity distribution of the nucleon in this way. In the case of e+ e- annihilation into two hadrons, our model predicts a Collins azimuthal asymmetry of about 5%.Comment: 12 pages, 15 figures. Figs. 11-14 changed, minor changes in discussion, few typos fixed and some references added. Final version to appear in PR