Hybrid connection technologies for hollow sections in steel construction

Circular hollow sections (CHS) offer a variety of constructional and architectural advantages. Up to now, hollow section structures have usually been connected by welding, and more rarely by bolting. However, these established connection methods have disadvantages. Despite its great success in the mobility sector, adhesive bonding is not yet used for joining hollow steel sections in steel construction. Adhesive bonding, however, has significant advantages, especially if combined with classical joining processes. To highlight these advantages, this article presents excerpts from the results obtained in two recently completed research projects. First, a hybrid brace connection for hollow section framework structures is presented which combines welding, bolting and adhesive bonding methods. In addition, the loadbearing behaviour of a novel hybrid grouted connection, which advantageously combines adhesive and grout materials, is analysed and discussed in this paper

Adhesive bonding of secondary steel components for offshore wind turbines

Offshore wind turbines consist of the main components tower, nacelle and rotor blades. Additionally, numerous secondary components are connected to the primary structure. These include amongst others boat landings, platforms, cable protection tubes and corrosion protection systems. Usually, these elements are connected to the primary structure by welding or bolts. Both joining techniques reduce the fatigue performance of the primary structure by inducing geometric and/or metallurgical notches. In contrast, by fastening the secondary components by adhesive bonding, no geometric or metallurgical notches are induced in the primary structure. Further-more, the bonding can be carried out directly on the coating. In contrast to welded or bolted joints, adhesively bonded joints require a differing geometry that allows large bonding areas.This paper highlights the results of experimental investigations regarding the load bearing behaviour of adhesively bonded secondary components under a combination of lateral load and bending varying different geometrical pa-rameters

Fatigue behaviour of hybrid grouted joints under axial loading

Steel constructions made of circular hollow sections are commonly joined by welding or ring-flange bolting. An additional, novel joining method is the so-called hybrid grouted joint. The hybrid grouted joint is characterised by its multi-layered composition. In contrast to state-of-the-art grouted joints, hybrid grouted joints include thin adhesive layers, which are applied on the steel surfaces prior to grouting. Sand grains are embedded in the yet uncured adhesive. After the curing of the adhesive, the surface has a high degree of roughness. This allows a high-performance interlock between fine grain grout and the adhesively bonded sand granules across the contact surfaces in the overlap area. The ability to transfer loads across a wide area with low stress concentrations makes the hybrid grouted joint a promising joint alternative especially regarding the fatigue performance. This paper summarises the main findings concerning fatigue behaviour of the hybrid grouted joint under axial loading. Wöhler diagrams were determined in numerous fatigue tests for two combinations of adhesive and grout

Coherent photon-photon interactions in very peripheral relativistic heavy ion collisions

Heavy ions at high velocities provide very strong electromagnetic fields for a very short time. The main characteristics of ultraperipheral relativistic heavy ion collisions are reviewed, characteristic parameters are identified. The main interest in ultraperipheral heavy ion collisions at relativistic ion colliders like the LHC is the interactions of very high energy (equivalent) photons with the countermoving (equivalent) photons and hadrons (protons/ions). The physics of these interactions is quite different from and complementary to the physics of the strong fields achieved with current and future lasers.Comment: 5 pages, 5 figures, invited talk presented at the ELI Workshop and School on Fundamental Physics with Ultra-high Fields (September 29- October 2, 2008, Frauenwoerth, German

Electromagnetic Dissociation as a Tool for Nuclear Structure and Astrophysics

Coulomb dissociation is an especially simple and important reaction mechanism. Since the perturbation due to the electric field of the (target) nucleus is exactly known, firm conclusions can be drawn from such measurements. Electromagnetic matrixelements and astrophysical S-factors for radiative capture processes can be extracted from experiments. We describe the basic elements of the theory of nonrelativistic and relativistic electromagnetic excitation with heavy ions. This is contrasted to electromagnetic excitation with leptons (electrons), with their small electric charge and the absence of strong interactions. We discuss various approaches to the study of higher order electromagnetic effects and how these effects depend on the basic parameters of the experiment. The dissociation of neutron halo nuclei is studied in a zero range model using analytical methods. We also review ways how to treat nuclear interactions, show their characteristics and how to avoid them (as far as possible). We review the experimental results from a theoretical point of view. Of special interest for nuclear structure physics is the appearence of low lying electric dipole strength in neutron rich nuclei. Applications of Coulomb dissociation to some selected radiative capture reactions relevant for nuclear astrophysics are discussed. The Coulomb dissociation of 8B is relevant for the solar neutrino problem. The potential of the method especially for future investigations of (medium) heavy exotic nuclei for nuclear structure and astrophysics is explored. We conclude that the Coulomb dissociation mechanism is theoretically well understood, the potential difficulties are identified and can be taken care of. Many interesting experiments have been done in this field and many more are expected in the future.Comment: review article accepted for publication in "Prog. in Part. and Nucl. Physics", 75 pages, 31 figure

The Benefits of Nonlinear Frequency Compression for People with Mild Hearing Loss

Nonlinear frequency compression compensates for hearing loss in frequency ranges where traditional amplification on its own does not provide sufficient benefit. The effectiveness of Phonak’s proprietary nonlinear frequency compression algorithm, SoundRecover, has been documented for more significant degrees hearing loss (Simpson, Hersbach & McDermott, 2005, 2006; Nyffeler, 2008). The purpose of this study was to test whether SoundRecover provides sufficient benefit for people with mild to moderate hearing loss. Sufficient benefit is defined as whether the person can more easily recognize quiet, high frequency sounds. This study focused particularly on the /s/ sound. To measure consonant identification, a special test, the Adaptive Logatom Test, was designed that is sufficiently sensitive for cases of mild and moderate hearing loss (i.e. phonemes cannot be discerned on the basis of word or sentence context). The Adaptive Logatom Test was administered using adaptive control of the presentation level, and the respective identification thresholds of various consonants in nonsense syllables (logatoms) were recorded. The identification threshold of the /s/ sound clearly improved with SoundRecover. In addition, subjects reported that listening with SoundRecover was more pleasant than listening without it. A summary of this study was previously published in Phonak Field Study News (April 2009). This article provides the entire study, results and discussion

Highly specific reasons for nonadherence to antiretroviral therapy: results from the German adherence study

Reasons for and frequency of nonadherence to antiretroviral therapy (ART) may have changed due to pharmacological improvements. In addition, the importance of known non-pharmacologic reasons for nonadherence is unclear.We performed a cross-sectional, noninterventional, multicenter study to identify current reasons for nonadherence. Patients were categorized by physicians into the following adherence groups: good, unstable, or poor adherence. Co-variables of interest included age, sex, time since HIV diagnosis, ART duration, current ART regimen, HIV transmission route, comorbidity, HIV-1 RNA viral load (VL), and CD4 cell count. Patients self-reported the number of missed doses and provided their specific reasons for nonadherent behavior. Statistical analyses were performed using Fisher's extended exact test, Kruskal-Wallis test, and logistic regression models.Our study assessed 215 participants with good (n=162), unstable (n=36), and poor adherence (n=17). Compared to patients with good adherence, patients with unstable and poor adherence reported more often to have missed at least one dose during the last week (good 11% vs unstable 47% vs poor 63%, <0.001). Physicians' adherence assessment was concordant with patients' self-reports of missed doses during the last week (no vs one or more) in 81% cases. Similarly, we found a strong association of physicians' assessment with viral suppression. Logistic regression analysis showed that "reduced adherence" - defined as unstable or poor - was significantly associated with patients <30 years old, intravenous drug use, history of acquired immune deficiency syndrome (AIDS), and psychiatric disorders (<0.05). Univariate analyses showed that specific reasons, such as questioning the efficacy/dosing of ART, HIV stigma, interactive toxicity beliefs regarding alcohol and/or party drugs, and dissatisfaction with regimen complexity, correlated with unstable or poor adherence (<0.05).Identification of factors associated with poor adherence helps in identifying patients with a higher risk for nonadherence. Reasons for nonadherence should be directly addressed in every patient, because they are common and constitute possible adherence intervention points