Welding of stainless steels. Duplex and superduplex steels

In the pulsed MAG welding with highly precise periodic drop transfer, welding current was analysed by fast Fourier transform (FFT). By this analysis, peculiar frequency of the molten pool was detected by resonance phenomena with the base plate vibration and it was confirmed that peculiar frequency falls according to growth of the molten pool. Furthermore, natural frequency was detected at the natural welding state that is without vibration of the base plate and confirmed by the resonance method with the base plate vibration. To amplify natural vibration of the molten pool, drop transfer pulse was modulated consisting of regular pulse peak current and higher pulse peak current. The higher pulse peak current makes a change in the arc pressure and the molten pool is pushed down in the period of higher pulse. Because short circuit is apt to occur at the time that the molten pool is at the top of the front side, so it is effective for amplifying the molten pool oscillation that higher pulse phase begins at this time instantaneously or somewhat later. According to this, higher peak was gained at peculiar frequency by FFT analysis. It means that amplifying of the molten pool oscillation was successful. Appropriate period of higher pulse for maintaining stable oscillation is from about 1/4 to 1/2 of the oscillation cycle.     

A review of the Namntall Tunnel project with regard to grouting performance

The 6 km tunnel under the Namntall hill is a part of the Botniabanan railway project in northern Sweden. The tunnels were excavated by means of drilling and blasting and with, for Scandinavian conditions, a normal grouting routine. The grouting is performed to reduce water ingress into the tunnel to the level defined in the contract. When the water ingress requirements proved difficult to meet, it was obvious that the geological and the hydrogeological conditions in the tunnel would dictate the work processes. A distinctive change in rock conditions influenced both grouting performance and seepage into the tunnel. The rock conditions and the grouting were quantified throughout the project and these are summarized in this paper. It can be concluded that the strongest correlation is between the water ingress, the hydrogeological conditions and the density of the zones and the conditions in and around these zones. The paper suggests a different approach to hydrogeological prognosis and the grouting process, such as distribution of grouting classes, increased mixer capacities and regular use of two grouting rounds.     

Assessing plastically dissipated energy as a condition for fatigue crack growth

The suitability of using a proposed condition for simulating cyclic crack propagation in a numerical scheme is qualitatively investigated, employing the finite element method. The propagation criterion is based on a condition that relates the plastically dissipated energy to a critical value. In the finite element simulation scheme, the crack is allowed to propagate when the criterion is satisfied, and the crack propagates until the condition is no longer fulfilled. Experimentally, it is well established that a negative load ratio increases the crack propagation rate, whereas a tensile overload tends to decrease the crack propagation rate. By simulating these load conditions, we show that the proposed propagation criterion closely captures these rate changes.     

Effect of nanofillers on the flame retardant properties of a polyethylene–calcium carbonate–silicone elastomer system

This study shows the effects of three different nanofillers on the viscosity properties and fire behavior of a halogen‐free flame retardant system. The original system, based on ethylene‐acrylate copolymer, calcium carbonate, and a silicone elastomer, shows good flame retardant properties. One of the nanofillers, montmorillonite (MMT), significantly increases the viscosity above 250^°C, resulting in reduced dripping and decreased heat release rate. The ash residue, however, is very brittle, indicating poor interactions between the MMT and other components of the system. The second nanofiller, sepiolite, shows no improvement on the flame retardant properties of the system. Reduced dripping is observed when a small amount of the third nanofiller, polyhedral oligomeric silsesquioxane, POSS, is incorporated into the system. In this case, high silica content on the surface indicates char formation originating from the POSS. However, an increased heat release is observed when POSS is used in the system. Copyright © 2010 John Wiley & Sons, Ltd.     

Kinematics of the heart: strain-rate imaging from time-resolved three-dimensional phase contrast MRI

A four-dimensional mapping (three spatial dimensions + time) of myocardial strain-rate would help to describe the mechanical properties of the myocardium, which affect important physiological factors such as the pumping performance of the ventricles. Strain-rate represents the local instantaneous deformation of the myocardium and can be calculated from the spatial gradients of the velocity field. Strain-rate has previously been calculated using one-dimensional (ultrasound) or two-dimensional (2-D) magnetic resonance imaging) techniques. However, this assumes that myocardial motion only occurs in one direction or in one plane, respectively. This paper presents a method for calculation of the time-resolved three-dimensional (3-D) strain-rate tensor using velocity vector information in a 3-D spatial grid during the whole cardiac cycle. The strain-rate tensor provides full information of both magnitude and direction of the instantaneous deformation of the myocardium. A method for visualization of the full 3-D tensor is also suggested. The tensors are visualized using ellipsoids, which display the principal directions of strain-rate and the ratio between strain-rate magnitude in each direction. The presented method reveals the principal strain-rate directions without a priori knowledge of myocardial motion directions.     

Coupled multipolar interactions in small-particle metallic clusters

We propose a new formalism for computing the optical properties of small clusters of particles. It is a generalization of the coupled dipole-dipole particle-interaction model and allows one in principle to take into account all multipolar interactions in the long-wavelength limit. The method is illustrated by computations of the optical properties of N = 6 particle clusters for different multipolar approximations. We examine the effect of separation between particles and compare the optical spectra with the discrete-dipole approximation and the generalized Mie theory.     

On optimality in auditory information processing

We study limits for the detection and estimation of weak sinusoidal signals in the primary part of the mammalian auditory system using a stochastic Fitzhugh-Nagumo model and an action-recovery model for synaptic depression. Our overall model covers the chain from a hair cell to a point just after the synaptic connection with a cell in the cochlear nucleus. The information processing performance of the system is evaluated using so-called phi-divergences from statistics that quantify "dissimilarity" between probability measures and are intimately related to a number of fundamental limits in statistics and information theory (IT). We show that there exists a set of parameters that can optimize several important phi-divergences simultaneously and that this set corresponds to a constant quiescent firing rate (QFR) of the spiral ganglion neuron. The optimal value of the QFR is frequency dependent but is essentially independent of the amplitude of the signal (for small amplitudes). Consequently, optimal processing according to several standard IT criteria can be accomplished for this model if and only if the parameters are "tuned" to values that correspond to one and the same QFR. This offers a new explanation for the QFR and can provide new insight into the role played by several other parameters of the peripheral auditory system.     

Seamless Integration: Standardisation across Multiple Local Settings

The pressure towards tighter or “seamless” integration of health information systems is a recurring issue with both practical and analytical relevance. It taps into a discourse in the IS literature in general and organisation and management science in particular. Unfortunately, the prevailing perception of integration in the IS literature is as a predominantly technical issue. The CSCW literature, however, is attentive to the socio-technical aspects of integration. Building on this – but supplemented with recent elaborations in science studies – we aim at exploring the unintended consequences of information systems integration. A user-led perspective implies emphasising the tailoring to local needs based on in-depth studies of the micro practices. We argue, however, that the condition for such an approach is radically undermined by politically motivated, regional changes towards integration with implicated standardisation. Enforcing order in the form of standards across multiple local settings, seemingly a prerequisite for tight integration, simultaneously produces disorder or additional work in other locations for other users. Empirically, our study is based on a large, ongoing integration effort at the University hospital of Northern Norway, specifically studying work practices and perceptions across multiple laboratories.     

Enhanced linear dynamic range of asymmetric Fabry-Pe/spl acute/rot modulator/detector

An InGaAsP multiple-quantum-well asymmetric Fabry-Pe/spl acute/rot modulator/detector has been developed for radio-over-fiber systems. The measured bandwidth is more than 6 GHz and the total insertion loss is 7.1 dB. The property of nonlinearity and spurious-free dynamic range (SFDR) has been studied theoretically. By optimizing the operation optical wavelength and bias voltage based on the numerical simulation, fifth-order nonlinearity dominates the intermodulation distortion and an SFDR of 101 dB/spl middot/Hz/sup 4/5/ has been achieved experimentally.     

Technical solutions for the 3G long-term evolution

Work has started in the 3GPP to define a long-term evolution for 3G, sometimes referred to as super-3G, which will stretch the performance of 3G technology, thereby meeting user expectations in a 10-year perspective and beyond. The fundamental targets of this evolution - to further reduce user and operator costs and to improve service provisioning - will be met through improved coverage and system capacity as well as increased data rates and reduced latency. This article presents promising technologies to fulfil these targets, including OFDM, multi-antenna solutions, evolved QoS and link layer concepts, and an evolved architecture. Furthermore, the results of a performance evaluation are presented, indicating that the requirements can indeed be reached using the proposed technologies.