Clutter filters adapted to tissue motion in ultrasound color flow imaging

The quality of ultrasound color flow images is highly dependent on sufficient attenuation of the clutter signals originating from stationary and slowly moving tissue. Without sufficient clutter rejection, the detection of low velocity blood flow will be poor, and the velocity estimates will have a large bias. In some situations, e.g., when imaging the coronary arteries or when the operator moves the probe in search for small vessels, there is considerable movement of tissue. It has been suggested that clutter rejection can be improved by mixing down the signal with an estimate of the mean frequency prior to high pass filtering. In this paper, we compare this algorithm with several other adaptive clutter filtering algorithms using both experimental data and simulations. We found that realistic accelerations of the tissue have a large effect on the clutter rejection. The best results were obtained by mixing down the signal with non-constant phase increments estimated from the signal. This adapted the filter to a possibly accelerated tissue motion and produced a significant improvement in clutter rejection     

CFL-Violating Numerical Schemes for a Two-Fluid Model

In this paper we propose a class of linearly implicit numerical schemes for a two-phase flow model, allowing for violation of the CFL-criterion for all waves. Based on the Weakly Implixit Mixture Flux (WIMF) approach [SIAM J. Sci. Comput., 26 (2005), pp. 1449–1484], we here develop an extension denoted as Strongly Implicit Mixture Flux (SIMF). Whereas the WIMF schemes are restricted by a weak CFL condition which relates time steps to the fluid velocity, the SIMF schemes are able to break the CFL conditions corresponding to both the sonic and advective velocities. The schemes possess some desirable features compared to current industrial pressure-based codes. They allow for sequential updating of the momentum and mass variables on a nonstaggered grid by solving two sparse linear systems. The schemes are conservative in all convective fluxes and consistency between the mass variables and pressure is formally maintained. Numerical experiments are presented to shed light on the inherent differences between the WIMF and SIMF families of schemes. In particular, we demonstrate that the WIMF scheme is able to give an exact resolution of a moving contact discontinuity. The SIMF schemes do not possess the “exact resolution” property of WIMF, however, the ability to take larger time steps can be exploited so that more efficient calculations can be made when accurate resolution of sharp fronts is not essential, e.g. to calculate steady state solutions.     

Maximum entropy angular response patterns of microwave transhorizon signals

The maximum entropy method (MEM) is applied in the computation of angular response patterns based on amplitude and phase measurements from a 12-element vertical array receiving transhorizon microwave signals. The patterns are compared with those obtained using conventional Fourier transform techniques (FTT). The MEM patterns exhibit higher resolution and lower sidelobes, revealing in some cases features not seen in the FTT patterns.     

Sources accounting for alliance and cohesion at three stages in group psychotherapy: Variance component analyses.

This study examined patient, therapist, and group variability accounting for alliance and cohesion over three stages in a sample of 145 patients attending short- and long-term psychodynamic group therapy. G-study variance components were estimated for the 14 sources of variation identifiable by the research design. Results indicated that patient variability represented the strongest clinically relevant contribution to both alliance and cohesion. Therapists were important for alliance at all stages, but for cohesion only in the middle stage. The therapist × group interaction was important to the alliance in early therapy and for cohesion within the two first stages, but this contribution then decreased. Group length did not account for any variability in the process measures. Theoretical implications were discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Design ideas for IT in public spaces

This paper examines the usability issues involved in ticketless travelling with an airport train. The main contribution of this paper is that it describes actual use situations in detail. We show how users’ intentions are difficult to anticipate, unless in explicit communication, e.g., with people whose job it is to help out with using the system. Being conspicuously assisted, however, only aggravates a situation where users usually prefer anonymity. Given a “private in public” type of design, users had little chance of learning from watching others. Moreover, users were quickly annoyed when they struggled with the machine. They seemed to treat it as an agent for the provider rather than an assistant or tool for themselves. At the end of this paper, we outline and illustrate some new design ideas, which we think ought to be considered for future designs of IT in public spaces.     

Digital dysfunctions in primary school: A pilot study

Learning often involves complex cognitive and motorical processes, and while most learners cope adequately with these challenges there are always some that struggle. When new kinds of knowledge are introduced there is a possibility that some learners will find this new knowledge hard to acquire, and thus manifest a dysfunction. Today the new knowledge can be found within the digital domain. Some learners need more time and more efforts to master the different aspects of digital literacy, some of these even need special attention from friends, teachers or others. Is it possible that this group of learners is experiencing some kind of dysfunctions? It is likely to think so, there are a variety of different learning dysfunctions related to many learning domains, and when a new domain is established it would not come as a surprise that a new form of dysfunction is discovered. This article seeks to answer the question: “Do digital dysfunctions exist?” The answer is given as indicators more than as solid proof. In this study a group of 144 pupils is reduced through a triangulation of qualitative and quantitative methods, and ends up with three cases where there are obvious lacks of digital literacy without any obvious reason. The study also deals with definitions on “digital literacy”, and tries to point out what construct the term “digital literacy” in the study material. This construct is then used for measuring digital literacy.     

Observability theorems for some linear hyperbolic systems

In this paper the observability of systems of first-order hyperbolic partial differential equations is investigated. Both systems with boundary measurements and systems with distributed measurements are considered. In the case of boundary measurements a sufficient condition is found for observability. This condition is shown also to be necessary for systems defined on a one-dimensional space domain, as well as in other special cases. In the case of linear distributed measurements, a necessary and sufficient condition for observability is derived. The theorems are applicable for example to linearized hydrodynamical flow equations and to industrial flow system equations.     

Micro-fibre and ultra-micro-fibre cloths, their physical characteristics, cleaning effect, abrasion on surfaces, friction, and wear resistance

The properties of 12 micro-fibre cloths and two ultra-micro-fibre cloths were studied and compared with conventional cleaning methods. The cloths made from micro-fibre and ultra-micro-fibre had very good cleaning effect. Scrubbing Plexiglas caused pitting and scratch marks on the Plexiglas surface with the largest damage being caused in dry condition. All the cloths tested were wear resistant. Most of the cloths showed high friction against the surfaces in damp condition. Micro- and ultra-micro-fibre cloths are good alternatives to conventional methods for cleaning interior surfaces. Furthermore, good cleaning results can be achieved without any use of polluting cleaning chemicals.