OBJECTIVES To find evidence, either corroborating or refuting, for many persisting beliefs regarding the feasibility of carrying out surgical randomised controlled trials with a placebo arm, with emphasis on the challenges related to recruitment, funding, anaesthesia or blinding. DESIGN Systematic review. DATA SOURCES AND STUDY SELECTION The analysis involved studies published between 1959 ...

This paper is devoted to simulate the arc movement in the quenching chamber of the low-voltage circuit breaker. Based on a group of governing equations, a three-dimensional (3-D) arc model is built and solved by a modified commercial code. According to the simulated results, some phenomena such as a ‘bulge’ in front of the arc column, a tail in the rear of the arc column, arc shrinkage near the...

Discrete groups of isometries provide a rich class of groups for detailed study in an undergraduate course in abstract algebra. After developing some geometric tools, we illustrate several important ideas from group theory via symmetry groups. In particular, we consider conjugation, homomorphisms, normal and nonnormal subgroups, generators and relations, quotient groups and direct and semidirec...

Data produced by three dimensional MHD calculations are often difficult to visualize. Here we present a technique to view field lines of vector fields and one to display multiple isosurfaces of scalar fields. These methods do not rely on expensive commercial software and are general enough to be applied to other research sectors where visualization of 3D fields is important. Printed copies of t...

Hot forging of an Fe-Ni-Co alloy used for aeronautical purposes has been modeled using the commercial software ABAQUSTM/Explicit in order to obtain all the mechanical and thermal information to proceed with piercing and ring rolling. The material used is a 909 Incoloy type super alloy and it is used for the energy generation industry. Information of the constitutive behaviour of the alloy was i...

MobiHealth and HealthService24 are two major EU projects targeting the development and validation, with extensive medical trials, of innovative systems and services for mobile health care. Biosignals are measured by sensor devices connected to a wireless Body Area Network. These signals are transmitted reliably and securely over public wireless networks (e.g. GPRS, UMTS) to a remote healthcare ...

Software free trial is a common practice that has both positive and negative effects. On the one hand, it helps firms to exploit the positive network externalities by building up the total user base; on the other hand, it cannibalizes partial demand for the commercial software. The objective of my dissertation is to determine the conditions under which the firms should introduce the free trial ...