Evaluating the effects of frame of reference on spatial collaboration using desktop collaborative virtual environments

Spatial collaboration is an everyday activity in which people work together to solve a spatial problem. For example, a group of people will often arrange furniture together or exchange directions with one another. Collaborative virtual environments using desktop PCs are particularly useful for spatial activities when the participants are distributed. This work investigates ways to enhance distributed, collaborative spatial activities. This paper explores how different frames of reference affect spatial collaboration. Specifically, it reports on an experiment that examines different combinations of exocentric and egocentric frames of reference with two users. Tasks involve manipulating an object, where one participant knows the objective (director) and the other performs the interactions (actor). It discusses the advantages and disadvantages of the different combinations for a spatial collaboration task. Findings from this study demonstrate that frames of reference affect collaboration in a variety of ways and simple exocentric-egocentric combinations do not always provide the most usable solution.     

A lower bound for structuring element decompositions

A theoretical lower bound on the number of points required in the decomposition of morphological structuring elements is described. It is shown that the decomposition of an arbitrary N-point structuring element will require at least [3 ln N/ln 3]points. Using this lower bound it is possible to find the optimal decompositions (in terms of the minimum number of unions or the minimum number of points) for all one-dimensional connected line segments. L-dimensional rectangles may be decomposed by optimally decomposing the L one-dimensional line segments that describe the rectangle     

The UK Cleanfeed system — Lessons for the German debate?

As readers of this journal will of course know, the Zugangserschwerungsgesetz has caused considerable and often very profound debate in Germany about the limits of legal and technological interference with the freedom of access to information, culminating in the temporary refusal of the President to sign the law into action. In the UK by contrast, a core aspect of this law, the technical prevention of access to sites hosting illegal content by ISPs, was introduced through the so called “Cleanfeed system” as early as 1996, with little or no public debate, and bypassing by and large all parliamentary procedure and scrutiny. This article has a threefold aim: First, it gives a brief account of the history and implementation of the UK Cleanfeed system1; second, it explains some of its more unusual aspects by putting them into the historical and constitutional context of policing in the UK, and third, it highlights those experiences made with the system that are of direct relevance for the German discussion.     

Geometrically non-linear behavior of structural systems with random material property: An asymptotic spectral stochastic approach

An asymptotic spectral stochastic approach is presented for computing the statistics of the equilibrium path in the post-bifurcation regime for structural systems with random material properties. The approach combines numerical implementation of Koiter’s asymptotic theory with a stochastic Galerkin scheme and collocation in stochastic space to quantify uncertainties in the parametric representation of the load–displacement relationship, specifically in the form of uncertain post-buckling slope, post-buckling curvature, and a family of stochastic displacement fields. Using the proposed method, post-buckling response statistics for two plane frames are obtained and shown to be in close agreement with those obtained from Monte Carlo simulation, provided a fine enough spectral representation is used to model the variability in the random dimension.     

Surveillance for the masses: the political and legal landscape of the UK Investigatory Powers Bill

In March 2016, the UK Government put the Investigatory Powers Bill before Parliament. The new law, if enacted, will considerably increase the powers of law enforcement and security services regarding mass data retention, mass surveillance and mass hacking. This raises considerable concerns not just about the content of the Bill and its impact on privacy, but also about the method of its enactment and the ever diminishing parliamentary and judicial scrutiny of surveillance legislation in the UK.     

Fundamentals of electrosorption on activated carbon for wastewater treatment of industrial effluents

The potential of electroadsorption/desorption on activated carbon for waste water treatment of industrial effluents is studied. Adsorption isotherms of hydrophobic differently charged model substances on activated carbon were measured in order to obtain specific information about the influence of the charge (+1,–1 and 0) on the adsorbability of comparable, aromatic species and the influence of the bed potential on the adsorption equilibria. In all these cases the adsorption equilibria show a dependence on applied potential in electrolyte of approximately 1m ionic strength. With electrosorption from aqueous solution, a fivefold enhancement of the concentration in one potential controlled adsorption/desorption cycle is achievable. The use of the solvent methanol instead of water for desorption allows for a concentration enhancement by a factor of hundred in the desorptive step. The adsorption capacity of the activated carbon changes only slightly with cycle number. Two cell designs for the performance of potential controlled adsorption/desorption cycles on the large scale are discussed.