The Management and Use of Social Network Sites in a Government Department

In this paper we report findings from a study of social network site use in a UK Government department. We have investigated this from a managerial, organisational perspective. We found at the study site that there are already several social network technologies in use, and that these: misalign with and problematize organisational boundaries; blur boundaries between working and social lives; present differing opportunities for control; have different visibilities; have overlapping functionality with each other and with other information technologies; that they evolve and change over time; and that their uptake is conditioned by existing infrastructure and availability. We find the organisational complexity that social technologies are often hoped to cut across is, in reality, something that shapes their uptake and use. We argue the idea of a single, central social network site for supporting cooperative work within an organisation will hit the same problems as any effort of centralisation in organisations. We argue that while there is still plenty of scope for design and innovation in this area, an important challenge now is in supporting organisations in managing what can best be referred to as a social network site 'ecosystem'.Comment: Accepted for publication in JCSCW (The Journal of Computer Supported Cooperative Work

Geophysics

Contains reports on three research projects

Geophysics

Contains reports on four research projects

Quarkonium production in hadronic collisions

We summarize the theoretical description of charmonium and bottonium production in hadronic collisions and compare it to the available data from hadron-nucleon interactions. With the parameters of the theory established by these data, we obtain predictions for quarkonium production at RHIC and LHC energies.Comment: 11 pages (Plain Tex), 16 figures available on request by fax (41-22) 782 391

A Coarse Pointing Assembly for Optical Communication

In the framework of a contract with the European Space Agency, RUAG Space are developing a Coarse Pointing Assembly for an Optical Communication Terminal with the goal to enable high-bandwidth data exchange between GEO and/or LEO satellites as well as to earth-bound ground stations. This paper describes some development and testing aspects of such a high precision opto-mechanical device, with emphasis on the influence of requirements on the final design, the usage of a Bearing Active Preload System, some of the lessons learned on the BAPS implementation, the selection of a flex print design as rotary harness and some aspects of functional and environmental testing

Closed solid-state-fluid mechanical model for calculating the transferable torque on wrapped rolls

Higher velocities of webs at the same or reduced web tension require basic improvement of the existing machine technique. Concerning the transferable torque between a web and a roll common work is restricted either to the foil bearing theory at constant web tension without solid-state contact, or to the solid-state friction, including in some cases the influence of a constant fluid pressure. In this paper a model for calculating the transferable torque between a roll and a web is introduced which is more conform to reality. In the web mounting and in the web launching area the gap width and the pressure are calculated taking into account the web tension. In the intermediate area, where contact occurs between the rough surfaces of web and roll, it is assumed that the gap width can be substituted by an equivalent gap width between smooth surfaces. The transferable torque is calculated taking into account the local fluid pressure. The calculations show that, in the contact area, the compressibility of the fluid has a significant influence on the pressure profile and, finally, on the transferable torque.A device reducing the air entrainment by means of the so called "gap throttle effect" is introduced. It needs no separate energy, works nearly without contact, and has our patent pending on it. The maximum velocity up to which torque is transferable, as well as the transferable torque at a constant velocity, can be increased by this considerably. The effectiveness could be verified at a test rig in our laboratory

Prevention of web floating at wrapped transport and guide rollers

Increasing productivity of web converting machines requires constructive improvements for the prevention of web floating at transport and guide rollers. Existing solutions which carry off the air like vacuum or grooved rollers as well as rough layers at the roller surfaces are on the one hand complicated and on the other hand limited in their effect.On this background a novel principle, the so-called "gap throttle effect", which was discovered at the institute of engineering design at the Ruhr-Universitat-Bochum (LMK) is presented.The following analysis contains initial practically orientated investigations of pressure development resp. air entrainment for the conventional system ,,wrapped roller" and subsequent investigations for the novel system "gap throttle". The aim is to analyse the influence parameters with aid of a developed simulation program based on the finite differences method as well as to verify the results with experimental investigations at a test rig.To show the influence and the potential of the "gap throttle effect'', LWC, SC, Tissue and Newsprint with different material properties especially, air permeability and surface roughness, are analysed by variation of relevant process, gap throttle and machine parameters.The results prove, that the effect can be used to achieve higher transferable friction forces and therefore higher web speed. Subsequent investigations show, that the effect amount and it's stability can be increased considerably by an additional small pressure on the web surface at the mounting area of the web. The innovation potential and the usefulness of this novel principle for web handling machines should be used for later research work, to increase the range of application, especially for winding and coating

Hadronic Cross-sections in two photon Processes at a Future Linear Collider

In this note we address the issue of measurability of the hadronic cross-sections at a future photon collider as well as for the two-photon processes at a future high energy linear $e^+e^-$ collider. We extend, to higher energy, our previous estimates of the accuracy with which the \gamgam\ cross-section needs to be measured, in order to distinguish between different theoretical models of energy dependence of the total cross-sections. We show that the necessary precision to discriminate among these models is indeed possible at future linear colliders in the Photon Collider option. Further we note that even in the $e^+e^-$ option a measurement of the hadron production cross-section via \gamgam processes, with an accuracy necessary to allow discrimination between different theoretical models, should be possible. We also comment briefly on the implications of these predictions for hadronic backgrounds at the future TeV energy $e^+e^-$ collider CLIC.Comment: 20 pages, 5 figures, LaTeX. Added an acknowledgemen

Resonant Production of Scalar Diquarks at the Next Generation Electron-Positron Colliders

We investigate the potential of TESLA and JLC/NLC electron-positron linear collider designs to observe diquarks produced resonantly in processes involving hard photons.Comment: 14 pages, 8 figures, coded in RevTEX, uses epsfi