Electronic Stimulator for Medical Research

Engineerin

A Method for Simultaneous Optimisation of Orbit and Dispersion in Storage Rings

An algorithm for the simultaneous optimisation of orbit and dispersion in a storage ring is presented. Based on orbit and dispersion measurements the algorithm determines the optimal corrector settings in order to simultaneously minimize the r.m.s orbit, the r.m.s dispersion and the r.m.s strenght of the dipoles correctors. A number of different options for error handling of beam position monitors, weighting, and correction have been introduced to ensure the stability of the algorithm in the environment of a large accelerator. Experimental results are presented for the LEP collider demonstrating the efficiency of the method. The use of this correction algorithm for LEP in 1999 allowed achieving about a factor of two smaller vertical emittances than in previous years

The use of remote sensing to quantify wetland loss in the Choke Mountain range, Upper Blue Nile basin, Ethiopia

Wetlands provide multiple ecosystem services such as storing and regulating water flows and water quality, providing unique habitats to flora and fauna, and regulating micro-climatic conditions. Conversion of wetlands for agricultural use is a widespread practice in Ethiopia, particularly in the southwestern part where wetlands cover large areas. Although there are many studies on land cover and land use changes in this region, comprehensive studies on wetlands are still missing. Hence, extent and rate of wetland loss at regional scales is unknown. The objective of this paper is to quantify wetland dynamics and estimate wetland loss in the Choke Mountain range (area covering 17 443 km<sup>2</sup>) in the Upper Blue Nile basin, a key headwater region of the river Nile. Therefore, satellite remote sensing imagery of the period 1986–2005 were considered. To create images of surface reflectance that are radiometrically consistent, a combination of cross-calibration and atmospheric correction (Vogelman-DOS3) methods was used. A hybrid supervised/unsupervised classification approach was used to classify the images. Overall accuracies of 94.1% and 93.5% and Kappa Coefficients of 0.908 and 0.913 for the 1986 and 2005 imageries, respectively were obtained. The results showed that 607 km<sup>2</sup> of seasonal wetland with low moisture and 22.4 km<sup>2</sup> of open water are lost in the study area during the period 1986 to 2005. The current situation in the wetlands of Choke Mountain is characterized by further degradation which calls for wetland conservation and rehabilitation efforts through incorporating wetlands into watershed management plans

Protection of the LHC against Unsynchronised Beam Aborts

An unsynchronised beam abort in the LHC could damage downstream accelerator components, in particular the extraction septum magnets, the experimental low-beta triplet magnet apertures and the tertiary collimators. Although the LHC beam dumping system includes design features to minimise their frequency, such unsynchronised aborts cannot be excluded. A system of protection devices comprising fixed and moveable diluters and collimators will protect the downstream LHC aperture from the misdirected bunches in case of such a failure. The sources of unsynchronised aborts are described, together with the requirements and design of the protection devices and their expected performance. The accompanying operational requirements and envisaged solutions are discussed, in particular the problem of ensuring the local orbit at the protection devices

Wire excitation experiments in the CERN SPS

In order to study the effect of long range interaction and its wire compensation experimentally, current carrying wires are installed in the CERN Super Proton Synchrotron (SPS). In this paper we summarize the main results of the 2007 wire excitation experiments at 26, 37 and 55 GeV including scans of wire current, beam-wire distance and chromaticity. A strong dependence on the chromaticity and indications of a threshold effect at 37 and 55 GeV were found. The results are compared with simulations, with a simple analytic scaling law and with experimental results from RHIC. Wire driven resonances have been observed through the Fourier spectrum of experimental BPM data and also studied in simulation

A LITERATURE ANALYSIS ABOUT SOCIAL INFORMATION CONTRIBUTION AND CONSUMPTION ON SOCIAL NETWORKING SITES

Social networking sites (SNSs) have emerged as a center for daily social interactions. Every day, millions of users contribute information about themselves, and consume information about others on SNSs. In recent years, we have witnessed a growing number of studies on the issue of social information contribution and consumption behaviors on SNSs. This paper aims to provide a systematic literature review on this topic across different disciplines to understand the current research state and shed light on controversial findings of SNS usage regarding users’ well-being. We identified 126 relevant articles published between 2008 and 2014, and provide an overview of their antecedents and associated outcomes. Our analysis reveals that a majority of existing work focused primarily on social information contribution, its antecedents and favorable outcomes. Only few studies have dealt with contribution behavior and the dark sides of SNS use. Nevertheless, we could identify different characteristics of social information determining the favorability of contribution behavior. Further, we categorized the scarce papers of consumption behavior regarding the social information characteristics and identified different underlying processes: social comparison, monitoring and browsing. These findings contribute to the Information Systems (IS) discipline by consolidating previous knowledge about SNS usage patterns and individual well-being

Trim Magnet Polarities, Dispersion, and Response Data in Sector 23

During the first LHC injection test, on 10 August 2008, the horizontal dispersion measured with beam 1 at the end of Sector 23 differed from the model prediction close to point 3. Beam-based polarity checks performed during the same period indicated an inversion of the trim quadrupole QTL11.R2. Combined with other evidence, like electrical drawings and earlier Hall-probe measurements of warm magnets, this gave rise to the hypothesis of a systematic error. Indeed a model inversion of all trim quadrupoles (QT or QTL) attached to a defocusing main quadrupole (actually the odd-numbered trim quadrupoles in Sector 23) reproduced the dispersion measurement. An analysis of kick-response measurements independently revealed an optics error left of point 3, and confirmed the inversion of the odd-numbered trim quadrupoles in this sector. After changing the polarity of the suspected set of quadrupoles prior to the second injection test on August 24, the measured dispersion nicely traced the model prediction

LEP Operation and Performance with 100 GeV Colliding Beams

Luminosity production in LEP was extended to 101 GeV beam energy in 1999 and 104.4 GeV in 2000. The performance was continually optimised, resulting in 1999 peak and integrated luminosities higher than in any previous year of LEP operation. In particular, the beam-beam tune shift reached 0.083 per interaction point. This was achieved with the help of a faster luminosity monitoring, a new tune working point, a reduced design vertical dispersion and new dispersion and coupling optimisation tools. A higher beam rate from the injectors, a better injection efficiency, a faster ramp and a newly automated control of the horizontal damping partition number Jx maximised the time available for physics and thus contributed to the higher integrated luminosity