A 20 kA Test Bench for High-Precision Current Measurements

The d.c. currents in the LHC dipole and quadrupole chains will require settings and adjustments with a precision of a few ppm. For an ultimate current level of 13 kA this represents an unprecedented accuracy. Compared to the requirements of previous accelerators at CERN, such as the LEP, this is a factor of ten better in accuracy at more than twice the current. State-of-the-art, zero-flux current transducers from Industry will be used for the precision measurements. As no existing laboratory would be capable of performing the calibrations of these transducers to the required precision, a major upgrading of the current Standards laboratory at CERN was decided. The paper describes the various phases of the project, from field calculations and design to construction and final commissioning of this unique test bench. The highly automated facility allows determination of off-sets, linearity and drift of transducers up to 20 kA but provides equally the means to study the sensitivity of the transducers to external stray fields as generated by currents in adjacent busbars

How to fill a narrow 27 KM long tube with a huge number of accelerator components?

As in large scale industrial projects, research projects, such as giant and complex particle accelerators, require intensive spatial integration studies using 3D CAD models, from the design to the installation phases. The future management of the LHC machine configuration during its operation will rely on the quality of the information, produced during these studies. This paper presents the powerful data-processing tools used in the project to ensure the spatial integration of several thousand different components in the limited space available. It describes how the documentation and information generated have been made available to a great number of users through a dedicated Web site and how installation nonconformities were handled

Effects of plot size, stand density, and scan density on the relationship between airborne laser scanning metrics and the gini coefficient of tree size inequality

© 2017, Canadian Science Publishing. All rights reserved. Estimation of the Gini coefficient (GC) of tree sizes using airborne laser scanning (ALS) can provide maps of forest structure across the landscape, which can support sustainable forest management. A challenge arise s in determining the optimal spatial resolution that maximizes the stability and precision of GC estimates, which in turn depends on stand density or ALS scan density. By subsampling different plot sizes within large field plots, we evaluated the optimal spatial resolution by observing changes in GC estimation and in its correlation with ALS metrics. We found that plot size had greater effects than either stand density or ALS scan density on the relationship between GC and ALS metrics. Uncertainty in GC estimates fell as plot size increased. Correlation with ALS metrics showed convex curves with maxima at 250–450m 2 , which thus was considered the optimal plot size and, consequently, the optimal spatial resolution. By thinning the density of the ALS point cloud, we deduced that at least 3 points·m −2 were needed for reliable GC estimates. Many nationwide ALS scan densities are sparser than this, so may be unreliable for GC estimation. Ours is a simple approach for evaluating the optimal spatial resolution in remote sensing estimation of any forest attribute

Review and Support of the Relationship between Alliance Competence and Alliance Orientation

This paper seeks to contribute to the understanding of the formation of strategic alliances among companies. Specifically, it seeks to understand the relationship between alliance competence (Lambe, Speakman & Hunt, 2002) and alliance orientation (Kandemir, Yaprak & Cavusgil, 2006), following some of the most important guidelines of the leading exponents of theories based on resources and dynamic capabilities.Once the concepts were developed we proceeded to establish a hypothesis that seeks to better understand the relationships between the constructs and how they interact to achieve alliances that are beneficial for the parties involved.In particular, the findings corroborate the proposed relationships, supporting a direct link between market orientation constructs and senior management commitment to the alliances, as well as the commitment of senior management and competencies for alliances. As a fundamental contribution to this work, a mediating role of the alliance orientation construct was also detected between the relationship of senior management commitment and alliance competence.Future research is proposed into the elements of the practical guidelines for alliances and the relationship of this construct with the others related to alliances and particularly to their performance

PROBABILISTIC MODELS TO ESTIMATE FIRE-INDUCED CABLE DAMAGE AT NUCLEAR POWER PLANTS

Even though numerous PRAs have shown that fire can be a major contributor to nuclear power plant risk, there are some specific areas of knowledge related to this issue, such as the prediction of fire-induced damage to electrical cables and circuits, and their potential effects in the safety of the nuclear power plant, that still constitute a practical enigma, particularly for the lack of approaches/models to perform consistent and objective assessments. This report contains a discussion of three different models to estimate fire-induced cable damage likelihood given a specified fire profile: the kinetic, the heat transfer and the IR "K Factor" model. These models not only are based on statistical analysis of data available in the open literature, but to the greatest extent possible they use physics based principles to describe the underlying mechanism of failures that take place among the electrical cables upon heating due to external fires. The characterization of cable damage, and consequently the loss of functionality of electrical cables in fire is a complex phenomenon that depends on a variety of intrinsic factors such as cable materials and dimensions, and extrinsic factors such as electrical and mechanical loads on the cables, heat flux severity, and exposure time. Some of these factors are difficult to estimate even in a well-characterized fire, not only for the variability related to the unknown material composition and physical arrangements, but also for the lack of objective frameworks and theoretical models to study the behavior of polymeric wire cable insulation under dynamic external thermal insults. The results of this research will 1) help to develop a consistent framework to predict fire-induced cable failure modes likelihood, and 2) develop some guidance to evaluate and/or reduce the risk associated with these failure modes in existing and new power plant facilities. Among the models evaluated, the physics-based heat transfer model takes into account the properties and characteristics of the cables and cable materials, and the characteristics of the thermal insult. This model can be used to estimate the probability of cable damage under different thermal conditions

Measurement and Analysis of Axial End Forces in a Full-Length Prototype of LHC Main Dipole Magnets

A full-length, twin aperture prototype (MBP2N1) dipole magnet for the LHC project was assembled at CERN with collared coils delivered by industry. The design of this prototype is close to that foreseen for the dipole series manufacture as far the coil geometry and that of the yoke components are concerned. The bolts that transfer the axial magnetic forces from the coil ends to the cold mass end plates were instrumented to verify the axial coil support. These axial forces were initially measured after partial assembly, during a standard and an accelerated cool down Introduction to 1.9 K, and during magnet excitation up to 9.2 T. High force levels were observed, triggering a comparison with analytical models and measurements routinely made on 1-m single aperture dipole models. The prototype magnet was re-assembled with lower initial axial force settings and with additional instrumentation, to monitor these forces during the entire assembly process, and re-tested, to possibly correlate axial forces with training behaviour. This paper reports about the experimental observations and provides models towards their understandin

The seed bank in Pinus stand regeneration in NW Spain after wildfire

P. 22-31In the Cantabrian area (northwest Spain) Pinus stands occupy many of the original shrub communities that have been considered unproductive. These Pinus stands represent the vegetation which is most affected by fire. Regeneration after fire may occur in different ways: by resprouting or by germination or both. Germination was the only regeneration mechanism in Pinus species that appeared in these areas. The aim of this study is to determine the role of the soil seed bank in regeneration in this type of ecosystem. In order to carry out the study, three communities dominated by Pinus sylvestris which had suffered wildfires were chosen. In each of the three experimental sites of Pinus sylvestris stands the seed bank composition and above-ground vegetation were studied. The results allowed three species groups in the seed bank to be differentiated: those favoured by fire, amongst which some hardseeds, mainly belonging to Cistaceae and Leguminosae, were found; another group formed by outsider or opportunist species from outside the community and which used anemochory as their main dispersion mechanism; and the third group formed by those negatively affected, amongst which were species using vegetative resprout as the main regeneration mechanism. The species of greatest quantitative importance in the seed bank was Erica australis. In general, anemochorous species were predominant in the soil seed bank. During the first stages of succession chamaephytes were dominant and in the two years after fire therophytes were. No great similarity was observed between the bank composition and field vegetation from a qualitative viewpoint, due to differences in the presence of seeds of outsider plants in the bank and to the significance of the resprouting species in the field.S

Remote Inspection, Measurement and Handling for LHC

Personnel access to the LHC tunnel will be restricted to varying extents during the life of the machine due to radiation, cryogenic and pressure hazards. The ability to carry out visual inspection, measurement and handling activities remotely during periods when the LHC tunnel is potentially hazardous offers advantages in terms of safety, accelerator down time, and costs. The first applications identified were remote measurement of radiation levels at the start of shut-down, remote geometrical survey measurements in the collimation regions, and remote visual inspection during pressure testing and initial machine cool-down. In addition, for remote handling operations, it will be necessary to be able to transmit several real-time video images from the tunnel to the control room. The paper describes the design, development and use of a remotely controlled vehicle to demonstrate the feasibility of meeting the above requirements in the LHC tunnel. Design choices are explained along with operating experience to-date and future development plans

Carbon monoxide oxidation on Pt-Ru electrocatalysts supported on high surface area carbon

This find is registered at Portable Antiquities of the Netherlands with number PAN-0000787