Basics of RF electronics

RF electronics deals with the generation, acquisition and manipulation of high-frequency signals. In particle accelerators signals of this kind are abundant, especially in the RF and beam diagnostics systems. In modern machines the complexity of the electronics assemblies dedicated to RF manipulation, beam diagnostics, and feedbacks is continuously increasing, following the demands for improvement of accelerator performance. However, these systems, and in particular their front-ends and back-ends, still rely on well-established basic hardware components and techniques, while down-converted and acquired signals are digitally processed exploiting the rapidly growing computational capability offered by the available technology. This lecture reviews the operational principles of the basic building blocks used for the treatment of high-frequency signals. Devices such as mixers, phase and amplitude detectors, modulators, filters, switches, directional couplers, oscillators, amplifiers, attenuators, and others are described in terms of equivalent circuits, scattering matrices, transfer functions; typical performance of commercially available models is presented. Owing to the breadth of the subject, this review is necessarily synthetic and non-exhaustive. Readers interested in the architecture of complete systems making use of the described components and devoted to generation and manipulation of the signals driving RF power plants and cavities may refer to the CAS lectures on Low-Level RF.Comment: 36 pages, contribution to the CAS - CERN Accelerator School: Specialised Course on RF for Accelerators; 8 - 17 Jun 2010, Ebeltoft, Denmar

Low-noise flow valve for air ducts

Valve assembly controls air flow from feeder into main duct, with minimum of turbulence, friction, pressure differential, and noise. Valve consists of damper, deflector, and spring. Streamlining of damper and deflector merges flow smoothly, while spring keeps damper and deflector in contact and eliminates valve chatter and damping vibrations

Bank institutional setting and risk-taking: The missing role of directors’ education and turnover

Purpose: This paper aims to analyze the relationship between bank institutional setting and risk-taking by exploring whether board education and turnover are drivers of the risk propensity of cooperative banks compared to jointstock banks. Design/methodology/approach: Based on a comprehensive dataset of Italian banks over the 2011-2017 period, we examine whether these board characteristics affect the risk propensity of cooperative and joint-stock banks. Bank risk is measured by the Zindex, profit volatility and the ratio of non-performing loans to total gross loans. Findings: The findings show that cooperatives take less risk than joint-stock banks and have lower board turnover and education. Furthermore, we find that while board education mediates the relationship between the cooperative model and bank risk-taking, we do not find evidence of board turnover. Thus, the lower educational level of cooperative directors contributes to explaining the lower risk-taking of cooperative banks. Implications: The findings have several implications. In terms of the more general policy debate, our results point to the need to strengthen the governance model for both joint-stock and cooperative banks while supporting the view that a more ad hoc perspective on the best models and practices for each type of institutional setting would be preferable. In particular, the study reveals how board education’s effects on bank risk-taking should be carefully monitored. Originality/value: Through a mediation framework, this study provides empirical evidence on the relationship between bankinstitutional setting (by distinguishing between cooperative and joint-stock banks) and risk-taking behavior by exploring the underlying mechanisms at the board level, which is novel in the literature

Independent board directors: How to improve their contribution to the family business

This study is based on information obtained from two questionnaires, one sent to the presidents and CEOs of a sample of family businesses and the other sent to independent members of the Boards of Directors of the same businesses. The main points of agreement and the main differences of opinion between these two groups are identified and grouped under the following headings: 1) governance practices; 2) reasons for retaining or seeking the resignation of independent board directors; 3) reasons why independent board directors do not give the best of themselves, and 4) most appreciated and most missed qualities in independent board directors. The most important findings are: a) The main reasons for including independent board directors are to improve the structure of corporate governance and to resolve succession problems; b) The main reasons for seeking the resignation of independent board directors are lack of the necessary personal qualities, lack of the right relationship with the other directors, and calls for their resignation from significant shareholders, and c) According to independent board directors, the main reasons why they fail to give the best of themselves are that the owners are not genuinely committed to having a professional and effective Board of Directors, and the fact that important decisions are made by the family without taking the independent directors' opinions into account. The authors put forward six propositions to help get the most out of independent board directors and offer some recommendations on how to improve the structure of family business governance.independent board directors; corporate governance; family business governance;

Four New Capabilities in NASTRAN for Dynamic and Aeroelastic Analyses of Rotating Cyclic Structures

Static aerothermoelastic design/analysis of axial-flow compressors, modal flutter analysis of axial-flow turbomachines, forced vibration analysis of rotating cyclic structures and modal flutter analysis of advanced turbopropellers with highly swept blades are four new capabilities developed and implemented in NASTRAN Level 17.7. The contents, applicability and usefulness of these capabilities which were developed and documented under the sponsorship of NASA's Lewis Research Center are discussed. Overall flowcharts and selected examples are presented

The origin of blue-shifted absorption features in the X-ray spectrum of PG 1211+143: Outflow or disc?

In some radio-quiet active galaxies (AGN), high-energy absorption features in the x-ray spectra have been interpreted as Ultrafast Outflows (UFOs) -- highly ionised material (e.g. Fe XXV and Fe XXVI) ejected at mildly relativistic velocities. In some cases, these outflows can carry energy in excess of the binding energy of the host galaxy. Needless to say, these features demand our attention as they are strong signatures of AGN feedback and will influence galaxy evolution. For the same reason, alternative models need to be discussed and refuted or confirmed. Gallo & Fabian proposed that some of these features could arise from resonance absorption of the reflected spectrum in a layer of ionised material located above and corotating with the accretion disc. Therefore, the absorbing medium would be subjected to similar blurring effects as seen in the disc. A priori, the existence of such plasma above the disc is as plausible as a fast wind. In this work, we highlight the ambiguity by demonstrating that the absorption model can describe the ~7.6 keV absorption feature (and possibly other features) in the quasar PG 1211+143, an AGN that is often described as a classic example of an UFO. In this model, the 2-10 keV spectrum would be largely reflection dominated (as opposed to power law dominated in the wind models) and the resonance absorption would be originating in a layer between about 6 and 60 gravitational radii. The studies of such features constitutes a cornerstone for future X-ray observatories like Astro-H and Athena+. Should our model prove correct, or at least important in some cases, then absorption will provide another diagnostic tool with which to probe the inner accretion flow with future missions.Comment: 4 pages. Accepted for publication in MNRAS Letter

Rapid sync acquisition system Patent

System designed to reduce time required for obtaining synchronization in data communication with spacecraft utilizing pseudonoise code