Substance without citation: evaluating the online impact of grey literature

Individuals and organisations producing information or knowledge for others sometimes need to be able to provide evidence of the value of their work in the same way that scientists may use journal impact factors and citations to indicate the value of their papers. There are many cases, however, when organisations are charged with producing reports but have no real way of measuring their impact, including when they are distributed free, do not attract academic citations and their sales cannot be tracked. Here, the web impact report (WIRe) is proposed as a novel solution for this problem. A WIRe consists of a range of web-derived statistics about the frequency and geographic location of online mentions of an organisation’s reports. WIRe data is typically derived from commercial search engines. This article defines the component parts of a WIRe and describes how to collect and analyse the necessary data. The process is illustrated with a comparison of the web impact of the reports of a large UK organisation. Although a formal evaluation was not conducted, the results suggest that WIRes can indicate different levels of web impact between reports and can reveal the type of online impact that the reports have.     

Evaluating altmetrics

The rise of the social web and its uptake by scholars has led to the creation of altmetrics, which are social web metrics for academic publications. These new metrics can, in theory, be used in an evaluative role, to give early estimates of the impact of publications or to give estimates of non-traditional types of impact. They can also be used as an information seeking aid: to help draw a digital library user’s attention to papers that have attracted social web mentions. If altmetrics are to be trusted then they must be evaluated to see if the claims made about them are reasonable. Drawing upon previous citation analysis debates and web citation analysis research, this article discusses altmetric evaluation strategies, including correlation tests, content analyses, interviews and pragmatic analyses. It recommends that a range of methods are needed for altmetric evaluations, that the methods should focus on identifying the relative strengths of influences on altmetric creation, and that such evaluations should be prioritised in a logical order.     

Data assimilation in weather forecasting: a case study in PDE-constrained optimization

Variational data assimilation is used at major weather prediction centers to produce the initial conditions for 7- to 10-day weather forecasts. This technique requires the solution of a very large data-fitting problem in which the major element is a set of partial differential equations that models the evolution of the atmosphere over a time window for which observational data has been gathered. Real-time solution of this difficult computational problem requires sophisticated models of atmospheric physics and dynamics, effective use of supercomputers, and specialized algorithms for optimization and linear algebra. The optimization algorithm can be accelerated by using a spectral preconditioner based on the Lanczos method. This paper shows how practical demands of the application dictate the various algorithmic choices that are made in the nonlinear optimization solver, with particular reference to the system in operation at the European Centre for Medium-Range Weather Forecasts.     

Study of intermetallic crystal growth between Nb and molten 52In-48Sn solder

The reactions between Nb and molten, eutectic In-Sn solder have been studied in the temperature range 130–240°C and for times ranging up to 12 months. Hexagonal platelet crystals of NbSn₂ form an intermetallic compound (IMC) layer that provides adhesion between solder and substate, but which grows extremely slowly even at 200°C. A model explaining the observed IMC growth kinetics is developed and relevant activation energies and model parameters are calculated. Applications include high-temperature electronics interconnection, where the device is secured to the substrate via an adhesive component and the solder is designed to melt, preventing fatigue failure by temperture cycling.     

用可编程DSP实现IEEE 802.16 PHY信号处理

IEEE802.16标准的各个版本都规定了PHY(物理层)的多种选项,包括调制、信道编码和天线分集技术。物理信道带宽可以在1.25MHz～20MHz之间变化。上述所有选项都会影响基站的性能和信号处理复杂度。许多客户希望提供一种可以从802.16-2004升级到802.16e标准的方法。上述需求以及对支持互通性(成功部署新标准的关键)的需求,都要求基站的PHY采用可编程的信号处理器件。图1为802.16基站基带信号链路基本框图。因为802.16-2004和802.16e标准都是在OFDM基础上建立的,所以FFT和IFFT起了很大的作用。这两种变换都用于频域副载波(携带编码的数…     

Elastic properties and electronic structure of vanadium silicides-a density functional investigation

Vanadium and silicon form several binary compounds; the most well characterized structures have the compositions V:Si = 3:1, 5:3, 6:5, 1:2. Spin-polarized density functional band-structure calculations using the projector augmented wave method have been carried out for the stable binary compounds in the Si–V system. As many rare earth and early transition metals are refractory materials, the study focuses on the ground state structures and their stabilities by determining their elastic properties. The magnetic properties are also investigated because structurally related Si–Mn compounds exhibit magnetism. All the silicides investigated were found to be refractory, hard, metallic materials and no magnetism was found in the ground state structures.