Information driven SDLC concepts

Although software engineering has matured greatly over the years, a large number of ICT projects continue to fail. Studies continue to identify non-technical issues such as poor communication, shifting requirements and poor executive involvement as the main causes of these failures. In a previous paper, the authors identified such causes and posed the question as to why currently available software development life cycles fall short of dealing with them. They also proposed the development of an information driven software development life cycle. In this paper, the concept of an information driven SDLC is explored further and a number of concepts are discussed in this regard.peer-reviewe

Lifelong verification of software systems

Computers systems are increasingly interacting with our day-to-day life, but for this interaction to be facilitating and supporting, rather than interfering with our actions, these systems have to be dependable and trustworthy. The area of system verification and validation has a long history in computer science, but scaling up existing approaches to complex and large real-life systems is still an open-ended research question. In this paper we summarise and relate several ongoing research projects and tool development efforts in this field taking place within the Department of Computer Science.peer-reviewe

Wake skew angle variation with rotor thrust for wind turbines in yaw based on the MEXICO experiment

The primary objective of the MEXICO (Model Experiments in Controlled Conditions) project was to generate experimental data from which the uncertainties of the computational tools employed to predict wind turbine performance and loads. Pressure sensors were used for pressure measurements while PIV was used with the major aim of tracking the tip vortex trajectory. The aerodynamic forces on the blades were derived found from the pressure measurements and were used in an inverse free wake lifting line model to compute the positions of the tip vortices. From these the wake skew angle was derived. A relationship between the skew angle and the thrust coefficient was thus drawn.peer-reviewe

The influence of photovoltaics on roof thermal performance - an analysis of convective heat transfer coefficients

In a Mediterranean climate, given the absence of snow, flat roofs are typical of both vernacular and modern architecture. Thermal mass, cross ventilation and night time cooling are standard passive design aids that inhibit indoor temperature build-up on hot summer days. Such flat roofs provide a golden opportunity for free-orientation of PV (photovoltaic) panels, unlike pitched roofs. There is established scientific evidence that their presence on flat roofs also helps curtail surface temperatures of the heavy mass structure, by means of (i) solar shading and (ii) convective cooling at given angles. Both factors in turn lower the convective heat transfer coefficient (CHTC) of the roof structure, thus inhibiting early seasonal temperature build-up. This contributes to lower cooling loads, thus reducing both the carbon footprint of the building as well as lowering energy costs for the owners. Such a holistic contribution is deemed to uphold the social, environmental and economic challenges of today. This study purports to do just that. Through CFD (computational fluid dynamics) this study investigates the effect of flow fields over a typical flat roof building mass in a free field for a range of wind velocities. Results indicate that for a higher wind speed, the convective cooling is more significant than at lower wind speeds. This will in turn influence the elemental U-value of the roof structure, thus reducing cooling loads indoors.peer-reviewe

On the Design of a Linear Delay Element for the Triggering Module at CERN LHC

This paper presents an analytical model of a linear delay element circuit to be employed in the triggering module for the High Momentum Particle Identification Detector (HMPID) at the CERN Large Hadron Collider (LHC). The aim of the analytical model is to facilitate the design of the linear delay element circuit, while maximizing its linearity and delay range. The analytical model avoids the need of time consuming parametric sweeps on the aspect ratios of the various transistors of the delay element in order to optimize it. In addition, the analytical model can be used to predict the variation of the delay with the input tuning voltage. The proposed analytical model is verified via the simulation of the delay element circuit using the 0.18 μm X-FAB technology

Search for transient optical counterparts to high-energy IceCube neutrinos with Pan-STARRS1

In order to identify the sources of the observed diffuse high-energy neutrino flux, it is crucial to discover their electromagnetic counterparts. IceCube began releasing alerts for single high-energy ($E > 60$ TeV) neutrino detections with sky localisation regions of order 1 deg radius in 2016. We used Pan-STARRS1 to follow-up five of these alerts during 2016-2017 to search for any optical transients that may be related to the neutrinos. Typically 10-20 faint ($m < 22.5$ mag) extragalactic transients are found within the Pan-STARRS1 footprints and are generally consistent with being unrelated field supernovae (SNe) and AGN. We looked for unusual properties of the detected transients, such as temporal coincidence of explosion epoch with the IceCube timestamp. We found only one transient that had properties worthy of a specific follow-up. In the Pan-STARRS1 imaging for IceCube-160427A (probability to be of astrophysical origin of $\sim$50 %), we found a SN PS16cgx, located at 10.0' from the nominal IceCube direction. Spectroscopic observations of PS16cgx showed that it was an H-poor SN at z = 0.2895. The spectra and light curve resemble some high-energy Type Ic SNe, raising the possibility of a jet driven SN with an explosion epoch temporally coincident with the neutrino detection. However, distinguishing Type Ia and Type Ic SNe at this redshift is notoriously difficult. Based on all available data we conclude that the transient is more likely to be a Type Ia with relatively weak SiII absorption and a fairly normal rest-frame r-band light curve. If, as predicted, there is no high-energy neutrino emission from Type Ia SNe, then PS16cgx must be a random coincidence, and unrelated to the IceCube-160427A. We find no other plausible optical transient for any of the five IceCube events observed down to a 5$\sigma$ limiting magnitude of $m \sim 22$ mag, between 1 day and 25 days after detection.Comment: 20 pages, 6 figures, accepted to A&

Measurement of the multi-TeV neutrino cross section with IceCube using Earth absorption

Neutrinos interact only very weakly, so they are extremely penetrating. However, the theoretical neutrino-nucleon interaction cross section rises with energy such that, at energies above 40 TeV, neutrinos are expected to be absorbed as they pass through the Earth. Experimentally, the cross section has been measured only at the relatively low energies (below 400 GeV) available at neutrino beams from accelerators \cite{Agashe:2014kda, Formaggio:2013kya}. Here we report the first measurement of neutrino absorption in the Earth, using a sample of 10,784 energetic upward-going neutrino-induced muons observed with the IceCube Neutrino Observatory. The flux of high-energy neutrinos transiting long paths through the Earth is attenuated compared to a reference sample that follows shorter trajectories through the Earth. Using a fit to the two-dimensional distribution of muon energy and zenith angle, we determine the cross section for neutrino energies between 6.3 TeV and 980 TeV, more than an order of magnitude higher in energy than previous measurements. The measured cross section is $1.30^{+0.21}_{-0.19}$ (stat.) $^{+0.39}_{-0.43}$ (syst.) times the prediction of the Standard Model \cite{CooperSarkar:2011pa}, consistent with the expectation for charged and neutral current interactions. We do not observe a dramatic increase in the cross section, expected in some speculative models, including those invoking new compact dimensions \cite{AlvarezMuniz:2002ga} or the production of leptoquarks \cite{Romero:2009vu}.Comment: Preprint version of Nature paper 10.1038/nature2445