An Empirical Study of a Software Maintenance Process

This paper describes how a process support tool is used to collect metrics about a major upgrade to our own electronic retail system. An incremental prototyping lifecycle is adopted in which each increment is categorised by an effort type and a project component. Effort types are Acquire, Build, Comprehend and Design and span all phases of development. Project components include data models and process models expressed in an OO modelling language and process algebra respectively as well as C++ classes and function templates and build components including source files and data files. This categorisation is independent of incremental prototyping and equally applicable to other software lifecycles. The process support tool (PWI) is responsible for ensuring the consistency between the models and the C++ source. It also supports the interaction between multiple developers and multiple metric-collectors. The first two releases of the retailing software are available for ftp from oracle.ecs.soton.ac.uk in directory pub/peter. Readers are invited to use the software and apply their own metrics as appropriate. We would be interested to correspond with anyone who does so

Experimental constraints on the astrophysical interpretation of the cosmic ray Galactic-extragalactic transition region

The energy region spanning from $\sim 10^{17}$ to $\lesssim 10^{19}$ eV is critical for understanding both, the Galactic and the extragalactic cosmic ray fluxes. This is the region where the propagation regime of nuclei inside the Galactic magnetic environment changes from diffusive to ballistic, as well as the region where, very likely, the most powerful Galactic accelerators reach their maximum output energies. In this work, a diffusion Galactic model is used to analyze the end of the Galactic cosmic ray spectrum and its mixing with the extragalactic cosmic ray flux. In particular, we study the conditions that must be met, from the spectral and composition points of view, by the Galactic and the extragalactic fluxes in order to reproduce simultaneously the total spectrum and elongation rate measured over the transition region by HiRes and Auger. Our analysis favors a mixed extragalactic spectrum in combination with a Galactic spectrum enhanced by additional high energy components, i.e., extending beyond the maximum energies expected from regular supernova remnants. The two additional components have mixed composition, with the lowest energy one heavier than the highest energy one. The potential impact on the astrophysical analysis of the assumed hadronic interaction model is also assessed in detail.Comment: 37 pages, 20 figure

Reducing the impact of demand process variability within a multi-echelon supply chain

Forrester analyzed Supply Chain and the different levels existing in it, as well as the participant companies and the role played by each of them inside the chain as a global group, and observed that small variations in end item demand caused oscillations that are amplified throughout the chain. This phenomenon, called the Bullwhip effect, has detrimental consequences on inventory levels and on all kind of inventory costs that may affect the added value of the activities throughout the logistics chain and ultimately affect the Net Present Value of all the activities in the chain. There is a set of collaborative supply chain structures which reduce these harmful consequences within the supply chain. The study presented in this paper quantifies how collaborative supply chain structures reduce the Bullwhip effect in terms of demand variability and inventory cost

Determination of physical properties of high-energy hadronic interactions from the XmaxX_{\mathrm{max}}-NμN_{\mu} anticorrelation

Seit der Entdeckung der kosmischen Strahlung Anfang des 20. Jahrhunderts wurden viele Experimente entwickelt, um sie direkt oder anhand der Luftschauer zu studieren, die sie beim Eintritt in die Erdatmosphäre erzeugen. Das größte Observatorium zur Erfassung von Luftschauern ist das Pierre-Auger-Observatorium in Malargüe, Argentinien. Hier werden viele Fragen der Astro- und Teilchenphysik behandelt. Da kosmische Strahlung Energien abdeckt, die weit über denen liegen, die in künstlichen Beschleunigern erreichbar sind, stellen sie hervorragende und einzigartige Objekete dar, an denen man physikalische Eigenschaften bei höchsten Energien studieren kann. Wenn ein Luftschauer die Atmosphäre durchquert, wächst die Anzahl der in ihm enthaltenen Teilchen. Gleichzeitig nehmen ihre Energien ab. Wenn diese tief genug sind, zerfallen die Teilchen oder werden in der Atmosphäre absorbiert, was die Zahl der Teilchen wieder verringert. Dies ergibt eine Position maximaler Entwicklung $X_\mathrm{max}$. Hadronisch wechselwirkende Teilchen bringen Myonen hervor, die am Boden gemessen werden können. Diese Zahl $N_{\mu}$ zusammen mit $X_\mathrm{max}$ sind Observablen, die in Auger gemessen werden und eine aussagekräftige Antikorrelation aufweisen. In der vorliegenden Arbeit wird diese Antikorrelation studiert. Es wird ein analytisches Modell entwickelt, das diese als Funktion von Parametern wiedergibt, die die hadronische Multiplizität, den hadronischen Energieanteil und die Inelastizität der ersten Interaktion beschreiben, zusammen mit entsprechenden effektiven Parametern, die für den gesamten Schauer repräsentativ sind. Dieses Modell wird dann anhand künstlicher neuronaler Netze weiter verbessert. Hierfür werden Werte der Parameter und Observablen von Simulationen benutzt, die mit CONEX durchgeführt wurden. Das resultierende Modell hängt nicht von dem während der Simulation verwendeten Hochenergie-Wechselwirkungsmodell ab. Schließlich wird ein Modell mit reduziertem Parametersatz auf einen Datensatz von Auger angewendet. Die Verteilungen der hadronischen Multiplizität und des hadronischen Energieanteils der ersten Wechselwirkung und die der effektiven Inelastizität werden diesem Datensatz entnommen. Sie zeigen, dass die Multiplizität und der Energieanteil der ersten Wechselwirkung in aktuellen Modellen, die für Simulationen verwendet werden, im Allgemeinen zu niedrig sind

Unravelling the Impact of Information Communication Technology (ICT) on Restaurant Productivity

Despite the continuous increase of investment in Information and Communication Technologies (ICT), research has not persuasively established corresponding productivity increases. In contrast, many studies investigating the ICT impact have found no significant relationships between productivity and ICT. However, several shortcomings have been identified in past studies, e.g. measurement errors, redistribution of impacts and mismanagement of ICT. This study proposes a methodology for assessing the ICT productivity impact that overcomes these shortcomings. The methodology is tested in a dataset of hotel restaurants in the UK by using a non-parametric technique called Data Envelopment Analysis (DEA). Findings revealed that productivity gains do not accrue from ICT investments per se, but from the exploitation of ICT “informate” and networking capabilities. Suggestions for enhancing the productivity impact of ICT are provided

The extension and exploitation of the inventory and order based production control system archetype from 1982 to 2015

In 1994, through classic control theory, John, Naim and Towill developed the ‘Automatic Pipeline, Inventory and Order-based Production Control System’ (APIOBPCS) which extended the original IOBPCS archetype developed by Towill in 1982 ─ well-recognised as a base framework for a production planning and control system. Due to the prevalence of the two original models in the last three decades in the academic and industrial communities, this paper aims to systematically review how the IOBPCS archetypes have been adopted, exploited and adapted to study the dynamics of individual production planning and control systems and whole supply chains. Using various databases such as Scopus, Web of Science, Google Scholar (111 papers), we found that the IOBPCS archetypes have been studied regarding the a) modification of four inherent policies related to forecasting, inventory, lead-time and pipeline to create a ‘family’ of models, b) adoption of the IOBPCS ‘family’ to reduce supply chain dynamics, and in particular bullwhip, c) extension of the IOBPCS family to represent different supply chain scenarios such as order-book based production control and closed-loop processes. Simulation is the most popular method adopted by researchers and the number of works based on discrete time based methods is greater than those utilising continuous time approaches. Most studies are conceptual with limited practical applications described. Future research needs to focus on cost, flexibility and sustainability in the context of supply chain dynamics and, although there are a few existing studies, more analytical approaches are required to gain robust insights into the influence of nonlinear elements on supply chain behaviour. Also, empirical exploitation of the existing models is recommended

The GFZ GRACE RL06 Monthly Gravity Field Time Series: Processing Details and Quality Assessment

Time-variable gravity field models derived from observations of the Gravity Recovery and Climate Experiment (GRACE) mission, whose science operations phase ended in June 2017 after more than 15 years, enabled a multitude of studies of Earth’s surface mass transport processes and climate change. The German Research Centre for Geosciences (GFZ), routinely processing such monthly gravity fields as part of the GRACE Science Data System, has reprocessed the complete GRACE mission and released an improved GFZ GRACE RL06 monthly gravity field time series. This study provides an insight into the processing strategy of GFZ RL06 which has been considerably changed with respect to previous GFZ GRACE releases, and modifications relative to the precursor GFZ RL05a are described. The quality of the RL06 gravity field models is analyzed and discussed both in the spectral and spatial domain in comparison to the RL05a time series. All results indicate significant improvements of about 40% in terms of reduced noise. It is also shown that the GFZ RL06 time series is a step forward in terms of consistency, and that errors of the gravity field coefficients are more realistic. These findings are confirmed as well by independent validation of the monthly GRACE models, as done in this work by means of ocean bottom pressure in situ observations and orbit tests with the GOCE satellite. Thus, the GFZ GRACE RL06 time series allows for a better quantification of mass changes in the Earth system.DFG, FOR 2736, New Refined Observations of Climate Change from Spaceborne Gravity Missions (NEROGRAV)BMBF, 03F0654A, GRACE-FO - Projektmanagement, Aufbau eines wissenschaftlichen Auswertesystems und Aufbau eines GRACE-FO Projektbüro

Optimizing selection of competing features via feedback-directed evolutionary algorithms

Software that support various groups of customers usually require complicated configurations to attain different functionalities. To model the configuration options, feature model is proposed to capture the commonalities and competing variabilities of the product variants in software family or Software Product Line (SPL). A key challenge for deriving a new product is to find a set of features that do not have inconsistencies or conflicts, yet optimize multiple objectives (e.g., minimizing cost and maximizing number of features), which are often competing with each other. Existing works have attempted to make use of evolutionary algorithms (EAs) to address this problem. In this work, we incorporated a novel feedback-directed mechanism into existing EAs. Our empirical results have shown that our method has improved noticeably over all unguided version of EAs on the optimal feature selection. In particular, for case studies in SPLOT and LVAT repositories, the feedback-directed Indicator-Based EA (IBEA) has increased the number of correct solutions found by 72.33% and 75%, compared to unguided IBEA. In addition, by leveraging a pre-computed solution, we have found 34 sound solutions for Linux X86, which contains 6888 features, in less than 40 seconds.No Full Tex