Observations of quiet-time moderate midlatitude L-band scintillation in association with plasma bubbles

Observations of moderate night time amplitude scintillation on the GPS L1C/A signal were recorded at the midlatitude station of Nicosia, corresponding geographic latitude and longitude of 35.18˚N and 33.38˚E respectively, on a geomagnetically quiet day. The variations of slant total electron content (STEC) and amplitude scintillation index (S4) on the night of June 12, 2014, indicate the presence of electron density depletions accompanying scintillation occurrence. The estimated apparent horizontal drift velocity and propagation direction of the plasma depletions are consistent with those observed for the equatorial plasma bubbles, thus suggesting that the moderate amplitude L-band scintillation observed over Nicosia may be associated with the extension of such plasma bubbles. The L-band scintillation occurrence was concurrent with the observations of range spread F on the ionograms recorded by the digisonde at Nicosia. The height–time–intensity plot generated using the ionogram data also showed features which can be attributed to off-angle reflections from electron density depletions, thus corroborating the STEC observations. This observation suggests that the midlatitude ionosphere is more active even during geomagnetically quiet days than previously thought and that further studies are necessary. This is particularly relevant for the GNSS user community and related applications

Agile Manifesto and Practices Selection for Tailoring Software Development: A Systematic Literature Review

peer reviewedAgile methods have been largely used for many years to provide developers with a flexible software development process leading to software quality improvement. To get the best results and eliminate unnecessary efforts, the development team should select the most appropriate methods and techniques. The fundamental core of an agile method has to be well-understood before deciding which parts of the method need to be adopted. We believe that the quickest way to do so is to understand the prescripts of the Agile Manifesto. Many researches have proposed different tailoring approaches based on the relation and straight-forward interpretation between each agile practice and agile values or principles. We however have observed that agile practitioners do not dedicate the necessary attention to the Agile Manifesto before adopting agile methods or practices and directly use them. It is because the importance of Agile Manifesto in tailoring context is not obvious enough to the community. This study aims at doing a systematic literature review on the existing case studies, to verify the relation between the Agile Manifesto and agile practice selection

Size-Dependent Materials Properties Toward a Universal Equation

Due to the lack of experimental values concerning some material properties at the nanoscale, it is interesting to evaluate this theoretically. Through a “top–down” approach, a universal equation is developed here which is particularly helpful when experiments are difficult to lead on a specific material property. It only requires the knowledge of the surface area to volume ratio of the nanomaterial, its size as well as the statistic (Fermi–Dirac or Bose–Einstein) followed by the particles involved in the considered material property. Comparison between different existing theoretical models and the proposed equation is done

GENESIS: Co-location of Geodetic Techniques in Space

Improving and homogenizing time and space reference systems on Earth and, more directly, realizing the Terrestrial Reference Frame (TRF) with an accuracy of 1mm and a long-term stability of 0.1mm/year are relevant for many scientific and societal endeavors. The knowledge of the TRF is fundamental for Earth and navigation sciences. For instance, quantifying sea level change strongly depends on an accurate determination of the geocenter motion but also of the positions of continental and island reference stations, as well as the ground stations of tracking networks. Also, numerous applications in geophysics require absolute millimeter precision from the reference frame, as for example monitoring tectonic motion or crustal deformation for predicting natural hazards. The TRF accuracy to be achieved represents the consensus of various authorities which has enunciated geodesy requirements for Earth sciences. Today we are still far from these ambitious accuracy and stability goals for the realization of the TRF. However, a combination and co-location of all four space geodetic techniques on one satellite platform can significantly contribute to achieving these goals. This is the purpose of the GENESIS mission, proposed as a component of the FutureNAV program of the European Space Agency. The GENESIS platform will be a dynamic space geodetic observatory carrying all the geodetic instruments referenced to one another through carefully calibrated space ties. The co-location of the techniques in space will solve the inconsistencies and biases between the different geodetic techniques in order to reach the TRF accuracy and stability goals endorsed by the various international authorities and the scientific community. The purpose of this white paper is to review the state-of-the-art and explain the benefits of the GENESIS mission in Earth sciences, navigation sciences and metrology.Comment: 31 pages, 9 figures, submitted to Earth, Planets and Space (EPS

Evaluating the Impact of User Story Quality on the Modelers Ability to Understand and Structure Requirements

peer reviewedScrum is essentially driven by user stories (US). The development team indeed uses, to fill the project and sprints’ content, sentences describing the user expectations w.r.t. the software. US are often written “on the fly” in structured natural language so their quality and the set’s consistency are not ensured. The Quality User Story (QUS) framework intends to evaluate and improve the quality of a given US set. Other research has built a unified model for tagging the elements of the WHO, WHAT and WHY dimensions of a US; each tag representing a concept with an inherent nature and granularity. Once tagged, the US elements of the set can be graphically represented through an icon and the modeler can link them when inter-dependencies are identified. One or more Rationale Trees (RT) are then built. This paper presents the result of an experiment conducted with novice modelers aimed to evaluate how well they are able to build a RT out of (i) a raw real-life US set (group 1) and (ii) a new version of the US set improved in quality using QUS (group 2). The experiment requires test subjects to identify the nature of US elements and to graphically represent and link them. The QUS compliant US set improved the ability of the test subjects to make this identification and linking. We cannot conclude that the use of the QUS framework improved the understanding the problem/solution domain but it increased the ability of modelers to identify Epic US. All in all, building an RT has a positive impact on identifying the structure of a US set’s functional elements

Bridging User Story Sets with the Use Case Model

User Stories (US) are mostly used as basis for representing requirements in agile development. Written in a direct manner, US fail in producing a visual representation of the main system-to-be functions. A Use-Case Diagram (UCD), on the other hand, intends to provide such a view. Approaches that map US sets to a UCD have been proposed; they however consider every US as a Use Case (UC). Nevertheless, a valid UC should not be an atomic task or a sub-process but enclose an entire scenario of the system use instead. A unified model of US templates to tag US sets was previously build. Within functional elements, it notably distinguishes granularity levels. In this paper, we propose to transform specific elements of a US set into a UCD using the granularity information obtained through tagging. In practice, such a transformation involves continuous round-tripping between the US and UC views; a CASE-tool supports this