Size-dependent melting: Numerical calculations of the phonon spectrum

In order to clarify the relationship between the phonon spectra of nanoparticles and their melting temperature, we studied in detail the size-dependent low energy vibration modes. A minimum model with atoms on a lattice and harmonic potentials for neighboring atoms is used to reveal a general behavior. By calculating the phonon spectra for a series of nanoparticles of two lattice types in different sizes, we found that density of low energy modes increases as the size of nanoparticles decreases, and this density increasing causes decreasing of melting temperature. Size-dependent behavior of the phonon spectra accounts for typical properties of surface-premelting and irregular melting temperature on fine scales. These results show that our minimum model captures main physics of nanoparticles. Therefore, more physical characteristics for nanoparticles of certain types can be given by phonons and microscopic potential models.Comment: 5 pages, 5 figure

Tropospheric jet stream as a source of traveling ionospheric disturbances observed by GPS

The integrity and the reliability of real-time precise positioning applications with Global Positioning System (GPS) are affected by the ionospheric variability with time and space. As a consequence, scientific community aims at describing, explaining and forecasting the occurrence and the amplitude of ionospheric irregularities observed by GPS. The use of the geometric-free combination of GPS dual frequency signals allows to retrieve the Total Electron Content (TEC) along the satellite-to-receiver path, which is the basic trans-ionospheric observable. Based on L1/L2 GPS phase measurements collected at a given station, the TEC high-frequency variability is isolated. A climatological study performed over 10 years in Western Europe shows that TEC irregularities are mostly observed daytime during quiet geomagnetic background in autumn and winter and correspond to classical Medium-Scale Traveling Ionospheric Disturbances (MSTIDs). The latter are generally understood as the ionospheric signature of Atmospheric Gravity Waves (AGWs), either generated in situ (solar terminator) or in the lower atmosphere and propagating upward. Because of its associated strong wind shears, the tropospheric jetstream, occurring mainly during autumn and winter months, constitutes an ideal candidate for AGW generation. This paper analyzes the spatial correlation between the presence of both MSTIDs and strong jetstream over Western Europe. This correlation is positive when the ionospheric pierce point of the satellite is located above regions of interest where wind shears are very large. In practice, we have selected regions for which wind speed is larger than 50 m/s. In addition, the propagation of AGWs up to the ionospheric layer is taken into account by assuming horizontal and vertical velocities of 200 and 50 m/s respectively. It comes that the region of interest of the correlation study is computed using an isotropic slant propagation of the AGW, which is supposed to be generated at a tropospheric level.Based on 30s GPS data collected over several stations in Belgium and on European Centre for Medium-Range Weather Forecasts (ECMWF) wind velocity maps, the correlation study covers a period ranging from January 2002 to December 2011. Preliminary results based on a limited number of cases show that large amplitude MSTIDs are generally observed during periods of strong wind speeds at an altitude corresponding to a pressure level of 250hPa (about 10 km)

Reflections on quasi-loss of nationality in comparative, international and European perspective. CEPS Liberty and Security in Europe No. 66/August 2014

This paper focuses on situations in which a person is said never to have had the nationality of a country, even though (s)he assumed (and in many cases the authorities of the country concerned shared that assumption) that (s)he possessed that nationality. Contrary to situations of loss of nationality, where something is taken away that had existed, quasi-loss involves situations in which nationality was never acquired. This contribution seeks to examine whether a person should under certain circumstances be protected against quasi-loss of nationality. In order to do so, the paper first maps out situations of quasi-loss in EU member states, describing typical cases in which a person never acquired the nationality of the country, although (s)he was at some time considered as a national. Drawing on this taxonomy, the paper attempts to uncover whether national, European and international laws offer some protection, and if yes, to which extent, for situations of quasi-loss. It concludes with outlining best practices which Member States should comply with in handling such situations

How to deal with quasi-loss of nationality situations? Learning from promising practices. CEPS Liberty and Security in Europe No. 71/December 2014

This paper was prepared as a Policy Brief for discussion at the final conference of the project on Involuntary Loss of European Citizenship: Exchanging Knowledge and Identifying Guidelines for Europe, 11-12 December 2014. Co-funded by the European Commission’s DG for Justice, Citizenship and Fundamental Rights, the ILEC project has aimed to establish a framework for debate on international norms on involuntary loss of nationality. For more information visit: www.ilecproject.eu

Multi-Agent Spiral Software Engineering: A Lakatosian Approach

This paper presents an epistemological approach for the development and validation of an original agent oriented software development methodology (see [Wautelet05a, Wautelet05b]). Agent orientation has been widely presented as a new modeling, design and programming paradigm that could be adopted to build systems mark to the determinant advantages it offers. This will be exposed and put into perspective in the paper through the Lakatosian approach. Spiral development (see [Boehm00a]) has become popular, especially through object-oriented software project development since it allows efficient software project management, continuous organizational modeling and requirements acquisition, early implementation, continuous testing and modularity, etc. The iterative nature of this requirements engineering process will be studied here through Herbert Simon's bounded rationality principle and Popper's knowledge growth principle but nuanced by Lakatos falsification principle criticism

Statistical study of passive portfolio management of risky assets

In this paper we consider the problem of creating the optimal investment portfolio. We reveal the concept of the securities portfolio and highlight the most significant parameters of its management.We prove the need of diversification. We implement classical Markowitz portfolio theory. Also we consider the features of passive portfolio management