Low Q2Q^2 proton structure function, using gluon and pseudoscalar meson clouds in the constituent quark framework

The idea of the meson cloud approach in the chiral quark model has been extended to include gluon cloud in order to achieve the parton densities in the nucleon, based on the constitute quark framework. The splitting function of the quark to the quark-meson and quark-gluon at low $Q^2$ value are used to obtain parton densities in the constituent quark. The phenomenological constituent model is employed to extract the parton distributions in the proton at low $Q^2$ value. Since we have access to the parton densities at low $Q^2$, we are able to obtain $F_{2}(x,Q^2)$ structure function at low $Q^2$ value. The result is in good agreement with available experimental data and some theoretical models. To confirm the validity of our calculations, the fraction of total momentum of proton which is carried by gluon at high $Q^2$ and also the Gottfried sum rule are computed. The results are in good agreement with what are expected.Comment: 13 pages, 3 figure

Gamification for Volunteer Cloud Computing.

Requirements engineering is a preliminary and cru- cial phase for the correctness and quality of software systems. Despite the agreement on the positive correlation between user involvement in requirements engineering and software success, current development methods employ a too narrow concept of that “user” and rely on a recruited set of users considered to be representative. Such approaches might not cater for the diversity and dynamism of the actual users and the context of software usage. This is especially true in new paradigms such as cloud and mobile computing. To overcome these limitations, we propose crowd-centric requirements engineering (CCRE) as a revised method for requirements engineering where users become primary contributors, resulting in higher-quality requirements and increased user satisfaction. CCRE relies on crowdsourcing to support a broader user involvement, and on gamification to motivate that voluntary involvement

Configuring Crowdsourcing for Requirements Elicitation

Crowdsourcing is an emerging paradigm which utilises the power of the crowd in contributing information and solving problems. Crowdsourcing can support requirements elicitation, especially for systems used by a wide range of users and working in a dynamic context where requirements evolve regularly. For such systems, traditional elicitation methods are typically costly and limited in catering for the high diversity, scale and volatility of requirements. In this paper, we advocate the use of crowdsourcing for requirements elicitation and investigate ways to configure crowdsourcing to improve the quality of elicited requirements. To confirm and enhance our argument, we follow an empirical approach starting with two focus groups involving 14 participants, users and developers, followed by an online expert survey involving 34 participants from the Requirements Engineering community. We discuss our findings and present a set of challenges of applying crowdsourcing to aid requirements engineering with a focus on the elicitation stage

Magnetic properties of the spin S=1/2S=1/2 Heisenberg chain with hexamer modulation of exchange

We consider the spin-1/2 Heisenberg chain with alternating spin exchange %on even and odd sites in the presence of additional modulation of exchange on odd bonds with period three. We study the ground state magnetic phase diagram of this hexamer spin chain in the limit of very strong antiferromagnetic (AF) exchange on odd bonds using the numerical Lanczos method and bosonization approach. In the limit of strong magnetic field commensurate with the dominating AF exchange, the model is mapped onto an effective $XXZ$ Heisenberg chain in the presence of uniform and spatially modulated fields, which is studied using the standard continuum-limit bosonization approach. In absence of additional hexamer modulation, the model undergoes a quantum phase transition from a gapped string order into the only one gapless L\"uttinger liquid (LL) phase by increasing the magnetic field. In the presence of hexamer modulation, two new gapped phases are identified in the ground state at magnetization equal to 1/3 and 2/3 of the saturation value. These phases reveal themselves also in magnetization curve as plateaus at corresponding values of magnetization. As the result, the magnetic phase diagram of the hexamer chain shows seven different quantum phases, four gapped and three gapless and the system is characterized by six critical fields which mark quantum phase transitions between the ordered gapped and the LL gapless phases.Comment: 21 pages, 5 figures, Journal of Physics: Condensed Matter, 24, 116002, (2012