Picture this: researching child workers

Visual methods such as photography are under-used in the active process of sociological research. As rare as visual methods are, it is even rarer for the resultant images to be made by rather than of research participants. Primarily, the paper explores the challenges and contradictions of using photography within a multi-method approach. We consider processes for analysing visual data, different ways of utilising visual methods in sociological research, and the use of primary and secondary data, or, simple illustration versus active visual exploration of the social. The question of triangulation of visual data against text and testimony versus a stand-alone approach is explored in depth

Collinear Factorization for Single Transverse-Spin Asymmetry in Drell-Yan Processes

We study the scattering of a single parton state with a multi-parton state to derive the complete results of perturbative coefficient functions at leading order, which appear in the collinear factorization for Single transverse-Spin Asymmetry(SSA) in Drell-Yan processes with a transversely polarized hadron in the initial state. We find that the factorization formula of SSA contains hard-pole-, soft-quark-pole- and soft-gluon-pole contributions. It is interesting to note that the leading order perturbative coefficient functions of soft-quark-pole- and soft-gluon-pole contributions are extracted from parton scattering amplitudes at one-loop, while the functions of hard-pole contributions are extracted from the tree level amplitudes at tree-level. Our method to derive the factorization of SSA is different than the existing one in literature. A comparison of our results with those obtained by other method is made.Comment: 27 pages, 14 figures, text improved, to appear in Phys. Rev.

Mission analysis and systems design of a near-term and far-term pole-sitter mission

This paper provides a detailed mission analysis and systems design of a near-term and far-term pole-sitter mission. The pole-sitter concept was previously introduced as a solution to the poor temporal resolution of polar observations from highly inclined, low Earth orbits and the poor high latitude coverage from geostationary orbit. It considers a spacecraft that is continuously above either the North or South Pole and, as such, can provide real-time, continuous and hemispherical coverage of the polar regions. Being on a non-Keplerian orbit, a continuous thrust is required to maintain the pole-sitter position. For this, two different propulsion strategies are proposed, which result in a near-term pole-sitter mission using solar electric propulsion (SEP) and a far-term pole-sitter mission where the SEP thruster is hybridized with a solar sail. For both propulsion strategies, minimum propellant pole-sitter orbits are designed. In order to maximize the spacecraft mass at the start of the operations phase of the mission, the transfer from Earth to the pole-sitter is designed and optimized assuming either a Soyuz or an Ariane 5 launch. The maximized mass upon injection into the polesitter orbit is subsequently used in a detailed mass budget analysis that will allow for a trade-off between mission lifetime and payload mass capacity. Also, candidate payloads for a range of applications are investigated. Finally, transfers between north and south pole-sitter orbits are considered to overcome the limitations in observations due to the tilt of the polar axis that causes the Poles to be alternately situated in darkness. It will be shown that in some cases these transfers allow for propellant savings, enabling a further extension of the pole-sitter mission

Reduction of cogging torque in interior-magnet brushless machines

An investigation into the cogging torque in a four-pole interior-magnet brushless machines having either a six-slot stator and a short-pitched nonoverlapping winding or a 12-slot stator and a full-pitched overlapping winding is described. It is shown by finite-element analyses and measurements that, by appropriately defining the pole-arc to pole-pitch ratio, the optimal pole-arc to pole-pitch ratio for minimum cogging torque, which has been derived for surface-mounted magnet machines, is equally applicable to interior-magnet machines