Mechanical flux weakening for a surface permanent magnet machine with split rotor

This paper presents a mechanical flux-weakening solution for Surface Permanent Magnet machines. In particular, a split rotor configuration (two independent rotor sections that can be phase-shifted) is discussed, in which the rotors shifting is achieved through a torque component generated inside the machine, without the need for any external actuation. The analysis demonstrates that the theoretical constant power speed range is infinite. The reliability of the active actuation through the shifting torque promises for a very wide achievable constant power speed range in practice

Sediment deposition in response to the glacial-interglacial changes on the continental slope of eastern Pennell-Iselin Bank in the Ross Sea, Antarctica

In order to understand the growth and retreat of glaciers in response to the glacial-interglacial changes, subglacial marine sedimentary sequences have been studied extensively in the continental shelf areas of the Ross Sea. The purpose is to comprehend the glaciomarine sedimentation change on the continental slope of eastern Pennell-Iselin Bank in the Ross Sea, using three gravity cores (C1, C2, C3) and three box cores (BC1, BC2, BC3) collected from sites (RS14-1, 2, 3), respectively, across the continental slope to the eastern side of the Pennell-Iselin Bank during XXIX° (2014) PNRA expedition (Rosslope Ⅱ project). Several sedimentological (grain size, magnetic susceptibility), elemental (XRF), geochemical (biogenic opal, total organic carbon, total nitrogen, C/N ratios, CaCO3), and isotopic (δ13C and δ15N of organic matter) parameters were measured along sediment cores with AMS 14C dating of bulk sediments. Core-sediments consist mostly of hemipelagic sandy clay or silty clay with scattered IRDs (Ice-Rafted Debris). A comparison of sediment properties between box cores and the top of gravity cores reveals that the loss of sediment during sampling is trivial. Sediment colors of gravity cores alternate between brown and gray downward. Based on the variation patterns of sediment properties, sediment lithology was divided into different units (A and B), and subunits (B1 and B2). AMS 14C dates and sediment properties assign Unit A, Unit B1, and Unit B2 to interglacial, deglacial, and glacial conditions, respectively. Unit A represents the Holocene and interglacial sediments deposited mainly by the suspension settling of biogenic particles with IRDs in the open marine condition. Unit B1 reflects the deglacial sediments with an increase in IRDs showing the transition of sediment properties from Unit B2 to Unit A by the retreat of subglacial ices. Unit B2 is characterized by different sediment properties, mainly supplied by the continuously lateral melt-water plume or distal part of debris flow originating from the front of grounding floes in the subglacial continental shelf under the ice shelf during the glacial period. Thus, Unit B contains mostly reworked and eroded sediments from the continental shelf with scattered IRDs. The influence of subglacial continental shelf sedimentation in terms of melt-water transport and/or distal stage of debris flow was limited as far as to the middle slope areas (Site 2) during the deglacial and glacial periods. The deeper Site 1 remains in seasonally open marine conditions during the glacial period, due to the peaks of biogenic opal and TOC contents. Keywords: sediment property, subglacial activity, continental slope, Ross Se

Direct oil cooling of end-windings in torus-type axial-flux permanent-magnet machines

For high power density applications, such as electric or hybrid electric vehicles, heat extraction is a crucial aspect in electrical machine design due to stringent machine volume specifications. In these cases, it is extremely difficult if at all possible, to satisfy the maximum temperature requirement when using conventional cooling systems such as housing fins, shaft-mounted fans or even water jackets, due to insufficiently low thermal resistances. To this end, a novel direct oil cooling system conceived for Torus-type axial-flux permanent-magnet machines, is proposed here. In order to demonstrate its effectiveness, lumped thermal equivalent circuit simulations, finite element analyses and experimental tests are presented. Furthermore, the expected performances of the machine using the proposed direct oil cooling are compared to those obtained using state-of-the-art water cooling

Caldera resurgence driven by magma viscosity contrasts

Calderas are impressive volcanic depressions commonly produced by major eruptions. Equally impressive is the uplift of the caldera floor that may follow, dubbed caldera resurgence, resulting from magma accumulation and accompanied by minor eruptions. Why magma accumulates, driving resurgence instead of feeding large eruptions, is one of the least understood processes in volcanology. Here we use thermal and experimental models to define the conditions promoting resurgence. Thermal modelling suggests that a magma reservoir develops a growing transition zone with relatively low viscosity contrast with respect to any newly injected magma. Experiments show that this viscosity contrast provides a rheological barrier, impeding the propagation through dikes of the new injected magma, which stagnates and promotes resurgence. In explaining resurgence and its related features, we provide the theoretical background to account for the transition from magma eruption to accumulation, which is essential not only to develop resurgence, but also large magma reservoirs