Application of spindle speed increaser as sustainable solution to upgrade machine tools

Due to varying machine operations, cutting material and feed motion of the respective milling machine, a wide range of spindle speed is required. Modern machine tools are therefore occasionally equipped with two spindles to cover a wider application scope. Especially while increasing the cutting removal rates for soft materials like aluminium alloys, outdated machine tools fail to provide high spindle speed. Spindle speed increasers (SSI) are possible solutions in order to flexibly increase the cutting removal rates of milling machines. In this paper, the state of the art of SSI is investigated regarding its application in different milling machines and with respect to resource and energy efficiency. Therefore, based on the respective machining operations, spindle input and milling machine, a selection methodology is provided to prove the feasibility of the application of existing SSI. This allows estimating the sustainable benefit on theoretical basis.DFG, 199828953, SFB 1026: Sustainable Manufacturing - Globale Wertschöpfung nachhaltig gestalte

Mexico-UK Sub-millimeter Camera for AsTronomy

MUSCAT is a large format mm-wave camera scheduled for installation on the Large Millimeter Telescope Alfonso Serrano (LMT) in 2018. The MUSCAT focal plane is based on an array of horn coupled lumped-element kinetic inductance detectors optimised for coupling to the 1.1mm atmospheric window. The detectors are fed with fully baffled reflective optics to minimize stray-light contamination. This combination will enable background-limited performance at 1.1 mm across the full 4 arcminute field-of-view of the LMT. The easily accessible focal plane will be cooled to 100 mK with a new closed cycle miniature dilution refrigerator that permits fully continuous operation. The MUSCAT instrument will demonstrate the science capabilities of the LMT through two relatively short science programmes to provide high resolution follow-up surveys of Galactic and extra-galactic sources previously observed with the Herschel space observatory, after the initial observing campaigns. In this paper, we will provide an overview of the overall instrument design as well as an update on progress and scheduled installation on the LMT.Comment: Accepted for publication in the Journal of Low Temperature Detector

Do High-Velocity Clouds trace the Dark Matter subhalo population?

Within the cosmological concordance model, Cold Dark Matter (CDM) subhalos form the building blocks which merge hierarchically to more massive galaxies. Since intergalactic gas is accreted by massive galaxies, observable e.g. as high- velocity clouds (HVCs) around the Milky Way, with extremely low metallicities, these can be suggested to represent the baryonic content of primordial Dark Matter (DM) subhalos. Another possibility of their origin is that they stem from disrupted satellite galaxies, but in this case, these gas clouds move unaccompanied by a bound DM structure. Since HVCs are observed with long gas tails and with irregular substructures, numerical models are performed aiming at exploring their structure and compare them with observations. If HVCs are engulfed by DM subhalos, their gas must leave the DM gravitational potential and reflect this in their dynamics. On the other hand, the evolution and survival of pure gas models must be tested to distinguish between DM-dominated and DM-free clouds and to allow conclusions on their origin. The models demonstrate that purely baryonic HVCs with low masses are disrupted by ram-pressure stripping and Kelvin-Helmholtz instabilities, while more massive ones survive, losing their initially spherical shape and develop significant substructures including cometary elongations in the column density distribution ("head-tail structure"). On the contrary, HVCs with DM subhalos survive with more than 90% of their gas mass still bound and spherically shaped, approaching the Galactic disk like bullets. In addition, we find that velocity gradients along the cometary head-tail structures does not necessarily offer a possibility to distinguish between DM-dominated and purely gaseous HVCs. Comparison of models with observations let us conclude that HVCs are not embedded in a DM substructure and do not trace the cosmological subhalo population.Comment: Accepted for publication in A&

High-Velocity Clouds in the Nearby Spiral Galaxy M 83

We present deep HI 21-cm and optical observations of the face-on spiral galaxy M 83 obtained as part of a project to search for high-velocity clouds (HVCs) in nearby galaxies. Anomalous-velocity neutral gas is detected toward M 83, with 5.6x10^7 Msolar of HI contained in a disk rotating 40-50 km/s more slowly in projection than the bulk of the gas. We interpret this as a vertically extended thick disk of neutral material, containing 5.5% of the total HI within the central 8 kpc. Using an automated source detection algorithm to search for small-scale HI emission features, we find eight distinct, anomalous-velocity HI clouds with masses ranging from 7x10^5 to 1.5x10^7 Msolar and velocities differing by up to 200 km/s compared to the HI disk. Large on-disk structures are coincident with the optical spiral arms, while unresolved off-disk clouds contain no diffuse optical emission down to a limit of 27 r' mag per square arcsec. The diversity of the thick HI disk and larger clouds suggests the influence of multiple formation mechanisms, with a galactic fountain responsible for the slowly-rotating disk and on-disk discrete clouds, and tidal effects responsible for off-disk cloud production. The mass and kinetic energy of the HI clouds are consistent with the mass exchange rate predicted by the galactic fountain model. If the HVC population in M 83 is similar to that in our own Galaxy, then the Galactic HVCs must be distributed within a radius of less than 25 kpc.Comment: 30 pages, 23 figures; accepted for publication in ApJ. Some figures have been altered to reduce their siz

Intelligent group movement and selection in realtime strategy games

Movement of groups in realtime strategy games is often a nuisance: Units travel and battle separately, resulting in huge losses and the AI looking dumb. This applies to computer as well as human commanded factions. We suggest to tackle that by using flocking improved by influence-map based pathfinding which leads to a much more natural and intelligent looking behavior. A similar problem occurs if the computer AI has to select groups to combat a specific target: Assignment of units to groups, especially for multiple enemy groups, is often suboptimal when units have very different attack skills. This can be cured by using offline prepared self-organizing feature maps that use all available information for looking up good matches. We demonstrate that these two approaches work well separately, but also that they go together very naturally, thereby leading to an improved and - via parametrization - very flexible group behavior. Opponent AI may be strenghtened that way as well as player-supportive AI. A thorough experimental analysis supports our claims

The Origin of Neutral Hydrogen Clouds in Nearby Galaxy Groups: Exploring the Range Of Galaxy Interactions

We combine high resolution N-body simulations with deep observations of neutral hydrogen (HI) in nearby galaxy groups in order to explore two well-known theories of HI cloud formation: HI stripping by galaxy interactions and dark matter minihalos with embedded HI gas. This paper presents new data from three galaxy groups, Canes Venatici I, NGC 672, and NGC 45, and assembles data from our previous galaxy group campaign to generate a rich HI cloud archive to compare to our simulated data. We find no HI clouds in the Canes Venatici I, NGC 672, or NGC 45 galaxy groups. We conclude that HI clouds in our detection space are most likely to be generated through recent, strong galaxy interactions. We find no evidence of HI clouds associated with dark matter halos above M_HI = 10^6 M_Sun, within +/- 700 km/s of galaxies, and within 50 kpc projected distance of galaxies.Comment: 35 pages, 10 figures, AJ accepte

A peculiar HI cloud near the distant globular cluster Pal 4

We present 21-cm observations of four Galactic globular clusters, as part of the on-going GALFA-HI Survey at Arecibo. We discovered a peculiar HI cloud in the vicinity of the distant (109 kpc) cluster Pal 4, and discuss its properties and likelihood of association with the cluster. We conclude that an association of the HI cloud and Pal 4 is possible, but that a chance coincidence between Pal 4 and a nearby compact high-velocity cloud cannot be ruled out altogether. New, more stringent upper limits were derived for the other three clusters: M 3, NGC 5466, and Pal 13. We briefly discuss the fate of globular cluster gas and the interaction of compact clouds with the Galactic Halo gas.Comment: Accepted for publication in MNRA