38 research outputs found
Postponing the decision of final destination: A potential way to make IKEA more flexible and responsive
No full textIKEA is a global retailer in the home furnishing business. The delivery lead time for products to reach IKEA stores or IKEA distribution centres from suppliers located across the globe can be up to 16 weeks and during this time the actual need will change. As a result the order quantity which is based on the forecasted quantity is not always matches the actual need. In addition to variation in demand, constraints in supplier capacity and distribution result in stock out, excess stock or early deliveries. In order for the company to stay competitive and grow in the e-commerce business, there is a need for a more flexible and responsive supply chain. Therefore IKEA has realised potentials in implementing a postponement strategy in the distribution network to achieve this. In order to explore if postponement is feasible for IKEA, the distribution network has been mapped. The consequences of deciding destinations early in the supply has been discussed for each IKEA stakeholder. Currently, IKEA decides the final destination, which can be a store, distribution centre or a customer distribution centre, when they place an order to a supplier. Customer distribution centres are used for online customer orders. IKEA has three different replenishment solutions from suppliers to stores or selling units, Direct Delivery, delivery through distribution centre and Combined Supply, which is a combination of the other two solutions. Some of the deliveries that is categorised as Direct Deliveries are cross-docked at a distribution centre. These deliveries are called Transit Deliveries. External companies have been interviewed about the use of deciding destination at a later stage. Their inputs in terms of benefits and challenges with the postponement concept has been used together with interviews with employees at IKEA entities and IKEA suppliers to create and analyse three different postponement scenarios. The first scenario is to postpone the destination decision until shortly before an order is dispatched from a supplier. This is most valuable for make-to-order suppliers who have a long production lead time. The second scenario is to postpone the destination decision until shortly before the goods are received at a distribution centre. This is only suitable for Transit Deliveries, where goods are cross-docked at distribution centres. The third scenario is to postpone the destination decision until shortly before the goods arrive at a consolidation point, port of loading or port of discharge. The scenario can be suitable for all the replenishment solutions. The thesis result can be an addition to the existing literature about postponement, which is mostly about delaying the production or movement of goods until the customer demand is known. However, postponement can be implemented by delaying the decision of final destination of products during the production phase or during the distribution
Probing Galaxy Dark Matter Haloes in COSMOS with Weak Lensing Flexion
No full textCurrent theories of structure formation predict specific density profiles of galaxy dark matter haloes, and with weak gravitational lensing we can probe these profiles on several scales. On small scales, higher-order shape distortions known as flexion add significant detail to the weak lensing measurements. We present here the first detection of a galaxy-galaxy flexion signal in space-based data, obtained using a new Shapelets pipeline introduced here. We combine this higher-order lensing signal with shear to constrain the average density profile of the galaxy lenses in the Hubble Space Telescope COSMOS survey. We also show that light from nearby bright objects can significantly affect flexion measurements. After correcting for the influence of lens light, we show that the inclusion of flexion provides tighter constraints on density profiles than does shear alone. Finally we find an average density profile consistent with an isothermal sphere
On the shear estimation bias induced by the spatial variation of colour across galaxy profiles
No full textThe spatial variation of the colour of a galaxy may introduce a bias in the measurement of its shape if the PSF profile depends on wavelength. We study how this bias depends on the properties of the PSF and the galaxies themselves. The bias depends on the scales used to estimate the shape, which may be used to optimise methods to reduce the bias. Here we develop a general approach to quantify the bias. Although applicable to any weak lensing survey, we focus on the implications for the ESA Euclid mission. Based on our study of synthetic galaxies we find that the bias is a few times 10^-3 for a typical galaxy observed by Euclid. Consequently, it cannot be neglected and needs to be accounted for. We demonstrate how one can do so using spatially resolved observations of galaxies in two filters. We show that HST observations in the F606W and F814W filters allow us to model and reduce the bias by an order of magnitude, sufficient to meet Euclid's scientific requirements. The precision of the correction is ultimately determined by the number of galaxies for which spatially-resolved observations in at least two filters are available. We use results from the Millennium Simulation to demonstrate that archival HST data will be sufficient for the tomographic cosmic shear analysis with the Euclid dataset
Nurses’ experiences of prehospital care encounters with children in pain
No full textBackground: Pain relief in children is a complex issue, partly an ethical dilemma and due to a lack of nursing competence. There are few studies regarding prehospital care encounters with children in pain. Aim: The aim of this study was to describe nurses’ experiences in prehospital care encounters with children in pain and the specific related challenges. Method: This study has a qualitative design. Eighteen Swedish nurses participated in three focus group interviews analysed using qualitative content analysis. Findings: The findings consist of a theme, “A challenge to shift focus and adjust to the child”, and three categories describing prehospital care encounters with children in pain: “Being receptive and focusing on care,” “Developing a trusting relationship,” and “Providing professional nursing care.” Caring for children in pain was stressful for the nurses. The nurses described how they had to shift focus and used different methods to build trust, such as playfulness, making eye contact, attracting curiosity, and using the parents to create trust. The also had to adjust to the child regarding dosages and materials. Conclusion: Nurses has to be practically, mentally, and theoretically prepared to care for children with prehospital pain. It is essential to evaluate the administration of adequate pain relief to children, and more evidence-based knowledge is necessary concerning the different modes of administering pain-relieving drugs to prehospital children. </p
Spatial matter density mapping of the STAGES Abell A901/2 supercluster field with 3D lensing
No full textWe present weak lensing data from the Hubble Space Telescope(HST)/Space Telescope A901/902 Galaxy Evolution Survey (STAGES) survey to study the three-dimensional spatial distribution of matter and galaxies in the Abell 901/902 supercluster complex. Our method improves over the existing 3D lensing mapping techniques by calibrating and removing redshift bias and accounting for the effects of the radial elongation of 3D structures. We also include the first detailed noise analysis of a 3D lensing map, showing that even with deep HST-quality data, only the most massive structures, for example M200≳ 1015M⊙h-1 at z∼ 0.8, can be resolved in 3D with any reasonable redshift accuracy (Δz≈ 0.15). We compare the lensing map to the stellar mass distribution and find luminous counterparts for all mass peaks detected with a peak significance >3σ. We see structures in and behind the z= 0.165 foreground supercluster, finding structure directly behind the A901b cluster at z∼ 0.6 and also behind the south-west (SW) group at z∼ 0.7. This 3D structure viewed in projection has no significant impact on recent mass estimates of A901b or the SW group components SWa and SWb. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS
Galaxy-galaxy lensing constraints on the relation between baryons and dark matter in galaxies in the Red Sequence Cluster Survey 2
No full textWe present the results of a study of weak gravitational lensing by galaxies using imaging data that were obtained as part of the second Red Sequence Cluster Survey (RCS2). In order to compare to the baryonic properties of the lenses we focus here on the ~300 square degrees that overlap with the DR7 of the SDSS. The depth and image quality of the RCS2 enables us to significantly improve upon earlier work for luminous galaxies at z>=0.3. Comparison with dynamical masses from the SDSS shows a good correlation with the lensing mass for early-type galaxies. For low luminosity (stellar mass) early-type galaxies we find a satellite fraction of ~40% which rapidly decreases to <10% with increasing luminosity (stellar mass). The satellite fraction of the late-types has a value in the range 0-15%. We find that early-types in the range 10^1
Mass distribution in an assembling super galaxy group at z = 0.37
No full textAims. We present a weak gravitational lensing analysis of supergroup SG1120−1202, consisting of four distinct X-ray-luminous groups that will merge to form a cluster comparable in mass to Coma at z = 0. These groups lie within a projected separation of 1 to 4 Mpc and within Δv = 550 km s-1 and form a unique protocluster to study the matter distribution in a coalescing system.
Methods. Using high-resolution HST/ACS imaging, combined with an extensive spectroscopic and imaging data set, we studied the weak gravitational distortion of background galaxy images by the matter distribution in the supergroup. We compared the reconstructed projected density field with the distribution of galaxies and hot X-ray emitting gas in the system and derived halo parameters for the individual density peaks.
Results. We show that the projected mass distribution closely follows the locations of the X-ray peaks and associated brightest group galaxies. One of the groups that lies at slightly lower redshift (z ≈ 0.35) than the other three groups (z ≈ 0.37) is X-ray luminous, but is barely detected in the gravitational lensing signal. The other three groups show a significant detection (up to 5σ in mass), with velocity dispersions between 355+ 55-70 and 530+ 45-55 km s-1 and masses between 0.8+ 0.4-0.3 × 1014 and 1.6+ 0.5-0.4 × 1014h-1 M⊙, consistent with independent measurements. These groups are associated with peaks in the galaxy and gas density in a relatively straightforward manner. Since the groups show no visible signs of interaction, this supports the hypothesis that we observe the groups before they merge into a cluster
Dark matter halo properties of GAMA galaxy groups from 100 square degrees of KiDS weak lensing data
No full textMV, MC, HHo, CS, AC, and CH acknowledge support from the European Research Council under FP7 grant number 279396 (MV, MC, CS, H.Ho) and 240185 (AC and CH). BJ acknowledges support by an STFC Ernest Rutherford Fellowship, grant reference ST/J004421/1. EvU acknowledges support from an STFC Ernest Rutherford Research Grant, grant reference ST/L00285X/1. PN acknowledges the support of the Royal Society through the award of a University Research Fellowship, the European Research Council, through receipt of a Starting Grant (DEGAS-259586) and support of the Science and Technology Facilities Council (ST/L00075X/1). RN and EvU acknowledge support from the German Federal Ministry for Economic Affairs and Energy (BMWi) provided via DLR under project no. 50QE1103. HHi is supported by the DFG Emmy Noether grant Hi 1495/2-1. This work is supported by the Netherlands Organization for Scientific Research (NWO) through grants 614.001.103 (MV) and 614.061.610 (JdJ) and by the Deutsche Forschungsgemeinschaft in the framework of the TR33 ‘The Dark Universe’. Date of Acceptance: 26/06/2015The Kilo-Degree Survey is an optical wide-field survey designed to map the matter distribution in the Universe using weak gravitational lensing. In this paper, we use these data to measure the density profiles and masses of a sample of ~1400 spectroscopically identified galaxy groups and clusters from the Galaxy And Mass Assembly survey. We detect a highly significant signal (signal-to-noise-ratio ~120), allowing us to study the properties of dark matter haloes over one and a half order of magnitude in mass, from M ~ 1013-1014.5 h-1M⊙. We interpret the results for various subsamples of groups using a halo model framework which accounts for the mis-centring of the brightest cluster galaxy (used as the tracer of the group centre) with respect to the centre of the group's dark matter halo. We find that the density profiles of the haloes are well described by an NFW profile with concentrations that agree with predictions from numerical simulations. In addition, we constrain scaling relations between the mass and a number of observable group properties. We find that the mass scales with the total r-band luminosity as a power law with slope 1.16 ± 0.13 (1σ) and with the group velocity dispersion as a power law with slope 1.89 ± 0.27 (1σ). Finally, we demonstrate the potential of weak lensing studies of groups to discriminate between models of baryonic feedback at group scales by comparing our results with the predictions from the Cosmo-OverWhelmingly Large Simulations project, ruling out models without AGN feedback.Peer reviewe
