Accelerating Dust Temperature Calculations with Graphics Processing Units

When calculating the infrared spectral energy distributions (SEDs) of galaxies in radiation-transfer models, the calculation of dust grain temperatures is generally the most time-consuming part of the calculation. Because of its highly parallel nature, this calculation is perfectly suited for massively parallel general-purpose Graphics Processing Units (GPUs). This paper presents an implementation of the calculation of dust grain equilibrium temperatures on GPUs in the Monte-Carlo radiation transfer code Sunrise, using the CUDA API. The GPU can perform this calculation 69 times faster than the 8 CPU cores, showing great potential for accelerating calculations of galaxy SEDs.Comment: 7 pages, 2 figures, accepted to New Astronomy. Minor updates to text and performance based on feedback from refere

Exploring problems related to the materials planning user environment

This paper explores the existence of various user-environment problems (i.e. problems related to the planning organization, basic planning data, software support, education, and knowledge) and explains the impact of userenvironment problems on the perceived planning performance of different materials planning methods (MRP, re-order point, kanban, run-out time, and periodic review methods). It is based on a survey of 153 manufacturing and 53 distributing companies in Sweden. Four distinct clusters of user environments are identified. It is shown how different materials planning methods perform differently in various user environments

Sunrise: Polychromatic Dust Radiative Transfer in Arbitrary Geometries

This paper describes Sunrise, a parallel, free Monte-Carlo code for the calculation of radiation transfer through astronomical dust. Sunrise uses an adaptive-mesh refinement grid to describe arbitrary geometries of emitting and absorbing/scattering media, with spatial dynamical range exceeding 10^4, and it can efficiently generate images of the emerging radiation at arbitrary points in space. In addition to the monochromatic radiative transfer typically used by Monte-Carlo codes, Sunrise is capable of propagating a range of wavelengths simultaneously. This ``polychromatic'' algorithm gives significant improvements in efficiency and accuracy when spectral features are calculated. Sunrise is used to study the effects of dust in hydrodynamic simulations of interacting galaxies, and the procedure for this is described. The code is tested against previously published results.Comment: 22 pages, 11 figures, submitted to MNRAS. Changed based on referee response. Section on benchmarks expande

Simulations of Dust in Interacting Galaxies

A new Monte-Carlo radiative-transfer code, Sunrise, is used to study the effects of dust in N-body/hydrodynamic simulations of interacting galaxies. Dust has a profound effect on the appearance of the simulated galaxies. At peak luminosities, about 90% of the bolometric luminosity is absorbed, and the dust obscuration scales with luminosity in such a way that the brightness at UV/visual wavelengths remains roughly constant. A general relationship between the fraction of energy absorbed and the ratio of bolometric luminosity to baryonic mass is found. Comparing to observations, the simulations are found to follow a relation similar to the observed IRX-Beta relation found by Meurer et al (1999) when similar luminosity objects are considered. The highest-luminosity simulated galaxies depart from this relation and occupy the region where local (U)LIRGs are found. This agreement is contingent on the presence of Milky-Way-like dust, while SMC-like dust results in far too red a UV continuum slope to match observations. The simulations are used to study the performance of star-formation indicators in the presence of dust. The far-infrared luminosity is found to be reliable. In contrast, the H-alpha and far-UV luminosity suffer severely from dust attenuation, and dust corrections can only partially remedy the situation.Comment: 4 pages, 5 figures, to appear in the proceedings of the conference "The Spectral Energy Distribution of Gas-Rich Galaxies", eds. C.C. Popescu & R.J. Tuffs (Heidelberg, October 2004

The impact of supply chain relationships and automatic data communication and registration on forecast information quality

Purpose – The purpose of this paper is to explain the effects of the customer-supplier relationship and of automatic forecast data communication and registration on the perceived information quality of forecasts. Design/methodology/approach – A conceptual model and three hypotheses are derived. The empirical analysis is based on survey data from 219 Swedish manufacturing companies. Findings – Findings show that the customer-supplier relationship and automatic data communication and registration have significant impact on the perceived quality of forecast information received from a downstream customer in the supply chain. The reliability and timeliness of the forecast information are affected to about the same extent byboth the relationship type andthe data communication andregistration strategy. Credibility is correlated with the relationship type, while the completeness, validity and conciseness of the received forecast are operative issues dependingmainly on the communication strategy. Research limitations/implications – Using single informants, focal customers and some single-item constructs in research design. Practical implications – The paper explains how various dimensions of forecast information quality are affected by different factors, thus guiding how to differentiate information quality improvement work in diverse situations. Originality/value – Detailed empirical studies of supply chain information exchange, especially focusing on explaining causes of high-quality information exchange, are lacking in the literature and demanded in industry

Assessing consequences of low cost sourcing in China

Purpose – The purpose of the paper is to develop a framework for low-cost sourcing assessment and to explore the consequences of low-cost sourcing in China for a European manufacturer.<p>Design/methodology/approach – The low-cost sourcing framework generated from literature and the consequence analysis is based on a case study of a European company that has outsourced part of its casting processes to Chinese suppliers.<p>Findings – Characteristics of low-cost sourcing are based on a literature review divided into three categories: country characteristics, supply network structure, and supply network relationships and the case study shows that these three categories of characteristics jointly create negative effects. A two-directional cause and effect relationship is proposed between the characteristics and the operational supply chain performances. The presented low-cost sourcing assessment framework should be a good starting point for low-cost sourcing assessment, including mapping a firm’s total characteristics, and for analysing their performance impact.<p>Research limitations/implications – The conducted single case study is not enough for identifying, formulating, and validating all existing relationships between the low-cost sourcing characteristics. The present study has identified the existence of the relationships but has not evaluated their levels of impact.<p>Practical implications – Managers should be aware of how suppliers in low-cost countries may affect the structures, relations, and operational supply chain performances of the supply network. This paper presents a sourcing assessment framework enabling describing what dimensions of the sourcing characteristics would be affected by sourcing to a specific area of the world and what consequences and performance effects this would have.<p>Originality/value – Few prior studies have focused on companies with already established relationships with low-cost-country suppliers and how these companies should make the best out of these supply chains. This study takes a holistic perspective on low-cost sourcing and identifies several streams for further research

Future of supply chain planning: Closing the gaps between practice and promise

The purpose is to develop a research agenda for supply chain planning (SCP) relevant to practice. We critically evaluate academic literature on SCP in order to understand how problems are addressed in their particular context, what the outcomes are, and the mechanisms producing the observed outcomes. Four categories of SCP are studied: sales and operations planning (S&OP), supply chain master planning, supply chain materials management, and collaborative materials management. We introduce the concept of enabling mechanisms to identify specific innovations in materials management and production management that can facilitate the future improvement of SCP. The critical evaluation of current SCP theory presents very limited results that are of practical relevance. SCP is not presented as an intervention and the results are not in a form that is actionable for practitioners. The body of literature is almost absent in addressing problems according to context, it presents limited evidence of intended outcomes, and it fails to identify unintended outcomes. As a consequence, research is unable to bolster theoretical understandings of how outcomes – both intended and unintended – are achieved. In our forward-looking research agenda we leverage our understanding of the enabling mechanisms in order to propose research to make mature S&OP and novel types of SCP implementable. The paper is an example of a structured approach to developing a research agenda that is relevant to practice and can be used more widely in logistics and supply chain management. This paper presents a research agenda to close the gap between practice and promise in SCP. We operationalize what constitutes practical relevance for an established field of research

The value of sharing planning information in supply chains

Purpose - The development of information technology has made it possible for companies to get access to information about their customers’ future demand. This paper outlines various approaches to utilize this kind of visibility when managing inventories of end products on an operative level. The purpose is to explain the consequences, for capital tied up in inventory, of sharing four different types of planning information (point-of-sales data, customer forecasts, stock-on-hand data, planned orders) when using re-order point (R,Q) inventory control methods in a distribution network. Design/methodology/approach - A simulation study based on randomly generated demand data with a compound Poisson type of distribution is conducted. Findings - The results show that the value of information sharing in operative inventory control varies widely depending on the type of information shared, and depending on whether the demand is stationary or not. Significantly higher value is achieved if the most appropriate types of information sharing are used, while other types of information sharing rather contribute to decreased value. Sharing stock-on-hand information is valuable with stationary demand. Customer forecast and planned order information are valuable with non-stationary demand. The value of information sharing increases when having fewer customers, and when the order quantities are large. Sharing point-of-sales data is not valuable, regardless of the demand type. Research limitations/implications - The use of simulation methodology is a limitation, because the study has to be limited to a specific model design, and because it is not based on primary empirical data. The study is especially limited to dyadic relationships in supply chains, and to distribution networks with a rather limited number of customers. Practical implications - Guidance is given about what type of information should be appropriate to share when different types of demand patterns and distribution networks, and how order batch sizes and lead times affect the value of information sharing when using re-order point (R,Q) methods. Originality/value - Very limited research providing specific assessments of potential inventory control consequences when sharing planning information in various contexts has been found in the literature. The findings and conclusions should also be valuable for the supply chain integration and collaborative planning literature

When should advanced planning and scheduling systems be used in sales and operations planning?

The purpose of this paper is to explore how the context affects successful use of advanced planning and scheduling (APS) systems in sales and operations planning (S&OP) processes, and how individual, technological, and organizational (ITO) dimensions affect this procedure. A qualitative case study of two APS system-supported S&OP processes is conducted. The work aims to generate propositions concerning the relationships among the use of APS system, the context, ITO dimensions, and fulfillment of S&OP aims. Findings show that the use of APS systems was especially appropriate in support of S&OP processes in complex planning environments and when S&OP aims were ambitious. ITO dimensions were important influences on successful APS system use in most contexts. APS systems were not considered appropriate when having S&OP processes with ambitious aims and low individual and organizational maturities. Use of APS systems was also inappropriate when the extent of technological maturity was minimal. S&OP processes with ambitious aims, operating within a complex planning environment, are difficult if not impossible to implement without the support of APS systems. The suggestions on when APS systems should be used in different S&OP environments will be useful to companies implementing or about to implement APS systems. APS systems offer great potential if they are effectively used to support S&OP, still the use of APS system in S&OP is unexplored. The paper shows how the context and the ITO dimensions affect the successful use of APS systems in S&OP processes