4,946 research outputs found
A Continuum,O(N) Monte-Carlo algorithm for charged particles
We introduce a Monte-Carlo algorithm for the simulation of charged particles
moving in the continuum. Electrostatic interactions are not instantaneous as in
conventional approaches, but are mediated by a constrained, diffusing electric
field on an interpolating lattice. We discuss the theoretical justifications of
the algorithm and show that it efficiently equilibrates model polyelectrolytes
and polar fluids. In order to reduce lattice artifacts that arise from the
interpolation of charges to the grid we implement a local, dynamic subtraction
algorithm. This dynamic scheme is completely general and can also be used with
other Coulomb codes, such as multigrid based methods
Phase fluctuations and first-order correlation functions of dissipative Bose-Einstein condensates
We investigate the finite lifetime effects on first-order correlation
functions of dissipative Bose-Einstein condensates. By taking into account the
phase fluctuations up to all orders, we show that the finite lifetime effects
are neglible for the spatial first-order correlation functions, but have an
important effect on the temporal correlations. As an application, we calculate
the one-particle density matrix of a quasi-condensate of photons. Finally, we
also consider the photons in the normal state and we demonstrate that the
finite lifetime effects decrease both the spatial and temporal first-order
correlation functions.Comment: 8 pages, 5 figure
Schwinger-Keldysh theory for Bose-Einstein condensation of photons in a dye-filled optical microcavity
We consider Bose-Einstein condensation of photons in an optical cavity filled
with dye molecules that are excited by laser light. By using the
Schwinger-Keldysh formalism we derive a Langevin field equation that describes
the dynamics of the photon gas, and in particular its equilibrium properties
and relaxation towards equilibrium. Furthermore we show that the finite
lifetime effects of the photons are captured in a single dimensionless damping
parameter, that depends on the power of the external laser pumping the dye.
Finally, as applications of our theory we determine spectral functions and
collective modes of the photon gas in both the normal and the Bose-Einstein
condensed phase
Vis en visserij in het IJsselmeergebied
Het visbestand in het IJsselmeer wordt sterk bepaald door de intensieve visserijactiviteiten. Het IJsselmeer biedt goede potenties voor trekkende en (nu nog) zeldzame vissoorten, zeker wanneer de dynamische aspecten van een estuarium meer kunnen worden ontwikkel
Preparing for new competitive challenges: special issue on the 24th annual IPSERA conference
The 24st IPSERA conference in Amsterdam addressed the various new competitive challenges organizations face now that business environments are changing. While we can observe an increased role of - but also an increased concentration in - logistic services and IT services acting as a bonding agent of the various business processes, we also see an increased specialisation among suppliers, resulting in roles like capacity supplier, co-maker and broker. In terms of Systems Thinking: the subsystem of âSuppliersâ is breaking up into three sub-systems with distinctive different characteristics,
and the traditional sub-system âPurchasingâ has transformed into an aspect-system connecting or
involving all other sub-systems, while similarly, âLogisticsâ and âITâ have developed into intertwined
aspect-systems, being part of each and every sub-system. These transformations have increased managerial complexity, greatly influencing the purchasing and supply chain functions within firms. The seven papers selected from the conference examine seven aspects of those changes in detail and elaborate on the role of the PSM field in this process: PSM answers to challenges by providing answers on how to move forward in practice
Consumer behaviour and order fulfilment in online retailing â a systematic review
This paper provides a systematic review of consumer behaviour and order fulfilment in online retailing. The objective of this review is threefold: first, to identify elements of orderâfulfilment operations that are relevant to online consumer behaviour (purchase, repurchase, product return); second, to understand the relationship between orderâfulfilment performance and consumer behaviour; and third, to inspire future research on developing consumer service strategies that takes account of these behavioural responses to orderâfulfilment performance outcomes. The paper is based on a systematic review of literature on online consumer behaviour and orderâfulfilment operations, mainly in the fields of marketing and operations, published in international peerâreviewed journals between 2000 and September 2015. This study indicates that the current literature on online consumer behaviour focuses mainly on the use of marketing tools to improve consumer service levels. Very little research has been conducted on the use of consumer service instruments to steer consumer behaviour or, consequently, to manage related orderâfulfilment activities better. The study culminates in a framework that encompasses elements of orderâfulfilment operations and their relationship to online consumer behaviour. This paper is the first comprehensive review of online consumer behaviour that takes aspects of orderâfulfilment operations into account from both marketing and operations perspectives
Ecologically friendly sourcing in developing countries: a non-food case study
The purpose of this paper is to investigate how nearby sourcing versus long-distance sourcing affects the ecological friendliness - operationalized in terms of energy efficiency - of a supply chain for a non-food item in a developing country. Using case research, we show that the average energy needed to supply a pair of imported shoes to a retailer in Morocco is less than the average energy needed to supply a pair of locally produced shoes. These findings highlight the need to assess the true total energy effects of nearby sourcing versus long-distance sourcing since the outcomes of such assessments may be more complicated than they appear upon first glance, particularly in developing countries
Performance management practices in humanitarian organisations
Purpose â We examine how design and implementation practices for supply chain performance management that have proven successful in commercial organisations apply to Humanitarian Organisations (HOs) to guide the process of designing and implementing performance management in humanitarian organisations.
Design/methodology/approach â We identify from the literature 10 successful practices regarding the design and implementation of supply chain performance management in commercial businesses. We apply these, using action research over a four-year period, at MĂ©decins sans FrontiĂšres (MSF) Belgium and draw conclusions from this.
Findings â We find that tools and techniques, such as workshops and technical sheets, are essential in designing and implementing supply chain performance measurement projects at HOs. Furthermore, making a link to an IT project is crucial when implementing performance measurement systems at HOs. Overall, our case study shows that performance management practices used in business can be applied and are relevant for humanitarian supply chains.
Originality/value â Previous research has argued that there are few empirical studies in the domain of performance management at humanitarian organisations. To the best of our knowledge, this paper is the first to provide a longitudinal understanding of the design and implementation of supply chain performance measurement at HOs
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