Detailed Inventory Record Inaccuracy Analysis

This dissertation performs a methodical analysis to understand the behavior of inventory record inaccuracy (IRI) when it is influenced by demand, supply and lead time uncertainty in both online and offline retail environment separately. Additionally, this study identifies the susceptibility of the inventory systems towards IRI due to conventional perfect data visibility assumptions. Two different alternatives for such methods are presented and analyzed; the IRI resistance and the error control methods. The discussed methods effectively countered various aspects of IRI; the IRI resistance method performs better on stock-out and lost sales, whereas error control method keeps lower inventory. Furthermore, this research also investigates the value of using a secondary source of information (automated data capturing) along with traditional inventory record keeping methods to control the effects of IRI. To understand the combined behavior of the pooled data sources an infinite horizon discounted Markov decision process (MDP) is generated and optimized. Moreover, the traditional cost based reward structure is abandoned to put more emphasis on the effects of IRI. Instead a new measure is developed as inventory performance by combining four key performance metrics; lost sales, amount of correction, fill rate and amount of inventory counted. These key metrics are united under a unitless platform using fuzzy logic and combined through additive methods. The inventory model is then analyzed to understand the optimal policy structure, which is proven to be of a control limit type

Continuum variational and diffusion quantum Monte Carlo calculations

This topical review describes the methodology of continuum variational and diffusion quantum Monte Carlo calculations. These stochastic methods are based on many-body wave functions and are capable of achieving very high accuracy. The algorithms are intrinsically parallel and well-suited to petascale computers, and the computational cost scales as a polynomial of the number of particles. A guide to the systems and topics which have been investigated using these methods is given. The bulk of the article is devoted to an overview of the basic quantum Monte Carlo methods, the forms and optimisation of wave functions, performing calculations within periodic boundary conditions, using pseudopotentials, excited-state calculations, sources of calculational inaccuracy, and calculating energy differences and forces

Modeling Inverter Losses for Circuit Simulation

Transformer-like inverter models can represent a very good alternative to common switch-diode models for simulation, reducing convergence problems and/or calculation time. They may also provide easier insight into the converter operation and power loss effects, at least from the point of view of the applicants, aiding for design and teaching purposes. The paper shows how conduction and switching losses can be incorporated in the transformer-like inverter model in a simple and intuitive way, which requires very few parameters and allows for separate modeling of lossless behavior, conduction losses and the switching losses. Loss models are proposed in some versions differing for the accuracy and simulation easiness. In any case, the resulting inverter lossy model is very compact and can be implemented by just a pair of nonlinear controlled sources as basic building blocks, available in any circuit simulation program, as the free of charge and widely used PSpice student version

The diffusion and impact of radio frequency identification in supply chains : a multi-method approach

As a promising and emerging technology for supply chain management, Radio Frequency Identification (RFID) is a new alternative to existing tracking technologies and also allows a range of internal control and supply chain coordination. RFID has generated a significant amount of interest and activities from both practitioners and researchers in recent years. However, the factors important for its diffusion in supply chains and the impact on supply chain performance have not been well understood. Many organizations are reluctant to participate in supply-chain level RFID projects because of this lack of understanding. My dissertation proposes to help understand RFID's use in supply chains through a multi-method approach - an empirical study to understand the diffusion and impact of RFID and a simulation study to understand RFID's impact on inventory accuracy in supply chains. My first study on the factors influencing RFID adoption decision showed that compatibility, trading partner's RFID capability, trading partner power, competitive pressure, transaction volume and financial resources are significant factors for RFID adoption in a supply chain context. The second study which looked into the post-adoption use of RFID for supply chain has found that adoption cost, complexity, organizational readiness, external pressure and trading partner readiness significantly influence RFID infusion, which finally improves firm's supply chain process performance. The third study used a simulation model to examine RFID's impact on inventory management in supply chains. The key findings were that the benefits reaped from RFID heavily depend on product type which implements RFID. The above findings indicate that organizations have to carefully evaluate their RFID project with different factors identified in this dissertation to successfully implement RFID and derive its full benefits. My dissertation has contributed to RFID research in particular, and supply chain technology adoption in general, by showing the importance of trading partner issues for supply chain technology diffusion and use

Data inaccuracy quantification and uncertainty propagation for bibliometric indicators

This study introduces an approach to estimate the uncertainty in bibliometric indicator values that is caused by data errors. This approach utilizes Bayesian regression models, estimated from empirical data samples, which are used to predict error-free data. Through direct Monte Carlo simulation -- drawing predicted data from the estimated regression models a large number of times for the same input data -- probability distributions for indicator values can be obtained, which provide the information on their uncertainty due to data errors. It is demonstrated how uncertainty in base quantities, such as the number of publications of a unit of certain document types and the number of citations of a publication, can be propagated along a measurement model into final indicator values. This method can be used to estimate the uncertainty of indicator values due to sources of errors with known error distributions. The approach is demonstrated with simple synthetic examples for instructive purposes and real bibliometric research evaluation data to show its possible application in practice.Comment: 31 pages, 5 figure

On Supra-Bayesian Weighted Combination of Available Data Determined by Kerridge Inaccuracy and Entropy

2010 Mathematics Subject Classification: 94A17.Every process in our environment can be described with a statistical model containing inner properties expressed by parameters. These are usually unknown and the determination of their values is of interest in the statistical branch called parameter estimation. This branch involves many methods solving different estimation cases, e.g. the estimation of location and scale parameters. To obtain the parameter estimate we exploit the data given by data sources. In particular, the estimate is their combination. Improvement of the parameter estimates involve the assignment of the weights to the data sources resulting in a weighted combination of data. Unfortunately this approach brings difficulties regarding the determination of the weights and their subjective affection. In recently introduced Supra-Bayesian approach it is proposed to use the Kerridge inaccuracy and the maximum entropy principle to overcome the problem of subjective influence. In this paper we focus on the derivation of the weights arisen within the Supra-Bayesian approach and on the simulation study of their behaviour and the behaviour of the final estimate

Extending Continuum Models for Atom Probe Simulation

This work describes extensions to existing level-set algorithms developed for application within the field of Atom Probe Tomography (APT). We present a new simulation tool for the simulation of 3D tomographic volumes, using advanced level set methods. By combining narrow-band, B-Tree and particle-tracing approaches from level-set methods, we demonstrate a practical tool for simulating shape changes to APT samples under applied electrostatic fields, in three dimensions. This work builds upon our previous studies by allowing for non-axially symmetric solutions, with minimal loss in computational speed, whilst retaining numerical accuracy

Mass Measurement Using Energy Spectra in Three-body Decays

In previous works we have demonstrated how the energy distribution of massless decay products in two body decays can be used to measure the mass of decaying particles. In this work we show how such results can be generalized to the case of multi-body decays. The key ideas that allow us to deal with multi-body final states are an extension of our previous results to the case of massive decay products and the factorization of the multi-body phase space. The mass measurement strategy that we propose is distinct from alternative methods because it does not require an accurate reconstruction of the entire event, as it does not involve, for instance, the missing transverse momentum, but rather requires measuring only the visible decay products of the decay of interest. To demonstrate the general strategy, we study a supersymmetric model wherein pair-produced gluinos each decay to a stable neutralino and a bottom quark-antiquark pair via an off-shell bottom squark. The combinatorial background stemming from the indistinguishable visible final states on both decay sides can be treated by an "event mixing" technique, the performance of which is discussed in detail. Taking into account dominant backgrounds, we are able to show that the mass of the gluino and, in favorable cases, that of the neutralino can be determined by this mass measurement strategy.Comment: 42 pages, 12 figures, Journal-submitted versio