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dissertation (10)


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2019 (10)

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Dissertation
Application of deep Learning for predictive maintenance
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Year: 2019 Publisher: Leuven KU Leuven. Faculteit Economie en Bedrijfswetenschappen

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Abstract

Prognostics accurately predicts the remaining useful lifetime of components in order to proactively perform maintenance. In recent years, deep learning algorithms have proved superior performance thanks to their ability to automatically extract degradation features from normalized data. However, recent scientific literature indicates that this trait is slightly eroded for convolutional neural networks when applied to non-stationary data. Indeed, researches in the field usually involve extracting time-frequency features from normalized data before implementing the convolutional neural network (signal processing techniques), but, as of today, it has not been empirically corroborated that non-stationarity undermines the performance of a convolutional neural network in prognostics. The present thesis therefore pursues a twofold objective. First, it aims to fill the research gap by conducting an extensive literature review of convolutional neural networks applied to prognostics and discovering patterns. Second, it aims to examine the viability of the direct implementation of a fundamental convolutional neural network on non-stationary bearing data without signal processing techniques. It is built on an incremental approach, where the capacity of the convolutional neural network structure is gradually increased. The results demonstrate that the generalization performance of the convolutional neural network applied on non-stationary bearing test data is consistently poor, regardless of the network capacity.

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Dissertation
A new policy for the dual sourcing problem with capacity constraints: a capacitated dual sourcing

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This master dissertation introduces the capacitated dual index policy which extends the traditional dual sourcing literature by including capacity constraints of the transport modes into the sourcing cost function. Based on the dual index policy, a prominent policy in the dual sourcing literature, the capacitated dual index policy introduces an extra step in the form of rounding the orders up or down to achieve full truckloads. This work demonstrates the excellent performance of the capacitated dual index policy, because the rounding makes sure that the inventory cost is significantly lower than the dual index policy. The sensitivity analysis of this policy points out that the holding cost that a company faces is the parameter that has the most influence on the total cost, when the capacitated dual index policy is applied. This is because the holding cost impacts the inventory cost, the cost of ordering, and the cost of transportation all in a negative way- meaning that the different costs grow bigger when the holding cost grows.

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Dissertation
On the use of machine learning for predictive maintenance: flagging anomalous behavior
Authors: --- --- ---
Year: 2019 Publisher: Leuven KU Leuven. Faculteit Economie en Bedrijfswetenschappen

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Machine learning has experienced a steep increase in interest for operational processes and becomes key to create competitive advantages. Unfortunately, most machine learning projects fail in achieving the expected results, which is caused by several short-comings such as budget, lack of knowledge, understandability, lack of IT architecture, false expectations, etc. Therefore, this master thesis addresses this gap and aims to find correct settings in which the benefits of using machine learning algorithms over existing quality management techniques as SPC are noticeable. This comparison is evaluated by looking at the possibility of handling unstructured data, clustering and outperforming the classification of anomalies in terms of accuracy and complexity. Moreover, evaluation is performed on several built supervised/unsupervised learning algorithms. The results of the comparison reveal that machine learning techniques can be used to improve the performance of anomaly detection by seeing anomalies not only as outliers. More specifically, machine learning techniques expand the viewpoint of anomalies by using clustering approaches and by coping with restrictions on the input data (i.e. data complexity, lack of anomalous data). Unfortunately, these improvements mostly come with an increase in complexity although some algorithms try to limit this increase by using a less complex variant or extra software packages to expand the interpretability (e.g. software package Lime). In addition, practical implementation guidelines are formulated out of these results as flagging anomalous behavior can be used for doing predictive maintenance.

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Dissertation
Predictive analytics in service maintenance: Impact of model misspecification on performance

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This thesis provides research regarding predictive analytics in service maintenance. More specific, it investigates the impact of model misspecification on performance of the condition-based maintenance policy. It analyses the impact of using different stochastic models to model component degradation. A simulation model is constructed and statistical analyses are performed to find the impact of model misspecification on performance of the condition-based maintenance policy.

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Dissertation
Horizontal collaboration with transshipment platforms

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An analysis of horizontal collaboration between competing manufacturers is performed in terms of their distribution costs. Comparisons are made between different distribution networks based on the type of collaboration implemented. The objective is to quantify efficiency gains due to reduced transportation costs when a coalition between manufactures is created. A mathematical optimisation model is used to create day-to-day operational schedules based on extensions of the classical vehicle routing problem.

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Dissertation
Synchromodality in the physical internet: real-time switching in a multimodal network with stochastic transit times

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Environmental concerns raise the need for more efficiency and sustainability in the freight transportation sector. For this purpose, the Physical Internet is introduced, which aims to connect logistics networks into one hyperconnected supernetwork. To transport freight over such an integrated network, the innovative concept of synchromodality is presented. Synchromodality is defined by the usage of multiple modalities when planning shipments, where real-time switching between transportation modes is possible. In this thesis, a synchromodal planning model is developed that constructs optimal transportation routes in a multimodal network with stochastic transit times, formulated as a mixed-integer linear programming problem. To cope with this transit time stochasticity, transportation routes are adapted in accordance to real-time information about the transit time outcomes. Hence, the model determines the optimal decision to be taken in a terminal depending on the realized transit time. A numerical study demonstrates the potential advantages of real-time planning adaptation in terms of costs, service quality and environmental impact.

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Dissertation
Machine learning in supply chain
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Year: 2019 Publisher: Leuven KU Leuven. Faculteit Economie en Bedrijfswetenschappen

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This thesis provides an overview where machine learning algorithms can be applied within supply chain management. A description is made of well-known supervised, unsupervised and reinforcement learning algorithms, together with a careful positioning of the application of these algorithms in the field of supply chain management. Lastly, a deep reinforcement algorithm is employed to a production scheduling optimization problem with stochastic demand. The model doesn’t significantly outperform the policy against which is benchmarked, but there is a possibility for a further expansion of the network as well as the model to create a possible improvement on existing policies.

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Dissertation
The impact of machine leaning on supply chain management
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Year: 2019 Publisher: Leuven KU Leuven. Faculteit Economie en Bedrijfswetenschappen

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Artificial intelligence, robots, virtual reality, ... objects and technological applications are evolving at high speed in many sectors including leisure, transport, education and industry. Machine learning has already shown high development potential with self-driving vehicles, object recognition, search engines and personalized interactions between machines and humans, but what is the current scope of machine learning in the industry? In the age of industry 4.0, this master thesis focuses on an overview of the impact of machine learning on supply chain management. First, a general explanation of the concepts of supply chain management and machine learning is given, intended for an audience that is not necessarily familiar with the subject. Then, several existing machine learning applications in supply chains are presented. A general description of these implementations, their benefits and concrete examples of companies and start-ups that are developing them are given.

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Dissertation
Collaborative shipping: reservation of backhaul trips

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In this thesis, the current problems and challenges in our logistic environment regarding empty trucks are reviewed by comparing different types of collaboration. The effects and cost savings of collaboration through backhauling are discussed in detail and a new policy relying on the usage of multiple can-order levels is introduced. Numerical examples based on simulation studies of three different situations are included. The distinction between no collaboration, collaboration with backhauls trips based on a can-order level and collaboration with reservation of backhauls using the newly introduced method with multiple can-orders. We conclude that the multiple can-order policy dominates previous policies and offers large benefits to collaborating partners.

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Dissertation
On the use of machine learning in predictive maintenance: classification models

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This thesis addresses the problem of the IEEE 2015 PHM Data Challenge, where one must predict plant breakdown of unknown plants in advance. This paper proposes three supervised machine learning algorithms based on classification approaches, namely decision trees, random forests and artificial neural networks as possible solutions. Two cost-sensitive variants of the decision tree approach and one costsensitive variant of the random forest approach and the artificial neural network approach are also modeled. These variants apply a similar methodology compared to the standard classifiers but are optimized using a cost function. This results in predictive maintenance models that attempt to avoid premature failure misclassifications. The forecasts, which are based on historical input data, support managers in the decision-making process to optimize the planning of maintenance actions. The structure of the thesis can be divided into four stages. The first stage consists of a literature review on the existing research that has been done on the use of machine learning in predictive maintenance. This is followed by the preprocessing of raw, unordered data of the problem under consideration into useful information. Descriptive statistics are performed on the cleaned data in the third stage. In the last stage, the predictive maintenance models are built. A combination of RapidMiner, Microsoft Excel and Groovy software is used to preprocess the data and to model the classifiers. Results show that the number of machines within a plant does not affect the prediction accuracy of the models and that the decision tree approach provides the most accurate results.

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