| 1. |
- Jang, Seon-Kyeong, et al.
(författare)
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Rare genetic variants explain missing heritability in smoking.
- 2022
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Ingår i: Nature human behaviour. - : Springer Science and Business Media LLC. - 2397-3374. ; 6:11, s. 1577-1586
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Tidskriftsartikel (refereegranskat)abstract
- Common genetic variants explain less variation in complex phenotypes than inferred from family-based studies, and there is a debate on the source of this 'missing heritability'. We investigated the contribution of rare genetic variants to tobacco use with whole-genome sequences from up to 26,257 unrelated individuals of European ancestries and 11,743 individuals of African ancestries. Across four smoking traits, single-nucleotide-polymorphism-based heritability ([Formula: see text]) was estimated from 0.13 to 0.28 (s.e., 0.10-0.13) in European ancestries, with 35-74% of it attributable to rare variants with minor allele frequencies between 0.01% and 1%. These heritability estimates are 1.5-4 times higher than past estimates based on common variants alone and accounted for 60% to 100% of our pedigree-based estimates of narrow-sense heritability ([Formula: see text], 0.18-0.34). In the African ancestry samples, [Formula: see text] was estimated from 0.03 to 0.33 (s.e., 0.09-0.14) across the four smoking traits. These results suggest that rare variants are important contributors to the heritability of smoking.
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| 2. |
- Kyösti, Petter, et al.
(författare)
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A decision support tool for optimising support site configuration of Functional Products
- 2014
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Ingår i: Proceedings of the 3rd International Conference in Through-life Engineering Services. - : Elsevier. ; , s. 175-180
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Konferensbidrag (refereegranskat)abstract
- The customization of the support site configuration (including the number, locations and capabilities of sites where maintenance staff are based) is of critical importance to functional product providers, who must provide maintenance support services for products operated by their customers at different locations and ensure that contractual guarantees for functional availability are met whilst keeping support costs under control. Since contract fulfilment costs are performance based and long term, they are difficult to predict without modelling. This paper discusses a decision support tool designed for use by management and engineering personnel at Functional Product providers to analyse and optimize the performance of their support base configuration. It features a graphical user interface for configuration customization, simulation modelling to predict performance and outputs a wide range of analytics that can be used to compare and optimize configurations. The tool is demonstrated via application to an industrial test case.
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| 3. |
- Kyösti, Petter, et al.
(författare)
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Prediction of service support costs for functional products
- 2015
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Ingår i: Simulation modelling practice and theory. - : Elsevier. - 1569-190X .- 1878-1462. ; 59, s. 52-70
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Tidskriftsartikel (refereegranskat)abstract
- In the functional product business model, a customer is provided with functionality at a guaranteed level of availability under a pre-agreed pricing structure whilst the provider retains ownership of the hardware and provides a service support system to deliver services such as maintenance. The ability to accurately predict the costs of supporting functional product contracts is crucial to the provider in correctly pricing those contracts and for the development and implementation of an efficient service support system. Since the costs incurred are performance based and accumulated over a long duration, they are difficult to predict without effective modelling and decision support tools. This paper discusses a decision support tool that has been developed to provide detailed analysis of the predicted long-term costs of supporting functional product contracts. The tool features a web based user interface to allow collaborative use of the tool by multiple users. The cost predictions are obtained through a discrete event simulation model that emulates the performance of the hardware and service support system used by the provider to fulfil the functional requirements specified in the contracts. The simulations are executed on automatically provisioned remote web based servers, meaning that the computing resources utilised are not limited by the user's client device. The tool is demonstrated via application to an industrial test case.
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| 4. |
- Lindström, John, et al.
(författare)
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Use of cloud services in functional products : availability implications
- 2014
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Ingår i: Product Services Systems and Value Creation. - : Elsevier. ; 16, s. 368-372
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Konferensbidrag (refereegranskat)abstract
- The paper addresses the potential use of cloud services in Functional Products (FP) and its possible implications for availability. Further, how the implications for availability can be understood via modelling and simulation is addressed. The paper adds further specificity to literature by indicating the FP constituents for which cloud services are applicable and adequate.
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| 5. |
- Löfstrand, Magnus, et al.
(författare)
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A model for predicting and monitoring industrial system availability
- 2012
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Ingår i: International Journal of Product Development. - Bucks, United Kingdom : InderScience Publishers. - 1477-9056 .- 1741-8178. ; 16:2, s. 140-157
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the integration of a sensor data stream monitoring system into a proposed functional product model capable of predicting functional availability. Such monitoring systems enable predictive maintenance to be carried out pre-emptive maintenance that is scheduled in response to imminent hardware failure and are in widespread use in industry. The industrial motivation for this research is that agreed upon system availability is a critical element of any business-to-business agreement regarding functional sales. Such a model is important when making strategic choices regarding FPs and can be used to develop a high availability product design through simulation driven development, as well as to provide operational decision support that reflects the current reality to enable optimal availability to be achieved in practice. The proposed model integrates hardware, support system and monitoring system models, and is able to incorporate actual operational data. It has been partly verified based on previous research.
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| 6. |
- Löfstrand, Magnus, 1974-, et al.
(författare)
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A model for predicting and monitoring industrial system availability
- 2012
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Ingår i: International Journal of Product Development. - Bucks, United Kingdom : InderScience Publishers. - 1477-9056 .- 1741-8178. ; 16:2, s. 140-157
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This paper describes the integration of a sensor data stream monitoring system into a proposed functional product model capable of predicting functional availability. Such monitoring systems enable predictive maintenance to be carried out pre-emptive maintenance that is scheduled in response to imminent hardware failure and are in widespread use in industry. The industrial motivation for this research is that agreed upon system availability is a critical element of any business-to-business agreement regarding functional sales. Such a model is important when making strategic choices regarding FPs and can be used to develop a high availability product design through simulation driven development, as well as to provide operational decision support that reflects the current reality to enable optimal availability to be achieved in practice. The proposed model integrates hardware, support system and monitoring system models, and is able to incorporate actual operational data. It has been partly verified based on previous research.
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| 7. |
- Löfstrand, Magnus, 1974-, et al.
(författare)
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Evaluating availability of functional products through simulation
- 2014
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Ingår i: Simulation Modelling Practice and Theory. - Amsterdam, Netherlands : Elsevier. - 1569-190X .- 1878-1462. ; 47, s. 196-209
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Tidskriftsartikel (refereegranskat)abstract
- A functional product is an integrated package consisting of hardware, software and a service support system that provides a customer with a certain function and is sold under a performance-based contract that includes a functional availability guarantee. For the availability performance, prediction, optimisation and management of risk are therefore important concerns during product development. This paper describes a software tool that can generate an integrated model of a functional product from its design details and analyse it through simulation to provide availability performance information. The model's application to the analysis of a real industrial system is demonstrated. Such tools are important for the development and widespread adoption of functional products. The resulting analysis gave an indication of a suitable guaranteed functional availability level for the product and could be used to compare the performance of different design options.
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| 8. |
- Löfstrand, Magnus, 1974-, et al.
(författare)
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Modelling and simulation of functional product system availability and support costs
- 2012
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Ingår i: International Journal of Product Development. - Bucks, United Kingdom : InderScience Publishers. - 1477-9056 .- 1741-8178. ; 16:3-4, s. 304-325
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Functional products (FP), total offers or product service systems, that comprise of both hardware (HW) and support services (SS) sold as an integrated offering under an availability guarantee, are becoming increasing popular in industry. This paper addresses, through modelling and simulation, the challenge faced by suppliers in developing an integrated HW and SS design to produce an FP which meets contracted availability. A recently published framework specified how an integrated model hardware and service support system model could be used to obtain functional availability predictions and perform simulation driven functional product development. This paper presents the first example of an integrated functional product model. It uses fault tree, Petri net and discrete event simulation techniques to enable the prediction of functional product availability and support costs. Such predictions are used here to evaluate and compare different service support system designs.
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| 9. |
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Overview of the JET results
- 2015
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 55:10
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Tidskriftsartikel (refereegranskat)
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| 10. |
- Reed, Sean, 1982-, et al.
(författare)
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An efficient algorithm for computing exact system and survival signatures of K-terminal network reliability
- 2019
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Ingår i: Reliability Engineering & System Safety. - : Elsevier. - 0951-8320 .- 1879-0836. ; 185, s. 429-439
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Tidskriftsartikel (refereegranskat)abstract
- An efficient algorithm is presented for computing exact system and survival signatures of K-terminal reliability in undirected networks with unreliable edges. K-terminal reliability is defined as the probability that a subset K of the network nodes can communicate with each other. Signatures have several advantages over direct reliability calculation such as enabling certain stochastic comparisons of reliability between competing network topology designs, extremely fast repeat computation of network reliability for different edge reliabilities and computation of network reliability when failures of edges are exchangeable but not independent. Existing methods for computation of signatures for K-terminal network reliability require derivation of cut-sets or path-sets which is only feasible for small networks due to the computational expense. The new algorithm utilises binary decision diagrams, boundary set partition sets and simple array operations to efficiently compute signatures through a factorisation of the network edges. The performance and advantages of the algorithm are demonstrated through application to a set of benchmark networks and a sensor network from an underground mine.
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| 11. |
- Reed, Sean, 1982-
(författare)
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An efficient algorithm for exact computation of system and survival signatures using binary decision diagrams
- 2017
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Ingår i: Reliability Engineering & System Safety. - : Elsevier. - 0951-8320 .- 1879-0836. ; 165, s. 257-267
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Tidskriftsartikel (refereegranskat)abstract
- System and survival signatures are important and popular tools for studying and analysing the reliability of systems. However, it is difficult to compute these signatures for systems with complex reliability structure functions and large numbers of components. This paper presents a new algorithm that is able to compute exact signatures for systems that are far more complex than is feasible using existing approaches. This is based on the use of reduced order binary decision diagrams (ROBDDs), multidimensional arrays and the dynamic programming paradigm. Results comparing the computational efficiency of deriving signatures for some example systems (including complex benchmark systems from the literature) using the new algorithm and a comparison enumerative algorithm are presented and demonstrate a significant reduction in computation time and improvement in scalability with increasing system complexity.
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| 12. |
- Reed, Sean, 1982-, et al.
(författare)
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Discrete Event Simulation Using Distributional Random Forests to Model Event Outcomes
- 2022
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Konferensbidrag (refereegranskat)abstract
- In discrete event simulation (DES), the events are random (aleatory) and typically represented by a probability distribution that fits the real phenomena that is studied. The true distributions of event outcomes, which may be multivariate, are often dependent on the values of covariates and this relationship may be complex. Due to difficulties in representing the influence of covariates within DES models, often only the averaged distribution or expected value of the conditional distribution is used. However, this can reduce modelling accuracy and prevent the model from being used to study the influence of covariates. Distributional random forests (DRF) are a machine learning technique for predicting the multivariate conditional distribution of an outcome from the values of covariates using an ensemble of decision trees. In this paper, the benefits of utilizing DRF in DES are explored through comparison with alternative approaches in a model of a powder coating industrial process.
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| 13. |
- Reed, Sean, 1982-, et al.
(författare)
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Effect of venepuncture process design on efficiency and failure rates : a simulation model study for secondary care
- 2017
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Ingår i: International Journal of Nursing Studies. - : Elsevier. - 0020-7489 .- 1873-491X. ; 68, s. 73-82
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Tidskriftsartikel (refereegranskat)abstract
- Background: Healthcare aims to deliver good patient outcomes. For many clinical procedures there are multiple alternative task sequences that can be performed. These deviations can influence procedure reliability, efficiency of usage of hospital resources and risk to staff and patient safety. Venepuncture is one of the most common invasive procedures in healthcare. Literature of clinical practice shows evidence of wide variability in the procedure order and the duration of each step, which can depend on attributes, such as patient health, sampling method and staff skills.Objective: To use a computer simulation model based on Petri nets to evaluate the impact on outcomes of commonly practiced deviations from the venepuncture procedure guideline and variations in key dependent variables. The outcomes considered include the probability of successfully obtaining a blood sample and the procedure completion time.Design: A computer simulation model was constructed using the Petri net technique which mimics the different variations of the venepuncture procedure. Qualitative and quantitative data for the model was collected from the literature and through interviews and questionnaire responses from doctors and phlebotomists. Statistics on the reliability and duration for different variations were then calculated from the model output.Setting: A digital laboratory to model venepuncture in secondary care.Results: The model showed that the common practice of applying the tourniquet prior to vein identification and releasing it after sample tubes are filled may result in a ten-fold increase in sample haemolysis, compared to the recommended guideline procedure. Equipment layout on wards and patient vein prominence were identified as the two most important factors influencing time efficiency of blood sample collection.Conclusions: Petri net computer models were shown to be an effective method for evaluating the success rate and completion time of the venepuncture procedure under alternative task sequences and variations in key dependent variables. The results obtained from the model showed a significant increase in the rate of sample laboratory rejection due to haemolysis when commonly practiced deviations from the guideline procedure were performed. The rate of failure to collect a sample and the mean time for performing the procedure increased significantly for patients with less prominent veins and when the procedure was performed on unfamiliar wards. These results highlight the need for healthcare providers to ensure guidelines are followed when performing venepuncture, equipment layouts are standardised across locations and that the vein prominence of different patient groups is considered when allocating resources for blood sample collection.
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| 14. |
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| 15. |
- Reed, Sean, 1982-, et al.
(författare)
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Improved efficiency in the analysis of phased mission systems with multiple failure mode components
- 2011
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Ingår i: IEEE Transactions on Reliability. - : IEEE. - 0018-9529 .- 1558-1721. ; 60:1, s. 70-79
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Tidskriftsartikel (refereegranskat)abstract
- Systems often operate in phased missions where their reliability structure varies over a set of consecutive time periods, known as phases. The reliability of a phased mission is defined as the probability that all phases in the mission are completed without failure. While the Binary Decision Diagram (BDD) method has been shown to be the most efficient solution for measuring the reliability of phased missions with non-repairable components with mutually exclusive failure modes, the existing BDD based methods are still unable to analyze large systems without considerable computational expense. This paper introduces a new BDD based method that is shown to provide improved efficiency and accuracy in the repeat analysis of this type of phased mission.
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| 16. |
- Reed, Sean, 1982-, et al.
(författare)
-
Modelling cycle for simulation digital twins
- 2021
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Ingår i: Manufacturing Letters. - : Elsevier. - 2213-8463. ; 28, s. 54-58
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Tidskriftsartikel (refereegranskat)abstract
- Digital twins (DT) form part of the Industry 4.0 revolution within manufacturing and related industries. A DT is a digital model (DM) of a real system that features continuous and automated synchronisation and feedback of optimisations between the real and digital domains. A core technology for predictive capabilities from DT is discrete event simulation (DES). The modelling cycle for developing and analysing DES models is significantly different compared to DM. A DT specific DES modelling cycle is introduced that is evolved from that of DM. The availability of specialised software tools for DT tailored to these differences would benefit industry.
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| 17. |
- Reed, Sean, 1982-, et al.
(författare)
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Modelling stochastic behaviour in simulation digital twins through neural nets
- 2022
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Ingår i: Journal of Simulation. - : Taylor & Francis. - 1747-7778 .- 1747-7786. ; 16:5, s. 512-525
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Tidskriftsartikel (refereegranskat)abstract
- In discrete event simulation (DES) models, stochastic behaviour is modelled by sampling random variates from probability distributions to determine event outcomes. However, the distribution of outcomes for an event from a real system is often dynamic and dependent on the current system state. This paper proposes the use of artificial neural networks (ANN) in DES models to determine the current distribution of each event outcome, conditional on the current model state or input data, from which random variates can then be sampled. This enables more realistic and accurate modelling of stochastic behaviour. An application is in digital twin models that aim to closely mimic a real system by learning from its past behaviour and utilising current data to predict its future. The benefits of the approach introduced in this paper are demonstrated through a realistic DES model of load-haul-dump vehicle operations in a production area of a sublevel caving mine.
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| 18. |
- Reed, Sean, 1982-, et al.
(författare)
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Quantified economic and environmental values through Functional Productization : A simulation approach
- 2018
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Ingår i: Environmental impact assessment review. - : Elsevier. - 0195-9255 .- 1873-6432. ; 70, s. 71-80
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Tidskriftsartikel (refereegranskat)abstract
- Industrial companies rely on hardware and services from external providers to deliver functions that are critical to their operations, increasingly demanding solutions that not only meet technical and availability requirements but are sustainable too. Traditionally, industrial companies choose and purchase hardware and maintenance support to fulfil their functional requirements. An alternative arrangement, known as Functional Product (FP), involves external providers supplying customers with the functionality they require through contracts that specify guaranteed functional availability whilst giving providers freedom to choose and retain ownership of the supplied hardware and services. This paper describes an innovative simulation modelling and optimization approach to quantitatively compare economic and environmental values resulting from transition from traditional to FP arrangements. The approach is demonstrated through the analysis of a scenario involving a hydraulic drive system provider and set of customers in Sweden, with the results exhibiting simultaneous improvement in economic and environmental values at each stage of the transition.
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| 19. |
- Reed, Sean, 1982-, et al.
(författare)
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Service support system modelling language for simulation-driven development of functional products
- 2013
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Ingår i: 2nd International Through-life Engineering Services Conference. - : Elsevier. ; 11, s. 420-424
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Konferensbidrag (refereegranskat)abstract
- A functional product (FP) comprises of an integrated package of hardware and support services sold under a performance-based contract. A barrier to the adoption of FP is the lack of tools for obtaining predictions of availability and support costs during product development. A previous paper by the authors described a simulation-driven development strategy for designing FP that are optimised for functional availability and support costs. This iterative strategy involves representing the FP design in a modelling language; using a software code to automatically generate and analyse a simulation model from this representation to produce detailed performance predictions; and using these predictions as feedback to improve the design. The use of a modelling language facilitates the representation of the design details within the hardware and support system that influence availability and support costs. This includes the maintenance process design, maintenance strategy design and maintenance resource availability design. In this paper, an overview of a modelling language the authors have developed for this purpose is described.
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| 20. |
- Zhang, Yang, et al.
(författare)
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Maintenance processes modelling and optimisation
- 2017
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Ingår i: Reliability Engineering & System Safety. - : Elsevier. - 0951-8320 .- 1879-0836. ; 168, s. 150-160
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Tidskriftsartikel (refereegranskat)abstract
- A Maintenance Procedure is conducted in order to prevent the failure of a system or to restore the functionality of a failed system. Such a procedure consists of a series of tasks, each of which has a distribution of times to complete and a probability of being performed incorrectly. The inclusion of tests can be used to identify any maintenance errors which have occurred. When an error is identified it can be addressed through a corresponding correction sequence which will have associated costs and add to the maintenance process completion time. A modified FMEA approach has been used to identify the possible tests. By incorporating any selection of tests into the maintenance process it can then analysed using a discrete-event simulation to predict the expected completion time distribution. The choice of tests to perform and when to do them is then made to successfully complete the maintenance objective in the shortest possible time using a genetic algorithm. The methodology is demonstrated by applying it to the repair process for a car braking system. The developed method is suitable for application in abroad range of industries.
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