Modelling optimal warranty price for lifetime policies taking into account the uncertainties in life measures
- Authors: Rahman, Anisur , Chattopadhyay, Gopinath
- Date: 2018
- Type: Text , Journal article
- Relation: International Journal of Management Science and Engineering Management Vol. 13, no. 2 (2018), p. 84-90
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- Description: Owing to the assurance of longer reliable service life and greater customer peace of mind, products with a lifetime warranty are becoming more and more popular. Under such policies, both the manufacturer and the buyer are exposed to uncertainties and risks of warranty pricing and product performance since product lifetimes are uncertain and are not well defined in these policies. Considering the uncertainties in the measure of lifetime (useful life), this paper extends previous work of the authors [Rahman, A., & Chattopadhay, G. N. (2010). Modelling risks to manufacturer and buyer for lifetime warranty policies. International Journal of Management Science and Engineering Management, 5, 203–209] to determine the optimal warranty price. Risk preference models are developed to find the optimal warranty price through the use of the manufacturer’s utility function for profit and the buyer’s utility function for repair costs. The sensitivity of the risk preferences models are analysed using numerical examples with respect to factors such as the buyer’s and the manufacturer/dealer’s risk preferences, the buyer’s anticipated and the manufacturer’s estimated product failure intensity, the buyer’s loyalty to the original manufacturer/dealer in repairing failed products, and the buyer’s repair costs for non-warrantied products. Analysis of the developed models reveals that the manufacturer’s decisions on warranty price are strictly related to useful life, failure intensity of the product, and risk preferences. On the other hand, the buyer’s acceptance of a lifetime warranty depends on the expected lifetime of the product, the buyer’s anticipated product failure intensity, anticipated repair costs, and most importantly the buyer’s risk preference. © 2017 International Society of Management Science and Engineering Management.
On topology optimization and canonical duality method
- Authors: Gao, David
- Date: 2018
- Type: Text , Journal article
- Relation: Computer Methods in Applied Mechanics and Engineering Vol. 341, no. (2018), p. 249-277
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- Description: Topology optimization for general materials is correctly formulated as a bi-level knapsack problem, which is considered to be NP-hard in global optimization and computer science. By using canonical duality theory (CDT) developed by the author, the linear knapsack problem can be solved analytically to obtain global optimal solution at each design iteration. Both uniqueness, existence, and NP-hardness are discussed. The novel CDT method for general topology optimization is refined and tested by both 2-D and 3-D benchmark problems. Numerical results show that without using filter and any other artificial technique, the CDT method can produce exactly 0-1 optimal density distribution with almost no checkerboard pattern. Its performance and novelty are compared with the popular SIMP and BESO approaches. Additionally, some mathematical and conceptual mistakes in literature are explicitly addressed. A brief review on the canonical duality theory for modeling multi-scale complex systems and for solving general nonconvex/discrete problems are given in Appendix. This paper demonstrates a simple truth: elegant designs come from correct model and theory. © 2018
Use of stochastic XFEM in the investigation of heterogeneity effects on the tensile strength of intermediate geotechnical materials
- Authors: Dyson, Ashley , Tang, Zhan , Tolooiyan, Ali
- Date: 2018
- Type: Text , Journal article
- Relation: Finite Elements in Analysis and Design Vol. 145, no. (2018), p. 1-9
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- Description: The numerical simulation of an Unconfined Expansion Test (UET) is presented with tensile strength fracture criteria assigned by stochastic methods to take into account material heterogeneity. Tests are performed by producing radial cavity expansion models of thinly sliced cylindrical specimens. The introduction of element-wise allocation of fracture parameters generates instances of specimen failure without the requirement of predefined fracture zones, permitting discontinuities to form naturally within zones containing weak strength parameters. The parallel application of an in-house Python scripts and eXtended Finite Element Method (XFEM) facilitates the investigation of heterogeneity effects on the tensile strength of intermediate geotechnical materials.
Characterizations of minimal elements of topical functions on semimodules with applications
- Authors: Hassani, Sara , Mohebi, Hossein
- Date: 2017
- Type: Text , Journal article
- Relation: Linear Algebra and Its Applications Vol. 520, no. (2017), p. 104-124
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- Description: In this paper, we first give characterizations of the superdifferential of extended valued topical functions defined on a semimodule with values in a semifield. Next, we characterize minimal elements of the upper support set of extended valued topical functions. Finally, as an application, we present a necessary and sufficient condition for global maximum of the difference of two strictly topical functions defined on a semimodule. (C) 2017 Elsevier Inc. All rights reserved.
The impact of handwriting difficulties on compositional quality in children with developmental coordination disorder
- Authors: Prunty, Mellissa , Barnett, Anna , Wilmut, Kate , Plumb, Mandy
- Date: 2016
- Type: Text , Journal article
- Relation: British Journal of Occupational Therapy Vol. 79, no. 10 (2016), p. 591-597
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- Description: Introduction There is substantial evidence to support the relationship between transcription skills (handwriting and spelling) and compositional quality. For children with developmental coordination disorder, handwriting can be particularly challenging. While recent research has aimed to investigate their handwriting difficulties in more detail, the impact of transcription on their compositional quality has not previously been examined. The aim of this exploratory study was to examine compositional quality in children with developmental coordination disorder and to ascertain whether their transcription skills influence writing quality. Method Twenty-eight children with developmental coordination disorder participated in the study, with 28 typically developing age and gender matched controls. The children completed the free-writing' task from the detailed assessment of speed of handwriting tool, which was evaluated for compositional quality using the Wechsler objective language dimensions. Results The children with developmental coordination disorder performed significantly below their typically developing peers on five of the six Wechsler objective language dimensions items. They also had a higher percentage of misspelled words. Regression analyses indicated that the number of words produced per minute and the percentage of misspelled words explained 55% of the variance for compositional quality. Conclusion The handwriting difficulties so commonly reported in children with developmental coordination disorder have wider repercussions for the quality of written composition.
A scaled boundary polygon formulation for elasto-plastic analyses
- Authors: Ooi, Ean Tat , Song, Chongmin , Tin-Loi, Francis
- Date: 2014
- Type: Text , Journal article
- Relation: Computer Methods in Applied Mechanics and Engineering Vol. 268, no. (January 2014 2014), p. 905-937
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- Description: This study presents a novel scaled boundary polygon formulation to model elasto-plastic material responses in structures. The polygons have flexible mesh generation capabilities and are more accurate than standard finite elements, especially for problems with cracks and notches. Shape functions of arbitrary n-sided polygons are constructed using the scaled boundary finite element method. These shape functions are conforming and linearly complete. When modeling a crack, strain singularities are analytically modeled without enrichment. Standard finite element procedures are used to formulate the stiffness matrix and residual load vector. The nonlinear material constitutive matrix and the internal stresses are approximated locally in each polygon by a polynomial function. The stiffness matrix and the residual load vector are matrix power integrals that can be evaluated analytically even when a strain singularity is present. Standard nonlinear equation solvers e.g. the modified Newton–Raphson algorithm are used to obtain the nonlinear response of the structure. The proposed formulation is validated using several numerical benchmarks.
Calibration of an articulated CMM using stochastic approximations
- Authors: Sultan, Ibrahim , Puthiyaveettil, Prajeesh
- Date: 2012
- Type: Text , Journal article
- Relation: International Journal of Advanced Manufacturing Technology Vol. 63, no. 1-4 (2012), p. 201-207
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- Description: A coordinate measuring machine (CMM) is meant to digitise the spatial locations of points and feed the resulting measurements to a CAD system for storing and processing. For reliable utilisation of a CMM, a calibration procedure is often undertaken to eliminate the inaccuracies which result from manufacturing, assembly and installation errors. In this paper, an Immersion digitizer coordinate measuring machine has been calibrated using an accurately manufactured master cuboid fixture. This CMM has been designed as an articulated manipulator to enhance its dexterity and versatility. As such, the calibration problem is tackled with the aid of a kinematic model similar to those employed for the analysis of serial robots. In addition, a stochastic-based optimisation technique is used to identify the parameters of the kinematic model in order for the accurate performance to be achieved. The experimental results demonstrate the effectiveness of this method, whereby the measuring accuracy has been improved considerably. © 2012 Springer-Verlag London Limited.
- Description: 2003010394
Detecting K-complexes for sleep stage identification using nonsmooth optimization
- Authors: Moloney, David , Sukhorukova, Nadezda , Vamplew, Peter , Ugon, Julien , Li, Gang , Beliakov, Gleb , Philippe, Carole , Amiel, Hélène , Ugon, Adrien
- Date: 2012
- Type: Text , Journal article
- Relation: ANZIAM Journal Vol. 52, no. 4 (2012), p. 319-332
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- Description: The process of sleep stage identification is a labour-intensive task that involves the specialized interpretation of the polysomnographic signals captured from a patient's overnight sleep session. Automating this task has proven to be challenging for data mining algorithms because of noise, complexity and the extreme size of data. In this paper we apply nonsmooth optimization to extract key features that lead to better accuracy. We develop a specific procedure for identifying K-complexes, a special type of brain wave crucial for distinguishing sleep stages. The procedure contains two steps. We first extract "easily classified" K-complexes, and then apply nonsmooth optimization methods to extract features from the remaining data and refine the results from the first step. Numerical experiments show that this procedure is efficient for detecting K-complexes. It is also found that most classification methods perform significantly better on the extracted features. © 2012 Australian Mathematical Society.