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Tolerance Design of Mechanical Parts Considering Degradation and Quality Loss in Manufacturing Process and Operating Conditions
, M.Sc. Thesis Sharif University of Technology ; Khodaygan, Saeed (Supervisor) ; Asempour, Ahmad (Supervisor)
Abstract
The tolerance stack-up in mechanical assemblies is closely related to the quality of finished products and to the costs of production. In practice, choosing a large tolerance range will result in performance reduction. On the other hand, with small tolerances considered, production costs will increase. Tolerance allocation is a useful tool to control the dimensional and geometric variables of the product, so design engineers can control the final product quality level, production cost, and other variables. The proposed method for tolerance design considers the effects of degradation and quality loss over time and allocates tolerances so that, the functional key characteristic satisfies, as...
Towards aging-induced approximations
, Article Proceedings - Design Automation Conference, 18 June 2017 through 22 June 2017 ; Volume Part 128280 , 2017 ; 0738100X (ISSN) ; 9781450349277 (ISBN) ; Khaleghi, B ; Gerstlauer, A ; Henkel, J ; Sharif University of Technology
Abstract
In recent technology nodes, wide guardbands are needed to overcome reliability degradations due to aging. Such guardbands manifest as reduced efficiency and performance. Existing approaches to reduce guardbands trade off aging impact for increased circuit overhead. By contrast, the goal of this work is to completely remove guardbands through exploring, for the first time, application of approximate computing principles in the context of aging. As a result of naively narrowing or removing guardbands, timing errors start to appear as transistors age. We demonstrate that even in circuits that may tolerate errors, aging can be catastrophic due to unacceptable quality loss. Furthermore,...
Economic-Statistical Design and Evaluation of Multivariate Control Charts; An Improvement of Cost Model and Constraints Approach
, M.Sc. Thesis Sharif University of Technology ; Akhavan Niaki, Taghi (Supervisor)
Abstract
Control charts are the best tools for determining the deviations in the main parameters of a process. Exponentially weighted moving average, EWMA, control charts are the best type for determining small deviations. Determining the control charts parameters by means of minimizing a cost model is economic design. Economic-statistical design is achieved by adding statistical constraints to the economic model. Average run length when the process is in control, ARL0, and average run length when the process is out of control, ARL1, are limited in the economic-statistical model. In this thesis the economic-statistical design of a multivariate EWMA control chart is considered and this model is solved...
Self-biased low loss conductor featured with skin effect suppression for high quality RF passives
, Article IEEE Transactions on Magnetics ; Volume 48, Issue 11 , 2012 , Pages 4139-4142 ; 00189464 (ISSN) ; Schellevis, H ; Rejaei, B ; Fitch, R ; Zhuang, Y ; Sharif University of Technology
IEEE
2012
Abstract
We present experimental data for artificial metaconductors exhibiting skin effect suppression at microwave frequencies. The metaconductor consists of a stack comprising twelve periods of alternating ferromagnetic (Permalloy) and normal metal (Cu) layers. Near the effective antiferromagnetic resonant frequency the average in-plane magnetic permeability of the stack approaches zero, leading to an increase in the skin depth. Compared to a Cu-based device, up to 70% loss reduction has been achieved by a metaconductor based coplanar wave guide at ∼ 10 GHz without changing the propagation wavelength. Moreover, unlike conventional magnetic devices, no external magnetic bias is required due to the...