Design of digital differentiators satisfying prescribed specifications using optimisation techniques

1991 ◽  
Vol 138 (3) ◽  
pp. 315 ◽  
Author(s):  
S. Sunder ◽  
W.-S. Lu ◽  
A. Antoniou ◽  
Y. Su
Keyword(s):  
Optimisation Techniques

Influence of weight modelling on the outcome of wing design using multidisciplinary design optimisation techniques

2013 ◽  
Vol 117 (1195) ◽  
pp. 871-895 ◽  
Author(s):  
J. Mariens ◽  
A. Elham ◽  
M. J. L. van Tooren
Keyword(s):  
Estimation Method ◽  
Lower Class ◽  
Multidisciplinary Design ◽  
Estimation Methods ◽  
Computational Time ◽  
Weight Estimation ◽  
Wing Design ◽  
Design Optimisation ◽  
Multidisciplinary Design Optimisation ◽  
Optimisation Techniques

Abstract Weight estimation methods are categorised in different classes based on their level of fidelity. The lower class methods are based on statistical data, while higher class methods use physics based calculations. Statistical weight estimation methods are usually utilised in early design stages when the knowledge of designers about the new aircraft is limited. Higher class methods are applied in later design steps when the design is mature enough. Lower class methods are sometimes preferred in later design stages, even though the designers have enough knowledge about the design to use higher class methods. In high level multidisciplinary design optimisation (MDO) fidelity is often sacrificed to obtain models with shorter computation times. There is always a compromise required to select the proper weight estimation method for an MDO project. An investigation has been performed to study the effect of using different weight estimation methods, with low and medium levels of fidelity, on the results of a wing design using multidisciplinary design optimisation techniques. An MDO problem was formulated to design the wing planform of a typical turboprop and a turbofan passenger aircraft. The aircraft maximum take-off weight was selected as the objective function. A quasi-three-dimensional aerodynamic solver was developed to calculate the wing aerodynamic characteristics. Five various statistical methods and a quasi-analytical method are used to estimate the wing structural weight. These methods are compared to each other by analysing their accuracy and sensitivity to different design variables. The results of the optimisations showed that the optimum wing shape is affected by the method used to estimate the wing weight. Using different weight estimation methods also strongly affects the optimisation convergence history and computational time.

scholarly journals Solving the nuclear dismantling project scheduling problem by combining mixed-integer and constraint programming techniques and metaheuristics

2021 ◽  
Author(s):  
Felix Hübner ◽  
Patrick Gerhards ◽  
Christian Stürck ◽  
Rebekka Volk
Keyword(s):  
Constraint Programming ◽  
Project Scheduling ◽  
Computational Study ◽  
Real Life ◽  
Mixed Integer ◽  
Extensive Literature ◽  
Scheduling Problem ◽  
Multiple Modes ◽  
Project Scheduling Problem ◽  
Optimisation Techniques

AbstractScheduling of megaprojects is very challenging because of typical characteristics, such as expected long project durations, many activities with multiple modes, scarce resources, and investment decisions. Furthermore, each megaproject has additional specific characteristics to be considered. Since the number of nuclear dismantling projects is expected to increase considerably worldwide in the coming decades, we use this type of megaproject as an application case in this paper. Therefore, we consider the specific characteristics of constrained renewable and non-renewable resources, multiple modes, precedence relations with and without no-wait condition, and a cost minimisation objective. To reliably plan at minimum costs considering all relevant characteristics, scheduling methods can be applied. But the extensive literature review conducted did not reveal a scheduling method considering the special characteristics of nuclear dismantling projects. Consequently, we introduce a novel scheduling problem referred to as the nuclear dismantling project scheduling problem. Furthermore, we developed and implemented an effective metaheuristic to obtain feasible schedules for projects with about 300 activities. We tested our approach with real-life data of three different nuclear dismantling projects in Germany. On average, it took less than a second to find an initial feasible solution for our samples. This solution could be further improved using metaheuristic procedures and exact optimisation techniques such as mixed-integer programming and constraint programming. The computational study shows that utilising exact optimisation techniques is beneficial compared to standard metaheuristics. The main result is the development of an initial solution finding procedure and an adaptive large neighbourhood search with iterative destroy and recreate operations that is competitive with state-of-the-art methods of related problems. The described problem and findings can be transferred to other megaprojects.

scholarly journals An extended Farm Site Development Method

2016 ◽  
Vol Volume 112 (Number 9/10) ◽  
Author(s):  
Eugene Hanekom ◽  
Andre Liebenberg ◽  
Marné de Vries ◽  
◽  
◽  
...  
Keyword(s):  
South Africa ◽  
Financial Planning ◽  
Agricultural Sector ◽  
Arable Land ◽  
Saturation State ◽  
Development Method ◽  
Demand Planning ◽  
Site Development ◽  
Current State ◽  
Optimisation Techniques

Abstract The inefficient and ineffective use of arable land in South Africa is one of the numerous challenges within its agricultural sector. Previous research has indicated that a method, the Farm Site Development Method (FSDM), could increase the effective and efficient use of arable land by providing a roadmap to the farm owner for incrementally transforming the current state facilities and resources of a farm towards a future saturation state. The FSDM was then demonstrated at a crop-producing farm and several opportunities existed to extend its utility. Here we suggest its extension for application to a livestock farm, and also include optimisation techniques, demand planning and financial planning.

scholarly journals Digital hajj: the pilgrimage to Mecca in Muslim cyberspace and the issue of religious online authority

2013 ◽  
Vol 25 ◽  
pp. 189-203 ◽  
Author(s):  
Dominik Schlosser
Keyword(s):  
Search Engine ◽  
The Internet ◽  
Web Pages ◽  
Religious Authority ◽  
Liminal Space ◽  
Online Presence ◽  
Optimisation Techniques

This paper attempts to give an overview of the different representations of the pilgrimage to Mecca found in the ‘liminal space’ of the internet. For that purpose, it examines a handful of emblematic examples of how the hajj is being presented and discussed in cyberspace. Thereby, special attention shall be paid to the question of how far issues of religious authority are manifest on these websites, whether the content providers of web pages appoint themselves as authorities by scrutinizing established views of the fifth pillar of Islam, or if they upload already printed texts onto their sites in order to reiterate normative notions of the pilgrimage to Mecca, or of they make use of search engine optimisation techniques, thus heightening the very visibility of their online presence and increasing the possibility of becoming authoritative in shaping internet surfers’ perceptions of the hajj.

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