A general genetic algorithm for one and two dimensional cutting and packing problems

Cutting and packing problems are combinatorial optimisation problems. The major interest in these problems is their practical significance, in manufacturing and other business sectors. In most manufacturing situations a raw material usually in some standard size has to be divided or be cut into smaller items to complete the production of some product. Since the cost of this raw material usually forms a significant portion of the input costs, it is therefore desirable that this resource be used efficiently. A hybrid general genetic algorithm is presented in this work to solve one and two dimensional problems of this nature. The novelties with this algorithm are: A novel placement heuristic hybridised with a Genetic Algorithm is introduced and a general solution encoding scheme which is used to encode one dimensional and two dimensional problems is also introduced

Container Loading Problems: A State-of-the-Art Review

Container loading is a pivotal function for operating supply chains efficiently. Underperformance results in unnecessary costs (e.g. cost of additional containers to be shipped) and in an unsatisfactory customer service (e.g. violation of deadlines agreed to or set by clients). Thus, it is not surprising that container loading problems have been dealt with frequently in the operations research literature. It has been claimed though that the proposed approaches are of limited practical value since they do not pay enough attention to constraints encountered in practice.In this paper, a review of the state-of-the-art in the field of container loading will be given. We will identify factors which - from a practical point of view - need to be considered when dealing with container loading problems and we will analyze whether and how these factors are represented in methods for the solution of such problems. Modeling approaches, as well as exact and heuristic algorithms will be reviewed. This will allow for assessing the practical relevance of the research which has been carried out in the field. We will also mention several issues which have not been dealt with satisfactorily so far and give an outlook on future research opportunities

Minimizing waste in the 2-dimensional cutting stock problem

The 2-dimensional cutting stock problem is an important problem in the garment manufacturing industry. The problem is to arrange a given set of 2-dimensional patterns onto a rectangular bolt of cloth such that the efficiency is maximised. This arrangement is called a marker. Efficiency is measured by pattern area I marker area. Efficiency varies depending on the shape and number of patterns being cut, but an improvement in efficiency can result in significant savings. Markers are usually created by humans with the aid of CAD software. Many researchers have attempted to create automatic marker making software but have failed to produce marker efficiencies as high as human generated ones. This thesis presents a mathematical model which optimally solves the 2-dimensional cutting stock problem. However, the model can only be solved in a practical amount of time for small markers. Subsequently, two compaction algorithms based on mathematical modelling have been developed to improve the efficiency of human generated markers. The models developed in this thesis make use of a geometrical calculation known as the no-fit polygon. The no-fit polygon is a tool for determining whether polygons A and B overlap. It also gives all feasible positions for polygons B with respect to polygon A, such that the two polygons do not overlap. For the case when both polygons A and B are non-convex, current calculation methods are either time consuming or unreliable. This thesis presents a method which is both computationally efficient and robust for calculating the no-fit polygon when polygons A and B are non-convex. When tested on a set of industrial markers, the compaction algorithms improved the marker efficiencies by over 1.5% on average

Algorithms and data structures for three-dimensional packing

Cutting and packing problems are increasingly prevalent in industry. A well utilised freight vehicle will save a business money when delivering goods, as well as reducing the environmental impact, when compared to sending out two lesser-utilised freight vehicles. A cutting machine that generates less wasted material will have a similar effect. Industry reliance on automating these processes and improving productivity is increasing year-on-year. This thesis presents a number of methods for generating high quality solutions for these cutting and packing challenges. It does so in a number of ways. A fast, efficient framework for heuristically generating solutions to large problems is presented, and a method of incrementally improving these solutions over time is implemented and shown to produce even higher packing utilisations. The results from these findings provide the best known results for 28 out of 35 problems from the literature. This framework is analysed and its effectiveness shown over a number of datasets, along with a discussion of its theoretical suitability for higher-dimensional packing problems. A way of automatically generating new heuristics for this framework that can be problem specific, and therefore highly tuned to a given dataset, is then demonstrated and shown to perform well when compared to the expert-designed packing heuristics. Finally some mathematical models which can guarantee the optimality of packings for small datasets are given, and the (in)effectiveness of these techniques discussed. The models are then strengthened and a novel model presented which can handle much larger problems under certain conditions. The thesis finishes with a discussion about the applicability of the different approaches taken to the real-world problems that motivate them

Index to 1986 NASA Tech Briefs, volume 11, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1986 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

Lux junior 2023: 16. Internationales Forum für den lichttechnischen Nachwuchs, 23. – 25. Juni 2023, Ilmenau : Tagungsband

Während des 16. Internationales Forums für den lichttechnischen Nachwuchs präsentieren Studenten, Doktoranden und junge Absolventen ihre Forschungs- und Entwicklungsergebnisse aus allen Bereichen der Lichttechnik. Die Themen bewegen sich dabei von Beleuchtungsanwendungen in verschiedensten Bereichen über Lichtmesstechnik, Kraftfahrzeugbeleuchung, LED-Anwendung bis zu nichtvisuellen Lichtwirkungen. Das Forum ist speziell für Studierende und junge Absolventen des Lichtbereiches konzipiert. Es bietet neben den Vorträgen und Postern die Möglichkeit zu Diskussionen und individuellem Austausch. In den 30 Jahren ihres Bestehens entwickelte sich die zweijährig stattfindende Tagung zu eine Traditionsveranstaltung, die das Fachgebiet Lichttechnik der TU Ilmenau gemeinsam mit der Bezirksgruppe Thüringen-Nordhessen der Deutschen Lichttechnischen Gesellschaft LiTG e. V. durchführt

Study of a common solar-electric-propulsion upper stage for high-energy unmanned missions. Volume 2 - Technical Final report

Versatile, multimission solar electric propulsion upper stage for high energy, unmanned interplanetary flights - technical detail

NASA Tech Briefs Index 1980

Tech Briefs are short announcements of new technology derived from the research and development activities of the National Aeronautics and Space Administration. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This Index to NASA Tech Briefs contains abstracts and four indexes -- subject,. personal author, originating Center, and Tech Brief number -- for 1980 Tech Briefs