The Experts below are selected from a list of 24441 Experts worldwide ranked by ideXlab platform
Gary W. Critchlow - One of the best experts on this subject based on the ideXlab platform.
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Novel methods, incorporating pre- and post-anodising steps, for the replacement of the Bengough–Stuart chromic acid anodising process in structural bonding applications
International Journal of Adhesion and Adhesives, 2009Co-Authors: Keith A. Yendall, Gary W. CritchlowAbstract:Abstract The present investigation focuses on novel anodising processes which are being developed for the replacement of the hexavalent chromium containing 40/50 V Bengough–Stuart process, with particular emphasis on their resultant performance in structurally bonded systems used in the demanding and harsh environments encountered on Operational Aircraft. An electrolytic phosphoric acid-based deoxidiser (EPAD) has been studied in combination with a standard sulphuric acid anodise. It has been shown that the EPAD provides an open porous structure in order to enhance adhesion to the modified sulphuric acid anodised (SAA) surface. Additionally, a post-anodising (PAD) treatment has been used to aid structural adhesion in combination with the SAA processes. As a control, the standard 40/50 V Bengough–Stuart chromic acid anodising (CAA) has been used as a baseline performance indicator in adhesion tests. Single-lap shear (SLS) and modified Boeing wedge tests were used to determine adhesion performance. SLS tests were used to determine initial, dry joint strengths whilst wedge test joints immersed in deionised water for up to 100 h gave a measure of joint durability. Overall, excellent initial joint strengths and durability have been found with both EPAD plus SAA and PAD plus SAA processes suggesting that these environmentally benign treatments may be used as possible drop-in replacements for the currently used hexavalent chromium process. Electron microscopy has been used to investigate the topographical changes introduced to the surface by the various surface pretreatments under investigation to provide an explanation for the observed adhesion test results.
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novel methods incorporating pre and post anodising steps for the replacement of the bengough stuart chromic acid anodising process in structural bonding applications
International Journal of Adhesion and Adhesives, 2009Co-Authors: Keith A. Yendall, Gary W. CritchlowAbstract:Abstract The present investigation focuses on novel anodising processes which are being developed for the replacement of the hexavalent chromium containing 40/50 V Bengough–Stuart process, with particular emphasis on their resultant performance in structurally bonded systems used in the demanding and harsh environments encountered on Operational Aircraft. An electrolytic phosphoric acid-based deoxidiser (EPAD) has been studied in combination with a standard sulphuric acid anodise. It has been shown that the EPAD provides an open porous structure in order to enhance adhesion to the modified sulphuric acid anodised (SAA) surface. Additionally, a post-anodising (PAD) treatment has been used to aid structural adhesion in combination with the SAA processes. As a control, the standard 40/50 V Bengough–Stuart chromic acid anodising (CAA) has been used as a baseline performance indicator in adhesion tests. Single-lap shear (SLS) and modified Boeing wedge tests were used to determine adhesion performance. SLS tests were used to determine initial, dry joint strengths whilst wedge test joints immersed in deionised water for up to 100 h gave a measure of joint durability. Overall, excellent initial joint strengths and durability have been found with both EPAD plus SAA and PAD plus SAA processes suggesting that these environmentally benign treatments may be used as possible drop-in replacements for the currently used hexavalent chromium process. Electron microscopy has been used to investigate the topographical changes introduced to the surface by the various surface pretreatments under investigation to provide an explanation for the observed adhesion test results.
Keith A. Yendall - One of the best experts on this subject based on the ideXlab platform.
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Novel methods, incorporating pre- and post-anodising steps, for the replacement of the Bengough–Stuart chromic acid anodising process in structural bonding applications
International Journal of Adhesion and Adhesives, 2009Co-Authors: Keith A. Yendall, Gary W. CritchlowAbstract:Abstract The present investigation focuses on novel anodising processes which are being developed for the replacement of the hexavalent chromium containing 40/50 V Bengough–Stuart process, with particular emphasis on their resultant performance in structurally bonded systems used in the demanding and harsh environments encountered on Operational Aircraft. An electrolytic phosphoric acid-based deoxidiser (EPAD) has been studied in combination with a standard sulphuric acid anodise. It has been shown that the EPAD provides an open porous structure in order to enhance adhesion to the modified sulphuric acid anodised (SAA) surface. Additionally, a post-anodising (PAD) treatment has been used to aid structural adhesion in combination with the SAA processes. As a control, the standard 40/50 V Bengough–Stuart chromic acid anodising (CAA) has been used as a baseline performance indicator in adhesion tests. Single-lap shear (SLS) and modified Boeing wedge tests were used to determine adhesion performance. SLS tests were used to determine initial, dry joint strengths whilst wedge test joints immersed in deionised water for up to 100 h gave a measure of joint durability. Overall, excellent initial joint strengths and durability have been found with both EPAD plus SAA and PAD plus SAA processes suggesting that these environmentally benign treatments may be used as possible drop-in replacements for the currently used hexavalent chromium process. Electron microscopy has been used to investigate the topographical changes introduced to the surface by the various surface pretreatments under investigation to provide an explanation for the observed adhesion test results.
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novel methods incorporating pre and post anodising steps for the replacement of the bengough stuart chromic acid anodising process in structural bonding applications
International Journal of Adhesion and Adhesives, 2009Co-Authors: Keith A. Yendall, Gary W. CritchlowAbstract:Abstract The present investigation focuses on novel anodising processes which are being developed for the replacement of the hexavalent chromium containing 40/50 V Bengough–Stuart process, with particular emphasis on their resultant performance in structurally bonded systems used in the demanding and harsh environments encountered on Operational Aircraft. An electrolytic phosphoric acid-based deoxidiser (EPAD) has been studied in combination with a standard sulphuric acid anodise. It has been shown that the EPAD provides an open porous structure in order to enhance adhesion to the modified sulphuric acid anodised (SAA) surface. Additionally, a post-anodising (PAD) treatment has been used to aid structural adhesion in combination with the SAA processes. As a control, the standard 40/50 V Bengough–Stuart chromic acid anodising (CAA) has been used as a baseline performance indicator in adhesion tests. Single-lap shear (SLS) and modified Boeing wedge tests were used to determine adhesion performance. SLS tests were used to determine initial, dry joint strengths whilst wedge test joints immersed in deionised water for up to 100 h gave a measure of joint durability. Overall, excellent initial joint strengths and durability have been found with both EPAD plus SAA and PAD plus SAA processes suggesting that these environmentally benign treatments may be used as possible drop-in replacements for the currently used hexavalent chromium process. Electron microscopy has been used to investigate the topographical changes introduced to the surface by the various surface pretreatments under investigation to provide an explanation for the observed adhesion test results.
Mohamed Haouari - One of the best experts on this subject based on the ideXlab platform.
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a model and optimization based heuristic for the Operational Aircraft maintenance routing problem
Transportation Research Part C-emerging Technologies, 2016Co-Authors: Nayla Ahmad Althani, Mohamed Ben Ahmed, Mohamed HaouariAbstract:Abstract This paper investigates the Operational Aircraft Maintenance Routing Problem ( OAMRP ). Given a set of flights for a specific homogeneous fleet type, this short-term planning problem requires building feasible Aircraft routes that cover each flight exactly once and that satisfy maintenance requirements. Basically, these requirements enforce an Aircraft to undergo a planned maintenance at a specified station before accumulating a maximum number of flying hours. This stage is significant to airline companies as it directly impacts the fleet availability, safety, and profitability. The contribution of this paper is twofold. First, we elucidate the complexity status of the OAMRP and we propose an exact mixed-integer programming model that includes a polynomial number of variables and constraints. Furthermore, we propose a graph reduction procedure and valid inequalities that aim at improving the model solvability. Second, we propose a very large-scale neighborhood search algorithm along with a procedure for computing tight lower bounds. We present the results of extensive computational experiments that were carried out on real-world flight networks and attest to the efficacy of the proposed exact and heuristic approaches. In particular, we provide evidence that the exact model delivers optimal solutions for instances with up to 354 flights and 8 Aircraft, and that the heuristic approach consistently delivers high-quality solutions while requiring short CPU times.
Christopher M Rump - One of the best experts on this subject based on the ideXlab platform.
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a branch and price approach for Operational Aircraft maintenance routing
European Journal of Operational Research, 2006Co-Authors: Abdulkadir Sarac, Rajan Batta, Christopher M RumpAbstract:Abstract In recent years, considerable effort in the field of operations research has been paid to optimizing airline operations, including the logistics of an airline’s fleet of Aircraft. We focus on the problem of Aircraft routing, which involves generating and selecting a particular route for each Aircraft of a sub-fleet that is already assigned to a set of feasible sequences of flight legs. Similar studies typically focus on long-term route planning. However, stochastic events such as severe weather changes, equipment failures, variable maintenance times, or even new regulations mandated by the Federal Aviation Administration (FAA) play havoc on these long-term plans. In addition, these long-term plans ignore detailed maintenance requirements by considering only one or two of the primary maintenance checks that must be performed on a regular, long-term basis. As a result, these plans are often ignored by personnel in airline operations who are forced on a daily basis to develop quick, ad hoc methods to address these maintenance requirements and other irregular events. To address this problem, we develop an Operational Aircraft maintenance routing problem formulation that includes maintenance resource availability constraints. We propose a branch-and-price algorithm for solving this problem, which, due to the resource constraints, entails a modification of the branch-on, follow-on branching rule typically used for solving similar problems. Through computational testing, we explore the efficiency of this solution approach under a combination of heuristic choices for column (route) generation and selection.
Umit Bilge - One of the best experts on this subject based on the ideXlab platform.
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Operational Aircraft maintenance routing problem with remaining time consideration
European Journal of Operational Research, 2014Co-Authors: Mehmet Basdere, Umit BilgeAbstract:The Aircraft maintenance routing problem is one of the most studied problems in the airline industry. Most of the studies focus on finding a unique rotation that will be repeated by each Aircraft in the fleet with a certain lag. In practice, using a single rotation for the entire fleet is not applicable due to stochasticity and Operational considerations in the airline industry. In this study, our aim is to develop a fast responsive methodology which provides maintenance feasible routes for each Aircraft in the fleet over a weekly planning horizon with the objective of maximizing utilization of the total remaining flying time of fleet. For this purpose, we formulate an integer linear programming (ILP) model by modifying the connection network representation. The proposed model is solved by using branch-and-bound under different priority settings for variables to branch on. A heuristic method based on compressed annealing is applied to the same problem and a comparison of exact and heuristic methods are provided. The model and the heuristic method are extended to incorporate maintenance capacity constraints. Additionally, a rolling horizon based procedure is proposed to update the existing routes when some of the maintenance decisions are already fixed.