Experimental investigation and optimisation in drilling of GFRP composites

Glass fibre-reinforced polymer (GFRP) composite materials are one of the important materials and are economic alternative to engineering materials because of their superior properties. This paper presents an effective approach for the optimisation of drilling parameters with multiple performance characteristics based on the Tagugch’s method with grey relational analysis. Taguchi’s L₁₆, 4-level orthogonal array has been used for the experimentation. The drilling parameters such as spindle speed and feed rate are optimised with consideration of multiple performance characteristics, such as thrust force, workpiece surface roughness and delamination factor. Response table and response graph are used for the analysis. The analysis of grey relational grade indicates that feed rate is the more influential parameter than spindle speed. The results indicate that the performance of drilling process can be improved effectively through this approach.     

Global supply chain planning for pharmaceuticals

The shortening of patent life periods, generic competition and public health policies, among other factors, have changed the operating context of the pharmaceutical industry. In this work we address a dynamic allocation/planning problem that optimises the global supply chain planning of a pharmaceutical company, from production stages at primary and secondary sites to product distribution to markets. The model explores different production and distribution costs and tax rates at different locations in order to maximise the company's net profit value (NPV).Large instances of the model are not solvable in realistic time scales, so two decomposition algorithms were developed. In the first method, the supply chain is decomposed into independent primary and secondary subproblems, and each of them is optimised separately. The second algorithm is a temporal decomposition, where the main problem is separated into several independent subproblems, one per each time period. These algorithms enable the solution of large instances of the problem in reasonable time with good quality results.     

Enhanced red emission in LiAl5O8:Fe phosphor by B doping

Fe³⁺, B³⁺ co-doping LiAl₅O₈ phosphor has been successfully synthesized by a solid-state reaction method assisted with wet chemical mixing route. Photoluminescence emission peak is observed at around 672 nm excited at both 290 nm ultraviolet and 565 nm green light. With introduction of a small amount of boric acid, the red emission intensity can be enhanced by 2.62 times under 290 nm excitation and 2.31 times under 565 nm excitation, respectively. It is believed that the substitution of B³⁺ ions for Al³⁺ sites decreases the symmetry of the luminescence center, intensifying the red emission.     

Antoni Gaudí and Frei Otto: Essential Precursors to the Parametricism Manifesto

As Senior Architect to the Basilica of the Sagrada Família in Barcelona, Mark Burry has been ‘thinking parametrically’ for almost his entire career. Here he describes how his longstanding role overseeing the completion of Antoni Gaudí's masterpiece has afforded unique insights into the work of a great geometer and parametric thinker. Burry places the contribution of Gaudí alongside that of Frei Otto – the other eminent 20th-century Proto-Parametricist.     

Active–reactive power approaches for optimal placement of charge stations in power systems

Electric Vehicles (EVs) have been suggested as alternatives to conventional vehicles for reducing petrol consumption and carbon dioxide (CO₂) emissions. When a large number of EVs connect to the grid, they can cause a large amount of power loss. Where to install multiple charge stations in the grid, so as to mitigate losses caused by EVs when providing energy to those EVs, is becoming vitally important. In this paper, a distribution test-network model is described. A new analytical method is proposed, using the stations’ cooperation in terms of optimal active and reactive power dispatch as well as power flow analysis for locating the optimal placement of charge stations, so as to reduce power losses. This method is compared with the previously developed current density method for single charge stations using system simulation results. It was demonstrated that the methods proposed in this paper are more accurate than the current density method, and that 17% of the average active power loss can be saved for three different types of load profile. In addition, 27% of the average active power loss was saved by installing two charge stations rather than no charge stations in the test-line. It is shown that this could represent a 2.6% annual yield above inflation for investing in installing and running such charge stations.     

Proximal schemes for parabolic optimal control problems with sparsity promoting cost functionals

Fast first-order proximal methods that solve linear and bilinear parabolic optimal control problems with a sparsity cost functional are discussed. Weak convergence of these methods is proved and, for benchmarking purposes, the proposed inexact proximal schemes are compared to an inexact semi-smooth Newton method. Results of numerical experiments are presented to demonstrate the computational effectiveness of proximal schemes and to validate the theoretical estimates.     

DOE applied to multi-response optimisation study on performance,combustion and emission characteristics of a VCR diesel engine

There are various parameters which may influence the IC engine performance. The trial and error method is a technique used to identify the best parameters. However, this method demands extensive experimental work and results in a great waste of time and resources. Thus, the design of experiments (DOEs) developed by Taguchi is employed. The multi-responses which need to be maximised are brake thermal efficiency, mechanical efficiency, cylinder pressure and cumulative heat release rate, whereas the responses which are to be minimised are specific fuel consumption, oxides of nitrogen and carbon monoxide. In the present study, an optimised DOE(L9) orthogonal array based on the Taguchi statistical method was formulated and a series of experiments were conducted under controlled supervision by considering three different injection operating pressures (IOPs) (200, 220 and 240 bar) and three different compression ratios (CRs) (16.5, 17.5 and 18.5). The main objective of this paper is to find the best suited IOP and CR values which obtain higher performance, better combustion and lower emissions.     

Hot wire chemical vapor deposition: limits and opportunities of protecting the tungsten catalyzer from silicide with a cavity

Hot Wire Chemical Vapor Deposition (HW-CVD) is one of the most promising techniques for depositing the intrinsic microcrystalline silicon layer for the production of micro-morph solar cells. However, the silicide formation at the colder ends of the tungsten wire drastically reduces the lifetime of the catalyzer, thus limiting its industrial exploitation. A simple but interesting strategy to decrease the silicide formation is to hide the electrical contacts of the catalyzer in a long narrow cavity which reduces the probability of the silane molecules to reach the colder ends of the wire. In this paper, the working mechanism of the cavity is elucidated. Measurements of the thickness profile of the silicon deposited in the internal walls of the cavity have been compared with those predicted using a simple diffusion model based on the assumption of Knudsen flow. A lifetime study of the protected and unprotected wires has been carried out. The different mechanisms which determine the deterioration of the catalyzer have been identified and discussed.     

On a branch-and-bound approach for a Huff-like Stackelberg location problem

Modelling the location decision of two competing firms that intend to build a new facility in a planar market can be done by a Huff-like Stackelberg location problem. In a Huff-like model, the market share captured by a firm is given by a gravity model determined by distance calculations to facilities. In a Stackelberg model, the leader is the firm that locates first and takes into account the actions of the competing chain (follower) locating a new facility after the leader. The follower problem is known to be a hard global optimisation problem. The leader problem is even harder, since the leader has to decide on location given the optimal action of the follower. So far, in literature only heuristic approaches have been tested to solve the leader problem. Our research question is to solve the leader problem rigorously in the sense of having a guarantee on the reached accuracy. To answer this question, we develop a branch-and-bound approach. Essentially, the bounding is based on the zero sum concept: what is gain for one chain is loss for the other. We also discuss several ways of creating bounds for the underlying (follower) sub-problems, and show their performance for numerical cases. This work has been supported by the Ministry of Education and Science of Spain through grant SEJ2005/06273/ECON. M. Elena Sáz was supported by a junior research grant of Mansholt Graduate School (Wageningen Universiteit).     

Large-area organic photovoltaic module—Fabrication and performance

Here we describe the fabrication of the largest (233 cm² total area) organic photovoltaic (OPV) module (polymer:fullerene) to be certified by the National Renewable Energy Laboratory (NREL). OPV solar cells were fabricated at Plextronics by spin coating a blend of poly 3-hexylthiophene-2,5 diyl (P3HT) and [6,6] phenyl C₆₁ butyric acid methyl ester (PCBM) on top of our hole transport layer (HTL), Plexcore^® OC. In laboratory-scale devices (0.09 cm²), this system routinely exhibits power conversion efficiencies exceeding 3.7%. This P3HT:PCBM active layer and HTL ink system was used to scale up to the larger area module (15.2 cm×15.2 cm module size, i.e. 233 cm² total area; 108 cm² active area), which was certified by NREL as having 1.1% total area efficiency (3.4% active area efficiency).