An Evolutionary Optimization Approach to Risk Parity Portfolio Selection

In this paper we present an evolutionary optimization approach to solve the risk parity portfolio selection problem. While there exist convex optimization approaches to solve this problem when long-only portfolios are considered, the optimization problem becomes non-trivial in the long-short case. To solve this problem, we propose a genetic algorithm as well as a local search heuristic. This algorithmic framework is able to compute solutions successfully. Numerical results using real-world data substantiate the practicability of the approach presented in this paper

Design of a capillary viscometer with numerical and computational methods

A high temperature and shear rate capillary viscometer has been designed, constructed and recently commissioned. This device will be used to measure the viscosity of semi-solid metals under the high temperature and shear rate conditions, similar to those found in industry. Design criteria for the device included a requirement for a highly controllable temperature (±1ºC) up to 650ºC, capability for injection shear rates above 10,000s−1 and controllable injection profiles. The design of this viscometer was aided with the use of numerical modelling methods based on a power law thixotropic fluid flow relation. This analysis allowed calculation of required injection speeds and expected system forces. Computational modelling work, based on current power law fluid models, was also performed in order to investigate how the viscosity would be expected to fluctuate with shear rate and fraction solid. This data could then be used to compare with experimental work. The computational model was a 2D two-phase theoretical unsteady state model. This was used to evaluate the viscosity of semi-solid metals passing through the designed capillary viscometer at injection speeds of 0.075, 0.5 and 1 m/sec. The effects of fractions solid (fs) of the metal from 0.25, 0.3, 0.33 and 0.50 were also investigated. Strong correlations between these parameters and the resulting viscosity were noted

Evolutionary Behavior Tree Approaches for Navigating Platform Games

Computer games are highly dynamic environments, where players are faced with a multitude of potentially unseen scenarios. In this article, AI controllers are applied to the Mario AI Benchmark platform, by using the Grammatical Evolution system to evolve Behavior Tree structures. These controllers are either evolved to both deal with navigation and reactiveness to elements of the game, or used in conjunction with a dynamic A* approach. The results obtained highlight the applicability of Behavior Trees as representations for evolutionary computation, and their flexibility for incorporation of diverse algorithms to deal with specific aspects of bot control in game environments

Effect of vibration on the shear strength of impacted bone graft in revision hip surgery

Aims: Studies on soil mechanics have established that when vibration is applied to an aggregate, it results in more efficient alignment of particles and reduces the energy required to impact the aggregate. Our aim was to develop a method of applying vibration to the bone impaction process and assess its impact on the mechanical properties of the impacted graft. Methods: Phase 1. Eighty bovine femoral heads were milled using the Noviomagus bone mill. The graft was then washed using a pulsed lavage normal saline system over a sieve tower. A vibration impaction device was developed which housed two 15V DC motors with eccentric weights attached inside a metal cylinder. A weight was dropped onto this from a set height 72 times so as to replicate the bone impaction process. A range of frequencies of vibration were tested, as measured using an accelerometer housed in the vibration chamber. Each shear test was then repeated at four different normal loads so as to generate a family of stress-strain curves. The Mohr-Coulomb failure envelope from which the shear strength and interlocking values are derived was plotted for each test. Phase 2. Experiments were repeated with the addition of blood so as to replicate a saturated environment as is encountered during operative conditions. Results Phase 1. Graft impacted with the addition of vibration at all frequencies of vibration showed improved shear strength when compared to impaction without vibration. Vibration at sixty Hertz was displayed the largest effect and was found to be significant. 3 Phase 2. Graft impacted with the addition of vibration in a saturated aggregate displayed lower shear strengths for all normal compressive loads than that of impaction without vibration. Conclusions Civil engineering principles hold true for the impaction bone grafting procedure. In a dry aggregate the addition of vibration may be beneficial to the mechanical properties of the impacted graft. In our system the optimal frequency of vibration was 60 Hz. Under saturated conditions the addition of vibration is detrimental the shear strength of the aggregate. This may be explained by the process of liquefaction

Strengthening mechanisms of graphene sheets in aluminium matrix nanocomposites

Uniform dispersion of SiC nanoparticles with a high propensity to agglomerate within a thixoformed aluminium matrix was attained using a graphene encapsulating approach. The analytical model devised in this study has demonstrated the significant role of shear lag and thermally activated dislocation mechanisms in strengthening aluminium metal matrix composites due to the exceptional negative thermal expansion coefficient of graphene sheets. This, in turn, triggers the pinning capacity of nano-sized rod-liked aluminium carbide, prompting strong interface bonding for SiC nanoparticles with the matrix, thereby enhancing tensile elongation

Silver nanoparticles and their orthopaedic applications

Implant-associated infection is a major source of morbidity in orthopaedic surgery. There has been extensive research into the development of materials that prevent biofilm formation, and hence, reduce the risk of infection. Silver nanoparticle technology is receiving much interest in the field of orthopaedics for its antimicrobial properties, and the results of studies to date are encouraging. Antimicrobial effects have been seen when silver nanoparticles are used in trauma implants, tumour prostheses, bone cement, and also when combined with hydroxyapatite coatings. Although there are promising results with in vitro and in vivo studies, the number of clinical studies remains small. Future studies will be required to explore further the possible side effects associated with silver nanoparticles, to ensure their use in an effective and biocompatible manner. Here we present a review of the current literature relating to the production of nanosilver for medical use, and its orthopaedic applications

Evolutionary estimation of a Coupled Markov Chain credit risk model

There exists a range of different models for estimating and simulating credit risk transitions to optimally manage credit risk portfolios and products. In this chapter we present a Coupled Markov Chain approach to model rating transitions and thereby default probabilities of companies. As the likelihood of the model turns out to be a non-convex function of the parameters to be estimated, we apply heuristics to find the ML estimators. To this extent, we outline the model and its likelihood function, and present both a Particle Swarm Optimization algorithm, as well as an Evolutionary Optimization algorithm to maximize the likelihood function. Numerical results are shown which suggest a further application of evolutionary optimization techniques for credit risk management

The effect of direct thermal method, temperature and time on microstructure of a cast aluminum alloy

The direct thermal method is used for the creation of globular microstructures suitable for semi-solid metal forming. In this paper both simulation and experimental results using direct thermal method are presented. ProCAST® software was used to estimate temperature distribution inside the aluminium billet. In validation work, molten aluminium A356 was poured into metallic copper tube moulds and cooled down to the semi-solid temperature before being quenched in water at room temperature. The effect of pouring temperatures of 630°C, 650°C, 665°C, 680°C and holding times of 45s and 60s on the microstructure of aluminium A356 alloy were investigated. The simulation results showed that the average temperature rate within the copper mould, from initial pouring temperature to just before quenching, was approximately 1°C/s. Examination of the solidified microstructures showed that the microstructure was more spherical when lower pouring temperatures and holding periods were used. From the micrographs it was found that the most globular and smallest structures were achieved at processing parameters of 630°C and 45s

A history of engineering education research in Portugal and Ireland

Comunicação apresentada em 121st Annual Conference & Exposition - "360º of Engineering Education", Indianapolis, IN - USA, June 15-18, 2014The American Society for Engineering Education is the oldest professional society in the world that is solely dedicated to the betterment of engineering education. In its early days, ASEE was a gathering of faculty who wanted to improve the practice of engineering education through experimentation with new curricula, new teaching styles, or new gadgets. Presentations often consisted of “this is what I did” and “this is how the students reacted.” Beginning in the 1990s, through the influx of federal dollars in the Coalitions, a new discipline began to emerge—Engineering Education—and along with this discipline a research area was born. At this point in time, the concept of rigorous Engineering Education Research (EER) is fairly well-established in the US, with dedicated programs for EER at the National Science Foundation, PhD degree programs in EER, and the reinvention of the Journal of Engineering Education to support this endeavour. Departments dedicated at least in part to Engineering Education Research are emerging on campuses across the country. There has also been an emergence of Engineering Education Research across the globe; however, efforts in other countries have often been slower due to many factors. This paper describes the emergence of Engineering Education Research in two countries in the European Union—Portugal and Ireland. The evolution of EER in these two countries is set in a larger global context