Modelling the boundaries of project fast-tracking

Fast-tracking a project involves carrying out sequential activities in parallel, partially overriding their original order of precedence, to reduce the overall project duration. The current predominant mathematical models of fast-tracking are based on the concepts of activity sensitivity, evolution, dependency and, sometimes, information exchange uncertainty, and aim to determine optimum activity overlaps. However, these models require some subjective inputs from the scheduler and most of them neglect the merge event bias. In this paper, a stochastic model for schedule fast-tracking is proposed. Relevant findings highlight the existence of a pseudo-physical barrier that suggests that the possibility of shortening a schedule by more than a quarter of its original duration is highly unlikely. The explicit non-linear relationship between cost and overlap has also been quantified for the first time. Finally, manual calculations using the new model are compared with results from a Genetic Algorithm through a case study

Modeling bidding competitiveness and position performance in multi-attribute construction auctions

Currently, multi-attribute auctions are becoming widespread awarding mechanisms for contracts in construction, and in these auctions, criteria other than price are taken into account for ranking bidder proposals. Therefore, being the lowest-price bidder is no longer a guarantee of being awarded, thus increasing the importance of measuring any bidder’s performance when not only the first position (lowest price) matters. Modeling position performance allows a tender manager to calculate the probability curves related to the more likely positions to be occupied by any bidder who enters a competitive auction irrespective of the actual number of future participating bidders. This paper details a practical methodology based on simple statistical calculations for modeling the performance of a single bidder or a group of bidders, constituting a useful resource for analyzing one’s own success while benchmarking potential bidding competitors

Human resource allocation to multiple projects based on members’ expertise, group heterogeneity and social cohesion

Project managers regularly allocate human resources to construction projects. This critical task is usually executed by fulfilling the minimum project staffing requirements normally based around the quantity and competence of project members. However, research has shown that team performance can increase by up to 10% and 18%, respectively, as a consequence of the group members’ heterogeneity and social cohesion. Also, there is currently no practical quantitative tool which incorporates these aspects to allow project managers to achieve this task efficiently and objectively. A new quantitative model for the effective allocation of human resources to multiple projects, which takes into account group heterogeneity and social cohesion is proposed. This model is easy to build, update and use in real project environments with the use of a spreadsheet and a basic optimization engine (e.g. Excel Solver). A case study is proposed and solved with a Genetic Algorithm to illustrate the model implementation. Finally, a validation example is provided to exemplify how group heterogeneity and social cohesion condition academic achievement in an academic setting

Estimating the number of new and repeated bidders in construction auctions

The number of new bidders – bidders from whom there is no previous registered participation – is an important variable in most bid tender forecasting models, since the unknown competitive profile of the former strongly limits the predictive accuracy of the latter. Analogously, when a bidder considers entering a bid or when an auctioneer is handling a procurement auction, assessing the likely proportion of experienced bidders is considered an important aspect, as some strategic decisions or even the awarding criteria might differ. However, estimating the number of bidders in a future auction that have not submitted a single bid yet is difficult, since there is no data at all linking their potential participation, an essential requirement for the implementation of any forecasting or estimation method. A practical approach is derived for determining the expected proportion of new bidders to frequent bidders as a function of the population of potential bidders. A multinomial model useful for selective and open tendering is proposed and its performance is validated with a dataset of actual construction auctions. Final remarks concern the valuable information provided by the model to an enduring unsolved bidding problem and the prospects for new research continuations

Nanoporous PMMA: A novel system with different acoustic properties

The acoustic properties of closed cell nanoporous and microporous poly(methyl methacrylate) (PMMA) foams have been well characterized, showing that nanoporous PMMA exhibit a different absorption coefficient and transmission loss behavior in comparison with microporous PMMA. Experimental differences may be explained by the different wave propagation mechanism in the micro and nanoscale, which is determined by the confinement of both the gas (Knudsen regime) and the solid phases. These results place nanoporous materials as a new class of polymeric porous material with potential properties in the field of acoustics, especially in multifunctional systems requiring a certain degree of soundproofing

Descripción, indexación, búsqueda y adquisición de secuencias de vídeo mediante descriptores MPEG-7

El proyecto que lleva como nombre descripción, indexación, búsqueda y adquisición de secuencias de video mediante descriptores MPEG-7, muestra como objetivo principal la realización de cuatro descriptores MPEG-7 para la indexación de imágenes y videos. Dichos descriptores se implementan en lenguaje C, bajo el entorno Linux. Y como software de desarrollo se utiliza Sof_Image, software del grupo de imagen del departamento de TSC

Validation of a method for the determination of sorbic acid (E200) and potassium sorbate (E202) in industrial bakery by high resolution liquid chromatography

 Processed foods production increase,  delay nutritional losses in foods and to guarantee the quality of products that reach the consumer makes the use of chemical preservatives as additives more and more widespread. Sorbic acid (E200) and some of its salts, such as potassium sorbate (E202), are widely used as antimicrobial agents in food preservation around the world. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) sets a concentration of 25 mg per kg of body weight as a permissible daily intake. The consumption of a high dose can produce adverse effects such as intolerance, allergy or hives, and both European legislation (Regulation Nº 1129/2011) and Spanish legislation (Real Decreto 142/2002) present a list of authorized additives and maximum concentrations allowed in foods (2000 ppm for sorbic acid and potassium sorbate). Therefore, an adequate quantification is important in order to guarantee consumer protection and compliance with quality controls. High-performance liquid chromatography (HPLC) is considered one of the most suitable techniques for the determination of E200 and E202 in food. The objective of this work is to optimize extraction methods in food samples in order to improve the analysis of both preservatives by HPLC. The samples selected for this study were nine industrial bakery products with similar characteristics but from three different companies. In the extraction process, different proportions of acetonitrile and water were evaluated and the extraction with a ratio of 40:60 v / v was found to be the most suitable for HPLC analysis of this type of food. Also, tests were carried out applying different ultrasound times and it was verified that the optimal time was 15 min. Finally, quantification of E200 and E202 was carried out on the chosen products and the validation of the proposed method was performed. In addition, it was verified that none of the products contained concentrations of E200 and / or E202 higher than those permitted by legislation. Results confirm that optimization and validation of a method for the analysis of these foods is necessary as it allows to continue improving the clarity, accuracy and reliability of the measurements

A direct anatomical study of additional renal arteries in a Colombian mestizo population

Traditional anatomy describes each kidney as receiving irrigation from a single renal artery. However, current literature reports great variability in renal blood supply, the number of renal arteries mentioned being the most frequently found variation. Such variation has great implications when surgery is indicated, such as in renal transplants, uroradiological procedures, renovascular hypertension, renal trauma and hydronephrosis. This article pretends to determine the frequency of additional renal arteries and their morphological expression in Colombian population in a cross-sectional study. A total of 196 of renal blocks were analysed from autopsies carried out in the Bucaramanga Institute of Forensic Medicine, Colombia; these renal blocks were processed by the injection- corrosion technique. The average age of the people being studied was 33.8 ± 15.6 years; 85.4% of them were male and the rest female. An additional renal artery was found in 22.3% of the whole population and two additional ones were found in 2.6% of the same sample. The additional renal artery was most frequently found on the left side. The additional artery arose from the aorta’s lateral aspect (52.4%); these additional arteries usually entered the renal parenchyma through the hilum. No difference was established according to gender. Nearly a third of the Colombian population presents one additional renal artery and about 3% of the same population presents two additional renal arteries. Most of them reached the kidney through its hilar region. (Folia Morphol 2008; 67: 129–13

Problem-based learning for the acquisition of scientific-technical skills in training of future teachers

En esta comunicación se plantea la necesidad de fomentar la capacitación de competencias científico-técnicas en estudiantes del Grado de Magisterio de Educación Infantil. Para ello, se ha diseñado una actividad basada en el aprendizaje basado en problemas en la asignatura de funciones del profesorado. Según los resultados muestran que los alumnos valoran de forma positiva el método, prefiriendo éste al método de enseñanza tradicional basado en la lección magistral. Además, los estudiantes se encuentran más motivados e interesados por el aprendizaje y mejoran en la adquisición de competencias científico-técnicas

On the influence of creativity in basic programming learning at a first-year Engineering course

Teaching fundamentals of programming is a complex task that involves the students’ acquisition of diverse knowledge and skills. It is also well known that programming often requires a certain degree of creativity. There are some studies on how to foster creativity with programming, but few studies have analyzed the influence of students creativity on their performance as programmers. In this paper we present the results of a study, with a sample of 89 freshmen engineering students. Our results suggest (p<0.01) that a high level of creativity is correlated with achieving excellence in programming. Creativity is a generic competence which is not currently covered with in most engineering curricula, and we conclude it should be taken into account. Females, diverse thinking student and some disadvantage groups may benefit from a free-thinking environment in the classroom, in particular at their first-year in college.Peer ReviewedPostprint (author's final draft