A sustainable infrastructure delivery model: value added strategy in the Nigerian construction industry

The current economy reforms strategy by the Nigerian government promotes competition among private contractors, which are comprised of local and foreign contractors, in order to achieve value added infrastructure delivery. Resulting competitive bidding processes between multinational construction corporations (MCC) and local construction contractors (LCC) has had mixed comments among stakeholders, with a need for a more sustainable and holistic value approach identified. The aim of this research is to develop a sustainable infrastructure delivery model (SID). The key research methodology is based on extensive literature review and questionnaire survey. SID is developed on the principles and philosophy of soft system methodology (SSM) and analytic network process (ANP). In order to evaluate the significance of MCC and LCC through SID model, questionnaire surveys were conducted. Feedback was collected from experts in the Nigerian construction sector who assessed the relative importance of formulated decision criteria, which were sought under 7 key factors. Data simulation revealed that, through competitive bidding, significant achievements have been made in the delivery of constructed facilities. It was also found that the policy lacked holistic value principles that integrated ethical stance and monetary returns on investment. In this study, SID framework has been presented, clearly showing needs for integration of economic and ethical stances in order to achieve a sustainable infrastructure delivery

Construction costs and value management: study of multinational practices in Nigeria

The practice of multinational construction corporations (MCC) in Nigeria construction industry has been viewed as a value for money approach through construction cost management. Assessment of the opportunity cost of the initiatives is equally important in order to gauge the progress of millennium development goals (MDGs), set up by the United Nations in 2000 on human development in developing countries. The study is aimed at the evaluation of current infrastructure procurement framework, introducing novel sustainable infrastructure delivery (SID) model as a holistic value management methodology and a decision making technique. Key components of the model are Checkland’s soft system methodology (SSM) and analytic network process (ANP) by Saaty. SID input data is collected from the pilot questionnaire with the professionals in Nigeria’s construction industry, reinforced by a thorough literature review. Questions sought paired comparison judgements on key aspects of project management and implications on sustainable infrastructure procurement. The concept is discussed in the methodology section. Preliminary findings reveal that current practice lacks a holistic decision making technique, reflected in divergent value interests among stakeholders on infrastructure procurement through different views on the constitution of values. Though there is practical evidence regarding the growth in the construction sector, quantification of the implications on local economy and human development are less visible and require further investigations

Mating system and population genetic structure of the bulldog ant Myrmecia pavida

Understanding the evolution of the alternative mating strategies of monandry and polyandry is a fundamental problem in evolutionary biology because of the cost-benefit trade-offs associated with mating for females. The problem is particularly intriguing in the social insects because queens in most species appear to be obligately monandrous (i.e., only a single male fathers their offspring), while those in a minority of species have evolved high, and sometimes extreme, polyandry. One group which may shed particular insight is the ant subfamily Myrmeciinae (Myrmecia and Nothomyrmecia). Here we examine the population and colony genetic structure of the bulldog ant Myrmecia pavida CLARK, 1951 by genotyping offspring workers from 45 colonies. We find little evidence of geographic structuring or inbreeding in the population, indicating that the species outbreeds, most probably in mating swarms. We also find that queens of M pavida show moderately high polyandry, with 84% having mated with between two and seven males, and an overall mean observed mating frequency of 3.8. This is significantly higher than previously reported for queens of Nothomyrmecia macrops, in which most females mate singly. This was similar to that of M pyriformis, M brevinoda, and M pilosula, the three congenerics for which mating frequencies have recently been reported. The two genera in the Myrmeciinae therefore appear to show multiple transitions in mating frequency and further investigation of the subfamily may be highly informative for disentangling the forces driving the evolution of alternative mating strategies

Simulation of a particle-laden turbulent channel flow using an improved stochastic Lagrangian model

The purpose of this paper is to examine the Lagrangian stochastic modeling of the fluid velocity seen by inertial particles in a nonhomogeneous turbulent flow. A new Langevin-type model, compatible with the transport equation of the drift velocity in the limits of low and high particle inertia, is derived. It is also shown that some previously proposed stochastic models are not compatible with this transport equation in the limit of high particle inertia. The drift and diffusion parameters of these stochastic differential equations are then estimated using direct numerical simulation (DNS) data. It is observed that, contrary to the conventional modeling, they are highly space dependent and anisotropic. To investigate the performance of the present stochastic model, a comparison is made with DNS data as well as with two different stochastic models. A good prediction of the first and second order statistical moments of the particle and fluid seen velocities is obtained with the three models considered. Even for some components of the triple particle velocity correlations, an acceptable accordance is noticed. The performance of the three different models mainly diverges for the particle concentration and the drift velocity. The proposed model is seen to be the only one which succeeds in predicting the good evolution of these latter statistical quantities for the range of particle inertia studied

Spectral Bounds for the Connectivity of Regular Graphs with Given Order

The second-largest eigenvalue and second-smallest Laplacian eigenvalue of a graph are measures of its connectivity. These eigenvalues can be used to analyze the robustness, resilience, and synchronizability of networks, and are related to connectivity attributes such as the vertex- and edge-connectivity, isoperimetric number, and characteristic path length. In this paper, we present two upper bounds for the second-largest eigenvalues of regular graphs and multigraphs of a given order which guarantee a desired vertex- or edge-connectivity. The given bounds are in terms of the order and degree of the graphs, and hold with equality for infinite families of graphs. These results answer a question of Mohar.Comment: 24 page