Amenability of Groupoids Arising from Partial Semigroup Actions and Topological Higher Rank Graphs

We consider the amenability of groupoids $G$ equipped with a group valued cocycle $c:G\to Q$ with amenable kernel $c^{-1}(e)$. We prove a general result which implies, in particular, that $G$ is amenable whenever $Q$ is amenable and if there is countable set $D\subset G$ such that $c(G^{u})D=Q$ for all $u\in G^{(0)}$. We show that our result is applicable to groupoids arising from partial semigroup actions. We explore these actions in detail and show that these groupoids include those arising from directed graphs, higher rank graphs and even topological higher rank graphs. We believe our methods yield a nice alternative groupoid approach to these important constructions.Comment: Revised as suggested by a very helpful referee. In particular, a gap in the proof of Theorem 5.13 has been repaired resulting in a much improved version (with fewer hypotheses

Magnitude bias of microlensed sources towards the Large Magellanic Cloud

There are lines of evidence suggesting that some of the observed microlensing events in the direction of the Large Magellanic Cloud (LMC) are caused by ordinary star lenses as opposed to dark Machos in the Galactic halo. Efficient lensing by ordinary stars generally requires the presence of one or more additional concentrations of stars along the line of sight to the LMC disk. If such a population behind the LMC disk exists, then the source stars (for lensing by LMC disk objects) will be drawn preferentially from the background population and will show systematic differences from LMC field stars. One such difference is that the (lensed) source stars will be farther away than the average LMC field stars, and this should be reflected in their apparent baseline magnitudes. We focus on red clump stars: these should appear in the color-magnitude diagram at a few tenths of a magnitude fainter than the field red clump. Suggestively, one of the two near-clump confirmed events, MACHO-LMC-1, is a few tenths of magnitude fainter than the clump.Comment: To appear in ApJ Letters. Shortened to match the accepted version, 8 pages plus 1 ps figur

An assessment of enterprise risk management process in construction firms

Abstract: Though the construction industry is project-based, risk management should address risks at both projects, and enterprise levels as an overemphasis on project risk management would lead to some limitations. As a comprehensive and strategy-focused risk management discipline, enterprise risk management (ERM), which agrees with the modern portfolio theory, manages the whole risk portfolio of a firm and has been recommended in the construction industry. This study provides an understanding of ERM and investigates an ERM process for construction firms. The work methodology included a comprehensive literature search relating to ERM. The literature review was conducted through accredited academic and Professional journals, books, the internet, theses, and dissertations. Literature revealed environment and strategy, risk identification, risk assessment and prioritising, risk mitigation and control, information and communication and monitoring, reporting and continuous improvement as the essentials of ERM. The investigated process could be used as a guide for ERM process in construction firms. As few studies have attempted to investigate ERM in construction firms, it is believed that this study expands the existing literature relating to ERM

A theoretical review of risk identification : perspective of construction industry

Abstract: Managing risks in construction projects has been acknowledged as an essential management process in order to accomplish the project objectives in terms of time, cost, quality, safety and environmental sustainability. However, up to now most studies have concentrated on some aspects of construction risk management rather than using a systematic and comprehensive approach to identifying risks and analyse the probability of occurrence and impacts of these risks. Risk management consists of identifying risks, assessing risks either quantitatively or qualitatively, selecting the appropriate method for handling risks, and then monitoring and documenting risks. By identifying risks in an early stage of planning and assessing their comparative significance, project managers can identify techniques employed to reduce risks and allocate the best people to mitigate them. Thus, this research focuses on risk identification, as opposed to other processes of risk management. This research is mainly a literature review and was conducted through accredited academic and Professional journals, books, the internet, theses, and dissertations. The reviewed literature revealed that the entire risk management process is not only limited to solving problem in advance but also for the occurrence of any unexpected future problems. The study further shown that issues with possible threats envisaged in a project are not only a means to reduce losses within the project, but also a means to transfer risks into opportunities, which can lead to economic profitability, environmental and other advantages. This paper is of value to managers and decision makers involved in managing risks where it is intended to boost their knowledge regarding the importance of risk identification as a crucial stage of the process to managing risks

Risk management in the construction industry : a new literature review

Abstract: The construction industry is well known as a highly risk prone industry owing to the complexity of its activities and dynamic project environments generating an atmosphere of risks that must be taken into consideration in the decision process. For this reason, we have developed this treatise to elucidate the fundamentals of risk management through a concise new proposal of literature review for risk management in construction. Our explanation of this is venture is that over the years, this area has been acknowledged as a crucial process in the business institutions and the most discussed subject among experts and researchers in the construction sector. We have tried in this report to present the most recent studies considering the impossibility to present all definitions of the concept of risk. This study is mainly a literature review; it looks at the literature relating to the concept of risk, risk management in construction as well as methods used in construction industry

Evaluating the use of risk-identification techniques in the South African construction industry

Abstract: Purpose of this paper: This paper seeks to investigate the current use of risk-identification techniques in the South African construction industry. Methodology: An extensive literature search was conducted to collect the secondary data; and these were supplemented by primary data via a questionnaire survey. These were then distributed to contractors, who were conveniently sampled in Gauteng (South Africa). The data were analysed by using the Mean-Item Score (MIS). Findings: A total of twelve risk-identification techniques were identified, of which checklist, flowchart and brainstorming were rated as the most used risk-identification techniques in construction projects in Gauteng. Research limitations: This research was conducted only with considered contractors in the Gauteng province. Further research could include an increased target population more representative of the South African construction industry. Practical implications: Practitioners and researchers are likely to find the study useful; as it discusses the risk-identification techniques used in construction; and in particular, it seeks to report empirically on the techniques mostly applied in identifying risks in construction projects. Valuable information about current risk-identification techniques are provided..