Risk based resilient network design

This paper presents a risk-based approach to resilient network design. The basic design problem considered is that given a working network and a fixed budget, how best to allocate the budget for deploying a survivability technique in different parts of the network based on managing the risk. The term risk measures two related quantities: the likelihood of failure or attack, and the amount of damage caused by the failure or attack. Various designs with different risk-based design objectives are considered, for example, minimizing the expected damage, minimizing the maximum damage, and minimizing a measure of the variability of damage that could occur in the network. A design methodology for the proposed risk-based survivable network design approach is presented within an optimization model framework. Numerical results and analysis illustrating the different risk based designs and the tradeoffs among the schemes are presented. © 2011 Springer Science+Business Media, LLC

Risk-based Survivable Network Design

Communication networks are part of the critical infrastructure upon which society and the economy depends; therefore it is crucial for communication networks to survive failures and physical attacks to provide critical services. Survivability techniques are deployed to ensure the functionality of communication networks in the face of failures. The basic approach for designing survivable networks is that given a survivability technique (e.g., link protection, or path protection) the network is designed to survive a set of predefined failures (e.g., all single-link failures) with minimum cost. However, a hidden assumption in this design approach is that the sufficient monetary funds are available to protect all predefined failures, which might not be the case in practice as network operators may have a limited budget for improving network survivability. To overcome this limitation, this dissertation proposed a new approach for designing survivable networks, namely; risk-based survivable network design, which integrates risk analysis techniques into an incremental network design procedure with budget constraints. In the risk-based design approach, the basic design problem considered is that given a working network and a fixed budget, how best to allocate the budget for deploying a survivability technique in different parts of the network based on the risk. The term risk measures two related quantities: the likelihood of failure or attack, and the amount of damage caused by the failure or attack. Various designs with different risk-based design objectives are considered, for example, minimizing the expected damage, minimizing the maximum damage, and minimizing a measure of the variability of damage that could occur in the network. In this dissertation, a design methodology for the proposed risk-based survivable network design approach is presented. The design problems are formulated as Integer Programming (InP) models; and in order to scale the solution of models, some greedy heuristic solution algorithms are developed. Numerical results and analysis illustrating different risk-based designs are presented

A Review of What is Known about Impacts of Coastal Pollution on Childhood Disabilities and Adverse Pregnancy Outcomes

Coastal pollution is getting global attention for its enormous impacts on human health by the means of consumptions of seafood, involvement of risky jobs and exposure to water related disastrous events. Critical review of published and unpublished literatures and documents show the effects of heavy metals, chemicals, and radioactive substances are considered as long termed and deadly, and children and pregnant women are the most vulnerable population to such exposures and at risk of adversely affecting their development. The physiological systems of children and fetuses are developing fast and usually sensitive to disruptions induced by environmental pollutants and exposures in utero increase the risk of future toxic insults. Almost sixty percent of the world‘s population is at risk of this contamination and coastal developing countries are facing significant challenges by this form of pollution. The main objective of this review was to explore the situation of coastal water pollution and its impact on child health and pregnancy outcomes globally. However, these observations are indecisive due to limitations of evidence to support. Therefore, further epidemiological studies are required to confirm these initial observations. Keywords: Coastal pollution, heavy metal, radionucleotides, childhood disability, adverse pregnancy outcome

Public Health and Air Pollution in Asia (PAPA): A Multicity Study of Short-Term Effects of Air Pollution on Mortality

Background and Objectives: Although the deleterious effects of air pollution from fossil fuel combustion have been demonstrated in many Western nations, fewer studies have been conducted in Asia. The Public Health and Air Pollution in Asia (PAPA) project assessed the effects of short-term exposure to air pollution on daily mortality in Bangkok, Thailand, and in three cities in China: Hong Kong, Shanghai, and Wuhan. Methods: Poisson regression models incorporating natural spline smoothing functions were used to adjust for seasonality and other time-varying covariates that might confound the association between air pollution and mortality. Effect estimates were determined for each city and then for the cities combined using a random effects method. Results: In individual cities, associations were detected between most of the pollutants [nitrogen dioxide, sulfur dioxide, particulate matter ≤ 10 μm in aerodynamic diameter (PM 10), and ozone] and most health outcomes under study (i.e., all natural-cause, cardiovascular, and respiratory mortality). The city-combined effects of the four pollutants tended to be equal or greater than those identified in studies conducted in Western industrial nations. In addition, residents of Asian cities are likely to have higher exposures to air pollution than those in Western industrial nations because they spend more time outdoors and less time in air conditioning. Conclusions: Although the social and environmental conditions may be quite different, it is reasonable apply estimates derived from previous health effect of air pollution studies in the West to Asia.published_or_final_versio

Airborne dust and high temperatures are risk factors for invasive bacterial disease

Background The Sahel region of West Africa has the highest bacterial meningitis attack and case fatality rate in the world. The effect of climatic factors on patterns of invasive respiratory bacterial disease is not well documented. Objective We aimed to assess the link between climatic factors and occurrence of invasive respiratory bacterial disease in a Sahel region of Niger. Methods We conducted daily disease surveillance and climatic monitoring over an 8-year period between January 1, 2003, and December 31, 2010, in Niamey, Niger, to determine risk factors for bacterial meningitis and invasive bacterial disease. We investigated the mechanistic effects of these factors on Streptococcus pneumoniae infection in mice. Results High temperatures and low visibility (resulting from high concentrations of airborne dust) were identified as significant risk factors for bacterial meningitis. Dust inhalation or exposure to high temperatures promoted progression of stable asymptomatic pneumococcal nasopharyngeal carriage to pneumonia and invasive disease. Dust exposure significantly reduced phagocyte-mediated bacterial killing, and exposure to high temperatures increased release of the key pneumococcal toxin pneumolysin through increased bacterial autolysis. Conclusion Our findings show that climatic factors can have a substantial influence on infectious disease patterns, altering density of pneumococcal nasopharyngeal carriage, reducing phagocytic killing, and resulting in increased inflammation and tissue damage and consequent invasiveness. Climatic surveillance should be used to forecast invasive bacterial disease epidemics, and simple control measures to reduce particulate inhalation might reduce the incidence of invasive bacterial disease in regions of the world exposed to high temperatures and increased airborne dust

An examination of executive leadership and organisational performance in publicly listed companies of Thailand

Despite great interest for many years on the effect of executive leadership on organisational performance, there has been limited research into executive leadership particularly the impact of CEOs’ behavioural complexity on organisational performance or the association between the behavioural complexity and CEO attributes in developing Asian countries such as Thailand. The main purpose of this thesis is to examine the impact of CEOs’ executive leadership on organisational performance in publicly listed companies of Thailand. This study has built upon Hart and Quinn’s (1993) study based on the Competing Values Framework about executive leadership roles and Zakliki’s (1996) study that further developed a new integrative framework to examine CEOs’ executive leadership by incorporating the concept of behavioural complexity and CEO attributes including demographic characteristics, personality traits and leadership styles. Executive leadership was tested against the three domains of organisational performance, namely financial, business and organisational effectiveness in publicly listed companies of Thailand. The contingency factors namely firm size, environmental conditions and business strategy were also incorporated into the study in order to describe CEOs’ executive leadership and its relationship with organisational performance under different conditions. The research fieldwork was conducted in Thailand by the use of personal interviews over a four and half-month period in 2003 and one hundred and twenty three CEOs participated in total, representing an effective response rate of 51.25 per cent. Non-response bias analysed showed that there was no important difference between the respondents and non-respondents in term of industry or size classification. Thai replication (H&Q) results showed a low significant relationship between the roles played by CEOs and organisational performance, which was consistent with Hart and Quinn’s (1993) study and Zakliki’s (1996) replication of Hart and Quinn. The Thai replication (H&Q) revealed similar results with the original (H&Q) study and showed that high behavioural complexity CEOs was predictive of higher firm performance with respect to business performance and organisational effectiveness. In all these three studies high behavioural complexity of the CEOs had little to do with financial performance of firms. Thai replication (Z) results showed that executive leadership including leadership roles and CEO characteristics had more impact on the organisational effectiveness than other aspects of firm performance. Both studies showed a similarity in that high behavioural complexity of CEOs was associated with higher firm performance for organisational effectiveness in general and for large firms and for firms following an analyser type of strategy. Both studies also revealed that there was no association between CEO behavioural complexity and financial performance regardless of situational factors. The major results from the extended Thai study were examined against each of the seven research questions generated for this research. It was found that CEOs make a difference but there is a limited connection between executive leadership and firm performance. Executive leadership including leadership roles and CEO attributes had greater impact on organisational effectiveness than other firm performance dimensions. High behavioural complexity of CEOs had a positive association with higher business performance and organisational effectiveness in general, in large firms and for firms following an analyser type of strategy. High behavioural complexity group also had a positive relationship with organisational effectiveness in a stable environment and for firms pursuing a prospector strategy. There was no association between high behavioural complexity and financial performance regardless of any situational factors except for the firms pursuing the analyser strategy. This study was able to show a broad pattern in firms following an analyser type of strategy, namely that they had high behavioural complexity CEOs with an internal locus of control and a positive association with all three firm performance dimensions namely financial performance, business performance, and organisational effectiveness. This pattern which was not detected in previous studies may have been identified because of the refinement of the instrument and the classification system. This finding is particularly important as it demonstrates an association between behavioural complexity and financial performance is possible in certain specific situations. This research identified that CEOs in high performing firms had a relatively longer tenure in the existing position, a longer tenure in the current firm, a higher need for achievement, a greater internal locus of control, an internal origin of appointment and an autocratic leadership style. Further by applying contingency factors, the results found that high performing firms tended to be associated with CEOs who have particular attributes with the specific attribute requirements being dependent on the situation. High behavioural complexity CEOs had a higher need for achievement, more internal locus of control, autocratic leadership style and were less likely to come from a planning and management background. Attributes required in CEOs to be effective were determined by the situational context namely firm size, environmental conditions and business strategy. CEO attributes differed in smaller firms compared to larger firms, in stable environments compared with turbulent environments as well as for defenders firms compared with prospector firms and analyser firms. Additional findings on other dimensions on executive leadership in Thailand identified the key success attributes required for effective leaders, the major strengths and weaknesses of CEOs, the main criteria for appointing CEOs, the important knowledge and skills required for executive development, the leadership style and the CEO’s origin of appointment. The data analyses were performed with respect to firm groups, contingency factors, behavioural complexity group, and leadership style. Overall, the findings from this research have significant implications for top management theory, executive development, CEO selection, management education, and research methodology. Future research with other types of organisations, replicating these findings in another context other than just in Thailand and expanding the list of contingency factors investigated would be worthwhile to help further understand the relationship between executive leadership and organisational performance