Problem-driven scenario generation: an analytical approach for stochastic programs with tail risk measure

Scenario generation is the construction of a discrete random vector to represent parameters of uncertain values in a stochastic program. Most approaches to scenario generation are distribution-driven, that is, they attempt to construct a random vector which captures well in a probabilistic sense the uncertainty. On the other hand, a problem-driven approach may be able to exploit the structure of a problem to provide a more concise representation of the uncertainty. In this paper we propose an analytic approach to problem-driven scenario generation. This approach applies to stochastic programs where a tail risk measure, such as conditional value-at-risk, is applied to a loss function. Since tail risk measures only depend on the upper tail of a distribution, standard methods of scenario generation, which typically spread their scenarios evenly across the support of the random vector, struggle to adequately represent tail risk. Our scenario generation approach works by targeting the construction of scenarios in areas of the distribution corresponding to the tails of the loss distributions. We provide conditions under which our approach is consistent with sampling, and as proof-of-concept demonstrate how our approach could be applied to two classes of problem, namely network design and portfolio selection. Numerical tests on the portfolio selection problem demonstrate that our approach yields better and more stable solutions compared to standard Monte Carlo sampling

Examining the Effects of Rational Emotive Behavior Therapy (REBT) on the Irrational Beliefs of Blue-Chip Professionals

The extant literature reveals a scarcity of research applying rational emotive behavior therapy (REBT) in business settings. Against the backdrop of severe market conditions and inevitable involuntary job loss, the application of psychological interventions to reduce mental and physical health issues is highly pertinent and potentially valuable. This paper reports the effects of an intensive REBT programme on the irrational beliefs of staff undergoing redundancy from a Blue-Chip organisation. A repeated-measures single-group intervention design was adopted so that changes in irrational beliefs could be assessed over the course of the REBT programme. Results indicated significant reductions in total irrational beliefs, other-depreciation, need for achievement, and demand for fairness from pretest to posttest phases. Social validation data indicated perceived psychological and performance benefits underpinned by shifts in irrational beliefs. Results are discussed with reference to mechanisms of change, study limitations, and applied research issues

Hydrological outlook UK - May 2020

The Hydrological Outlook provides an insight into future hydrological conditions across the UK. Specifically, it describes likely trajectories for river flows and groundwater levels on a monthly basis, with a particular focus on the next three months. Well established monitoring programmes provide the current status of both river flows and groundwater levels at many sites across the UK, and data from these programmes provide the starting point for the Outlook. A number of techniques are used to project forwards from the current state and results from these are used to produce a summary that includes a highlights map

Hydrological outlook UK - October 2020

The Hydrological Outlook provides an insight into future hydrological conditions across the UK. Specifically, it describes likely trajectories for river flows and groundwater levels on a monthly basis, with a particular focus on the next three months. Well established monitoring programmes provide the current status of both river flows and groundwater levels at many sites across the UK, and data from these programmes provide the starting point for the Outlook. A number of techniques are used to project forwards from the current state and results from these are used to produce a summary that includes a highlights map

Variables that May Affect the Transmission of Dengue – A Case Study for Health Management in Asia

Funding for Open Access provided by the UMD Libraries Open Access Publishing Fund.Dengue, an emergent viral infection, has increased exponentially since the 1960s [1]. In spite of the alarming escalation of cases reported, the WHO still believes the disease is significantly underreported [2]. The effects of climate change are expected to dramatically increase the global incidence and geographic locations of dengue. According to the WHO, the number of countries reporting dengue cases has increased from nine countries before 1960 to more than 64 countries in 2007 [2]. Dengue cases continue to climb despite numerous interventions globally to halt the progression. Climate change allows the primary dengue vectors to thrive in more geographical locations; increased population, urbanization and deforestation have also provided favorable conditions for vectors. In areas with poor or nonexistent infrastructure, sanitation, and unreliable water supplies, water storage systems provide ideal breeding grounds for mosquitos. These issues are compounded by intercontinental commerce, specifically the transport of tires, which harbor rainwater and mosquito larvae, allowing introduction of non-native mosquitos to other countries. No cure currently exists for dengue and vaccine development has been fraught with difficulties. Dengue should be categorized as one of the most imperative global health issues in need of effective solutions. Drastic changes need to occur in public health approaches and health management policies for dengue. Without serious and immediate attention to the escalation of dengue the global burden of disease will significantly intensify

An investigation of the effects of normal aging on reasoning ability : A dual-process approach

Research has provided a great deal of evidence that reasoning performance declines with age (De Neys & Van Gelder, 2009; Fisk & Sharp, 2002; Gilinsky & Judd, 1994; Salthouse, 2005). Understanding these age-related differences is important because reasoning is an integral part of everyday cognitive functioning, the decline of which may result in older adults relying on heuristic strategies that can result in bias (Bacon, Handley, & Newstead, 2003). The objective of the current research was to use a dual-process theory framework to explain why there are age-related differences in reasoning. In addition to a variety of reasoning tests (i.e., a syllogistic task, base rate task, and the Cognitive Reflection Test), the present dissertation included independent tests of capacity (working memory, processing speed, and inhibition) and thinking styles to account for these age-related differences. Chapter 2 focused on two recently proposed levels of Type 2 analytic thinking, algorithmic (individual differences in capacity) and reflective (individual differences in rational thinking dispositions) (Stanovich, 2009). It was hypothesized that a) both reasoning performance and capacity performance would differ with age, b) these components would contribute independently to performance on three reasoning tasks, and c) that they would explain at least some of the age-related differences in reasoning performance. Older adults demonstrated lower algorithmic capacity relative to younger adults and measures of capacity were related to performance on all three tasks. Furthermore, capacity attenuated the age-related differences in reasoning. Older adults also demonstrated a lower score than young adults on the measure of thinking dispositions; however, this predicted age-related differences only on the base rate task (and marginally on the syllogistic task). Furthermore, on the syllogistic reasoning task, a belief-bias component of reasoning was related to the age-related differences in reasoning. Chapter 3 focused on whether the performance differences between young and older adults demonstrated in Chapter 2 could be attributed to differences in metacognitive skills. Four aspects of metacognition were examined: 1) differences in conflict detection, 2) confidence in individual answers, 3) confidence in overall performance, and 4) scores on the self-report measure Metamemory in Adulthood. There was little evidence to suggest that there were difference in metacognitive ability between young and older adults, thus the results were not consistent with the hypothesis that metacognition plays a role in the age-related reasoning differences. In Chapter 3, I also investigated the hypothesis that conclusion believability and latency may be cues to confidence, and that perceived difficulty of the task may be an alternate measure of confidence, that is related to performance and response time. The data reveal that the conclusion believability and latency cues were important predictors of confidence, especially for the older adults, and that perceived task difficulty was related to performance and latency on both the syllogistic and base rate tasks. Chapter 4 focused on the effects of perspective instructions on age-related differences in reasoning. In particular, I investigated whether reasoners would engage in a more logical, analytic style of thinking when prompted to reason from an alternative perspective. Results indicated that a shift in perspective may be advantageous for the older adults. This is promising because although older adults’ limited capacity increases reliance on heuristic output and decreases processing power, there may be a straightforward way to mediate these age-related differences in reasoning ability, simply by asking them to reason from another’s perspective. Overall, this research significantly expanded the current knowledge regarding age-related differences in reasoning. Moreover, the findings were consistent with a dual-process theory of reasoning, which provided an integrative framework that accounts for the patterns of findings presented in this dissertation

Islamic religious epistemology

This chapter aims to lay out a map of the diverse epistemological perspectiveswithin the Islamic theological tradition, in the conceptual framework of con-temporary analytic philosophy of religion. In order achieve that goal, it aims toconsider epistemological views in light of their historic context, while at thesame time seeking to “translate” those broadly medieval perspectives intocontemporary philosophical language. In doing so, the chapter offers a succinctoverview of the main epistemic trends within the Islamic theological traditionconcerning religious epistemology. The chapter is divided into two main sectionsdesignated for discussions of differing accounts found in distinct trends of thetradition, namely the Rationalist and Traditionalist trends. The discussion con-cerning the Rationalist trend focuses on the philosophical-theologians of thedominant Mu’tazilite, Ash’arite, and Maturidite schools. The section on IslamicTraditionalism focuses on the Atharite scripturalism of Ibn Qudāma, and inparticular the thought of Ibn Taymiyya. In order to map out these historicpositions in light of contemporary religious epistemology, reference is made toa threefold typology of current views in the literature: (1) theistic evidentialism,(2) reformed epistemology, and (3) fideism.1 As such, the remainder of thechapter will attempt to outline the different approaches toward religious episte-mology in the Islamic theological tradition with this threefold typology in mind

A metaphysical inquiry into Islamic theism

The effervescent and dynamic history of Islamic theology in its formative years bears witness to organic, philosophical, intra-religious, and politically charged developments over the question of God’s nature. Following the sudden and explosive expansion of Islamic civilization in the first 200 years since its advent, Muslims quickly developed a religious and political unity which saw them govern over large sways of disparate religious communities, with Muslims being a technical religious minority political ruling class. This rather distinct socio-political context in which Muslims found themselves gave rise to a whole host of developments in both religious and secular disciplines. To be sure, the religious diversity within the Umayyad and Abbasid empires did not impose or necessarily act as the primary influence upon these developments, but it and the combination of organic dialogue from within, followed by a touch here and there of politico-religious dogmatism (i.e., the miḥna of the Mu’tazila), led to a theological conversation which oversaw the flowering of distinct Islamic theological schools, and the advent of Muslim peripatetic philosophies..

Turbocompounding the Opposed-Piston 2-Stroke Engine

This paper presents analytical research conducted into the level of fuel consumption improvement that can be expected from turbocompounding a medium-duty opposed-piston 2-stroke engine, which is part of a hybridized vehicle propulsion system. It draws on a successful earlier study which showed a non-compounded opposed-piston engine to be clearly superior to other forms of 2-stroke engine, such as the widely adopted uniflow-scavenged poppet valve configuration. Electrical power transmission is proposed as the method of providing the necessary variable-speed drive to transmit excess turbine power to the system energy storage medium. The work employs one-dimensional engine simulation on a single-cylinder basis, using brake specific fuel consumption (BSFC) as the reportable metric, coupled with positive or negative power flow to the engine from the compounder; this is a variation on an approach successfully used in earlier work. Here it shows the sensitivities of the overall system to cylinder pressure, the compressor and turbine efficiencies, exhaust backpressure and also provides a means to investigate the effect of the power transmission efficiency on the overall benefit. Reheating the air before the turbine is also investigated as a means of providing a “burst” performance facility, albeit at the expense of extra fuel consumption. Positive compounding work is shown to be achievable across all investigated engine operating points under certain conditions. Operating points at lower engine speeds showed an increased propensity for turbocompounding, with 5-6% of the brake torque arising from the compounder, compared to those at higher engine speeds, where a maximum of 4% was seen. BSFC was found to be highly dependent on compounding torque with improvements only arising from reducing backpressure. A better understanding of the flow restrictions of the exhaust aftertreatment and muffler systems, for a given application, would allow for more accurate determination of the possibility for BSFC reduction within realistic operating conditions