115 research outputs found
Investigating the inclusion of online discussions to enhance students' learning in general education undergraduate classes
No full textDiscussion of class material has many educational benefits. In today's modern computerized society, these discussions no longer need to be confined to the classroom setting. This paper discusses students' reactions to the inclusion of online discussions at the undergraduate level. In addition, the author illustrates how the students' comments and concerns have been incorporated over three semesters to improve the assignment for future students
Variable importance measures for random forests
No full textMeasuring variable importance is often a difficult task: among others models can be complex and covariates can interact with each other and can be correlated. This study focuses on two questions: First, what should be the theoretical measure of variable importance under a given data-generating model? And second, what are the best estimates of these theoretical measures? Two theoretical measures and some corresponding estimates are presented of which one is the well-known random forests variable importance measure (Breiman, 2001). A simulation study is done for both linear and nonlinear models to find out what are the best estimates of variable importance measures for given data-generating models. Most measures struggle when covariates are correlated, but make an improvement in performance when the number of split variables is tuned.Applied Mathematic
ACHIEVEMENT OF COMPANY VALUE IN THE FOOD AND BEVERAGE SECTOR BASED ON FINANCIAL PERFORMANCE
No full text<p><strong>Abstract</strong></p>
<p>The company value reflected in the share price is an important focus for investors and companies so it is necessary to analyze the factors that can influence it. Conceptually, the increase in company value can be driven by financial performance including ROE, EPS, MVA and EVA. However, in the initial survey, an empirical gap was found at PT Indofood CBP Sukses Makmur Tbk, where these four variables did not always influence stock prices, and the research gap that occurred required the author to further examine the influence of these four variables on stock prices. The difference between this research and the previous one lies in the longer research period, namely 10 years, so it is more representative. With a population of 58 companies, a purposive sample was obtained of 21 companies. Though Robust Least Square Analysis, it is on found that simultaneously and partially Roe, EPS, MVA and EVA have a significant effect on firm value, thus the four variables can be used to measure the value of F&B companies listed on the IDX</p>
The use of digital photos to assess visual cover for wildlife in rangelands
No full textGrassland vegetation can provide visual cover for terrestrial vertebrates. The most commonly used method to assess visual cover is the Robel pole.We test the use of digital photography as a more accurate and repeatable method. We assessed the digital photography method on four forage grassland species (Pseudoroegneria spicata, Festuca campestris, Poa pratensis, Achnatherum richardsonii). Digital photos of 2-dimensional cutout silhouettes of three bird species sharp-tailed grouse, western meadowlark and savannah sparrow were used to model the impact of clipping (i.e., grazing) on visual cover. In addition, photos of artificial voles were used to model litter on cover available to small mammals. Nine sites were sampled and data were analyzed by the dominant grass species in each study plot. Regression analysis showed that digital photos (r2¼ 0.62) were a better predictor than the Robel pole (r2¼ 0.26) for assessment of cover. Clipping heights showed that clipping at less than 15 cm left the silhouettes 50% exposed. Digital photo analysis revealed that visual cover was affected by the type of grass species, with F. campestris > P. pratensis > A. richardsonii > P. spicata. Biomass and litter were both positively related to cover for small mammals.Peer reviewedBunchgrassDigital image analysisGrazingLitterRange managementRobel poleWildlife managemen
Microbial attachment to sulfide minerals in a bioleach environment
No full textIncludes bibliographical references (leaves 119-125).This research pertains to bioleaching of copper containing ores with particular reference to the copper sulfide mineral chalcopyrite (CuFeS₂). While it is focused on heap bioleaching, it has applications to stirred tank bioleaching operations. Industrial heap bioleaching offers opportunities for processing of low grade ores but poses process operational challenges. These challenges include ineffective heap inoculation, a lag period before effective leaching commences and poor heap performance. These aspects are attributed to several contributing factors, such as heap construction, engineering and microbial activity. To date little attention has been paid to colonisation as a means of mitigating these challenges and effectively improving process operation. Current literature regarding microbial attachment to sulfide minerals is limited to pure culture studies using iron oxidising mesophiles, and the use of sulfide mineral concentrates. In a heap environment, mineral dissolution is accelerated through the presence of a mixed consortium of microbial species; with the contribution of each not yet fully understood. In addition, gangue minerals comprise the bulk of the minerals present and thus cannot be neglected when attempting to better understand microbial attachment and the role of micro-organisms in a heap environment. The predominant methodology employed to study microbial attachment in a bioleach context has used batch agitated systems (shake flasks). This may not adequately represent attachment under heap-like fluid dynamics. The idea of this project stemmed from a requirement to contribute to the mitigation of challenges faced by industry through addressing the aforementioned gaps prevailing in literature and improving understanding of the role of microbial attachment and colonisation under conditions simulating a heap. The aim of this study was to investigate attachment of three bioleach micro-organisms (A. ferrooxidans, L. ferriphilum and S. metallicus)to complex, sulfide-containing minerals ores in a bioleach environment using methodologies simulating heap-like conditions
People with pets: Understanding the influence of human-companion animal attachment on empathy and resilient coping in adulthood.
No full textThis research investigated the association of current human-companion animal attachment with adult levels of empathy and resilient coping. Various research findings have reported benefits from people interacting with companion animals. A better understanding is needed of the human-companion animal relationship, and the associations which that relationship has with human prosocial and protective factors. Pet-owning adults (n = 352) completed an online survey measuring attachment with a current pet, interpersonal empathy, resilient coping, and current attachment with another adult as a possible covariate. Current human-animal attachment does not appear to be related to current human attachment. There are not significant associations between current human-animal attachment and overall empathy or any of the measured dimensions of empathy, or with resilient coping. Institutions, therapists, and other practitioners of animal-assisted therapies may not need to rely on the formation of a strong human-companion animal bond in order for some benefits to occur. --P. ii.The original print copy of this thesis may be available here: http://wizard.unbc.ca/record=b175449
On the sensitivity of coastal storm surge to atmospheric forcing
No full textStorm surge represents a major threat for coastal communities in the United States, accounting for 50% of fatalities due to tropical cyclones (TCs) and causing significant economic losses. Cyclones along the Northeast United States have been some of the most destructive, partly due to their effect in regions with high population density. Hurricane Sandy was a high-impact event producing record-breaking storm surges around the Mid-Atlantic Bight region and causing billions of dollars in damages. Much of the impact from Hurricane Sandy is attributed to its atypical near-perpendicular angle of landfall. This event prompted the need to study a wide range of possible TC scenarios and to understand the role of atmospheric forcing in modulating storm surge. Motivated by the damages from TC-induced storm surge events, we seek to determine the sensitivity of storm surge to atmospheric forcing, in our attempt to contribute towards improved predictions and mitigation of storm surge impacts. Improvement of storm surge predictions can be accomplished by advancing and developing modeling systems, and by understanding the relation between storm surge and TC physical parameters. The work in this dissertation seeks to determine the influence of different wind models on storm surge forecasts and to assess the sensitivity of storm surge to cyclone landfall angle.
To address these goals, we perform simulations of TCs, and their associated storm surge, by coupling state-of-the-art atmospheric and hydrodynamic models, namely the Weather Research and Forecasting model and the Advanced Circulation Model. The modeling framework facilitates the use of different wind models and the creation of synthetic cyclones that provide the desired spread in TC characteristics, particularly the angle of landfall. The coupled simulations are also used to inform an artificial neural network (ANN) model on the relationship between various TC parameters and storm surge, in our attempt to make accurate storm surge predictions at various station locations around the Mid-Atlantic Bight. We show that a higher resolution atmospheric simulation is not necessary to accurately depict the storm surge magnitude and spatial extent. While the sensitivity of storm surge and inundation to the TC impact angle varies along the coast, cyclones perpendicular to the coast generally produce the largest impacts. Results also emphasize the dependency of the storm surge impact to cyclone landfall location. We successfully train the ANN model to formulate timely storm surge predictions with a mean squared error of 0.08 m, demonstrating the potential of ANNs as forecasting tools.
We develop a modeling framework that can be employed to study the fundamental mechanisms modulating storm surge. Our results have important implications in how storm surge modeling can be improved, informing us on the current limitations in storm surge assessment and on alternative methods for improved forecasts that will ultimately lead to a reduction of impacts from TC-induced storm surge.Ph.D.Includes bibliographical reference
Light transmittance in human atrial tissue and transthoracic illumination in rats support translatability of optogenetic cardioversion of atrial fibrillation
No full textBackground: Optogenetics could offer a solution to the current lack of an ambulatory method for the rapid automated cardioversion of atrial fibrillation (AF), but key translational aspects remain to be studied. Objective: To investigate whether optogenetic cardioversion of AF is effective in the aged heart and whether sufficient light penetrates the human atrial wall. Methods: Atria of adult and aged rats were optogenetically modified to express light-gated ion channels (i.e., red-activatable channelrhodopsin), followed by AF induction and atrial illumination to determine the effectivity of optogenetic cardioversion. The irradiance level was determined by light transmittance measurements on human atrial tissue. Results: AF could be effectively terminated in the remodeled atria of aged rats (97%, n = 6). Subsequently, ex vivo experiments using human atrial auricles demonstrated that 565-nm light pulses at an intensity of 25 mW/mm2 achieved the complete penetration of the atrial wall. Applying such irradiation onto the chest of adult rats resulted in transthoracic atrial illumination as evidenced by the optogenetic cardioversion of AF (90%, n = 4). Conclusion: Transthoracic optogenetic cardioversion of AF is effective in the aged rat heart using irradiation levels compatible with human atrial transmural light penetration.Electronic Components, Technology and Material
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