Discovering an active subspace in a single-diode solar cell model

Predictions from science and engineering models depend on the values of the model's input parameters. As the number of parameters increases, algorithmic parameter studies like optimization or uncertainty quantification require many more model evaluations. One way to combat this curse of dimensionality is to seek an alternative parameterization with fewer variables that produces comparable predictions. The active subspace is a low-dimensional linear subspace defined by important directions in the model's input space; input perturbations along these directions change the model's prediction more, on average, than perturbations orthogonal to the important directions. We describe a method for checking if a model admits an exploitable active subspace, and we apply this method to a single-diode solar cell model with five input parameters. We find that the maximum power of the solar cell has a dominant one-dimensional active subspace, which enables us to perform thorough parameter studies in one dimension instead of five

Making Health Equity Real: Implementing a Commitment to Engage the Community Through Fellowships

Between 2016 and 2019, Richmond Memorial Health Foundation jumpstarted its transformation from a health legacy foundation committed to increasing access to health care to one promoting regional health equity through a racial and ethnic lens. A central component of this new focus was the trustees’ decision to invite community members to inform and advance the health equity strategy through two distinct community fellowship programs — the Equity + Health Fellowships. These programs ultimately provided the foundation with a new language, benchmarks, and structure for welcoming broader community engagement. This article highlights the outcomes of both programs, how the experience with the Fellowships enhanced the foundation’s impact and learning, and how the foundation identified areas that require strengthening as its transformation continues. The article also shares four lessons for any philanthropic organization seeking to work in direct partnership with community members. With these insights, foundations can use their social and financial capital to address power and health inequities directly and become stronger, trusted allies of community partners

Education and Philanthropy in the American South: A Case History of the Danville Regional Foundation's Investment in Smart Beginnings

This study investigates and analyzes Danville Regional Foundation’s (DRF) $5.4 million investment to support the Smart Beginnings Danville Pittsylvania County (“Smart Beginnings”) early childhood program. Findings are presented as an historical case study. The study applies the perspective of strategic philanthropy, paying particular attention to the elements of asset-based social policy and the context of the American South. The study uses qualitative methods including textual analysis of key internal and external documents as well as structured interviews with four participants deeply engaged in the conceptualization and execution of Smart Beginnings. Careful consideration of DRF’s investment in Smart Beginnings surfaces at least six questions that merit explicit consideration by philanthropic leaders when attempting to address issues of persistent inequity.Doctor of Philosoph

Getting more, and less from charcoal: A reconstruction of the fire histories of two lakes in the Sydney Basin, south-eastern Australia, using FTIR spectroscopy and chemometrics

This study investigated a new method for determining fire severity/intensity using FITR spectroscopy and chemometrics on sedimentary charcoal and applied it to two charcoal records from Thirlmere Lakes, located in the Blue Mountains World Heritage Area in eastern Australia; a 135-ka BP record spanning two glacial/interglacial cycles at Lake Couridjah, and a 900-year record encompassing the pre- and post-colonisation of Australia by Europeans at Lake Werri Berri. The larger aims of this thesis were to develop a tool for determining fire severity/intensity of past fire regimes and examine the long-term fire history of Lake Couridjah to investigate how and when (and if) people used fire to change the environment as a consequence of changing climatic and environmental conditions. It was also applied to Lake Werri Berri to examine the transition between Aboriginal and European custodianship of the area around the lake and to determine if their markedly different methods of land-use are apparent in the charcoal record. A new method for determining fire severity/intensity in past environments using FTIR spectroscopy and multivariate statistical modelling (Partial Least Squares regression, PLS-R) is introduced in Chapter 2. FTIR spectra were obtained from a reference library of laboratory produced charcoal derived from common Australian species at Charring Intensities (CI, representing the integration of pyrolysis temperature and duration of heat exposure) frequently reached in bushfires. The modelled coefficients from the charcoal library were then used to quantify the CI of charcoal of unknown heating duration (e.g., modern charcoal, fossil sedimentary charcoal). Although the more homogenous reference library of laboratory produced charcoal is not an exact analogue for charcoal produced in a wildfire, it has the potential to offer insights into the severity/intensity of past fire regimes and may offer an inexpensive and easily applicable tool for evaluating recent wildfires. In the course of exploring Charring Intensity on fossil charcoal, it was found that very little charcoal had CI values below ~3.0°C·s·106 (~400° C). It was hypothesized that the use of a light oxidant, a common treatment for concentrating sedimentary charcoal, was degrading lightly-pyrolyzed material. To test this hypothesis, a series of charcoal samples was produced in a nitrogen purged tube furnace at 250-800 C, then the total surface area of 20 replicates of each temperature group was measured before and after 24 hours of immersion in a 4% bleach (sodium hypochlorite) solution. It was found that charcoal particles formed ≤400 C were almost completely degraded in the bleach treatment and particles formed above at ≥400 C were much more resistant to oxidation. These results suggest that use an oxidant to concentrate charcoal removes material formed at temperatures below ~400 C from techniques commonly used for the analysis of macrocharcoal, with the result being fire histories might be biased toward high intensity (high temperature) fires. The insights from these studies on FTIR and charcoal methods were then applied to the elucidation of the past fire regime at Thirlmere Lakes. This included consideration of the fire history of Lake Couridjah, a record that spans 135 calibrated kilo anni Before Present (ka BP), and thereby encompassing the present and previous interglacial periods (albeit, with a hiatus between ~18-105 ka BP). Importantly, this record covers two climatically similar glacial-interglacial transitions and interglacials (MIS 6-5 and MIS 2-1) ,but notably one was without, and MIS 2-1 had people present. CHAR during both glacial/interglacial transitions was high and variable, followed by interglacial periods of reduced charcoal influx, suggesting that the transitions were times of high fire activity, likely a consequence of climatic instability and increasing biomass accumulation in the catchment. CI, however, was high but relatively stable throughout MIS 6-5, with higher levels often occurring during periods of low CHAR, suggesting that the influx of charcoal into the lake may in part be attributed to catchment stability reducing sedimentation rather reductions in area burned. CI values were often higher during periods of low CHAR, however, suggesting that periods of increased biomass led to higher intensity fires. In contrast to the relatively high but stable CI of MIS 6-5, the transition into interglacial conditions during MIS 2-1 had highly variable CI values that were much lower (~2°C·s·106), suggesting that despite increasing biomass accumulation and a warming climate, the fires were of lower severity/intensity, perhaps the result of human interference in the fire regime. This study suggests that late Pleistocene human populations perhaps attempted to (but ultimately failed) to maintain a more open woodland vegetation structure through selective burning as the ameliorating climate led to increasing productivity in the environment following the glacial termination. At around 10 ka BP, it appears this attempt was abandoned, and CI values suggest that fire severity/intensity increased, and CHAR (area burnt) decreased and remained stable until present, suggestive of a fire regime largely controlled by the stable climate of the Holocene. Five common charcoal analysis methods (4 using an oxidant and one control using H2O) were tested in conjunction with CI and CHAR on a 900-year core (WB3) from Lake Werri Berri. The five treatment groups (4 oxidants and a simple H2O wash as a control) showed very similar peaks in CHAR. However, minimum CI values were significantly lower in the samples treated with H2O, again suggesting that oxidative treatments are preferentially removing lightly-pyrolyzed material. This study considered CI using two combined treatments (H2O and 6 hours in 4% bleach), which captured the largest range of Charring Intensity values (2.8-5.4°C·s·106) and CHAR through the 6-hour treatment of 4% bleach. CI was relatively high and stable throughout the core, with infrequent peaks coinciding with periods of climate fluctuation (~500 BP, late-20th and early 21st century). Interestingly, there was no apparent change in fires (CI or CHAR) during the transition between Aboriginal custodianship and the European occupation of Australia, even after settlement around the Thirlmere Lakes region. It is possible that the people who lived in the area prior to European settlement may not have benefitted from the sustained and systematic application of fire to the environment during the majority of the Holocene, given the resources at hand associated with the freshwater lakes. In contrast, from the latter part of the 20th century, fire frequency and intensity/severity dramatically increased, suggesting that anthropogenic climate change, perhaps in combination with changing land use, caused unprecedented change to the fire regime at Lake Werri Berri, a trend found at a number of other sites in eastern Australia

Evolving web-based test automation into agile business specifications

Usually, test automation scripts for a web application directly mirror the actions that the tester carries out in the browser, but they tend to be verbose and repetitive, making them expensive to maintain and ineffective in an agile setting. Our research has focussed on providing tool-support for business-level, example-based specifications that are mapped to the browser level for automatic verification. We provide refactoring support for the evolution of existing browser-level tests into business-level specifications. As resulting business rule tables may be incomplete, redundant or contradictory, our tool provides feedback on coverage

Decision Counseling in Prostate Cancer Screening

No abstract available

Mind the gap: quantification of incomplete ablation patterns after pulmonary vein isolation using minimum path search

Pulmonary vein isolation (PVI) is a common procedure for the treatment of atrial fibrillation (AF). A successful isolation produces a continuous lesion (scar) completely encircling the veins that stops activation waves from propagating to the atrial body. Unfortunately, the encircling lesion is often incomplete, becoming a combination of scar and gaps of healthy tissue. These gaps are potential causes of AF recurrence, which requires a redo of the isolation procedure. Late-gadolinium enhanced cardiac magnetic resonance (LGE-CMR) is a non-invasive method that may also be used to detect gaps, but it is currently a time-consuming process, prone to high inter-observer variability. In this paper, we present a method to semi-automatically identify and quantify ablation gaps. Gap quantification is performed through minimum path search in a graph where every node is a scar patch and the edges are the geodesic distances between patches. We propose the Relative Gap Measure (RGM) to estimate the percentage of gap around a vein, which is defined as the ratio of the overall gap length and the total length of the path that encircles the vein. Additionally, an advanced version of the RGM has been developed to integrate gap quantification estimates from different scar segmentation techniques into a single figure-of-merit. Population-based statistical and regional analysis of gap distribution was performed using a standardised parcellation of the left atrium. We have evaluated our method on synthetic and clinical data from 50 AF patients who underwent PVI with radiofrequency ablation. The population-based analysis concluded that the left superior PV is more prone to lesion gaps while the left inferior PV tends to have less gaps (p<0.05 in both cases), in the processed data. This type of information can be very useful for the optimization and objective assessment of PVI interventions

Nonlinear Nanophotonic Devices in the Ultraviolet to Visible Wavelength Range

Although the first lasers invented operated in the visible, the first on-chip devices were optimized for near-infrared (IR) performance driven by demand in telecommunications. However, as the applications of integrated photonics has broadened, the wavelength demand has as well, and we are now returning to the visible (Vis) and pushing into the ultraviolet (UV). This shift has required innovations in device design and in materials as well as leveraging nonlinear behavior to reach these wavelengths. This review discusses the key nonlinear phenomena that can be used as well as presents several emerging material systems and devices that have reached the UV–Vis wavelength range