Ray optical light trapping in silicon microwires: exceeding the 2n^2 intensity limit

We develop a ray optics model of a silicon wire array geometry in an attempt to understand the very strong absorption previously observed experimentally in these arrays. Our model successfully reproduces the n^2 ergodic limit for wire arrays in free space. Applying this model to a wire array on a Lambertian back reflector, we find an asymptotic increase in light trapping for low filling fractions. In this case, the Lambertian back reflector is acting as a wide acceptance angle concentrator, allowing the array to exceed the ergodic limit in the ray optics regime. While this leads to increased power per volume of silicon, it gives reduced power per unit area of wire array, owing to reduced silicon volume at low filling fractions. Upon comparison with silicon microwire experimental data, our ray optics model gives reasonable agreement with large wire arrays (4 μm radius), but poor agreement with small wire arrays (1 μm radius). This suggests that the very strong absorption observed in small wire arrays, which is not observed in large wire arrays, may be significantly due to wave optical effects

The Disclosure Practices of Realtors when Selling Property Adjacent to U.S. Army Corps of Engineers Lakes: A Study of Lake Hartwell

The U.S. Army Corps of Engineers manages over 400 lakes across the United States. In addition to managing their creation purposes, like flood control and hydropower generations, the Corps manages shoreline use of over 12 million acres of land surrounding these lake. Lake Hartwell, located on the Savannah River between South Carolina and Georgia, is one of the most developed. However, there is little research on how lake adjacent property owners are educated on the rules they face when using the shoreline. This study focused on real estate agents in the Lake Hartwell area and how they facilitate the transfer of information about the Corps of Engineers to lakefront buyers. While there is nothing in state law requiring that such information be disclosed, real estate agents are marketing properties using the amenities the Corps provides, and buyers have an interest in understanding the effect Corps regulations can have on their use of the lake and the value of their property

Photoelectrochemical water splitting: silicon photocathodes for hydrogen evolution

The development of low cost, scalable, renewable energy technologies is one of today's most pressing scientific challenges. We report on progress towards the development of a photoelectrochemical water-splitting system that will use sunlight and water as the inputs to produce renewable hydrogen with oxygen as a by-product. This system is based on the design principle of incorporating two separate, photosensitive inorganic semiconductor/liquid junctions to collectively generate the 1.7-1.9 V at open circuit needed to support both the oxidation of H_2O (or OH^-) and the reduction of H^+ (or H_2O). Si microwire arrays are a promising photocathode material because the high aspect-ratio electrode architecture allows for the use of low cost, earth-abundant materials without sacrificing energy-conversion efficiency, due to the orthogonalization of light absorption and charge-carrier collection. Additionally, the high surfacearea design of the rod-based semiconductor array inherently lowers the flux of charge carriers over the rod array surface relative to the projected geometric surface of the photoelectrode, thus lowering the photocurrent density at the solid/liquid junction and thereby relaxing the demands on the activity (and cost) of any electrocatalysts. Arrays of Si microwires grown using the Vapor Liquid Solid (VLS) mechanism have been shown to have desirable electronic light absorption properties. We have demonstrated that these arrays can be coated with earth-abundant metallic catalysts and used for photoelectrochemical production of hydrogen. This development is a step towards the demonstration of a complete artificial photosynthetic system, composed of only inexpensive, earth-abundant materials, that is simultaneously efficient, durable, and scalable

Western Kentucky University Stormwater Utility Survey 2023

The main goal of this survey is to identify as many U.S. Stormwater Utilities (SWUs) as possible. Because many stormwater professionals do not have the time to respond to questionnaires, our primary method of identification was Internet searches. We searched key terms such as “stormwater utility”, “stormwater fee”, and “drainage fee”. We scoured online municipal codes such as Municode, AmLegal, Sterling, LexisNexis, General Code, and others. We searched through many city web websitesing to find utilities. We have also had many people contact me to update fees and identify new utilities. However, the data primarily comes from Internet sources and is prone to errors. Some community websites are not very clear on whether the fee given is monthly, bi-monthly, quarterly, or annually. In cases like that, we made the best guess we could. We hope the readers of this document will continue to help us correct mistakes. However, it is difficult to keep up with fee changes in more than 2000 utilities, so if you discover errors in our data please contact me at [email protected]

Public libraries, museums and physical convergence. Context, issues, opportunities: a literature review. Part 2

There has recently been a growth in physical convergence in cultural heritage domains. The second of a two-part article that considers this trend with particular regard to public libraries and museums provides an overview of factors to be considered by those planning or developing physically converged services. This has been achieved through thematic analysis of a review of international literature from both domains. It begins with consideration of obstacles to convergence, ethical challenges, organisational and strategic complexity, organisational culture and resistance. It moves on to discuss factors, general and physical, that can lead to success in convergence: vision, strategy and planning, communication and trust, for example, and, how these can be led and managed. It also considers the role of professional education and training, the benefits of convergence, for example, improved cultural offer and visibility, financial savings, with viewpoints from around the world. Part 2 ends with a critical note on the ‘convergence narrative’, and a conclusion that focuses on physical convergence which draws on both Parts

Beta: Bioprinting engineering technology for academia

Higher STEM education is a field of growing potential, but too many middle school and high school students are not testing proficiently in STEM subjects. The BETA team worked to improve biology classroom engagement through the development of technologies for high school biology experiments. The BETA project team expanded functionality of an existing product line to allow for better student and teacher user experience and the execution of more interesting experiments. The BETA project’s first goal was to create a modular incubating Box for the high school classroom. This Box, called the BETA Box was designed with a variety of sensors to allow for custom temperature and lighting environments for each experiment. It was completed with a clear interface to control the settings and an automatic image capture system. The team also conducted a feasibility study on auto calibration and dual-extrusion for SE3D’s existing 3D bioprinter. The findings of this study led to the incorporation of a force sensor for auto calibration and the evidence to support the feasibility of dual extrusion, although further work is needed. These additions to the current SE3D educational product line will increase effectiveness in the classroom and allow the target audience, high school students, to better engage in STEM education activities

Are U.S. Congregations Patching the Social Safety Net? Trends from 1998 to 2012

As social services become increasingly privatized amid a federal policy environment that provides a means-tested, temporary social safety net, there is potential for a larger contribution by congregations as social service providers. Using data from a nationally representative sample of religious congregations collected in 1998, 2006, and 2012, we examine whether congregations have increased service activity over time, and whether provision varies by the congregation’s community-level context. We find that post-Great Recession, congregations are more likely to engage in broad social services and in “core” services that address basic economic needs. Congregations in high-poverty neighborhoods were less likely to provide services in 1998 than congregations in low-poverty neighborhoods; after the recession, not only are significantly more congregations in high-poverty neighborhoods providing services than in 1998, they have closed the gap with congregations in low-poverty neighborhoods and are equally likely to be providing any services regardless of neighborhood poverty. Our findings highlight the importance of service measurement to determine the prevalence of congregation-level service provision and suggest that congregational service provision may be a substantial yet inadequate substitute for the public safety net

Public libraries, museums and physical convergence: Context, issues, opportunities: A literature review Part 1

There has recently been a growth in physical convergence in cultural heritage domains. Part 1 examines this ‘trend’, its drivers and related issues, with particular focus on public libraries and museums. It offers an overview of practice, challenges and opportunities. Through thematic analysis of a comprehensive, literature review of both domains that looked at the wider aspects of collaboration, cooperation, partnerships and integration in the sector as well as physical convergence, it provides insight into background, theory and activities worldwide. It presents discussion on the meaning of convergence, the concept of ‘memory institutions’, the relationship between public libraries and museums in the context of convergence, shared mission and values, convergence and re-convergence, and professionalism and divergence. It concludes with consideration of practical aspects such as motivations for convergence, including digital technology, changing user expectations and culture, and economic and political challenges that impact on physical convergence in a dynamic local government environment

pH-Independent, 520 mV Open-Circuit Voltages of Si/Methyl Viologen^(2+/+) Contacts Through Use of Radial n^+p-Si Junction Microwire Array Photoelectrodes

The effects of introducing an n^+-doped emitter layer have been evaluated for both planar Si photoelectrodes and for radial junction Si microwire-array photoelectrodes. In contact with the pH-independent, one-electron, outer-sphere, methyl viologen redox system (denoted MV^(2+/+)), both planar and wire array p-Si photoelectrodes yielded open-circuit voltages, V_(oc), that varied with the pH of the solution. The highest V_(oc) values were obtained at pH = 2.9, with V_(oc) = 0.53 V for planar p-Si electrodes and V_(oc) = 0.42 V for vapor−liquid−solid catalyzed p-Si microwire array samples, under 60 mW cm^(−2) of 808 nm illumination. Increases in the pH of the electrolyte produced a decrease in V_(oc) by approximately −44 mV/pH unit for planar electrodes, with similar trends observed for the Si microwire array electrodes. In contrast, introduction of a highly doped, n^+ emitter layer produced V_(oc) = 0.56 V for planar Si electrodes and V_(oc) = 0.52 V for Si microwire array electrodes, with the photoelectrode properties in each system being essentially independent of pH over six pH units (3 < pH < 9). Hence, formation of an n^+ emitter layer not only produced nearly identical photovoltages for planar and Si microwire array photoelectrodes, but decoupled the band energetics of the semiconductor (and hence the obtainable photovoltage) from the value of the redox potential of the solution. The formation of radial junctions on Si microwire arrays thus provides an approach to obtaining Si-based photoelectrodes with high-photovoltages that can be used for a variety of photoelectrochemical processes, including potentially the hydrogen evolution reaction, under various pH conditions, regardless of the intrinsic barrier height and flat-band properties of the Si/liquid contact