Supercapacitor assisted LDO (SCALDO) techniquean extra low frequency design approach to high efficiency DC-DC converters and how it compares with the classical switched capacitor converters

Supercapacitor assisted low dropout regulators (SCALDO) were proposed as an alternative design approach to DC-DC converters, where the supercapacitor circulation frequency (switching frequency) is in the order of few Hz to few 10s of Hz, with an output stage based on a low dropout regulator stage. For converters such as 12–5V, 5–3.3V and 5–1.5V, the technique provides efficiency improvement factors of 2, 1.33 and 3 respectively, in compared to linear converters with same input-output combinations. In a 5–1.5V SCALDO regulator, using thin profile supercapacitors in the range of fractional farads to few farads, this translates to an approximate end to end efficiency of near 90%. However, there were concerns that this patented technique is merely a variation of well-known switched capacitor (charge pump) converters. This paper is aimed at providing a broad overview of the capability of SCALDO technique with generalized theory, indicating its capabilities and limitations, and comparing the practical performance with a typical switched capacitor converter of similar current capability

Public debt and aggregate risk

This paper assesses the long-run optimal level of public debt in a framework where aggregate fluctuations are taken into account. Households are subject to both aggregate and idiosyncratic shocks and the market structure prevents them from perfectly insuring against risk. We find that the long-run optimal level of public debt is generally higher in a setting embedding aggregate fluctuations than in a setting without. Aggregate fluctuations modify both the cost and the motive for precautionary saving. Higher levels of public debt, by effectively reducing the cost of precautionary saving, help agents to smooth consumption when they face price and employment fluctuations.Public debt, aggregate risk, precautionary saving, credit constraints.

Numerical study of cold-formed steel beams subject to lateral torsional buckling

The use of cold-formed steel members as structural columns and beams in residential, industrial and commercial buildings has increased significantly in recent times. This study is focused on the use of cold-formed steel sections as flexural members subject to lateral-torsional buckling. For this purpose a finite element model of a simply supported lipped channel beam under uniform bending was developed, validated using available numerical and experimental results, and used in a detailed parametric study. The moment capacity results were then compared with the predictions from the current ambient temperature design rules in the cold-formed steel structures codes of Australia, New Zealand, North America and Europe. European design rules were found to be conservative while Australian and American design rules were unsafe. This paper presents the results of the numerical study, the comparison with the current design rules and the new proposed design rules

The Impact of Public Information on Bidding in Highway Procurement Auctions

A number of papers in the theoretical auction literature show that the release of information regarding the seller’s valuation of an item can cause bidders to bid more aggressively. This widely accepted result in auction theory remains largely untested in the empirical literature. Recent theoretical work has also shown that this effect can be more pronounced in auctions with larger common cost uncertainty. We examine the impact of a policy change by the Oklahoma Department of Transportation that led to the release of the state’s internal estimate of the costs to complete highway construction projects. We perform a differences-in-differences analysis comparing bidding in Texas, a state that had a uniform policy of revealing the same information all throughout the period of analysis, to bidding in Oklahoma. Our results show that, in comparison to Texas auctions, the average bid in Oklahoma fell after the change in engineers’ cost estimate (ECE) policy. This decline in bids was even larger for projects where the common uncertainty in costs is greater. Moreover, the within-auction standard deviation of bids fell after the change in ECE policy with the most significant decline observed again in projects with greater common cost uncertainty.Information Release, Procurement Auctions

Optoelectronic and Structural Properties of Group III-Nitride Semiconductors Grown by High Pressure MOCVD and Migration Enhanced Plasma Assisted MOCVD

The objective of this dissertation is to understand the structural and optoelectronic properties of group III-nitride materials grown by High-Pressure Metal Organic Chemical Vapor Deposition (HP-MOCVD) and Migration Enhanced Plasma Assisted MOCVD by FTIR reflectance spectroscopy, Raman spectroscopy, X-ray diffraction, and Atomic Force Microscopy. The influence of the substrates/templates (Sapphire, AlN, Ga-polar GaN, N-polar GaN, n-GaN, and p-GaN) on the free carrier concentration, carrier mobility, short-range crystalline ordering, and surface morphology of the InN layers grown on HP-MOCVD were investigated using those techniques. The lowest carrier concentration of 7.1×1018 cm-3 with mobility of 660 cm2V-1s-1 was found in the InN film on AlN template, by FTIR reflectance spectra analysis. Furthermore, in addition to the bulk layer, an intermediate InN layers with different optoelectronic properties were identified in these samples. The best local crystalline order was observed in the InN/AlN/Sapphire by the Raman E2 high analysis. The smoothest InN surface was observed on the InN film on p-GaN template. The influence of reactor pressures (2.5–18.5 bar) on the long-range crystalline order, in plane structural quality, local crystalline order, free carrier concentration, and carrier mobility of the InN epilayers deposited on GaN/sapphire by HP-MOCVD has also been studied using those methods. Within the studied process parameter space, the best material properties were achieved at a reactor pressure of 12.5 bar and a group-V/III ratio of 2500 with a free carrier concentration of 1.5x1018 cm-3, a mobility in the bulk InN layer of 270 cm2 V-1s-1 and the Raman (E2 high) FWHM of 10.3 cm-1. The crystalline properties, probed by XRD 2θ–ω scans have shown an improvement with the increasing reactor pressure. The effect of an AlN buffer layer on the free carrier concentration, carrier mobility, local crystalline order, and surface morphology of InN layers grown by Migration-Enhanced Plasma Assisted MOCVD were also investigated. Here, the AlN nucleation layer was varied to assess the physical properties of the InN layers. This study was focused on optimization of the AlN nucleation layer (e.g. temporal precursor exposure, nitrogen plasma exposure, and plasma power) and its effect on the InN layer properties

Marketing channels and internet technology used by specialty crop farmers

An online survey was used to collect data on specialty crop farms in 2010 in Louisiana. The objectives included evaluation of familiarity with the Louisiana Food MarketMaker website and the All about Blueberries website, about marketing channels used, and the adoption of electronic and Internet based technologies to assist with marketing of differentiated products. Variables included use and effectiveness of marketing channels, level of use and quality of internet service, use of Internet-based functions and applications, barriers to internet use, frequency of use and usefulness of social media and smart phones, effectiveness of and familiarity with MarketMaker and All about Blueberries websites and specific application. Generally, despite small sample size, farmer characteristics from the Louisiana survey were reasonably consistent with results from the Census of Agriculture 2007. Descriptive analysis and Logit model were used for data analysis. Results from this study can provide useful information about these new (to many farmers) technologies for marketing. Familiarity with MarketMaker was strongly associated with share of total sales from vegetable crops, farmer occupation, Internet speed as a barrier, Internet use in farming and finding markets through MarketMaker in 5 percent significant level. Social media use in farming was statistically significant in explaining familiarity with All about Blueberries website. Internet use and specialty crop acreage also were significant. In addition, large impacts on the odds ratios were found. When speed of internet service was rated as not a barrier, familiarity with MarketMaker was higher. Significant impact of coefficients on odds ratios were found for both websites. Future questionnaires could segment users based on level of activity such as initial and intermediate involvement, improved ability to use the site for partners and for research, to manage risk, and for feedback for further development of the program. Length of the survey questionnaire was a limitation

Air Flow and Rain Water Penetration Analysis on Generator Enclosures Using CFD Simulations

Rain water penetration testing on power generator units requires a number of complicated procedures, requiring many resources. As such, a Computational Fluid Dynamics (CFD) tool, FloEFD for Creo is used to study the water penetration behavior on a OM924 diesel power generator enclosure in a computational environment. First, the three governing equations in fluid dynamics are derived and explained using simple methods. Next, behavior of rain water droplets upon impact is briefly discussed. Air velocity, volumetric flow rate and static pressure drop were measured physically in the OM924 generator enclosure. Then, a CFD model for the OM924 enclosure was developed and validated using the measured data. Using the particle studies option in FloEFD, rain water penetration studies were conducted on the CFD model. The terminal velocity of the droplets was assumed as a function of droplet diameter and the co-efficient of restitution was measured using basic observational methods. In an enclosure, the water penetration can be explained using three methods; free flowing, dripping and splashing. Each of the methods was tested using water droplet diameters that ranged from 0.1 to 2.5 mm. Results verified that the current baffle plate design was capable of preventing water penetration with the exception of those droplets with the smallest diameters

Entrepreneurship, Labor Market Mobility and the Role of Entrepreneurial Insurance

This paper introduces a quantitative model with risky entrepreneurship and search frictions matching the occupational flows between entrepreneurship, paid-employment, and unemployment. We account for the general shape of these flows and key entrepreneurial and labor market features based mostly on micro CPS and SCF data. Using this model, we show that an insurance providing Self-Employment Assistance (SEA) policy mitigates the bias disfavoring self-employment inherent in unemployment insurance programs. Moreover, ability-dependent SEA programs select more productive and wealthier new entrepreneurs out of unemployment. Finally, we show that the interaction between UI design and SEA programs has a significant impact on entrepreneurship

Carbon footprint of food services at the University of Oulu

Abstract. This thesis examines the impacts of food on biodiversity and quantifies the carbon footprint of food services at the University of Oulu. It aims to provide recommendations for reducing the carbon footprint of food services and minimizing the impacts on biodiversity. The motivation for the study is that reducing the carbon footprint and biodiversity impacts of food services are necessary to achieve carbon neutrality and sustainability goals. The carbon footprint of food services at the University of Oulu was calculated as 770tCO2eq for the year 2022. Food categories identified as top contributors to carbon footprint and biodiversity impacts are meat and dairy milk products; therefore, their consumption should be reduced. To reduce carbon footprint, five scenarios were considered, each offering potential solutions. The most effective scenario involves substituting all meat and milk consumption with plant-based alternatives, resulting in a 50% reduction in the carbon footprint. Another scenario focuses on substituting 60% of meat consumption with low-carbon footprint fish, broiler, and plant-based products, leading to a 22% reduction in the carbon footprint. It is important to systematically address the substitution of high-carbon footprint food items with low-carbon footprint alternatives, in order to achieve carbon neutrality objectives. To motivate sustainable and low-carbon footprint food choices, substituting plant-based alternatives and diversifying recipes while maintaining the sensory pleasure of meals is crucial. Offering a number of vegetarian or vegan meals, price rewards, and supporting environmentally conscious suppliers are effective strategies. Good communication with restaurant providers and customers is also essential, including sharing research findings, utilizing customer feedback, and implementing innovative recipes and meal plans. Balancing customer satisfaction with climate mitigation and sustainability goals is a top priority for restaurants. Several limitations regarding the data uniformity and reliability have been identified in the study. Suggestions and recommendations were provided for successful future work and other related research studies

Continuous-time Algorithms and Analog Integrated Circuits for Solving Partial Differential Equations

Analog computing (AC) was the predominant form of computing up to the end of World War II. The invention of digital computers (DCs) followed by developments in transistors and thereafter integrated circuits (IC), has led to exponential growth in DCs over the last few decades, making ACs a largely forgotten concept. However, as described by the impending slow-down of Moore’s law, the performance of DCs is no longer improving exponentially, as DCs are approaching clock speed, power dissipation, and transistor density limits. This research explores the possibility of employing AC concepts, albeit using modern IC technologies at radio frequency (RF) bandwidths, to obtain additional performance from existing IC platforms. Combining analog circuits with modern digital processors to perform arithmetic operations would make the computation potentially faster and more energy-efficient. Two AC techniques are explored for computing the approximate solutions of linear and nonlinear partial differential equations (PDEs), and they were verified by designing ACs for solving Maxwell\u27s and wave equations. The designs were simulated in Cadence Spectre for different boundary conditions. The accuracies of the ACs were compared with finite-deference time-domain (FDTD) reference techniques. The objective of this dissertation is to design software-defined ACs with complementary digital logic to perform approximate computations at speeds that are several orders of magnitude greater than competing methods. ACs trade accuracy of the computation for reduced power and increased throughput. Recent examples of ACs are accurate but have less than 25 kHz of analog bandwidth (Fcompute) for continuous-time (CT) operations. In this dissertation, a special-purpose AC, which has Fcompute = 30 MHz (an equivalent update rate of 625 MHz) at a power consumption of 200 mW, is presented. The proposed AC employes 180 nm CMOS technology and evaluates the approximate CT solution of the 1-D wave equation in space and time. The AC is 100x, 26x, 2.8x faster when compared to the MATLAB- and C-based FDTD solvers running on a computer, and systolic digital implementation of FDTD on a Xilinx RF-SoC ZCU1275 at 900 mW (x15 improvement in power-normalized performance compared to RF-SoC), respectively