FRAM based low power systems for low duty cycle applications

Thesis (M.S.) University of Alaska Fairbanks, 2019Ferro-Electric Random Access Memory (FRAM) is a leap forward in non-volatile data storage technology for embedded systems. It allows for persistent storage without any power consumption, fulfilling the same role as flash memory. FRAM, however, provides several major advantages over flash memory, which can be leveraged to substantially reduce sleep current in a device. In applications where most of the time is spent sleeping these reductions can have a large impact on the average current. With careful design sleep currents as low as 72 nA have been demonstrated. A lower current consumption allows for more flexibility in deploying the device; smaller batteries or alternative power sources can be considered, and operating life can be extended. FRAM is not appropriate for every situation and there are some considerations to obtain the maximum benefit from its use. An MSP430FR2311 microcontroller is used to measure the performance of the FRAM and how to structure a program to achieve the lowest power consumption. Clock speed and instruction caching in particular have a large effect on the power consumption and tests are performed to quantify their effect. Two case studies are considered, a feedback control system and a data logger. Both cases involve large amounts of data writes and allow for the effects of the FRAM to be easily observed. Expected battery life is determined for each case when the sample rate is varied, suggesting that average operating current for the two solutions will nearly converge when the sampling period exceeds 1000 s. For sampling periods on the order of one second operating current can be reduced from 15.4 μA to 730 nA by utilizing FRAM in lieu of flash

Predicting switchgrass biomass and ethanol potential on claypan soil landscapes

Switchgrass (Panicum virgatum L.) yield on claypan soils was evaluated with a crop growth model and for actual ethanol production potential. Specifically, Agricultural Land Management Alternatives with Numerical Assessment Criteria (ALMANAC) was evaluated for switchgrass production on claypan soils. Switchgrass was established on the Soil Productivity and Resource Conservation (SPARC) plots near Columbia, MO in 2009. ALMANAC soil inputs were modified with soil texture and bulk density from measured soil samples. ALMANAC results were compared to yearly SPARC measured switchgrass yields and consistently underestimated yields. Yield simulated by repeating a single weather year was cyclical for consecutive years based on three of the four weather year patterns. The model was run over a 30-year simulation period where mean simulated yields matched mean measured yields only when model N-rates were increased to levels greater than actual. Model yields did not increase with increased DTC as was observed with measured results for drier than average years of precipitation. ALMANAC simulated results were closer to measured results when harvest dates were artificially made earlier in the fall and N-rates were increased above actual application amounts. From the SPARC switchgrass plots Biomass was analyzed with near-infrared spectroscopy (NIRS). NIRS was used to determine 20 compositional parameters and predict actual ethanol yield. The ethanol yield was then multiplied by the biomass yield to determine ethanol production. Switchgrass ethanol production increased with greater DTC and N-rates for years with drier than average years of precipitation. Ethanol yield decreased at greater DTC for the driest years

A macroeconometric analysis of South Africa’s post-liberalisation capital inflow components

Includes bibliographical references.In common with emerging countries in Asia and Latin America, South Africa received substantial capital inflows following socio-political and financial liberalisation in the mid-1990s. However, unlike many other emerging countries, the bulk of South Africa’s post-liberalisation inflows have been in the traditionally short-term forms of portfolio and other investment. Hence, in this thesis, a macroeconometric analysis of South Africa’s post-liberalisation capital flow components is conducted to investigate the extent to which their divergent impacts have complicated, or even rendered impotent, the dual policy goals of attracting capital inflows on the one hand, while mitigating any significant detrimental impacts on the other. The results of the analysis show that foreign direct investment is responsive to domestic factors, while portfolio and other flows respond to a combination of domestic and foreign factors. However, domestic business cycle fluctuations are found to have a greater effect on the capital outflows than the capital inflows, and are thus associated with heightened capital flight and repatriation during expansionary phases. Although the capital flow components are found to have varied effects on South Africa’s macroeconomy, transmission mechanisms, nominal Rand/U.S. Dollar exchange rate, and economic growth dynamics, the ‘hot’ flows are found to demonstrate greater boom-bust characteristics compared to foreign direct investment. Conventional economic theory posits that the destabilising effects can be controlled using fiscal and monetary policy mechanisms. However, analysis of the cyclical relationships between the capital flows and fiscal policy finds that net direct investment and net other investment tend to be counter-cyclically associated with fiscal policy, while net portfolio investment tends to be acyclical, indicating that the bulk of South Africa’s net capital inflows do not have a significant cyclical relationship with fiscal policy. In addition, net direct investment and net other investment are found to have inconsistent cyclical relationships with monetary policy, while net portfolio investment tends to be procyclical. Thus, this research finds that although South Africa has been able to use exchange rate flexibility and sterilisation to neutralise the early stages of capital inflows, the divergent characteristics of the country’s post-liberalisation capital flow components have limited the fiscal and monetary policy options available to mitigate the detrimental capital flow effects arising from structural factors

Dense spectrum of resonances and spin-1/2 particle capture in a near-black-hole metric

We show that a spin-1/2 particle in the gravitational field of a massive body of radius R which slightly exceeds the Schwarzschild radius r_s, possesses a dense spectrum of narrow resonances. Their lifetimes and density tend to infinity in the limit R -> r_s. We determine the cross section of the particle capture into these resonances and show that it is equal to the spin-1/2 absorption cross section for a Schwarzschild black hole. Thus black-hole properties may emerge in a non-singular static metric prior to the formation of a black hole.Comment: 6 pages, submitted to PR

Resonant scattering of light in a near-black-hole metric

We show that low-energy photon scattering from a body with radius R slightly larger than its Schwarzschild radius r_s resembles black-hole absorption. This absorption occurs via capture to one of the many long-lived, densely packed resonances that populate the continuum. The lifetimes and density of these meta-stable states tend to infinity in the limit r_s -> R. We determine the energy averaged cross-section for particle capture into these resonances and show that it is equal to the absorption cross-section for a Schwarzschild black hole. Thus, a non-singular static metric may trap photons for arbitrarily long times, making it appear completely `black' before the actual formation of a black hole.Comment: 6 pages, 4 figure

Dense spectrum of resonances and particle capture in a near-black-hole metric

We show that a quantum scalar particle in the gravitational field of a massive body of radius R which slightly exceeds the Schwarzschild radius r_s, possesses a dense spectrum of narrow resonances. Their lifetimes and density tend to infinity in the limit R -> r_s. We determine the cross section of the particle capture into these resonances and show that it is equal to the absorption cross section for a Schwarzschild black hole. Thus, a non-singular static metric acquires black-hole properties before the actual formation of a black hole.Comment: 6 pages, 6 figures, accepted for publication in Physical Review

Rigor and Relevance: Enforcing dialogue between media management research and practice

There is a strong demand in media management to strengthen the bridge between theory and practice. Following the debate on rigor and relevance, the approach of engaged scholarship and arguments from our community, we see the need to develop a research agenda in dialogue with practice. Therefore, we explore the following questions: Which topics do media managers consider relevant to research? How can these issues be contrasted with the research agendas proclaimed by media management research? To answer these questions, we first summarize current issues in media management research through a literature review. Second, current issues in media management practice are captured based on an online survey with German media managers (N=46). Finally, the two perspectives are contrasted to develop relevant questions for media management research and practice