Browsing by Subject "storage"

Now showing 1 - 6 of 6
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    The Applications of Workload Characterization in The World of Massive Data Storage
    (2015-08) He, Weiping
    The digital world is expanding exponentially because of the growth of various applications in domains including scientific fields, enterprise environment and internet services. Importantly, these applications have drastically different storage requirements including parallel I/O performance and storage capacity. Various technologies have been developed in order to better satisfy different storage requirements. I/O middleware software, parallel file systems and storage arrays are developed to improve I/O performance by increasing I/O parallelism at different levels. New storage media and data recording technologies such as shingled magnetic recording (SMR) are also developed to increase the storage capacity. This work focuses on improving existing technologies and designing new schemes based on I/O workload characterizations in corresponding storage environments. The contributions of this work can be summarized into four pieces, two on improving parallel I/O performance and two on increasing storage capacity. First, we design a comprehensive parallel I/O workload characterization and generation framework (called PIONEER) which can be used to synthesize a particular parallel I/O workload with desired I/O characteristics or precisely emulate a High Performance Computing (HPC) application of interest. Second, we propose a non-intrusive I/O middleware (called IO-Engine) to automatically improve a given parallel I/O workload in Lustre which is a widely used HPC or parallel I/O system. IO-Engine can explore the correlations between different software layers in the deep I/O path, as well as workload patterns at runtime to transparently transform the workload patterns and tune related I/O parameters in the system. Third, we design several novel static address mapping schemes for shingled write disks (SWDs) to minimize the write amplification overhead in hard drives adopting SMR technology. Fourth, we propose a track-level shingled translation layer (T-STL) for SWDs with hybrid update strategy (in-place update plus out-of-place update). T-STL uses dynamic address mapping scheme and performs garbage collection operations by migrating selected disk tracks. This scheme can provider larger storage capacity and better overall performance with the same effective storage percentages when compared to the static address mapping schemes.
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    Bearingless AC Homopolar Machine Design and Control for Distributed Flywheel Energy Storage
    (2015-06) Severson, Eric
    The increasing ownership of electric vehicles, in-home solar and wind generation, and wider penetration of renewable energies onto the power grid has created a need for grid-based energy storage to provide energy-neutral services. These services include frequency regulation, which requires short response-times, high power ramping capabilities, and several charge cycles over the course of one day; and diurnal load-/generation-following services to offset the inherent mismatch between renewable generation and the power grid's load profile, which requires low self-discharge so that a reasonable efficiency is obtained over a 24 hour storage interval. To realize the maximum benefits of energy storage, the technology should be modular and have minimum geographic constraints, so that it is easily scalable according to local demands. Furthermore, the technology must be economically viable to participate in the energy markets. There is currently no storage technology that is able to simultaneously meet all of these needs. This dissertation focuses on developing a new energy storage device based on flywheel technology to meet these needs. It is shown that the bearingless ac homopolar machine can be used to overcome key obstacles in flywheel technology, namely: unacceptable self-discharge and overall system cost and complexity. Bearingless machines combine the functionality of a magnetic bearing and a motor/generator into a single electromechanical device. Design of these machines is particularly challenging due to cross-coupling effects and trade-offs between motor and magnetic bearing capabilities. The bearingless ac homopolar machine adds to these design challenges due to its 3D flux paths requiring computationally expensive 3D finite element analysis. At the time this dissertation was started, bearingless ac homopolar machines were a highly immature technology. This dissertation advances the state-of-the-art of these machines through research contributions in the areas of magnetic modeling, winding design, control, and power-electronic drive implementation. While these contributions are oriented towards facilitating more optimal flywheel designs, they will also be useful in applying the bearingless ac homopolar machine in other applications. Example designs are considered through finite element analysis and experimental validation is provided from a proof-of-concept prototype that has been designed and constructed as a part of this dissertation.
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    Data for: Catalytic Resonance Theory: Negative Dynamic Surfaces for Programmable Catalysts
    (2021-08-14) Gathmann, Sallye R; Ardagh, M Alexander; Dauenhauer, Paul J; hauer@umn.edu; Dauenhauer, Paul J; Dauenhauer Group
    Catalysts that change with time via programmed variation of their electronic occupation to accelerate surface reactions were evaluated in the case of negative adsorption energy scaling relations. Defined as the relative change in adsorption enthalpy, the gamma linear scaling parameter is negative when two adsorbates alternatively weaken and strengthen as catalysts are electronically perturbed. Simulations were conducted of a single transition state connecting two generic adsorbates representative of multiple reaction classes to understand the resulting negative gamma catalytic ratchet mechanism and its ability to accelerate catalytic reactions above the Sabatier peak and away from equilibrium. Relative to conventional positive gamma catalytic ratchets, the Sabatier volcanoes of negative gamma catalysis are narrower with greater enhancement of dynamic turnover frequency when catalysts are electronically oscillated. Promotion of the catalytic surface reaction forwards or backwards was predictable by a descriptor accounting for the relative rates of forward and reverse kinetics under oscillatory conditions.
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    The Effect of Annual and Seasonal Variation in Precipitation on Temporal Water Storage Dynamics in Six Headwater Peatland Catchments: Marcell Experimental Forest, Minnesota
    (2023-06) Adams, David
    Using data collected from six headwater peatland catchments at the Marcell Experimental Forest in northern Minnesota, I assessed the relationship between variability in annual precipitation and annual changes in catchment water storage. Three hypotheses are addressed; (1) annual variability in precipitation is a primary driver of catchment storage change, (2) years of below average precipitation drive the relationship between precipitation and catchment water storage change, and (3) winter and fall precipitation variability are significant seasonal drivers of the annual catchment water storage change. The above relationships were analyzed via cross-correlation lag analysis and linear regression analysis of long-term precipitation, peatland water table elevation (WTE), and upland soil moisture (SM) time series, where WTE and SM served to quantify catchment water storage. Results indicate strong correlations between annual water storage change and annual precipitation variability, both in contemporaneous and antecedent years. Concurrent fall precipitation and antecedent winter precipitation were found to have the most influence on a given year’s water storage change. Years in which precipitation fell below the catchment average (dry years) exhibited a moderately significant linear relationship with annual catchment water storage change. Results of the above analysis were used to create a series of multivariate linear regression models, both with and without moving-average (MA) errors; these models were able to explain between approximately 50% and 70% of the variance found in the annual water storage change time series. Boreal peatlands play a vital role in the planet’s carbon cycle; developing a better understanding of the hydrologic function of these environments will likely prove important to future climate management practices.
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    Evaluation of the Chemical and Functional Stability of Intermediate Wheatgrass (Thinopyrum intermedium) over Storage and in Response to Steam Treatment
    (2018-12) Mathiowetz, Amy
    Annual crop farming is degrading the environment at a faster rate than it can be restored, causing soil erosion and water run-off with subsequent loss of nutrients and biodiversity. Yet, the world population currently relies on annual cereal grains to supply 40% of their calorie needs and 60% of their protein needs. The high dietary demand for cereal grains, together with the high rate of soil degradation from annual farming and growing consumer interest in sustainably-sourced food creates space in the market for a more sustainable grain. Perennial intermediate wheatgrass (IWG), Thinopryum intermedium, is a promising grain to fulfill this role, owing to its good flavor, breeding potential, and superior environmental benefits due to its extensive root system and long growing season. Understanding the storage stability of IWG and identifying ways to improve its stability will not only help incentivize farmers to plant IWG, but will also help make IWG competitive against existing grains on the market. The objectives of this study were: (1) evaluate the effect of steam treatment on antioxidant content and activity, enzyme activity, and progression of hydrolytic and oxidative rancidity in IWG compared to hard red wheat (HRW) over storage at different temperatures; (2) evaluate the effect of steam treatment of IWG grains on the functionality of its whole flour over storage at different temperatures; (3) determine the overall safety of the grains by assessing presence of chemical residues, such as pesticides and mycotoxins, heavy metals, allergens, and anti-nutrient factors. Pre-storage, compositional analysis of IWG and HRW was carried out following official AOAC and AACCI methods. Steam treatment was carried out by subjecting 30 g aliquots of IWG and HRW groats to 100°C and 95% relative humidity conditions in a proofing oven for 60 minutes. Steamed and non-steamed samples were stored at 45°C, ambient (22 ± 2°C), and 4°C at 0.43 water activity for 6 weeks, 6 months, and 12 months respectively. Samples were analyzed periodically for lipoxygenase and lipase activity, hydroxycinnamic acid content, carotenoid content, antioxidant activity, and indicators of hydrolytic and oxidative rancidity, including free fatty acids and hydroperoxides, respectively. Lipoxygenase activity pre- and post-steam treatment was analyzed using the ferrous oxidation-xylenol orange (FOX) assay, and lipase activity was determined spectrophotometrically using a copper soap assay. Hydroxycinnamic acids and carotenoids were quantified using high performance liquid chromatography. Antioxidant activity pre- and post-steam treatment was analyzed using 1,1-Diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging and leucomethylene blue (LMB) assays. Free fatty acids and hydroperoxides were quantified according to AOAC titration methods 940.28 and 965.33, respectively. Functionality parameters were also measured at the beginning, middle, and end of storage at each storage temperature. Rheological and mixing properties were assessed using a Farinograph® and a texture analyzer equipped with a Kieffer rig. Starch pasting properties were monitored using a MicroVisco-Amylograph®. Bread baking tests were performed according to AACCI 10-10.03 method. IWG had significantly higher protein, insoluble fiber, and fat content than HRW, along with a higher lipase activity. HRW had a relatively higher lipoxygenase activity than IWG. IWG also had significantly higher hydroxycinnamic acid and carotenoids concentrations than HRW, along with higher antioxidant activity. The steam treatment employed in the present study did not inactivate lipoxygenase and lipase. Throughout storage, lipase activity significantly decreased in non-steamed grains over ambient (22 ± 2°C) storage but otherwise was retained over accelerated (45°C) and refrigerated (4°C) storage. However, an after-ripening effect was evident in lipoxygenase activity at ambient and 45°C temperatures, with significant increases in activity over storage. Hydroxycinnamic acid content was retained throughout storage, with prolonged storage inducing increases to its content, as well as increases to antioxidant activity at higher storage temperatures. Carotenoid content decreased throughout storage in IWG and HRW, to a greater degree at higher storage temperatures, as was expected due to its high susceptibility to oxidation. Development of oxidative and hydrolytic rancidity in IWG was minimal throughout storage of groats. Although the steam treatment was not able to effective in inactivating enzymes, it demonstrated a minimal, but positive effect on antioxidant activity and content, as well as a slight inhibitory effect on hydroperoxide formation over storage. IWG demonstrated a significantly higher antioxidant content and antioxidant activity and lower hydroperoxide content than HRW throughout storage. In terms of hydrolytic rancidity, IWG showed higher lipase activity and free fatty acid concentration than HRW throughout storage. IWG showed increases to dough development time, resistance to extension, and loaf volumes over storage, denoting an increase in dough strength, although no significant increases to dough stability time were evident. IWG also had improvements to starch pasting viscosities over storage, including peak viscosity and hold viscosity, at all temperatures. The effects of steaming on functionality were temperature-dependent, with positive effects on dough development time and resistance to extension during storage at 45°C and improvements to starch pasting viscosities during storage at ambient temperature. Steaming appeared to have a negative impact on functionality at refrigerated storage temperatures. Steaming did not have an effect on bread loaf volumes of IWG over storage. Although overall functionality of IWG remained inferior to HRW throughout storage, HRW had significant decreases in several functionality parameters over storage. While steaming had a positive effect on some of these parameters (e.g. extensibility, loaf volume), it had a negative impact on others (e.g. starch pasting viscosities). Bread firmness was not significantly affected over storage in either grain. The present study was the first to evaluate the storage stability of IWG and investigate steam treatment as a mode of improving storage stability of IWG. The results of the study provide additional incentives to farmers and food manufacturers alike by highlighting IWG’s competitive storage stability. The present study demonstrated not only its high tolerance to storage but in some regards, its positive response to storage. Furthermore, this research formed the foundation for establishing a more effective method of steam treatment in a currently ongoing storage study on IWG flour.
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    Storage stability of a commercial spray dried hen egg yolk powder
    (2016-03) Guo, Mufan
    Dehydration is a good process approach for food preservation. However, dried food products may still suffer from deterioration if store in an abused environment such as high humidity (water activity (aw) > 0.6) and/or high temperature (> 45°C). These storage conditions can induce undesirable chemical reactions (disulfide bond interactions, Maillard reaction and/or lipid oxidation), resulting in a significant decrease in food quality. In this study, the storage stability of a commercial spray-dried egg yolk powder was evaluated. The dried egg yolk powder (DEY) was stored at three temperatures (room temperature, 35°C, and 45°C) and at six aw (0.05, 0.12, 0.37, 0.44, 0.54, 0.66) for at least two months, and several physicochemical changes and extent of protein aggregation were measured. The overall color change of DEY was that it became slightly darker (decrease of L* value), more red (increase of a* value), and less yellow (decrease of b* value) with increased storage time. The reaction kinetics of the L* value of DEY was also calculated using a first-order hyperbolic model. Its Q10 (rate increase with temperature increase at 10°C) was 2.9, which was more indicative of lipid oxidation, and the Ea (activation energy) was around 83 kJ/mole. The color change was mostly due to the browning pigments that were produced from the Maillard reaction and lipid oxidation. The glucose content went to zero after one-week during storage at 45°C at an aw of 0.66, confirming the occurrence of the Maillard reaction. The peroxide value of DEY storage at 45°C at aw of 0.66 was significantly increased compared to the control (vacuum packaged at -20°C), proving the occurrence of lipid oxidation. In addition, the Maillard reaction products and lipid oxidation products were both detected using the front face fluorescence spectrometer. After storage at an aw of 0.66 at 45°C for 8 weeks, protein solubility of DEY in TBS-SDS buffer [Tris-buffered saline (TBS: 20 mM Tris and 500 mM sodium chloride, pH 7.5) containing 1% sodium dodecyl sulfate (SDS, g/ml)] decreased to ~ 78% compared with that of the original DEY. Formations of buffer-soluble and –insoluble protein aggregates were discovered using SDS-PAGE. The protein aggregates were mainly formed through unfolded intermediates and unfolded states as well as direct chemical linkages. The proteins in DEY were all denatured after storage at an aw of 0.66 at 45°C for 8 weeks, resulting in numerous unfolded intermediates and states that could interact with each other to form aggregates. The spray drying process during the manufacturing of DEY also caused denaturation of protein, which explained the detection of buffer-insoluble protein aggregates in the original sample. Increases of disulfide bond links and protein-lipid interaction during storage were also found using techniques such as Raman spectrometry, fourier transform infrared spectroscopy, and front-face fluorescence spectrometry, indicating that some of the protein aggregates were induced by chemical reactions. The high molecular weight protein aggregates (HMWPAs) were further evaluated. Results showed that 32 proteins were involved with formation of buffer-soluble and -insoluble HMWPAs. They were products of natural egg yolk proteins and egg white proteins including serum albumin, vitellogenin, apovitellenin, as well as ovotansferrin, ovalbumin, lysozyme, ovomucoid, and ovastatin. Most of them contain disulfide bonds and some of them contain ligand and fatty acid binding sites, which corresponded with the theory of the direct chemical linkages induced protein aggregates. Overall, physicochemical changes and protein aggregates were found during the storage of DEY and it is mostly due to three undesirable chemical reactions, i.e., disulfide bond interactions, the Maillard reaction and/or lipid oxidation. Therefore, most effective approaches to reduce and/or inhibit the occurrence of those reactions include adjusting storage temperature and humidity as well as vacuum packaging after drying.