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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Real-Time Communication over Wormhole-Switched On-Chip Networks

Liu, Meng January 2017 (has links)
In a modern industrial system, the requirement on computational capacity has increased dramatically, in order to support a higher number of functionalities, to process a larger amount of data or to make faster and safer run-time decisions. Instead of using a traditional single-core processor where threads can only be executed sequentially, multi-core and many-core processors are gaining more and more attentions nowadays. In a multi-core processor, software programs can be executed in parallel, which can thus boost the computational performance. Many-core processors are specialized multi-core processors with a larger number of cores which are designed to achieve a higher degree of parallel processing. An on-chip communication bus is a central intersection used for data-exchange between cores, memory and I/O in most multi-core processors. As the number of cores increases, more contention can occur on the communication bus which raises a bottleneck of the overall performance. Therefore, in order to reduce contention incurred on the communication bus, a many-core processor typically employs a Network-on-Chip (NoC) to achieve data-exchange. Real-time embedded systems have been widely utilized for decades. In addition to the correctness of functionalities, timeliness is also an important factor in such systems. Violation of specific timing requirements can result in performance degradation or even fatal problems. While executing real-time applications on many-core processors, the timeliness of a NoC, as a communication subsystem, is essential as well. Unfortunately, many real-time system designs over-provision resources to guarantee the fulfillment of timing requirements, which can lead to significant resource waste. For example, analysis of a NoC design yields that the network is already saturated (i.e. accepting more traffic can incur requirement violation), however, in reality the network actually has the capacity to admit more traffic. In this thesis, we target such resource wasting problems related to design and analysis of NoCs that are used in real-time systems. We propose a number of solutions to improve the schedulability of real-time traffic over wormhole-switched NoCs in order to further improve the resource utilization of the whole system. The solutions focus mainly on two aspects: (1) providing more accurate and efficient time analyses; (2) proposing more cost-effective scheduling methods.
72

The Effect of the Antecedent Dry Conditions on Nitrogen Removal for a Modified Bioretention System

Peterson, Mackenzie 02 November 2016 (has links)
Eutrophication is defined as the ‘over enrichment’ of a water body from nutrients, resulting in uncontrolled growth of primary producers, leading to periods of oxygen depletion from decomposition of the algal organic matter. According to the 2010 Water Infrastructure Needs and Investment (a U.S. Congressional Report), 40% of U.S. water bodies are contaminated with pollutants, including nutrients. Non-point sources of nutrient pollution are a major cause of this reduction in water quality. One way to decrease eutrophication is to manage nutrients found in stormwater runoff, before they reach a receiving water body. Bioretention cells containing an internal water storage zone (IWSZ) have been shown to remove higher amounts of nitrogen than conventional cells (without an IWSZ). The IWSZ contains an organic carbon substrate, usually derived from wood chips submerged in water, which supports the biochemical process of denitrification. Characteristics of wood chips that affect nitrogen removal include carbon content (%), leaching of dissolved organic carbon (DOC), and wood chip size and type. However, there is limited information on how the intermittent hydraulic loading that is associated with these field systems impacts their performance. Accordingly, the overall goal of this research is to improve understanding of the effect that the antecedent dry conditions (ADC) have on the performance of a field scale bioretention cell modified to contain an IWSZ. The nine different types of wood chips used in laboratory and field studies identified in the literature were categorized as hardwood and softwood. Literature showed that total organic carbon (TOC) leached from softwood chips is almost double the TOC measured from the hardwood chips, 138.3 and 70.3 mg/L, respectively. The average observed nitrogen removal for softwood chips was found to be greater than the removal for the average of the hardwood chips (75.2% and 63.0%, respectively). Literature also suggests that larger wood chip size may limit the availability of the carbon for the denitrifying organisms and provides less surface area for the biofilm growth. A field study conducted for this research compared the performance of a modified bioretention system designed to enhance denitrification, addition of an IWSZ, with a conventional system that does not contain an IWSZ. Fourteen storm events were completed from January 2016 to July 2016 by replicating storm events previously completed in the laboratory using hydraulic loading rates (HLR) of 6.9 cm/h, 13.9 cm/h, and 4.1 cm/h. The goal was to have results from storm events with ADCs of two, four, and eight days, with the varying durations of hydraulic loading of two, four, and six hours. Synthetic stormwater, simulating nitrogen levels common in urban runoff, was used as the system’s influent to assist in running a controlled experiment. The resultant ADCs ranged from 0 to 33 days, with the average ADC being 9 days. The fourteen sets of influent samples were averaged to obtain mean influent concentrations for the synthetic stormwater. These values were used when calculating the percent nitrogen removal for the four measured nitrogen species (NOx – N, NH4+– N, organic N, and TN). The field storm events were separated into three groups based on HLR and duration to eliminate the affects of both variables on nitrogen removal for these results, since the focus is the ADC. For the low HLR (4.1 cm/hr), there were four storm events (ADCs of 4 to 33 days), as the ADC increased, greater percentages of ammonium – nitrogen, organic nitrogen, and total nitrogen were removed. For nitrate/nitrite – nitrogen, the percent removal was rather consistent for all four storm events, not significantly increasing or decreasing with changes in the ADC. There were five storm events (ADCs of 0 to 28 days) tested with the median HLR (6.9 cm/hr), nitrogen removal for all four species increased as the ADC increased. The increase was significant (p0.05) for nitrate/nitrite – nitrogen. The third group also contained five storm events (ADCs from 0 to 11 days) that were tested with the highest HLR (13.9 cm/hr). Ammonium – nitrogen, nitrate/nitrite – nitrogen, and total nitrogen all increased with the ADC, and organic nitrogen removal decreased with the increasing ADC. As a result, this research concluded that the difference in HLR affects the nitrogen removal efficiency, but overall increasing the ADC increased nitrogen removal for NOx – N, NH4+ - N, organic N, and TN.
73

Development and Application of Membraneless Electron Microscopy

Batra, Nitin M 21 November 2019 (has links)
Transmission electron microscopy (TEM) is an important tool for the characterization of materials as it can provide clear understanding of the relationship between structure, property and composition of nanomaterials. For this, the in-situ TEM analysis is performed and requires specially manufactured sample holders. In particular, those designed to carry out electrical biasing can be used to understand not just the I-V characteristics but also the failure mechanism, structure-property relationship, Joule heating dynamics, electromigration, field emission properties, etc. at the nanoscale. The platforms holding the sample in most modern in-situ TEM holders rely on an insulating ceramic membrane which needs to be (almost) transparent to the imaging electron beam. Electrodes are defined through lithography and patterned on this membrane. Unfortunately, the presence of this membranes introduces several limitations such as electrostatic charging, reduction of image contrast and poor mechanical stability. To circumvent this issue it is necessary to fabricate a novel type of sample platform which does not rely on the presence of a membrane. In this work, novel membraneless sample-holding platforms were designed and manufactured using advanced microfabrication methods and tools. Besides fitting into an array of analytical tools, the novel platforms (or “chips”) can be subjected to thermal and/or chemical processing without compromising their function or structure. To test these, the electrical response of one-, two- and zero-dimensional nanoparticles were studied. Firstly, we investigated current-induced modifications in silver nanowires and expandable graphite flakes and studied various phenomenon involved. Along with these, corresponding ex-situ studies were also performed. Next, graphene oxide was explored as an alternative support platform for in-situ TEM. We successfully achieved temperature as high as 2000o C by Joule heating of graphene oxide. Furthermore, this graphene oxide platform was used as a heater and chemical processing substrate for investigating thermal stability and synthesis of inorganic nanoparticles, respectively.
74

Optimalizace provozu kotelny Brno-Bystrc / Optimizing boiler operation Brno-Bystrc

Drahokoupilová, Lucie January 2010 (has links)
Content of the thesis is to optimize fuel economy boiler in Brno-Bystrc. The work is designed adjustment Infrastructure fuel in boilers and increase storage capacity.
75

Aging-Aware Routing Algorithms for Network-on-Chips

Bhardwaj, Kshitij 01 August 2012 (has links)
Network-on-Chip (NoC) architectures have emerged as a better replacement of the traditional bus-based communication in the many-core era. However, continuous technology scaling has made aging mechanisms, such as Negative Bias Temperature Instability (NBTI) and electromigration, primary concerns in NoC design. In this work, a novel system-level aging model is proposed to model the effects of aging in NoCs, caused due to (a) asymmetric communication patterns between the network nodes, and (b) runtime traffic variations due to routing policies. This work observes a critical need of a holistic aging analysis, which when combined with power-performance optimization, poses a multi-objective design challenge. To solve this problem, two different aging-aware routing algorithms are proposed: (a) congestion-oblivious Mixed Integer Linear Programming (MILP)-based routing algorithm, and (b) congestion-aware adaptive routing algorithm and router micro-architecture. After extensive experimental evaluations, proposed routing algorithms reduce aging-induced power-performance overheads while also improving the system robustness.
76

Material flow in a wood-chip refiner

Fan, Xiaolin January 1987 (has links)
No description available.
77

Hardwood whole tree chips: a fuel storage model analysis

Argent, Robert M. January 1983 (has links)
A pile of mixed hardwood whole tree chips was monitored for one year to identify the effects outside storage would have on the fuel potential of the exposed pile. A 20 foot conical pile was built by gravity feed from an overhead conveyor. Moisture content, fiber loss, ash, specific gravity, higher heating value (HHV), temperature, packing density and pH were the variables examined and from these changes, Total Net Heating Value was estimated. Moisture content and packing density showed a significant increase with time. Pile temperature remained below freezing for the first ten weeks of the study then rapidly rose above the ambient air temperature to a maximum of 82 degrees C before falling to near ambient where it remained. After six months,moisture content within the pile stratified into layers reflecting steep moisture content gradients. The outermost layer became saturated, primarily due to rainfall while spontaneous drying reduced the innermost layer's moisture content. The Total Net Heating Value (TNHV) was found to decrease 1.14 percent per month or 13.7 percent a year. Increased moisture content accounts for 88.5 percent of the loss. Lower HHV accounts for 11.5 percent of the loss in TNHV. Storage suggestions and recommendations are included / M.S.
78

Analysis of shaker unit parameters to separate whole-tree wood chips

Weeks, Gregory Andrew January 1988 (has links)
The quality of whole-tree wood chips has been the focus of much attention during the past few years because of the increased use of lower grade wood über in pulp production. The need to up-grade the quality has resulted in the use of some form of screening system to separate acceptable wood chips from unwanted material at most pulp mills. In order to upgrade the chip quality, a study was conducted to determine the effect of selected parameters of a separation system with an inclined, vibrating screen on screening efficiency. The parameters studied included screen aperture size and frequency of oscillation. Two screen sizes (3/8 and 1/4 inch apertures) and four different frequencies (1.25, 1.50, 1.75, and 2.00 Hertz) were considered. All other shaker unit parameters were held constant. Statistical analysis revealed that the lowest frequency resulted in the highest screening efficiencies for both the pin chips and fines categories. Screening efficiencies were higher with 3/8 inch screen as opposed to 1/4 inch screen, for all frequencies considered, but at 1.25 Hertz, the screening efficiency of fines was only 6 percent better with 3/8 inch screen. This analysis revealed that the lowest acceleration vectors produced the best screening efficiencies. Velocity and acceleration vectors were directly related to frequency of oscillation since all other parameters were held constant for this study. A Programmer’s Hierarchical Interactive Graphics System (PHIGS) program was developed to graphically simulate the screen motion and to analyze the maximum velocity and acceleration vectors of the upper swing arm (input link). By interactively changing the shaker unit parameters, the screen motion was animated and viewed, with the calculated vectors used in the statistical analysis. / Master of Science
79

Improving sawmill residue chip quality

Wallace, Robert D. 24 March 2009 (has links)
The primary objective of this study was to improve residue chip quality at high production southern pine Sawmills. A general economic analysis suggested that improving sawmill residue chip quality could be beneficial to both pulp and sawmills. Studies were conducted at several sawmills to determine methods of improving residue chip quality. The first study examined the composition of material entering a residue chipper. Trim ends and oversize chips contributed the most pieces, but only 10% of the residue weight. Two-foot trim blocks accounted for the remaining material, 90% by weight. A number of these pieces resulted from slashing entire boards or cutting longer trim lengths into 2-foot pieces to clear them from the mill. Two studies were conducted to examine the possibility of leaving trim in longer lengths to improve piece orientation and stability. Both studies found significant improvements in chip quality, the over-thick chips decreased while the percentage of acceptable chips increased. Chip quality improved with each incremental increase in trim length, but increasing trim length to four feet alone accounted for 50% of the overall improvements. Four-foot trim lengths would generate an additional 4-5 tons of acceptable chips per day for the sawmill. Feed conveyor loading was found to affect chip quality. Highest chip quality was achieved when the feed conveyor was half-full, with two or three pieces entering simultaneously. An overloaded conveyor produced higher percentages of large chips, whereas chipping single pieces increased the percentage of smaller chips. The effect of seasonal temperatures on pin chip and fine production at southern pine and hardwood chip mills was examined as a secondary objective. The pin chip and fine content at the hardwood mills increased as temperatures decreased, but variability in species and inventory obscured the relationship. Southern pine chip mills experienced 4-5% increases in the pin chip and fine content during the winter months. Pin chips and fines increased 1% for every 10°F drop in temperature. / Master of Science
80

Modeling the fixed bed drying characteristics of biomass particles

Yang, Hai 21 June 2012 (has links)
The fixed bed drying of western hemlock and Douglas-fir biomass particles at temperatures ranging from 50��C to 200��C and air velocities from 0.3 to 0.9 m/s was investigated. The objectives were to describe the drying characteristics of the particles, fit a model for thin-layer drying, and develop and test a deep bed drying model based on the thin-layer model. The effects of temperature and air velocity were determined in a bed approximately 1.3 cm in depth and a model for the drying curve was developed. The thin-layer model was then used to predict what would happen in a deeper bed. Model results were compared to drying curves measured in a 23-cm-deep bed. The deep bed model predicted both the experimental drying times and the moisture and temperature profiles in the bed. / Graduation date: 2013

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