Opportunistic Third-Party Backhaul for Cellular Wireless Networks

With high capacity air interfaces and large numbers of small cells, backhaul -- the wired connectivity to base stations -- is increasingly becoming the cost driver in cellular wireless networks. One reason for the high cost of backhaul is that capacity is often purchased on leased lines with guaranteed rates provisioned to peak loads. In this paper, we present an alternate \emph{opportunistic backhaul} model where third parties provide base stations and backhaul connections and lease out excess capacity in their networks to the cellular provider when available, presumably at significantly lower costs than guaranteed connections. We describe a scalable architecture for such deployments using open access femtocells, which are small plug-and-play base stations that operate in the carrier's spectrum but can connect directly into the third party provider's wired network. Within the proposed architecture, we present a general user association optimization algorithm that enables the cellular provider to dynamically determine which mobiles should be assigned to the third-party femtocells based on the traffic demands, interference and channel conditions and third-party access pricing. Although the optimization is non-convex, the algorithm uses a computationally efficient method for finding approximate solutions via dual decomposition. Simulations of the deployment model based on actual base station locations are presented that show that large capacity gains are achievable if adoption of third-party, open access femtocells can reach even a small fraction of the current market penetration of WiFi access points.Comment: 9 pages, 6 figure

An Integrated Modelling and Optimization Approach for Hydrogen Energy Network

Issues related to global warming have moved hydrogen into the spotlight as a promising energy carrier. As hydrogen is considered as a promising energy carrier from concerns driven by global warming, the goal of this work was a development and optimization of an integrated modelling and optimization of hydrogen energy network for Texas. To achieve such goal, the hydrogen energy network formulation based on Mixed Integer Linear Programming (MILP) was performed. In the hydrogen energy network, five raw materials and three electricity potential sources were introduced, and they highly affected on the technology availability when they are depleted. Hydrogen was produced from technologies such as SMR, coal and biomass gasification, and alkaline/PEM/solid oxide electrolysis. The produced hydrogen was compressed or liquefied to be ready for use. The produced hydrogen was sold at $5/kg, and could be transported from one region to other through tube trailers, tanker trucks, tube railcars, and tank railcars to maximize the profit and meet hydrogen demand. Lastly, some possible scenarios were tested such as discounting electricity price scenarios and limiting raw material availability. When electricity price was reduced, there were technology transitions from SMR to the electrolysis at some geographical regions. Additionally, the electricity price discount triggered an increase in hydrogen autonomy of each geographical region as it decreased the amount of hydrogen transported. When the fossil fuel based raw material availability was gradually reduced over time period according to Horizon 2020, there were increased raw material transportations as the raw materials depleted faster in some geographical regions at certain time periods. The combined scenarios regarding both electricity price and raw material limitation were also tested, and it showed the competence of two technologies, biomass gasification and solid oxide electrolysis, as both required natural gas which was limited

Evaluating the Effects of Reactor Type on Pyrolysis of Nannochloropsis Oculata on Bio-Oil and Bio-Char Products, and Bio-Oil Upgrading Using Catalysts

Pyrolysis products from microalgae using two types of reactors, a batch and an auger, will be investigated and compared at a temperature of 500oC. Also, the bio-oil will be upgraded through hydrotreatment to be used as a substitution of petroleum fuels. The pyrolysis products of bio-char, bio-oil, and combustible gases will be analyzed. The ultimate analysis will also completed and it shows the HHV (Higher heating value) of the bio-oil from a batch reactor. Chemical compositions of bio-oils using Gas Chromatography-Mass Spectrometry (GC-MS) will be categorized which indicates a potential of bio-oil as a substitute for crude petroleum oil. HHV of bio-char will also evaluated and it is anticipated to contain considerable energy and to be used for additional energy sources or other applications. Then, the produced bio-oil from a batch reactor will be upgraded in a catalytic reactor. A hydrotreatment process will be applied that uses catalysts with hydrogenation and deoxygenation, which reduces the oxygen contents of bio-oil. The initial oxygen content in algae bio-oil will be reduced with catalysts while the carbon and hydrogen contents will be increased. The O/C ratio of bio-oil will be obtained and it will be compared to the O/C ratio of petroleum products (less than 0.06). The pyrolysis results using the microalgae feedstock (N.oculata) will show that the products are potentially valuable sources of fuels and chemicals

Preparation and Electrochemical Characterization of Concrete Containing Microencapsulated Calcium Nitrate Corrosion Inhibitor

We present the preparation and inhibition behavior of rebar in the presence of calcium nitrate (CN)-containing microcapsules with concentrations of 0.50, 2.00, and 5.00 wt.% in concrete. From both open circuit potential (OCP) and electrochemical impedance spectroscopy spectra, it was found that an addition of microcapsules containing CN corrosion inhibitor into concrete beams successfully repassivated or maintained the passivity of the rebar when the concrete was cracked. This corrosion inhibitor repassivated the rebar by forming a passive layer on the rebar surface under the crack. This repassivation process was evident by an increase of OCP values to more positive values or by stable OCP values at around -100 mV vs SCE. An increase in phase angle after corrosion activation for the sample with 2.00 wt.% microcapsule clearly showed this repassivation process. The optimum concentration for maintaining the passivity on rebar in the cracked concrete was found to be 5.00 wt.%

A technology-scalable composable architecture

textClock rate scaling can no longer sustain computer system performance scaling due to power and thermal constraints and diminishing performance returns of deep pipelining. Future performance improvements must therefore come from mining concurrency from applications. However, increasing global on-chip wire delays will limit the amount of state available in a single cycle, thereby hampering the ability to mine concurrency with conventional approaches. To address these technology challenges, the processor industry has migrated to chip multiprocessors (CMPs). The disadvantage of conventional CMP architectures, however, is their relative inflexibility to meet the wide range of application demands and operating targets that now exist. The granularity (e.g., issue width), the number of processors in a chip and memory hierarchies are fixed at design time based on the target workload mix, which result in suboptimal operation as the workload mix and operating targets change over time. In this dissertation, we explore the concept of composability to address both the increasing wire delay problem and the inflexibility of conventional CMP architectures. The basic concept of composability is the ability to dynamically adapt to diverse applications and operating targets, both in terms of granularity and functionality, by aggregating finegrained processing units or memory units. First, we propose a composable on-chip memory substrate, called Non-Uniform Access Cache Architecture (NUCA) to address increasing on-chip wire delay for future large caches. The NUCA substrate breaks large on-chip memories into many fine-grained memory banks that are independently accessible, with a switched network embedded in the cache. Lines can be mapped into this array of memory banks with fixed mappings or dynamic mappings, where cache lines can move around within the cache to further reduce the average cache hit latency. Second, we evaluate a range of strategies to build a composable processor. Composable processors provide flexibility of adapting the granularity of processors to various application demands and operating targets, and thus choose the hardware configurations best suited to any given point. A composable processor consists of a large number of lowpower, fine-grained processor cores that can be aggregated dynamically to form more powerful logical processors. We present architectural innovations to support composability in a power- and area-efficient manner.Computer Science