B+-tree Index Optimization by Exploiting Internal Parallelism of Flash-based Solid State Drives

Previous research addressed the potential problems of the hard-disk oriented design of DBMSs of flashSSDs. In this paper, we focus on exploiting potential benefits of flashSSDs. First, we examine the internal parallelism issues of flashSSDs by conducting benchmarks to various flashSSDs. Then, we suggest algorithm-design principles in order to best benefit from the internal parallelism. We present a new I/O request concept, called psync I/O that can exploit the internal parallelism of flashSSDs in a single process. Based on these ideas, we introduce B+-tree optimization methods in order to utilize internal parallelism. By integrating the results of these methods, we present a B+-tree variant, PIO B-tree. We confirmed that each optimization method substantially enhances the index performance. Consequently, PIO B-tree enhanced B+-tree's insert performance by a factor of up to 16.3, while improving point-search performance by a factor of 1.2. The range search of PIO B-tree was up to 5 times faster than that of the B+-tree. Moreover, PIO B-tree outperformed other flash-aware indexes in various synthetic workloads. We also confirmed that PIO B-tree outperforms B+-tree in index traces collected inside the Postgresql DBMS with TPC-C benchmark.Comment: VLDB201

Examining Nebraska\u27s Local Finance Picture

CPACS Urban Research Awards Part of the mission of the College of Public Affairs and Community Service (CPACS) is to conduct research, especially as it relates to concerns of our local and statewide constituencies. CPACS has always had an urban mission, and one way that mission is served is to preform applied research relevant to urban society in general, and the Omaha metropolitan area and other Nebraska urban communities in particular. Beginning in 2014, the CPACS Dean provided funding for the projects with high relevance to current urban issues, with the potential to apply the findings to practice in Nebraska, Iowa, and beyond

FPGA-Based Low-Power Speech Recognition with Recurrent Neural Networks

In this paper, a neural network based real-time speech recognition (SR) system is developed using an FPGA for very low-power operation. The implemented system employs two recurrent neural networks (RNNs); one is a speech-to-character RNN for acoustic modeling (AM) and the other is for character-level language modeling (LM). The system also employs a statistical word-level LM to improve the recognition accuracy. The results of the AM, the character-level LM, and the word-level LM are combined using a fairly simple N-best search algorithm instead of the hidden Markov model (HMM) based network. The RNNs are implemented using massively parallel processing elements (PEs) for low latency and high throughput. The weights are quantized to 6 bits to store all of them in the on-chip memory of an FPGA. The proposed algorithm is implemented on a Xilinx XC7Z045, and the system can operate much faster than real-time.Comment: Accepted to SiPS 201

Delivering Value for Money with BIM-embedded Housing Refurbishment

The aim of this research is to examine if BIM is feasible as an information management platform to determine a financially and environmentally affordable housing refurbishment solution based on the LCC and LCC calculation. A case study in conjunction with BIM simulation approach using BIM tools (Autodesk Revit and IES VE/IMPACT) was adopted to identify the feasibility of BIM for the simultaneous formulation of LCC and LCA in housing refurbishment. This research reveals that BIM is a suitable for the information management platform to enable construction professionals to consider trade-off relationship between LCC and LCA simultaneously, and determine the most financially and environmentally affordable refurbishment solution. The interoperability issues in data exchange among different BIM tools and unstandardized BIM object libraries with incomplete datasets of construction materials are recognized as the major shortcomings in a BIM system. Essential remedial actions to overcome the shortcomings in the current BIM tools are identified. Actual housing information and various refurbishment materials for the BIM simulation are limited. This research contribute to supporting construction professionals to prepare practical BIM adoption for the integration of the LCC and LCA that can significantly improve early decision makings on sustainable housing refurbishment. This research will contribute to providing proper remedial actions to overcome the shortcomings in the current BIM tools, and insights for construction professionals to understand the implication of BIM-embedded housing refurbishment

Housing Information Modelling for BIM-embedded Housing Refurbishment

The aim of this research is to identify BIM input datasets within a BIM-embedded housing refurbishment process and enabling construction professionals to utilize BIM as an information management platform for housing refurbishment projects. A hypothetical case study using BIM tools for a housing refurbishment project is adopted to identify BIM input datasets to create a housing information model within a BIM system. Reliability of the research outcome is examined by conducting a comparative analysis between existing and simulated research outcomes. This research identifies essential BIM input datasets during the early design phase. The importance of a well-integrated housing information model containing accurate as-built condition, cost and thermal performance information is essential to utilize BIM for housing refurbishment. BIM can be feasible for housing refurbishment when an information enriched housing information model is constructed. Furthermore, the capability of BIM that can enable key project stakeholders to determine the most affordable refurbishment solution among various alternatives is identified since BIM can provide reliable cost estimations and thermal performance of refurbishment alternatives at the early design stage. The examined refurbishment processes and input datasets are confined to the early design phases since BIM use for housing refurbishment is limited. This research will contribute to utilize BIM for housing refurbishment by providing essential BIM input datasets and BIM-embedded refurbishment processes. This research reveals primary housing information datasets and BIM-embedded refurbishment processes at the early design phase

Renewable Thermoplastic Composites for Environmentally Friendly and Sustainable Applications

Thermoplastic composites using natural fibres are studied intensively and widely used in applications including automotive, packaging, consumer goods and construction. Good balance of mechanical properties, processability and low cost are great advantages of these materials on top of the environmental benefits. Recently, there have been various efforts to amplify the positive effects on the environment by replacing the conventional polymers by bio-derived renewable polymers in the composites. Recent studies conducted from our research group showed competitiveness of plant fibre-thermoplastic composites. Implementing the promising results and experience, a new composite design using renewable polyethylene as the matrix material was studied. This polyethylene is a renewable thermoplastic that was derived from sugar cane ethanol. The objectives of this study were to employ renewable high density polyethylene (HDPE) into composites using wheat straw and flax fibre to extend the range of properties of the HDPE while keeping the amount of renewable content to nearly 100%. The chemical resistance of these materials has not been reported before and it was investigated here by measuring and comparing the properties before and after accelerated chemical ageing. Both wheat straw and flax fibre had two different grades in size. Each of them was compounded with HDPE and additives (antioxidant and coupling agent) in a co-rotating twin screw extruder. The concentrations of fibres were varied from 0 to 30 wt-%. Then, injection molded samples were prepared for measurement of properties: tensile, flexural, impact tests. The effects of reinforcing fibre size were studied first. Both length and aspect ratio were considered. For both types of fibre composites, a general trend was observed. There was no clear evidence of improvements in flexural (strength and modulus) and tensile (strength, percentage elongation at break) properties with respect to the change in fibre size. However, impact (IZOD impact strength, Gardner impact failure energy) properties showed some improvements. This result was due to no substantial difference in size and aspect ratios in post-processed fibres that were actually residing in the matrix. There were remarkable improvements in flexural strength and modulus when the fibre content increased. However, minor decreases in tensile properties were observed. Furthermore, the impact properties were very sensitive to the concentration of fibres. As the fibre concentration went up, there were significant decreases in both IZOD impact strength and Gardner impact failure energy. Chemical resistance of these composites was studied by exposing them in six different chemical solutions (hydrochloric acid, acetic acid, sodium hydroxide, ethyl alcohol, industrial detergent, water) for up to thirty days. The increase in weight and leaching behaviour was observed. As the fibre content increased within the composites, the weight gain was more rapid during chemical ageing. Because there were more fibres exposed on the surface after chemical ageing, it is likely that they contributed to the higher flux of liquids (used for chemical ageing) inside the sample. Among the physical properties, tensile properties were most susceptible to the chemical ageing. One possible reason could be due to the exposed surface area to volume ratio, which was the highest in tensile bars and therefore faster mass transfer taking place into the matrix per volume. Finally, morphological study using scanned electron spectroscopy (SEM) revealed the damage on the surface when exposed to the chemicals. The fibres on the surface had been leached out in the sodium hydroxide solution leaving empty spaces. The fractured surface was also monitored via SEM. Though there was not enough evidence of strong interfacial interactions between the fibre and the polymer, good dispersions were observed

The Case for Sustainable Concrete Waste Management in Qatar

The construction industry is a major generator of waste. There are many challenges associated with implementing sustainable methods to manage construction waste. While the construction industry in the State of Qatar has been adopting plenty of progressive practices, waste management, especially of concrete waste, has not advanced notably. In addition to the limited supply of limestone suitable for use as natural aggregate for concrete production in Qatar, the ability to recycle and reuse concrete waste is critical to reducing environmental impacts to meet national, regional and global environmental goals. Therefore, this research aims to identify the current status of concrete waste management practices in construction projects in Qatar exemplified by a local case-study project. Concrete waste was particularly monitored over the span of the construction stage of a large research and development facility in Qatar, benchmarking trends and practices on a certified “green” building. In response, this study addresses key challenges to concrete waste recycling and reuse to then recommend opportunities of advancements in local concrete waste management and reuse

A verilog-hdl implementation of virtual channels in a network-on-chip router

As the feature size is continuously decreasing and integration density is increasing, interconnections have become a dominating factor in determining the overall quality of a chip. Due to the limited scalability of system bus, it cannot meet the requirement of current System-on-Chip (SoC) implementations where only a limited number of functional units can be supported. Long global wires also cause many design problems, such as routing congestion, noise coupling, and difficult timing closure. Network-on-Chip (NoC) architectures have been proposed to be an alternative to solve the above problems by using a packet-based communication network. The processing elements (PEs) communicate with each other by exchanging messages over the network and these messages go through buffers in each router. Buffers are one of the major resource used by the routers in virtual channel flow control. In this thesis, we analyze two kinds of buffer allocation approaches, static and dynamic buffer allocations. These approaches aim to increase throughput and minimize latency by means of virtual channel flow control. In statically allocated buffer architecture, size and organization are design time decisions and thus, do not perform optimally for all traffic conditions. In addition, statically allocated virtual channel consumes a waste of area and significant leakage power. However, dynamic buffer allocation scheme claims that buffer utilization can be increased using dynamic virtual channels. Dynamic virtual channel regulator (ViChaR), have been proposed to use centralized buffer architecture which dynamically allocates virtual channels and buffer slots in real-time depending on traffic conditions. This ViChaR’s dynamic buffer management scheme increases buffer utilization, but it also increases design complexity. In this research, we reexamine performance, power consumption, and area of ViChaR’s buffer architecture through implementation. We implement a generic router and a ViChaR architecture using Verilog-HDL. These RTL codes are verified by dynamic simulation, and synthesized by Design Compiler to get area and power consumption. In addition, we get latency through Static Timing Analysis. The results show that a ViChaR’s dynamic buffer management scheme increases the latency and power consumption significantly even though it could increase buffer utilization. Therefore, we need a novel design to achieve high buffer utilization without a loss

Novel Starch Nanocomposites

Thermoplastic materials using bio-derived renewable resources are studied intensively and are widely used in applications including packaging, agriculture and other consumer goods. Starch-based plastics exhibit a good balance between environmental benefits, mechanical properties, processability, and low cost. Recently, there have been numerous efforts to amplify the positive effects on the environment while maintaining competitive physical properties in order to meet the needs of the market. Canadian companies have developed new starch-based products to amplify the positive environmental impacts. Polymer Specialties International developed a new thermoplastic starch copolymer resin with competitive characteristics. However, there is very little information on the reaction mechanisms and chemical compositions. Another Canadian company, Ecosynthetix, is producing starch nanoparticle materials for applications such as paper coating. Recent studies conducted by our research group showed promising results by applying these materials as filler in polyethylene composites. These research problems generated opportunities to investigate and develop new applications. The goal of this research was to develop a technology to characterize and process environmentally friendly materials using starch as co-polymer and as nanoparticle. The research aimed to extend the range of properties of starch materials while maintaining environmental benefits and competitive physical properties for applications such as packaging and agriculture. The first research objective was to characterize the new thermoplastic starch copolymer resin. In-depth characterization of its molecular structure and measurement of its thermal and mechanical properties were conducted. The material was also investigated in the presence of nanocellulose as reinforcement. Furthermore, the esterification process using maleic anhydride was done through three different systems: a reactive microwave reactor, a vacuum rotary evaporator, and a twin-screw extruder. A series of studies was conducted and the materials were compared via chemical composition analysis. Mechanisms for maleation were confirmed and this is an important step for manufacturing copolymer resin. The second objective was to investigate the application of starch as nanoparticle. The focus was on the dispersion of starch nanoparticles in a green polyethylene matrix. Achieving uniform distribution and desired particle size through tuning of the processing conditions and additives were the keys. Detailed characterization of the composite materials were conducted. By designing and applying a systematic approach, uniform nano-sized dispersions of the fillers were achieved within the matrix, and this was confirmed by morphological analysis