4,907 research outputs found
Behaviour of polymeric materials in machining
The machining characteristics of a glassy thermoplastic
(Polyvinyl Chloride) and a semi-crystalline thermoplastic (High
Density Polyethylene) have been studied. Chip formation
mechanisms, cutting forces and surface integrity were found to
be dependent, on the cutting conditions and tool geometry.
Results were explained by considering the different nature of
the microstructure. Segmented and discontinuous chips were
produced with PVC, and continuous and segmented chips were
produced with HDPE. It was observed that surface damage was
closely related to the nature of chip formation in these
plastics.
Chip formation, surface damage and tool wear mechanisms when
machining Glass-Fibre-Reinforced-Plastic (GFRP) were also
studied. Cutting tools used were High-Speed-Steel (HSS),
cemented carbide (P type and K type) and coated carbide
(titanium carbide - and triple-coated). Discontinuous chips
were always produced when machining GFRP. Sliding contact is
present at the tool/chip and tool/work interface. The
principal aspects of surface damage include fibre breakage,
resin cracking, resin decomposition and fibre/resin interface
debonding. Cutting temperature is not high, but excessive heat
generates when the flank wear land develops. Coated carbide
tools showed the best performance and HSS tools the poorest.
The main wear mechanisms are abrasive wear with HSS tools,
attrition wear with cemented carbides, and discrete plastic
deformation followed by attrition wear with coated carbides
Indexing and Retrieving Photographic Images Using a Combination of Geo-Location and Content-Based Features
This paper presents a novel method that automatically indexes searches for relevant images using a combination of geo-coded information and content-based visual features. Photographic images are labeled with their corresponding GPS (Global Positioning System) coordinates and UTC time (Coordinated Universal Time) information at the moment of capture, which are then utilized to create spatial and temporal indexes for photograph retrieval. Assessing the performance in terms of average precision and F-score with real-world image collections revealed that the proposed approach significantly improved and enhanced the retrieval process compared to searches based on visual content alone. Combining content and context information thus offers a useful and meaningful new approach to searching and managing large image collections
Adsorption and thermal decomposition characteristics of organic contaminants in coal conversion wastewater
Call number: LD2668 .T4 1984 K55Master of Scienc
Sustainable Transportation Decision-Making: Spatial Decision Support Systems (SDSS) and Total Cost Analysis
Building a new infrastructure facility requires a significant amount of time and expense. This is particularly true for investments in transportation for their longstanding and great degree of impact on society. The scope of time and money involved does not mean, however, we only focus on the economies of scale and may ignore other aspects of the built environment. To this extent, how can we achieve a more balanced perspective in infrastructure decision-making? In addition, what aspects should be considered when making more sustainable decisions about transportation investments? These two questions are the foundations of this study.
This dissertation shares its process in part with a previous research project – Texas Urban Triangle (TUT). Although the TUT research generated diverse variables and created possible implementations of spatial decision support system (SDSS), the methodology still demands improvement. The current method has been developed to create suitable routes but is not designed to rank or make comparisons. This is admittedly one of the biggest shortfalls in the general SDSS approach, but is also where I see as an opportunity to make alternative interpretation more comprehensive and effective. The main purpose of this dissertation is to develop a Spatial Decision Support System (SDSS) that will lead to more balanced decision-making in transportation investment and optimize the most sustainable high-speed rail (HSR) route.
The decision support system developed here explicitly elaborates the advantages and disadvantages of a transportation corridor in three particular perspectives: construction (fixed costs); operation (maintenance costs); and externalities (social and environmental costs), with a specific focus on environmental externalities. Considering more environmental features in rail routing will offset short-term economic losses and creates more sustainable environments in long-term infrastructure planning
Neutrophil-lymphocyte ratio predicts pathologic tumor response and survival after preoperative chemoradiation for rectal cancer
Adaptive Pilot Signaling in the Uplink of OFDM-Based Wireless Systems
Orthogonal frequency division multiplexing (OFDM)
has been considered as one of key transmission technologies for
high-speed wireless communication systems. For channel-adaptive
transmission of OFDM signal, base stations transmit a common
pilot signal in the downlink, but mobile stations transmit
individual pilot signal in the uplink. As a consequence, the uplink
may suffer from poorer channel estimation accuracy than the
downlink. This problem can be alleviated by increasing the pilot
signal density. But this reduces the time and frequency resources
for the data transmission, deteriorating the actual transmission
throughput. In this paper, we propose an adaptive pilot signaling
scheme that adjusts the pilot density in response to the change of
channel characteristics. Simulation results show that the proposed
scheme can remarkably reduce the pilot overhead without
performance degradation, compared to conventional schemes
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