35 research outputs found
Simulated annealing reconstruction and characterization of a LiCoO2 Lithium-ion battery cathode
No full textWe reconstruct the three-dimensional microstructure of a cathode from a commercial LiCoO2 Lithium-ion battery with an adapted simulated annealing approach. The real size distribution curve of LiCoO2 particles is applied to regulate the reconstruction process. By discretizing a 40 mu mx40 mu mx40 mu m cathode volume with 8000000 numerical cubes, the cathode involving three individual phases: (1) LiCoO2 as active material, (2) pores or electrolyte, and (3) additives (polyvinylidene fluoride+carbon black) is reconstructed. Characterization of the reconstructed cathode gives important structural and transport properties including volume-specific surface area between phases, tortuosity and geometrical connectivity of individual phase
Simulated annealing reconstruction and characterization of the three-dimensional microstructure of a LiCoO2 Lithium-ion battery cathode
No full textWe adapt the simulated annealing approach for reconstruction of the 3D microstructure of a LiCoO2 cathode from a commercial Li-ion battery. The real size distribution curve of LiCoO2 particles is applied to regulate the reconstruction process. By discretizing a 40 x 40 x 40 mu m cathode volume with 8,000,000 numerical cubes, the cathode involving three individual phases: 1) LiCoO2 as active material, 2) pores or electrolyte, and 3) additives (polyvinylidene fluoride + carbon black) is reconstructed. The microstructural statistical properties required in the reconstruction process are extracted from 2D focused ion beam/scanning electron microscopy images or obtained by analyzing the powder mixture used to make the cathode. Characterization of the reconstructed cathode gives important structural and transport properties including the two-point correlation functions, volume-specific surface area between phases, tortuosity and geometrical connectivity of individual phase. (C) 2013 Elsevier Inc. All rights reserved
Microstructure reconstruction and impedance spectroscopy study of LiCoO2, LiMn2O4 and LiFePO4 Li-ion battery cathodes
No full textCathode materials have been the focal point of research in the quest for high-performance secondary battery technology in consumer electronics and electric vehicles. The present work investigates the effect of the microstructural morphology of major cathode materials (LiCoO2, LiMn2O4, and LiFePO4) on the performance of the Li-ion battery related to the charge and species transport. Simulated annealing method (SAM) was implemented to generate a virtual 3D domain of the electrode microstructure using a spherical particles, average radius of 3 and 6 mu m. An equivalent circuit composed of resistance, capacitance and Warburg impedance was used to model the impedance response of the overall electrochemical reaction occur inside a typical battery system. Electrochemical impedance spectroscopy (EIS) results show that the ionic and electronic mobility in the solid electrode and bulk electrolyte were significantly determined by the morphology of the electrode microstructure. Higher porosity microstructures usually tend to have larger solid-electrolyte interface (SEI) area and lower pore tortuosity which improves the ionic diffusivity in solid and electrolyte phase. Furthermore, the Bruggeman's exponent for effective conductivity and diffusivity was derived from geometrical parameters of the reconstructed microstructure. The real and imaginary parts of the impedance were then presented in Nyquist plot on a frequency range of 20 kHz to 10 mHz
Detailed analysis of DISE algorithm and its application
No full textIn this report, the author has a detailed discussion on the Direction-Informed Speech Extraction (DISE) method based on the performance. The application of implementing the algorithm on hand phone is also proposed.
DISE is a blind source separation method. With specific direction informed, it gives similar results as fixed beam forming producing. To test the capability of reducing undesired signal, the tests on signal to noise and interference ratio (SIR), signal to distortion ratio (SDR) and signal to artifacts ratio (SAR) are performed with the variable of input SIR, microphone number, reverberation time and source number. The results show DISE has a better overall performance that fixed beamforming. The performance for sound classification is adopted from peer work. Overall it has a negative effect on sound classification. The application of the algorithm on phone is tested with 12 designs for 3 to 5 microphones. The designs with most aperture size give the best performances.
To further test the algorithm in real life, more tests are suggested to be carried on with more variation of input such as different source heights, different source types and more tests that implemented on physical model is also recommended.
Keywords: Blind Source Separation, DISE, Fixed Beamforming, Delay and Sum, Filter and Sum, Noise Reducing on Cell Phone, Sound Classification.Bachelor of Engineerin
Enhanced stability of Thermus thermophiles SG0.5JP17-16 laccase immobilized by CuF-MOF and its application in the Congo red decolorization
No full textLaccase attracts the extensive attention in degradation of pollutants due to its environmental friendliness and high efficiency. Free laccase has the disadvantages of easy inactivity, poor stability and difficulty in reuse, so its application in industry is confined. The immobilization of laccase can protect the laccase and actualize the cycle. In this work, copper fumarate metal-organic-frameworks (CuF-MOFs) were prepared and utilized to immobilize the Thermus thermophiles SG0.5JP17 - 16 laccase (lacTT) by encapsulation and surface adsorption at room temperature. The results from SEM, FTIR, XRD and BET indicated that lacTT was immobilized successfully. The optimal pH and temperature of lacTT@CuF-MOF and lacTT#CuF-MOF were determined to be pH 6.5 at 95 degrees C and pH 5.0 at 95 degrees C respectively. The immobilized laccase had the elevated stability in storage and reuse. The lacTT@CuF-MOF displayed higher thermal stability as compared with lacTT#CuF-MOF. But the V max (11.15 mu M. min -1 ) value of lacTT@CuF-MOF was lower than that of lacTT#CuF-MOF ( V max = 37.61 mu M.min - 1 ). The degradation efficiencies of lacTT@CuF-MOF and lacTT#CuF-MOF on Congo red were 41 % and 30 % at 6th cycle respectively. Therefore, the MOF was beneficial and could serve as sustainable carrier for laccase immobilization. The immobilized laccase might be more efficient to degrade the dyes in wastewater from textile industry than free enzyme
Prediction of cutting forces and surface errors in face milling with generalized cutter and workpiece geometry
No full textFace milling is a widely used material removal process in the automotive industry for machining the flat surface of components such as an engine block and cylinder head, etc. The surface flatness error of the machined workpiece is a key variable affecting the quality of the part and the productivity of the process.The main cause of the surface flatness error in face milling is the elastic deflection of the cutter/spindle and workpiece/fixture assemblies due to forces generated during cutting. To predict the surface flatness error in face milling, knowledge of the cutting forces is required. Numerous models for prediction of cutting forces in face milling have been presented in the literature. However, these models are limited in their scope of applicability. In this thesis, an improved mechanistic cutting force model is developed for face milling with generalized cutter/workpiece geometries and cutter feed paths. The model allows a variety of cutter and insert geometries to be used. It is also capable of simulating the cutting forces for 2-D curvilinear cutter feed paths. Systematic procedures/models to define the cutter-insert-workpiece geometries and variable cutter feed paths and to calculate the undeformed chip thickness, chip area and the cutter entry-exit angles are developed. The surface flatness error model developed here is based on the equivalent flexibility influence coefficients approach which uses the cutting force model and the flexibility influence coefficients of the cutter/spindle and workpiece/fixture assemblies. The model accounts for the effects of changes in cutting conditions and machine setup error (spindle tilt).Experiments have been conducted to study the effects of cutter-insert geometries, cutter feed path on the cutting force, and the effect of cutting conditions on the surface flatness error. The measured cutting forces have been used to calibrate and verify the developed model for prediction of cutting forces. Comparison between the measured and predicted cutting forces and surface flatness errors show good agreement. From this research, it was also shown that the surface flatness error due to the static spindle axis tilt could be significant, and the roughness error of the machined surface could contribute to the total surface flatness error.Made available in DSpace on 2011-05-07T12:12:58Z (GMT). No. of bitstreams: 2
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Integrating natural language processing and web GIS for interactive knowledge domain visualization
No full textThesis, (M.S.) Geological Sciences\ud
Includes bibliographical references (pages 51-53)Recent years have seen a powerful shift towards data-rich environments throughout society. This has extended to a change in how the artifacts and products of scientific knowledge production can be analyzed and understood. Bottom-up approaches are on the rise that combine access to huge amounts of academic publications with advanced computer graphics and data processing tools, including natural language processing. Knowledge domain visualization is one of those multi-technology approaches, with its aim of turning domain-specific human knowledge into highly visual representations in order to better understand the structure and evolution of domain knowledge. For example, network visualizations built from co-author relations contained in academic publications can provide insight on how scholars collaborate with each other in one or multiple domains, and visualizations built from the text content of articles can help us understand the topical structure of knowledge domains. These knowledge domain visualizations need to support interactive viewing and exploration by users. Such spatialization efforts are increasingly looking to geography and GIS as a source of metaphors and practical technology solutions, even when non-georeferenced information is managed, analyzed, and visualized. When it comes to deploying spatialized representations online, web mapping and web GIS can provide practical technology solutions for interactive viewing of knowledge domain visualizations, from panning and zooming to the overlay of additional information. This thesis presents a novel combination of advanced natural language processing -- in the form of topic modeling -- with dimensionality reduction through self-organizing maps and the deployment of web mapping/GIS technology towards intuitive, GIS-like, exploration of a knowledge domain visualization. A complete workflow is proposed and implemented that processes any corpus of input text documents into a map form and leverages a web application framework to let users explore knowledge domain maps interactively. This workflow is implemented and demonstrated for a data set of more than 66,000 conference abstract
Coercivity enhancement in Dy-free Nd-Fe-B sintered magnets by using Pr-Cu alloy
No full textThe grain boundary phase of Dy-free sintered Nd-Fe-B magnets is modified by using Pr68Cu32 eutectic alloy. The coercivity of the modified magnets reaches 21 kOe, which is the highest value in Dy-free Nd-Fe-B sintered magnets. Microstructural investigations show that a smooth and thick grain boundary layer is formed, and the content of the ferromagnetic elements in the grain boundary layer decreases from 65 at.% to 9 at. %. In addition, the mean grain size (4.5 mu m) in the doped sintered magnets is smaller than that (6.5 mu m) in the original sintered magnets. The modification in grain boundary and grain size reduces the magnetic interactions among grains and hinders nucleation of reversed magnetic domains, resulting in a coercivity enhancement. (C) 2014 AIP Publishing LLC.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000337143500063&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Physics, AppliedSCI(E)[email protected]; [email protected]
Effect of Basketweave Microstructure on Very High Cycle Fatigue Behavior of TC21 Titanium Alloy
No full textThis paper discusses the effect of basketweave microstructure on the very high cycle fatigue behavior of TC21 titanium alloy. Ultrasonic fatigue tests at 20 kHz are done on a very high cycle fatigue (VHCF) property of the alloys with 60 μm and 40 μm basketweave size, respectively. Results show that the alloys illustrate step-wise S-N characteristics over the 105–109 cycle regimes and that fatigue fracture in both of the alloys occur beyond the conventional fatigue limit of 107 cycles. Subsurface crack initiation occurs at low stress amplitude. A fine granular area (FGA) is observed along the α lamella at the subsurface crack initiation site. The mechanism for the subsurface crack initiation is revealed using layer-by-layer-polishing, due to the micro-voids that are introduced at the granular α phase. The colony of α lamella is due to the local stress concentrated between them under the cyclic load. The stress intensity factor range at the FGA front is regarded as the threshold value controlling the internal crack propagation. Furthermore, the effect of the baseketweave size on the very high cycle fatigue limits of the TC21 titanium alloy is evaluated based on the Murakami model, which is consistent with the experimental results. The fatigue life of TC21 titanium alloy is well predicted using the energy-based crack nucleation life model
Microstructure and Mechanical Property of 6082 Aluminum Alloy via Sc and Zr Addition Combined with Squeeze Casting
No full textTo enhance the mechanical properties of 6082 aluminum alloy, a novel Sc- and Zr-microalloyed 6082 alloy was fabricated through squeeze casting technology. Microalloying with Sc and Zr substantially refined the microstructure of alloy, achieving an average grain size of 136.36 μm—a 31.7% reduction compared to the baseline 6082 alloy. Furthermore, the addition of Sc and Zr effectively refined the coarse AlFeMnSi intermetallic phases, mitigating their inherent brittleness. The Sc/Zr-modified alloy exhibited delayed age-hardening kinetics, requiring 100% longer aging time to reach peak hardness due to Sc/Zr-induced retardation of β’’-phase precipitation. The optimized alloy demonstrated better mechanical properties, showing 10.4%, 8.0%, and 71.8% enhancements in yield strength, ultimate tensile strength, and elongation, respectively, over the non-microalloyed counterpart. The squeeze-cast Sc/Zr-modified alloy valve body showed yield strength exceeding 300 MPa and elongation above 10% across various sections, which verifies the effectiveness of this integrated microalloying and forming approach
