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524 Research products, page 1 of 53

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  • Publication . Other literature type . Article . 2005
    Open Access
    Authors: 
    Craig Hulet; Cedric Briens; Franco Berruti; Edward Chan;
    Publisher: Walter de Gruyter GmbH
    Country: Canada

    This review examines the key features and configurations of short residence time cracking processes from a diverse range of industries that have been developed over the past 25 years. These industries include: bitumen or heavy oil upgrading, biomass pyrolysis, olefin production, catalytic cracking, and coal gasification. Characterization of the gas, liquid, and solid products and feedstock is provided wherever possible. In addition, a description of the source and mechanism of heat transfer, and how the feedstock is brought into contact with and separated from – this source is also given.There is a strong economic incentive for considering short residence time cracking processes. Not only do such processes increase the yields of the more valuable liquid and gaseous products, but more compact designs would also decrease capital costs. Careful control of the vapour residence times appears to be crucial in order to prevent secondary cracking and yet allow for maximum cracking of the feedstock. Rapid and thorough mixing of the feedstock with the heat source, not just creating a uniform dispersion, is also a key design aspect to consider. Finally, rapid and complete separation must also be carefully considered; again, to help control product residence time and avoid secondary cracking but also from a heat balance point of view.

  • Open Access English
    Authors: 
    ElGhamrawy, Islam;
    Publisher: Scholarship@Western
    Country: Canada

    Plastics are versatile, durable, and can be manipulated to match different needs. The COVID-19 pandemic has demonstrated the importance of reducing plastic waste and is believed to be responsible for increasing the generation of plastic waste by 54,000 tons/day which was reported in 2020. Another widely available waste is biomass waste. Agriculture and agroforestry, forest and wood processing, municipal waste, and the food industry are all considered major producers of biowaste. Co-gasification is considered one of the most promising methods of chemical recycling that targets the production of syngas (hydrogen and carbon monoxide) and light hydrocarbon gases. In this study, the gasification of pure birch sawdust wood (BSD) and pure rice husk (RH) was compared with mixtures where each BSD and RH was mixed with both LDPE and HDPE in the presence of three different bed materials, namely silica sand, olivine, and red mud. It was found that mixing the biomass with LDPE and HDPE increased hydrogen gas (H2) production. The Hydrogen gas concentration in the product gas increased slightly from 10% to 12% by volume when birch sawdust (BSD) was mixed with LDPE with a ratio of 1:1, while the hydrogen gas concentration increased to 15-16% by volume when birch sawdust was mixed with HDPE with a ratio of 1:1 and olivine has been used as bed material. The lower heating value of the produced gas, which has a direct relationship with the hydrogen and light hydrocarbons concentration, increased from 2.8 to 5.7 MJ/Nm3. Red mud increased the lower heating value of the produced gas when rice husk was premixed with HDPE from 3-4 MJ/Nm3 to 5.5-6 MJ/J/Nm3, however, the main drawback of using red mud as a bed material was the occurrence of attrition which requires a precautionary measure to control the dust produced and prevent air pollution. The produced gases from the gasification processes are commonly used in internal combustion engines applications, but due to the high content of hydrogen gas (H2/CO range 2-3) in the product, it can be considered a renewable source of hydrogen by further processing the gas mixture to obtain pure hydrogen gas that is utilized in various chemical industries.

  • Open Access English
    Authors: 
    Joseph Rozario; Ankit Vora; Sanjay Debnath; M. Pathak; Joshua M. Pearce;
    Publisher: HAL CCSD
    Countries: France, Canada
    Project: NSERC

    International audience; The effects of dispatch strategy on electrical performance of amorphous silicon-based solar photovoltaic-thermal systems, Renewable Energy 68, pp. 459-465 (2014). http://dx. Abstract: Previous work has shown that high-temperature short-term spike thermal annealing of hydrogenated amorphous silicon (a-Si:H) photovoltaic thermal (PVT) systems results in higher electrical energy output. The relationship between temperature and performance of a-Si:H PVT is not simple as high temperatures during thermal annealing improves the immediate electrical performance following an anneal, but during the anneal it creates a marked drop in electrical performance. In addition, the power generation of a-Si:H PVT depends on both the environmental conditions and the Staebler-Wronski Effect kinetics. In order to improve the performance of a-Si:H PVT systems further, this paper reports on the effect of various dispatch strategies on system electrical performance. Utilizing experimental results from thermal annealing, an annealing model simulation for a-Si:H-based PVT was developed and applied to different cities in the U. S. to investigate potential geographic effects on the dispatch optimization of the overall electrical PVT systems performance and annual electrical yield. The results showed that spike thermal annealing once per day maximized the improved electrical energy generation.

  • Publication . Article . Preprint . 2021 . Embargo End Date: 01 Jan 2021
    Open Access
    Authors: 
    Khushwant Rai; Farnam Hojatpanah; Firouz Badrkhani Ajaei; Katarina Grolinger;
    Publisher: arXiv
    Country: Canada
    Project: NSERC

    High-impedance faults (HIF) are difficult to detect because of their low current amplitude and highly diverse characteristics. In recent years, machine learning (ML) has been gaining popularity in HIF detection because ML techniques learn patterns from data and successfully detect HIFs. However, as these methods are based on supervised learning, they fail to reliably detect any scenario, fault or non-fault, not present in the training data. Consequently, this paper takes advantage of unsupervised learning and proposes a convolutional autoencoder framework for HIF detection (CAE-HIFD). Contrary to the conventional autoencoders that learn from normal behavior, the convolutional autoencoder (CAE) in CAE-HIFD learns only from the HIF signals eliminating the need for presence of diverse non-HIF scenarios in the CAE training. CAE distinguishes HIFs from non-HIF operating conditions by employing cross-correlation. To discriminate HIFs from transient disturbances such as capacitor or load switching, CAE-HIFD uses kurtosis, a statistical measure of the probability distribution shape. The performance evaluation studies conducted using the IEEE 13-node test feeder indicate that the CAE-HIFD reliably detects HIFs, outperforms the state-of-the-art HIF detection techniques, and is robust against noise.

  • Open Access
    Authors: 
    Nikolas K. Knowles; G. Daniel G. Langohr; Mohammadreza Faieghi; Andrew J. Nelson; Louis M. Ferreira;
    Publisher: Scholarship@Western
    Country: Canada
    Project: NSERC

    © 2019 Subject- and site-specific modeling techniques greatly improve the accuracy of computational models derived from clinical-resolution quantitative computed tomography (QCT) data. The majority of shoulder finite element (FE) studies use density–modulus relationships developed for alternative anatomical locations. As such, the objectives of this study were to compare the six most commonly used density–modulus relationships in shoulder finite element (FE) studies. To achieve this, ninety-eight (98) virtual trabecular bone cores were extracted from uCT scans of scapulae from 14 cadaveric specimens (7 male; 7 female). Homogeneous tissue moduli of 20 GPa, and heterogeneous tissue moduli scaled by CT-intensity were considered. Micro finite element models (µ-FEMs) of each virtual core were compressively loaded to 0.5% apparent strain and apparent strain energy density (SED app ) was collected. Each uCT virtual core was then co-registered to clinical QCT images, QCT-FEMs created, and each of the 6 density–modulus relationships applied (6 × 98 = 588 QCT-FEMs). The loading and boundary conditions were replicated and SED app was collected and compared to µ-FEM SED app . When a homogeneous tissue modulus was considered in the µ-FEMs, SED app was best predicted in QCT-FEMs with the density–modulus relationship developed from pooled anatomical locations (QCT-FEM SED app = 0.979µ-FEM SED app + 0.0066, r 2 = 0.933). A different density–modulus relationship best predicted SED app (QCT-FEM SED app = 1.014µ-FEM SED app + 0.0034, r 2 = 0.935) when a heterogeneous tissue modulus was considered. This study compared density–modulus relationships used in shoulder FE studies using an independent computational methodology for comparing these relationships.

  • Open Access
    Authors: 
    Weis, Tony;
    Publisher: Scholarship@Western
    Country: Canada

    The productivity of industrial capitalist agriculture is central to dominant development narratives. It is also highly unstable, with intractable biophysical problems created in the substitution of labour, skill and knowledge with technology, and overridden with unsustainable ‘technological fixes’ and masked by a host of externalized costs. Relatively cheap oil is central to this, effectively subsidizing the low-priced industrial grains and oilseeds on which global food security has come to hinge. However, the chronic biophysical contradictions of industrial capitalist agriculture are accelerating, at the same time as the surge in biofuels has augmented the still-rising demand of livestock feed to embolden industrial producers. A period of acute and ominously regressive food price volatility looms in the short term, with more ruinous outcomes ahead. But this might also widen openings for rebuilding biodiverse food systems and remaking and valorizing agricultural work, which will involve rethinking agriculture's place in conceptions of development and modernity.

  • Open Access
    Authors: 
    P. G. Komorowski; Sree Ram Valluri; Martin Houde;
    Publisher: Scholarship@Western
    Country: Canada
    Project: NSERC

    The last stable orbit (LSO) of a compact object (CO) is an important boundary condition when performing numerical analysis of orbit evolution. Although the LSO is already well understood for the case where a test-particle is in an elliptical orbit around a Schwarzschild black hole (SBH) and for the case of a circular orbit about a Kerr black hole (KBH) of normalised spin, S (|J|/M^2, where J is the spin angular momentum of the KBH); it is worthwhile to extend our knowledge to include elliptical orbits about a KBH. This extension helps to lay the foundation for a better understanding of gravitational wave (GW) emission. The mathematical developments described in this work sprang from the use of an effective potential (V) derived from the Kerr metric, which encapsulates the Lense-Thirring precession. That allowed us to develop a new form of analytical expression to calculate the LSO Radius for circular orbits (R_LSO) of arbitrary KBH spin. We were then able to construct a numerical method to calculate the latus rectum (l_LSO) for an elliptical LSO. Abstract Formulae for E^2 (square of normalised orbital energy) and L^2 (square of normalised orbital angular momentum) in terms of eccentricity, e, and latus rectum, l, were previously developed by others for elliptical orbits around an SBH and then extended to the KBH case; we used these results to generalise our analytical l_LSO equations to elliptical orbits. LSO data calculated from our analytical equations and numerical procedures, and those previously published, are then compared and found to be in excellent agreement. Comment: 42 pages, 9 figures, accepted for publication in Classical and Quantum Gravity

  • Open Access English
    Authors: 
    Ankit Vora; Jephias Gwamuri; Nezih Pala; Anand V. Kulkarni; Joshua M. Pearce; Durdu Ö. Güney;
    Publisher: HAL CCSD
    Countries: Canada, France
    Project: NSF | Metamaterials: Making Opt... (1202443), NSF | Increasing Solar Energy C... (1235750)

    Using metamaterial absorbers, we have shown that metallic layers in the absorbers do not necessarily constitute undesired resistive heating problem for photovoltaics. Tailoring the geometric skin depth of metals and employing the natural bulk absorbance characteristics of the semiconductors in those absorbers can enable the exchange of undesired resistive losses with the useful optical absorbance in the active semiconductors. Thus, Ohmic loss dominated metamaterial absorbers can be converted into photovoltaic near-perfect absorbers with the advantage of harvesting the full potential of light management offered by the metamaterial absorbers. Based on experimental permittivity data for indium gallium nitride, we have shown that between 75%-95% absorbance can be achieved in the semiconductor layers of the converted metamaterial absorbers. Besides other metamaterial and plasmonic devices, our results may also apply to photodectors and other metal or semiconductor based optical devices where resistive losses and power consumption are important pertaining to the device performance. Main text, 23 pages with 7 figures. Supplementary information, 10 pages with 14 figures

  • Open Access English
    Authors: 
    Bian, Bin;
    Publisher: Scholarship@Western
    Country: Canada

    Microbial fuel cells (MFCs) are widely researched for application in wastewater treatment. However, the current anodes used in MFCs often suffer from high fabrication cost and uncontrollable pore sizes. In this thesis, three-dimensional printing technique was utilized to fabricate anodes with different micro pore sizes for MFCs. Copper coating and carbonization were applied to the printed polymer anodes to increase the conductivity and specific surface area. Voltages of MFCs with various anodes were measured as well as other electrochemical tests such as linear sweep voltammetry and electrochemical impedance spectroscopy. 3D copper porous anode produced higher maximum voltages and power densities compared to copper mesh anode, illustrating the advantage of 3D porous structures in MFC application. However, due to copper corrosion, copper anodes presented much lower power output than carbon cloth anode. As carbon materials are known for their chemical stability, relatively good conductivity and excellent biocompatibility, MFCs with 3D carbon porous anodes were thus developed via carbonization, with larger surface area, higher electricity output, lower diffusion resistance and more bacterial biofilm formation compared to carbon cloth anode. This research project is the first application of 3D printing in MFCs and has developed several simple methods of 3D porous anode fabrication.

  • Open Access
    Authors: 
    Gwamuri, Jephias; Venkatesan, Ragavendran; Sadatgol, Mehdi; Mayandi, Jeyanthinath; Guney, Durdu O.; Pearce, Joshua M.;
    Publisher: Scholarship@Western
    Country: Canada

    The agglomeration/dewetting process of thin silver films provides a scalable method of obtaining self-assembled nanoparticles (SANPs) for plasmonics-based thin-film solar photovoltaic (PV) devices. We show the effect of annealing ambiance on silver SANP average size, particle/cluster finite shape, substrate area coverage/particle distribution, and how these physical parameters influence optical properties and surface-enhanced Raman scattering (SERS) responses of SANPs. Statistical analysis performed indicates that generally Ag SANPs processed in the presence of a gas (argon and nitrogen) ambiance tend to have smaller average size particles compared to those processed under vacuum. Optical properties are observed to be highly dependent on particle size, separation distance, and finite shape. The greatest SERS enhancement was observed for the argon-processed samples. There is a correlation between simulation and experimental data that indicate argon-processed AgNPs have a great potential to enhance light coupling when integrated to thin-film PV.

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Include:
The following results are related to Canada. Are you interested to view more results? Visit OpenAIRE - Explore.
524 Research products, page 1 of 53
  • Publication . Other literature type . Article . 2005
    Open Access
    Authors: 
    Craig Hulet; Cedric Briens; Franco Berruti; Edward Chan;
    Publisher: Walter de Gruyter GmbH
    Country: Canada

    This review examines the key features and configurations of short residence time cracking processes from a diverse range of industries that have been developed over the past 25 years. These industries include: bitumen or heavy oil upgrading, biomass pyrolysis, olefin production, catalytic cracking, and coal gasification. Characterization of the gas, liquid, and solid products and feedstock is provided wherever possible. In addition, a description of the source and mechanism of heat transfer, and how the feedstock is brought into contact with and separated from – this source is also given.There is a strong economic incentive for considering short residence time cracking processes. Not only do such processes increase the yields of the more valuable liquid and gaseous products, but more compact designs would also decrease capital costs. Careful control of the vapour residence times appears to be crucial in order to prevent secondary cracking and yet allow for maximum cracking of the feedstock. Rapid and thorough mixing of the feedstock with the heat source, not just creating a uniform dispersion, is also a key design aspect to consider. Finally, rapid and complete separation must also be carefully considered; again, to help control product residence time and avoid secondary cracking but also from a heat balance point of view.

  • Open Access English
    Authors: 
    ElGhamrawy, Islam;
    Publisher: Scholarship@Western
    Country: Canada

    Plastics are versatile, durable, and can be manipulated to match different needs. The COVID-19 pandemic has demonstrated the importance of reducing plastic waste and is believed to be responsible for increasing the generation of plastic waste by 54,000 tons/day which was reported in 2020. Another widely available waste is biomass waste. Agriculture and agroforestry, forest and wood processing, municipal waste, and the food industry are all considered major producers of biowaste. Co-gasification is considered one of the most promising methods of chemical recycling that targets the production of syngas (hydrogen and carbon monoxide) and light hydrocarbon gases. In this study, the gasification of pure birch sawdust wood (BSD) and pure rice husk (RH) was compared with mixtures where each BSD and RH was mixed with both LDPE and HDPE in the presence of three different bed materials, namely silica sand, olivine, and red mud. It was found that mixing the biomass with LDPE and HDPE increased hydrogen gas (H2) production. The Hydrogen gas concentration in the product gas increased slightly from 10% to 12% by volume when birch sawdust (BSD) was mixed with LDPE with a ratio of 1:1, while the hydrogen gas concentration increased to 15-16% by volume when birch sawdust was mixed with HDPE with a ratio of 1:1 and olivine has been used as bed material. The lower heating value of the produced gas, which has a direct relationship with the hydrogen and light hydrocarbons concentration, increased from 2.8 to 5.7 MJ/Nm3. Red mud increased the lower heating value of the produced gas when rice husk was premixed with HDPE from 3-4 MJ/Nm3 to 5.5-6 MJ/J/Nm3, however, the main drawback of using red mud as a bed material was the occurrence of attrition which requires a precautionary measure to control the dust produced and prevent air pollution. The produced gases from the gasification processes are commonly used in internal combustion engines applications, but due to the high content of hydrogen gas (H2/CO range 2-3) in the product, it can be considered a renewable source of hydrogen by further processing the gas mixture to obtain pure hydrogen gas that is utilized in various chemical industries.

  • Open Access English
    Authors: 
    Joseph Rozario; Ankit Vora; Sanjay Debnath; M. Pathak; Joshua M. Pearce;
    Publisher: HAL CCSD
    Countries: France, Canada
    Project: NSERC

    International audience; The effects of dispatch strategy on electrical performance of amorphous silicon-based solar photovoltaic-thermal systems, Renewable Energy 68, pp. 459-465 (2014). http://dx. Abstract: Previous work has shown that high-temperature short-term spike thermal annealing of hydrogenated amorphous silicon (a-Si:H) photovoltaic thermal (PVT) systems results in higher electrical energy output. The relationship between temperature and performance of a-Si:H PVT is not simple as high temperatures during thermal annealing improves the immediate electrical performance following an anneal, but during the anneal it creates a marked drop in electrical performance. In addition, the power generation of a-Si:H PVT depends on both the environmental conditions and the Staebler-Wronski Effect kinetics. In order to improve the performance of a-Si:H PVT systems further, this paper reports on the effect of various dispatch strategies on system electrical performance. Utilizing experimental results from thermal annealing, an annealing model simulation for a-Si:H-based PVT was developed and applied to different cities in the U. S. to investigate potential geographic effects on the dispatch optimization of the overall electrical PVT systems performance and annual electrical yield. The results showed that spike thermal annealing once per day maximized the improved electrical energy generation.

  • Publication . Article . Preprint . 2021 . Embargo End Date: 01 Jan 2021
    Open Access
    Authors: 
    Khushwant Rai; Farnam Hojatpanah; Firouz Badrkhani Ajaei; Katarina Grolinger;
    Publisher: arXiv
    Country: Canada
    Project: NSERC

    High-impedance faults (HIF) are difficult to detect because of their low current amplitude and highly diverse characteristics. In recent years, machine learning (ML) has been gaining popularity in HIF detection because ML techniques learn patterns from data and successfully detect HIFs. However, as these methods are based on supervised learning, they fail to reliably detect any scenario, fault or non-fault, not present in the training data. Consequently, this paper takes advantage of unsupervised learning and proposes a convolutional autoencoder framework for HIF detection (CAE-HIFD). Contrary to the conventional autoencoders that learn from normal behavior, the convolutional autoencoder (CAE) in CAE-HIFD learns only from the HIF signals eliminating the need for presence of diverse non-HIF scenarios in the CAE training. CAE distinguishes HIFs from non-HIF operating conditions by employing cross-correlation. To discriminate HIFs from transient disturbances such as capacitor or load switching, CAE-HIFD uses kurtosis, a statistical measure of the probability distribution shape. The performance evaluation studies conducted using the IEEE 13-node test feeder indicate that the CAE-HIFD reliably detects HIFs, outperforms the state-of-the-art HIF detection techniques, and is robust against noise.

  • Open Access
    Authors: 
    Nikolas K. Knowles; G. Daniel G. Langohr; Mohammadreza Faieghi; Andrew J. Nelson; Louis M. Ferreira;
    Publisher: Scholarship@Western
    Country: Canada
    Project: NSERC

    © 2019 Subject- and site-specific modeling techniques greatly improve the accuracy of computational models derived from clinical-resolution quantitative computed tomography (QCT) data. The majority of shoulder finite element (FE) studies use density–modulus relationships developed for alternative anatomical locations. As such, the objectives of this study were to compare the six most commonly used density–modulus relationships in shoulder finite element (FE) studies. To achieve this, ninety-eight (98) virtual trabecular bone cores were extracted from uCT scans of scapulae from 14 cadaveric specimens (7 male; 7 female). Homogeneous tissue moduli of 20 GPa, and heterogeneous tissue moduli scaled by CT-intensity were considered. Micro finite element models (µ-FEMs) of each virtual core were compressively loaded to 0.5% apparent strain and apparent strain energy density (SED app ) was collected. Each uCT virtual core was then co-registered to clinical QCT images, QCT-FEMs created, and each of the 6 density–modulus relationships applied (6 × 98 = 588 QCT-FEMs). The loading and boundary conditions were replicated and SED app was collected and compared to µ-FEM SED app . When a homogeneous tissue modulus was considered in the µ-FEMs, SED app was best predicted in QCT-FEMs with the density–modulus relationship developed from pooled anatomical locations (QCT-FEM SED app = 0.979µ-FEM SED app + 0.0066, r 2 = 0.933). A different density–modulus relationship best predicted SED app (QCT-FEM SED app = 1.014µ-FEM SED app + 0.0034, r 2 = 0.935) when a heterogeneous tissue modulus was considered. This study compared density–modulus relationships used in shoulder FE studies using an independent computational methodology for comparing these relationships.

  • Open Access
    Authors: 
    Weis, Tony;
    Publisher: Scholarship@Western
    Country: Canada

    The productivity of industrial capitalist agriculture is central to dominant development narratives. It is also highly unstable, with intractable biophysical problems created in the substitution of labour, skill and knowledge with technology, and overridden with unsustainable ‘technological fixes’ and masked by a host of externalized costs. Relatively cheap oil is central to this, effectively subsidizing the low-priced industrial grains and oilseeds on which global food security has come to hinge. However, the chronic biophysical contradictions of industrial capitalist agriculture are accelerating, at the same time as the surge in biofuels has augmented the still-rising demand of livestock feed to embolden industrial producers. A period of acute and ominously regressive food price volatility looms in the short term, with more ruinous outcomes ahead. But this might also widen openings for rebuilding biodiverse food systems and remaking and valorizing agricultural work, which will involve rethinking agriculture's place in conceptions of development and modernity.

  • Open Access
    Authors: 
    P. G. Komorowski; Sree Ram Valluri; Martin Houde;
    Publisher: Scholarship@Western
    Country: Canada
    Project: NSERC

    The last stable orbit (LSO) of a compact object (CO) is an important boundary condition when performing numerical analysis of orbit evolution. Although the LSO is already well understood for the case where a test-particle is in an elliptical orbit around a Schwarzschild black hole (SBH) and for the case of a circular orbit about a Kerr black hole (KBH) of normalised spin, S (|J|/M^2, where J is the spin angular momentum of the KBH); it is worthwhile to extend our knowledge to include elliptical orbits about a KBH. This extension helps to lay the foundation for a better understanding of gravitational wave (GW) emission. The mathematical developments described in this work sprang from the use of an effective potential (V) derived from the Kerr metric, which encapsulates the Lense-Thirring precession. That allowed us to develop a new form of analytical expression to calculate the LSO Radius for circular orbits (R_LSO) of arbitrary KBH spin. We were then able to construct a numerical method to calculate the latus rectum (l_LSO) for an elliptical LSO. Abstract Formulae for E^2 (square of normalised orbital energy) and L^2 (square of normalised orbital angular momentum) in terms of eccentricity, e, and latus rectum, l, were previously developed by others for elliptical orbits around an SBH and then extended to the KBH case; we used these results to generalise our analytical l_LSO equations to elliptical orbits. LSO data calculated from our analytical equations and numerical procedures, and those previously published, are then compared and found to be in excellent agreement. Comment: 42 pages, 9 figures, accepted for publication in Classical and Quantum Gravity

  • Open Access English
    Authors: 
    Ankit Vora; Jephias Gwamuri; Nezih Pala; Anand V. Kulkarni; Joshua M. Pearce; Durdu Ö. Güney;
    Publisher: HAL CCSD
    Countries: Canada, France
    Project: NSF | Metamaterials: Making Opt... (1202443), NSF | Increasing Solar Energy C... (1235750)

    Using metamaterial absorbers, we have shown that metallic layers in the absorbers do not necessarily constitute undesired resistive heating problem for photovoltaics. Tailoring the geometric skin depth of metals and employing the natural bulk absorbance characteristics of the semiconductors in those absorbers can enable the exchange of undesired resistive losses with the useful optical absorbance in the active semiconductors. Thus, Ohmic loss dominated metamaterial absorbers can be converted into photovoltaic near-perfect absorbers with the advantage of harvesting the full potential of light management offered by the metamaterial absorbers. Based on experimental permittivity data for indium gallium nitride, we have shown that between 75%-95% absorbance can be achieved in the semiconductor layers of the converted metamaterial absorbers. Besides other metamaterial and plasmonic devices, our results may also apply to photodectors and other metal or semiconductor based optical devices where resistive losses and power consumption are important pertaining to the device performance. Main text, 23 pages with 7 figures. Supplementary information, 10 pages with 14 figures

  • Open Access English
    Authors: 
    Bian, Bin;
    Publisher: Scholarship@Western
    Country: Canada

    Microbial fuel cells (MFCs) are widely researched for application in wastewater treatment. However, the current anodes used in MFCs often suffer from high fabrication cost and uncontrollable pore sizes. In this thesis, three-dimensional printing technique was utilized to fabricate anodes with different micro pore sizes for MFCs. Copper coating and carbonization were applied to the printed polymer anodes to increase the conductivity and specific surface area. Voltages of MFCs with various anodes were measured as well as other electrochemical tests such as linear sweep voltammetry and electrochemical impedance spectroscopy. 3D copper porous anode produced higher maximum voltages and power densities compared to copper mesh anode, illustrating the advantage of 3D porous structures in MFC application. However, due to copper corrosion, copper anodes presented much lower power output than carbon cloth anode. As carbon materials are known for their chemical stability, relatively good conductivity and excellent biocompatibility, MFCs with 3D carbon porous anodes were thus developed via carbonization, with larger surface area, higher electricity output, lower diffusion resistance and more bacterial biofilm formation compared to carbon cloth anode. This research project is the first application of 3D printing in MFCs and has developed several simple methods of 3D porous anode fabrication.

  • Open Access
    Authors: 
    Gwamuri, Jephias; Venkatesan, Ragavendran; Sadatgol, Mehdi; Mayandi, Jeyanthinath; Guney, Durdu O.; Pearce, Joshua M.;
    Publisher: Scholarship@Western
    Country: Canada

    The agglomeration/dewetting process of thin silver films provides a scalable method of obtaining self-assembled nanoparticles (SANPs) for plasmonics-based thin-film solar photovoltaic (PV) devices. We show the effect of annealing ambiance on silver SANP average size, particle/cluster finite shape, substrate area coverage/particle distribution, and how these physical parameters influence optical properties and surface-enhanced Raman scattering (SERS) responses of SANPs. Statistical analysis performed indicates that generally Ag SANPs processed in the presence of a gas (argon and nitrogen) ambiance tend to have smaller average size particles compared to those processed under vacuum. Optical properties are observed to be highly dependent on particle size, separation distance, and finite shape. The greatest SERS enhancement was observed for the argon-processed samples. There is a correlation between simulation and experimental data that indicate argon-processed AgNPs have a great potential to enhance light coupling when integrated to thin-film PV.