This paper presents the development of a system dynamics model as a decision support tool for the... more This paper presents the development of a system dynamics model as a decision support tool for the integrated asset management of water distribution and wastewater collection systems. The proposed system dynamics model integrates physical infrastructure with finance and consumer sectors, and enables user rate-setting and planning of integrated water infrastructure operational and capital works over the life-cycle of the infrastructure (10 to 100 year planning horizon). In practice, the proposed decision support tool helps water utilities to evaluate various management strategies for meeting infrastructure service and financial performance indicators, comply with legislations, and make optimized asset management decisions.
This paper presents the development of a novel system dynamics (SD) model for better understandin... more This paper presents the development of a novel system dynamics (SD) model for better understanding the interrelation and feedback mechanism between the wastewater collection (WWC) and wastewater treatment plant (WWTP) systems. Causal loop diagrams (CLDs) are developed and discussed to depict and understand feedback and inter-connections between physical, financial, and consumer sectors. The developed SD model is then extended to include the greenhouse gas (GHG) emissions, as a proxy for the environmental sector and for an environmental sustainability assessment of strategic decisions related to asset management planning of wastewater infrastructure system. It also adds new policy levers, such as population growth and urban densification in the social sector, and minimum fee-hike rates in the finance sector to enhance the representation of real-world conditions in the asset management planning. This new SD model will enable decision-makers to assess the sustainability impacts of thei...
This work is motivated by the need for prediction of pulling forces during pulling back phase in ... more This work is motivated by the need for prediction of pulling forces during pulling back phase in the horizontal directional drilling (HDD) installations for steel or polyethylene pipe. Six current prediction models are reviewed and components of pulling force resistance used in calculations are discussed. Two HDD installations are used to evaluate the accuracies of six models, including a 1816.2 m steel pipe crossing of the Yangtze River, Nanjing, China, and a 200 m polyethylene pipe installation at the University of Waterloo, Waterloo, Canada. Comparison of the results show that Driscopipe method and Drillpath method underestimate the maximum pulling forces in both steel pipe and polyethylene pipe cases, ASTM F 1962 method underestimates the maximum pulling force in steel pipe case while PRCI method and NEN 3650 method overestimate the maximum pulling force in polyethylene case, PRCI method, NEN 3650 method and developed PipeForce method are suitable for steel pipe case, ASTM F 1962 method and the PipeForce method are acceptable for polyethylene pipe case.
ABSTRACT Cast iron pipe has been used as a water distribution technology in North America since t... more ABSTRACT Cast iron pipe has been used as a water distribution technology in North America since the early nineteenth century. The first cast iron pipes were made of grey cast iron which was succeeded by ductile iron as a pipe material in the 1940s. These different iron alloys have significantly different microstructures which give rise to distinct mechanical properties. Insight into the non-destructive structural condition assessment of aging pipes can be advantageous in developing mitigation strategies for pipe failures. This paper examines the relationship between the small-strain and large-strain properties of exhumed cast iron water pipes. Nondestructive and destructive testing programs were performed on eight pipes varying in age from 40 to 130 years. The experimental program included microstructure evaluation and ultrasonic, tensile, and flexural testing. New applications of frequency domain analysis techniques including Fourier and wavelet transforms of ultrasonic pulse velocity measurements are presented. A low correlation between wave propagation and large-strain measurements was observed. However, the wave velocities were consistently different between ductile and grey cast iron pipes (14% to 18% difference); the ductile iron pipes showed the smaller variation in wave velocities. Thus, the variation of elastic properties for ductile iron was not enough to define a linear correlation because all the measurements were practically concentrated in single cluster of points. The cross-sectional areas of the specimens tested varied as a result of minor manufacturing defects and levels of corrosion. These variations affect the large strain testing results; but, surface defects have limited effect on wave velocities and may also contribute to the low correlations observed. Lamb waves are typically not considered in the evaluation of ultrasonic pulse velocity. However, Lamb waves were found to contribute significantly to the frequency content of the ultrasonic signals possibly resulting in the poor correlations observed. Therefore, correlations between wave velocities and large strain properties obtained using specimens manufactured in the laboratory must be used with caution in the condition assessment of aged water pipes especially for grey cast iron pipes.
A series of pilot studies across North America have been held to demonstrate that the Sahara ® le... more A series of pilot studies across North America have been held to demonstrate that the Sahara ® leak detection system can be adapted to detect leaks in pressurized wastewater forcemains and siphons under typical North American operating conditions. Likewise, the Water Research Council (WRc) in the UK has demonstrated the applicability of the Sahara ® leak detection system to similar environments in the UK. Sahara ® wastewater is a new technology that allows utilities to assess the condition of critical wastewater forcemains and siphons, such as major non-redundant lines, waterway crossings, and lines through environmentally sensitive areas, while keeping the line in service; it is the first to allow full length inspections of in-service force mains. This paper discusses the need for inspections of wastewater forcemains and siphons, the Saraha ® wastewater acoustic system, and the need for benchmarking of new technologies by third party organizations. The application of the Sahara system for the inspection of six wastewater pipelines in North America will also be discussed in detail.
This paper presents an innovative patent-pending, environmentally-friendly, "waterless" method of... more This paper presents an innovative patent-pending, environmentally-friendly, "waterless" method of pressure pipe cleaning using airborne abrasives. This innovative cleaning method not only removes corrosion products quickly, it leaves the pipe interior in a "ready state" for the trenchless application of spray-in-place (SIPP), cured-in-place (CIPP) and/or cement linings. SIPP liners are often referred to semi-structural while CIPP liners are referred to as structural. Unlike other methods that are intended only for cleaning pipe, this new method provides enhanced pipe surface preparation and dries the pipe for superior liner bond. This paper highlights the importance of pipe cleaning and preparation in advance of installing semistructural or structural pressure-pipe liners. It also provides details and limitations of this novel patent-pending technology. Early and promising results from a recent trenchless water main rehabilitation project, in Cambridge Ontario, showed that coal-tar coatings on ductile/cast iron pipe can be removed effectively and efficiently and the pipe can be prepared for bonding/adhesion with a SIPP liner.
Recently enacted regulations in Canada and elsewhere require water utilities to be financially se... more Recently enacted regulations in Canada and elsewhere require water utilities to be financially self-sustaining over the long-term. This implies full cost recovery for providing water and wastewater services to users. This study proposes a new approach to help water utilities plan to meet the requirements of the new regulations. A causal loop diagram is developed for a financially self-sustaining water utility which frames water and wastewater network management as a complex system with multiple interconnections and feedback loops. The novel System Dynamics approach is used to develop a demonstration model for water and wastewater network management. This is the first known application of System Dynamics to water and wastewater network management. The network simulated is that of a typical Canadian water utility that has under invested in maintenance. Model results show that with no proactive rehabilitation strategy the utility will need to substantially increase its user fees to achieve financial sustainability. This increase is further exacerbated when price elasticity of water demand is considered. When the utility pursues proactive rehabilitation, financial sustainability is achieved with lower user fees. Having demonstrated the significance of feedback loops for financial management of water and wastewater networks, the paper makes the case for a more complete utility model that considers the complexity of the system by incorporating all feedback loops.
Paper Prepared for Presentation at the Soils and Materials Session of the 2004 Annual Conference ... more Paper Prepared for Presentation at the Soils and Materials Session of the 2004 Annual Conference of the Transportation Association of Canada Quebec City September 2004 ... Horizontal directional drilling (HDD) has been successfully used to perform trenchless pipeline installations ...
This paper presents the development of a system dynamic model for the sustainability assessment o... more This paper presents the development of a system dynamic model for the sustainability assessment of strategic asset management plans for municipal wastewater collection systems. A causal loop diagram is constructed to present the links between sewer-network and sewagetreatment-plant systems and to depict the feedback mechanisms existing between physical, financial, and consumer sectors. Then, the presented cause-effect chains are mathematically parametrized and modeled in the novel system dynamic model. Unlike other sustainability assessment tool, this one captures the non-linearities and variations in the energy footprints of wastewater-collection and -treatment services, as well as both the positive and negative impacts on upstream and downstream processes. Application of this model will enable decision makers to assess the sustainability impacts of their strategic decisions on sewage collection and treatment systems, find synergistic costsaving opportunities, and improve the susta...
Canada's infrastructure is aging and deteriorating. New legislation requires the municip... more Canada's infrastructure is aging and deteriorating. New legislation requires the municipalities to estimate operating and capital expenditures for running the systems into the future and to develop financial sustainability plans. Wastewater pipelines deterioration ...
The study of ionospheric scintillation belongs to the class of problems dealing with wave diffrac... more The study of ionospheric scintillation belongs to the class of problems dealing with wave diffraction and propagation through a random medium, and its complete theoretical solution is presently not available. Approximate solutions or models, such as the 'thin phase diffraction screen model' and the 'Rytov solution for weak scintillation', have been proposed and do apply under restrictive conditions. Some probability density functions (PDF) have been derived analytically, or semi-analytically, from the proposed models, such as log-normal, Rician and Nakagami functions for the amplitude scintillation and the normal function for phase scintillation, but all show some discrepancies to the measured scintillation histograms.
Nanoscale gaps between adjacent metallic nanostructures give rise to extraordinarily large field ... more Nanoscale gaps between adjacent metallic nanostructures give rise to extraordinarily large field enhancements, known as "hot spots", upon illumination. Incident light with the electric field polarized across the gap (along the interparticle axis) is generally known to induce the strongest surface enhanced Raman spectroscopy (SERS) enhancements. However, here we show that, for a nanogap located within a nanowire linking extended Au electrodes, the greatest enhancement and resulting SERS emission occurs when the electric field of the incident light is polarized along the gap (transverse to the interelectrode axis). This surprising and counterintuitive polarization dependence results from a strong dipolar plasmon mode that resonates transversely across the nanowire, coupling with dark multipolar modes arising from subtle intrinsic asymmetries in the nanogap. These modes give rise to highly reproducible SERS enhancements at least an order of magnitude larger than the longitudi...
Canada's aged wastewater infrastructure is failing. New financial and environmental regu... more Canada's aged wastewater infrastructure is failing. New financial and environmental regulatory requirements demand municipalities to estimate operating and capital expenditures for running the systems into the future, and to develop plans for financial ...
As the millennium approaches we are faced with aperiod of increasing solar flux and intense ionos... more As the millennium approaches we are faced with aperiod of increasing solar flux and intense ionosphericscintillation. Not only single-frequency, but also dualfrequencyGPS measurements will be badly affected bydeep scintillation, due to its temporal and spatialdecorrelation characteristics. Using the scintillationobservables derived from dual-frequency phase andsignal-to-noise ratio measurements, real-timescintillation detection, tracking and indicationalgorithms have been developed. By ...
Proceedings of the National Academy of Sciences of the United States of America, 2014
Aluminum is abundant, low in cost, compatible with complementary metal-oxide semiconductor manufa... more Aluminum is abundant, low in cost, compatible with complementary metal-oxide semiconductor manufacturing methods, and capable of supporting tunable plasmon resonance structures that span the entire visible spectrum. However, the use of Al for color displays has been limited by its intrinsically broad spectral features. Here we show that vivid, highly polarized, and broadly tunable color pixels can be produced from periodic patterns of oriented Al nanorods. Whereas the nanorod longitudinal plasmon resonance is largely responsible for pixel color, far-field diffractive coupling is used to narrow the plasmon linewidth, enabling monochromatic coloration and significantly enhancing the far-field scattering intensity of the individual nanorod elements. The bright coloration can be observed with p-polarized white light excitation, consistent with the use of this approach in display devices. The resulting color pixels are constructed with a simple design, are compatible with scalable fabrication methods, and provide contrast ratios exceeding 100:1.
Gallium has recently been demonstrated as a phase-change plasmonic material offering UV tuneabili... more Gallium has recently been demonstrated as a phase-change plasmonic material offering UV tuneability, facile synthesis, and a remarkable stability due to its thin, self-terminating native oxide. However, the dense irregular nanoparticle (NP) ensembles fabricated by molecular-beam epitaxy make optical measurements of individual particles challenging. Here we employ hyperspectral cathodoluminescence (CL) microscopy to characterize the response of single Ga NPs of various sizes within an irregular ensemble by spatially and spectrally resolving both in-plane and out-of-plane plasmonic modes. These modes, which include hybridized dipolar and higher-order terms due to phase retardation and substrate interactions, are correlated with finite difference time domain (FDTD) electrodynamics calculations that consider the Ga NP contact angle, substrate, and native Ga/Si surface oxidation. This study experimentally confirms previous theoretical predictions of plasmonic size-tuneability in single G...
The results of five field tests on instrumented polyethylene (PE) pipes installed using horizonta... more The results of five field tests on instrumented polyethylene (PE) pipes installed using horizontal directional drilling (HDD) are presented in the paper. The focus is on mechanical behavior of pipes, their stiffness, strength and deformations. The testing methodology is presented and correlation between different readings is discussed. The test results are presented in a form of pipe strains along the borepaths and vs. time of installation. The test program involved 200 mm (8 inch) diameter, standard dimension ratio (SDR) 17 and 150 mm (6 inch) diameter, SDR 11, high density and medium density polyethylene pipes pulled along 90 and 177 m borepaths. The parameters were the quality of the drilling fluids, the ratio of borehole to pipe diameters, pipe material, and construction sequence. The presented results show the variation of pipe strains with time and along the borepath. Strain gauge readings indicate both flexural and axial deformations. Included in the paper are also readings from a load cell indicating the value of the pulling force. The experimental results are analyzed in terms of different mechanisms that contribute to the increase of the pulling forces and straining of the pipe. Influence of the field test parameters is presented. Conclusions are drawn on the effects of the mechanisms and test parameters on the pipe mechanical behavior. ᮊ
Nanoantennas are key optical components for light harvesting; photodiodes convert light into a cu... more Nanoantennas are key optical components for light harvesting; photodiodes convert light into a current of electrons for photodetection. We show that these two distinct, independent functions can be combined into the same structure. Photons coupled into a metallic nanoantenna excite resonant plasmons, which decay into energetic, "hot" electrons injected over a potential barrier at the nanoantenna-semiconductor interface, resulting in a photocurrent. This dual-function structure is a highly compact, wavelength-resonant, and polarization-specific light detector, with a spectral response extending to energies well below the semiconductor band edge.
This paper presents the development of a system dynamics model as a decision support tool for the... more This paper presents the development of a system dynamics model as a decision support tool for the integrated asset management of water distribution and wastewater collection systems. The proposed system dynamics model integrates physical infrastructure with finance and consumer sectors, and enables user rate-setting and planning of integrated water infrastructure operational and capital works over the life-cycle of the infrastructure (10 to 100 year planning horizon). In practice, the proposed decision support tool helps water utilities to evaluate various management strategies for meeting infrastructure service and financial performance indicators, comply with legislations, and make optimized asset management decisions.
This paper presents the development of a novel system dynamics (SD) model for better understandin... more This paper presents the development of a novel system dynamics (SD) model for better understanding the interrelation and feedback mechanism between the wastewater collection (WWC) and wastewater treatment plant (WWTP) systems. Causal loop diagrams (CLDs) are developed and discussed to depict and understand feedback and inter-connections between physical, financial, and consumer sectors. The developed SD model is then extended to include the greenhouse gas (GHG) emissions, as a proxy for the environmental sector and for an environmental sustainability assessment of strategic decisions related to asset management planning of wastewater infrastructure system. It also adds new policy levers, such as population growth and urban densification in the social sector, and minimum fee-hike rates in the finance sector to enhance the representation of real-world conditions in the asset management planning. This new SD model will enable decision-makers to assess the sustainability impacts of thei...
This work is motivated by the need for prediction of pulling forces during pulling back phase in ... more This work is motivated by the need for prediction of pulling forces during pulling back phase in the horizontal directional drilling (HDD) installations for steel or polyethylene pipe. Six current prediction models are reviewed and components of pulling force resistance used in calculations are discussed. Two HDD installations are used to evaluate the accuracies of six models, including a 1816.2 m steel pipe crossing of the Yangtze River, Nanjing, China, and a 200 m polyethylene pipe installation at the University of Waterloo, Waterloo, Canada. Comparison of the results show that Driscopipe method and Drillpath method underestimate the maximum pulling forces in both steel pipe and polyethylene pipe cases, ASTM F 1962 method underestimates the maximum pulling force in steel pipe case while PRCI method and NEN 3650 method overestimate the maximum pulling force in polyethylene case, PRCI method, NEN 3650 method and developed PipeForce method are suitable for steel pipe case, ASTM F 1962 method and the PipeForce method are acceptable for polyethylene pipe case.
ABSTRACT Cast iron pipe has been used as a water distribution technology in North America since t... more ABSTRACT Cast iron pipe has been used as a water distribution technology in North America since the early nineteenth century. The first cast iron pipes were made of grey cast iron which was succeeded by ductile iron as a pipe material in the 1940s. These different iron alloys have significantly different microstructures which give rise to distinct mechanical properties. Insight into the non-destructive structural condition assessment of aging pipes can be advantageous in developing mitigation strategies for pipe failures. This paper examines the relationship between the small-strain and large-strain properties of exhumed cast iron water pipes. Nondestructive and destructive testing programs were performed on eight pipes varying in age from 40 to 130 years. The experimental program included microstructure evaluation and ultrasonic, tensile, and flexural testing. New applications of frequency domain analysis techniques including Fourier and wavelet transforms of ultrasonic pulse velocity measurements are presented. A low correlation between wave propagation and large-strain measurements was observed. However, the wave velocities were consistently different between ductile and grey cast iron pipes (14% to 18% difference); the ductile iron pipes showed the smaller variation in wave velocities. Thus, the variation of elastic properties for ductile iron was not enough to define a linear correlation because all the measurements were practically concentrated in single cluster of points. The cross-sectional areas of the specimens tested varied as a result of minor manufacturing defects and levels of corrosion. These variations affect the large strain testing results; but, surface defects have limited effect on wave velocities and may also contribute to the low correlations observed. Lamb waves are typically not considered in the evaluation of ultrasonic pulse velocity. However, Lamb waves were found to contribute significantly to the frequency content of the ultrasonic signals possibly resulting in the poor correlations observed. Therefore, correlations between wave velocities and large strain properties obtained using specimens manufactured in the laboratory must be used with caution in the condition assessment of aged water pipes especially for grey cast iron pipes.
A series of pilot studies across North America have been held to demonstrate that the Sahara ® le... more A series of pilot studies across North America have been held to demonstrate that the Sahara ® leak detection system can be adapted to detect leaks in pressurized wastewater forcemains and siphons under typical North American operating conditions. Likewise, the Water Research Council (WRc) in the UK has demonstrated the applicability of the Sahara ® leak detection system to similar environments in the UK. Sahara ® wastewater is a new technology that allows utilities to assess the condition of critical wastewater forcemains and siphons, such as major non-redundant lines, waterway crossings, and lines through environmentally sensitive areas, while keeping the line in service; it is the first to allow full length inspections of in-service force mains. This paper discusses the need for inspections of wastewater forcemains and siphons, the Saraha ® wastewater acoustic system, and the need for benchmarking of new technologies by third party organizations. The application of the Sahara system for the inspection of six wastewater pipelines in North America will also be discussed in detail.
This paper presents an innovative patent-pending, environmentally-friendly, "waterless" method of... more This paper presents an innovative patent-pending, environmentally-friendly, "waterless" method of pressure pipe cleaning using airborne abrasives. This innovative cleaning method not only removes corrosion products quickly, it leaves the pipe interior in a "ready state" for the trenchless application of spray-in-place (SIPP), cured-in-place (CIPP) and/or cement linings. SIPP liners are often referred to semi-structural while CIPP liners are referred to as structural. Unlike other methods that are intended only for cleaning pipe, this new method provides enhanced pipe surface preparation and dries the pipe for superior liner bond. This paper highlights the importance of pipe cleaning and preparation in advance of installing semistructural or structural pressure-pipe liners. It also provides details and limitations of this novel patent-pending technology. Early and promising results from a recent trenchless water main rehabilitation project, in Cambridge Ontario, showed that coal-tar coatings on ductile/cast iron pipe can be removed effectively and efficiently and the pipe can be prepared for bonding/adhesion with a SIPP liner.
Recently enacted regulations in Canada and elsewhere require water utilities to be financially se... more Recently enacted regulations in Canada and elsewhere require water utilities to be financially self-sustaining over the long-term. This implies full cost recovery for providing water and wastewater services to users. This study proposes a new approach to help water utilities plan to meet the requirements of the new regulations. A causal loop diagram is developed for a financially self-sustaining water utility which frames water and wastewater network management as a complex system with multiple interconnections and feedback loops. The novel System Dynamics approach is used to develop a demonstration model for water and wastewater network management. This is the first known application of System Dynamics to water and wastewater network management. The network simulated is that of a typical Canadian water utility that has under invested in maintenance. Model results show that with no proactive rehabilitation strategy the utility will need to substantially increase its user fees to achieve financial sustainability. This increase is further exacerbated when price elasticity of water demand is considered. When the utility pursues proactive rehabilitation, financial sustainability is achieved with lower user fees. Having demonstrated the significance of feedback loops for financial management of water and wastewater networks, the paper makes the case for a more complete utility model that considers the complexity of the system by incorporating all feedback loops.
Paper Prepared for Presentation at the Soils and Materials Session of the 2004 Annual Conference ... more Paper Prepared for Presentation at the Soils and Materials Session of the 2004 Annual Conference of the Transportation Association of Canada Quebec City September 2004 ... Horizontal directional drilling (HDD) has been successfully used to perform trenchless pipeline installations ...
This paper presents the development of a system dynamic model for the sustainability assessment o... more This paper presents the development of a system dynamic model for the sustainability assessment of strategic asset management plans for municipal wastewater collection systems. A causal loop diagram is constructed to present the links between sewer-network and sewagetreatment-plant systems and to depict the feedback mechanisms existing between physical, financial, and consumer sectors. Then, the presented cause-effect chains are mathematically parametrized and modeled in the novel system dynamic model. Unlike other sustainability assessment tool, this one captures the non-linearities and variations in the energy footprints of wastewater-collection and -treatment services, as well as both the positive and negative impacts on upstream and downstream processes. Application of this model will enable decision makers to assess the sustainability impacts of their strategic decisions on sewage collection and treatment systems, find synergistic costsaving opportunities, and improve the susta...
Canada's infrastructure is aging and deteriorating. New legislation requires the municip... more Canada's infrastructure is aging and deteriorating. New legislation requires the municipalities to estimate operating and capital expenditures for running the systems into the future and to develop financial sustainability plans. Wastewater pipelines deterioration ...
The study of ionospheric scintillation belongs to the class of problems dealing with wave diffrac... more The study of ionospheric scintillation belongs to the class of problems dealing with wave diffraction and propagation through a random medium, and its complete theoretical solution is presently not available. Approximate solutions or models, such as the 'thin phase diffraction screen model' and the 'Rytov solution for weak scintillation', have been proposed and do apply under restrictive conditions. Some probability density functions (PDF) have been derived analytically, or semi-analytically, from the proposed models, such as log-normal, Rician and Nakagami functions for the amplitude scintillation and the normal function for phase scintillation, but all show some discrepancies to the measured scintillation histograms.
Nanoscale gaps between adjacent metallic nanostructures give rise to extraordinarily large field ... more Nanoscale gaps between adjacent metallic nanostructures give rise to extraordinarily large field enhancements, known as "hot spots", upon illumination. Incident light with the electric field polarized across the gap (along the interparticle axis) is generally known to induce the strongest surface enhanced Raman spectroscopy (SERS) enhancements. However, here we show that, for a nanogap located within a nanowire linking extended Au electrodes, the greatest enhancement and resulting SERS emission occurs when the electric field of the incident light is polarized along the gap (transverse to the interelectrode axis). This surprising and counterintuitive polarization dependence results from a strong dipolar plasmon mode that resonates transversely across the nanowire, coupling with dark multipolar modes arising from subtle intrinsic asymmetries in the nanogap. These modes give rise to highly reproducible SERS enhancements at least an order of magnitude larger than the longitudi...
Canada's aged wastewater infrastructure is failing. New financial and environmental regu... more Canada's aged wastewater infrastructure is failing. New financial and environmental regulatory requirements demand municipalities to estimate operating and capital expenditures for running the systems into the future, and to develop plans for financial ...
As the millennium approaches we are faced with aperiod of increasing solar flux and intense ionos... more As the millennium approaches we are faced with aperiod of increasing solar flux and intense ionosphericscintillation. Not only single-frequency, but also dualfrequencyGPS measurements will be badly affected bydeep scintillation, due to its temporal and spatialdecorrelation characteristics. Using the scintillationobservables derived from dual-frequency phase andsignal-to-noise ratio measurements, real-timescintillation detection, tracking and indicationalgorithms have been developed. By ...
Proceedings of the National Academy of Sciences of the United States of America, 2014
Aluminum is abundant, low in cost, compatible with complementary metal-oxide semiconductor manufa... more Aluminum is abundant, low in cost, compatible with complementary metal-oxide semiconductor manufacturing methods, and capable of supporting tunable plasmon resonance structures that span the entire visible spectrum. However, the use of Al for color displays has been limited by its intrinsically broad spectral features. Here we show that vivid, highly polarized, and broadly tunable color pixels can be produced from periodic patterns of oriented Al nanorods. Whereas the nanorod longitudinal plasmon resonance is largely responsible for pixel color, far-field diffractive coupling is used to narrow the plasmon linewidth, enabling monochromatic coloration and significantly enhancing the far-field scattering intensity of the individual nanorod elements. The bright coloration can be observed with p-polarized white light excitation, consistent with the use of this approach in display devices. The resulting color pixels are constructed with a simple design, are compatible with scalable fabrication methods, and provide contrast ratios exceeding 100:1.
Gallium has recently been demonstrated as a phase-change plasmonic material offering UV tuneabili... more Gallium has recently been demonstrated as a phase-change plasmonic material offering UV tuneability, facile synthesis, and a remarkable stability due to its thin, self-terminating native oxide. However, the dense irregular nanoparticle (NP) ensembles fabricated by molecular-beam epitaxy make optical measurements of individual particles challenging. Here we employ hyperspectral cathodoluminescence (CL) microscopy to characterize the response of single Ga NPs of various sizes within an irregular ensemble by spatially and spectrally resolving both in-plane and out-of-plane plasmonic modes. These modes, which include hybridized dipolar and higher-order terms due to phase retardation and substrate interactions, are correlated with finite difference time domain (FDTD) electrodynamics calculations that consider the Ga NP contact angle, substrate, and native Ga/Si surface oxidation. This study experimentally confirms previous theoretical predictions of plasmonic size-tuneability in single G...
The results of five field tests on instrumented polyethylene (PE) pipes installed using horizonta... more The results of five field tests on instrumented polyethylene (PE) pipes installed using horizontal directional drilling (HDD) are presented in the paper. The focus is on mechanical behavior of pipes, their stiffness, strength and deformations. The testing methodology is presented and correlation between different readings is discussed. The test results are presented in a form of pipe strains along the borepaths and vs. time of installation. The test program involved 200 mm (8 inch) diameter, standard dimension ratio (SDR) 17 and 150 mm (6 inch) diameter, SDR 11, high density and medium density polyethylene pipes pulled along 90 and 177 m borepaths. The parameters were the quality of the drilling fluids, the ratio of borehole to pipe diameters, pipe material, and construction sequence. The presented results show the variation of pipe strains with time and along the borepath. Strain gauge readings indicate both flexural and axial deformations. Included in the paper are also readings from a load cell indicating the value of the pulling force. The experimental results are analyzed in terms of different mechanisms that contribute to the increase of the pulling forces and straining of the pipe. Influence of the field test parameters is presented. Conclusions are drawn on the effects of the mechanisms and test parameters on the pipe mechanical behavior. ᮊ
Nanoantennas are key optical components for light harvesting; photodiodes convert light into a cu... more Nanoantennas are key optical components for light harvesting; photodiodes convert light into a current of electrons for photodetection. We show that these two distinct, independent functions can be combined into the same structure. Photons coupled into a metallic nanoantenna excite resonant plasmons, which decay into energetic, "hot" electrons injected over a potential barrier at the nanoantenna-semiconductor interface, resulting in a photocurrent. This dual-function structure is a highly compact, wavelength-resonant, and polarization-specific light detector, with a spectral response extending to energies well below the semiconductor band edge.
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Papers by Mark Knight