Advances in intelligent systems and computing, 2020
Over the last few years, establishments in the Philippines have slowly moved towards full utiliza... more Over the last few years, establishments in the Philippines have slowly moved towards full utilization of automated car parking ticket machines that have been employed all over the world. However, because this is new to the Philippine setting, there have been issues and complaints from users in operating the current machines, resulting to establishments reverting to hiring personnel to manually manage parking fee payments. A physical and cognitive usability study was conducted on a parking ticket machine in a shopping mall in the National Capital Region through observing users as they performed the process of paying through the machine. Task completion rates and errors were recorded for 100 users of the machine, who also answered a System Usability Scale (SUS) questionnaire. Three key metrics were measured: (1) the average time spent by new and experienced users, (2) the relative efficiency of manual and automated payment modes, and (3) overall user satisfaction. Results of the study showed a significant difference between average completion times of new and experienced users. SUS survey results showed that users found the machine to be fairly easy to learn, and that transactions through the machine can be faster than that of a cashier. However, a wide range in task completion times was observed for the automated process. This can be attributed to several errors and issues encountered during the payment process of some customers, primarily with the cash inlet rejecting certain bills and new users having difficulty identifying the appropriate slots of the machine. It was also observed that users encountered problems due to a mismatch between machine dimensions and their anthropometric measurements, particularly height. The study proved that poor parking ticket machine utilization was due to problems in human-machine interaction as well as mismatches between physical dimensions and user population anthropometry. Recommendations were provided in order to improve machine dimensions, layout and overall usability.
Runoff from glacierised Andean river basins is essential for sustaining the livelihoods of millio... more Runoff from glacierised Andean river basins is essential for sustaining the livelihoods of millions of people. By running a high-resolution climate model over the two most glacierised regions of Peru we unravel past climatic trends in precipitation and temperature. Future changes are determined from an ensemble of statistically downscaled global climate models. Projections under the high emissions scenario suggest substantial increases in temperature of 3.6 °C and 4.1 °C in the two regions, accompanied by a 12% precipitation increase by the late 21st century. Crucially, significant increases in precipitation extremes (around 75% for total precipitation on very wet days) occur together with an intensification of meteorological droughts caused by increased evapotranspiration. Despite higher precipitation, glacier mass losses are enhanced under both the highest emission and stabilization emission scenarios. Our modelling provides a new projection of combined and contrasting risks, in a...
Within the past decade, the aerospace engineering industry has evolved outside the constraints of... more Within the past decade, the aerospace engineering industry has evolved outside the constraints of using single, large, custom satellites. Due to increased reliability and robustness of commercial off the shelf (COTS) printed circuit board (PCB) components, missions instead have transitioned towards deploying swarms of smaller satellites. This approach significantly decreases the mission cost by reducing custom engineering and deployment expenses. Nanosatellites are able to be quickly developed with a more modular design at lowered risk. The Alpha mission at Cornell Space Systems Studio is fabricated in this manner. However, for the purpose of this mission, only one satellite was initially developed. This manuscript will discuss a systems engineering approach to the development of this satellite. As a disclaimer, this manuscript is written from a systems perspective. Therefore it will follow many subsystems from a wide range of functionalities. The research in this manuscript was kep...
<p>The Sibinacocha catchment is located in the southern region of Peru, ins... more <p>The Sibinacocha catchment is located in the southern region of Peru, inside the Vilcanota Urubamba Basin (VUB) system, and provides a range of important ecosystem services that local people depend on in their daily lives. Mapping highland ecosystems such as these is challenging because of cloud cover, and thus large-scale mapping activities are frequently applied. For this reason, there is a lack of studies focused on annual-scale land cover changes that may reveal sudden changes, or expose the interaction of changes between ecosystems. In this study, we identify five different land covers comprising the Sibinacocha catchment, namely glaciers, water bodies, wetlands, pastures, and low-vegetation areas. The evolution of the land cover of these ecosystems is mapped using a Random Forest classification model, which is a supervised machine-learning algorithm developed in Google Earth Engine. We apply it to a 36 year-long stack of Landsat images (Landsat 5, 7, and 8) from 1984 to 2020, using five classification criteria such as different normalized indices and a slope discrimination criteria obtained from SRTM information. Overall results were validated using the Kappa coefficient (K; 0.97) and overall accuracy analysis (97%) both based on collected field data, highlighting a good performance of the Random Forest model at classifying highland ecosystems. The results of the land cover evolution from 1984 and 2020, show significant area changes mainly on glaciers (-35%), wetlands (-17%), and water bodies (+14%) with noticeable trends, and low changes in pastures (+2%) and low-vegetation areas (+8%). For the time period of analysis, we identify an increase less than +0.8ºC in the annual temperature and 20 mm in annual precipitation. Using simple linear regression and correlation analysis, the changes we observe can be explained by the ecosystem responding to a warming climate. As glaciers recede, they are replaced by water bodies and low-vegetation ecosystems, low-vegetation ecosystems have generally become wetter, and wetlands and pastures transition backward and forward depending on their management. With these results, it is possible to understand the ecosystem’s natural evolution, enhanced by external factors, and to observe that it is ultimately conditioned by accelerated glacier retreat in the catchment headwaters.</p>
<p>Precipitation, snow and ice melt from Andean river basins provide a cruc... more <p>Precipitation, snow and ice melt from Andean river basins provide a crucial water source to mountain and downstream communities equally. Precipitation and temperature changes due to global climate change are likely to affect agriculture, hydropower generation and hazard risks, but are poorly constrained, especially in future projections.</p><p>Here we focus on two heavily glacierised regions of the Peruvian Andes, the Cordillera Blanca, and the Cordillera Vilcanota-Urubamba, to assess projected changes in extreme meteorological events and droughts. Previous work suggests increasing temperatures in both regions in the 21<sup>st</sup> century, with contrasting projections of precipitation trends. There has been little focus, however, on how extremes in precipitation and temperature might vary in the future. Having created a bias-corrected regional climate model from 1980-2018, we use empirical quantile mapping to statistically downscale 30 CMIP5 models. This ensemble is analysed to determine future changes in climate extremes.  </p><p>Both minimum and maximum daily temperatures are projected to increase in the from 2018 to 2100. This leads to a large reduction in the number of frost days in both regions, and suggests that under a high-emissions scenario, almost every day in the late 21<sup>st</sup> century will be in the 90<sup>th</sup> percentile of temperatures experienced during 1980-2018. The number of wet and dry days is not projected to change, but precipitation falling on very wet days (in the 95<sup>th</sup> percentile of the 1980-2018 period) is projected to increase significantly.</p><p>Lastly, we consider changes in future meteorological droughts using the standardised precipitation evapotranspiration index (SPEI) which considers potential evapotranspiration, as well as precipitation. We estimate potential evapotranspiration from temperature projections, using the Hargreaves method. Despite projected precipitation increases, temperature increases leading to an increase in evaporation may be large enough to increase meteorological droughts in the future, with the total number of drought months projected to almost double under high emission scenarios by the end of the 21<sup>st</sup> century. In a region that already experiences water stress and hazards, these changes to both extreme rainfall and drought could have a significant impact for communities in the Peruvian Andes, and for the downstream urban areas and industry that rely on mountain river flow.</p><p> </p>
<p>Glacier meltwater is a vital component of river discharge in the... more <p>Glacier meltwater is a vital component of river discharge in the Peruvian Andes, providing an important source of dry season runoff for communities, agriculture and fragile mountain ecosystems. Previous hydrochemical and modelling studies have identified the importance of glacier meltwater to downstream runoff and analysis of runoff records suggest ‘peak water’ has passed already. These studies, however, have been confined to the Rio Santa basin and the models applied have simplifications in their treatment of glacier melt and evolution. Our objectives are to i) determine the past glacier contribution to streamflow, determining when peak water passed and quantifying the recession of the glacier contribution to runoff; ii) predict future glacier evolution and its consequent impacts on water resources; and iii) to compare the hydrological response of catchments in central and southern Peru and establish their future response to glacier recession.</p><p>To meet these objectives we have applied the hourly physically-oriented, glacio-hydrological model TOPKAPI-ETH to two catchments in the Peruvian Andes: the Rio Santa in the Cordillera Blanca (4953 km<sup>2</sup>) and the Rio Urubamba draining the Cordilleras Vilcanota, Urubamba and Vilcabamba (11048 km<sup>2</sup>), the two most glacierised catchments in Peru. Past glacier recession has been substantial and future temperature rise is likely to lead to further glacier retreat, threatening water security in both regions. The model is forced with hourly atmospheric inputs from high-resolution (4 km), bias-corrected Weather Research and Forecasting (WRF) model outputs, which are downscaled to the TOPKAPI-ETH model resolution (100 m), using temperature and precipitation lapse rates defined from the WRF data for all sub-catchments of each domain. To reduce equifinality in model parameters we calibrate the model in a stepwise manner, using a combination of in-situ and remotely sensed data. Melt model parameters are calibrated based on full energy balance simulations at five sites across the two domains, with albedo parameters also derived from calibration with measured data. We calibrate the temperature decrease over glacier ice in an iterative manner using the WRF air temperatures, observed weather station data and the energy balance model outputs. Precipitation undercatch is a key unknown but it is constrained by careful comparison of modelled glacier surface mass balances with those inverted from remotely sensed data, while hydrological routing parameters are identified through calibration against hourly runoff records collected within the catchments. </p><p>We use the model outputs to unravel the water balance characteristics of both catchments, their main drivers, including the relative importance of glacier and snow melt components within catchment runoff, and how they vary seasonally, inter-annually and through time due to glacier recession. By applying the model to two catchments with contrasting climatologies and glacier characteristics we are also able to disentangle the reasons for their distinct future trajectories. </p>
Around 70% of the world’s tropical glaciers are located in Peru, and they are melting rapidly in ... more Around 70% of the world’s tropical glaciers are located in Peru, and they are melting rapidly in response to climate change. The glaciers of the data-sparse Southern Peruvian Andes, comprising the Cordilleras Vilcanota, Vilcabamba, and Urubamba, are a primary water source for thousands of people living in the rural foothills, and support people throughout the wider Cusco region. Here, we calculate geodetic mass balance for the Cordillera Vilcanota (−0.48 ± 0.07 m w.e. yr−1) using the ASTER satellite archive and derive a total loss of 3.18 ± 0.44 Gt ice between 2000 and 2020. Glacierised area has shrunk rapidly since the 1970s (losses of 54, 56, and 64% for the Cordilleras Vilcanota, Vilcabamba, and Urubamba respectively) as a consequence of changing climatic patterns, with low-lying glaciers receding the most across all regions. We calculate a rise in the median elevation of glaciers ranging from 15.9 m per decade over the Quelccaya ice cap in the Cordillera Vilcanota, to 32.8 m per...
This paper presents an orbit-to-ground model for the atmospheric entry of ChipSats, gram-scale sp... more This paper presents an orbit-to-ground model for the atmospheric entry of ChipSats, gram-scale spacecraft that offer unique advantages over their conventionally larger counterparts. ChipSats may prove particularly useful for in-situ measurements in the upper atmosphere, where spatially and temporally varying phenomena are especially difficult to characterize. Globally distributed ChipSats would enable datasets of unprecedented detail, assuming they could survive. The model presented is used to assess the survival and dispersion of a swarm of ChipSats when deployed over the Earth, Moon, Mars, and Titan. These planetary exploration case studies focus on the Monarch, the newest-generation ChipSat developed at Cornell University, in order to evaluate technology readiness for such missions. A parametric study is then conducted to inform future ChipSat design, highlighting the role of the ballistic coefficient in both peak entry temperature and mission duration.
Over the last few years, establishments in the Philippines have slowly moved towards full utiliza... more Over the last few years, establishments in the Philippines have slowly moved towards full utilization of automated car parking ticket machines that have been employed all over the world. However, because this is new to the Philippine setting, there have been issues and complaints from users in operating the current machines, resulting to establishments reverting to hiring personnel to manually manage parking fee payments. A physical and cognitive usability study was conducted on a parking ticket machine in a shopping mall in the National Capital Region through observing users as they performed the process of paying through the machine. Task completion rates and errors were recorded for 100 users of the machine, who also answered a System Usability Scale (SUS) questionnaire. Three key metrics were measured: (1) the average time spent by new and experienced users, (2) the relative efficiency of manual and automated payment modes, and (3) overall user satisfaction. Results of the study...
Charge collection is critical in any photodetector or photovoltaic device. Novel materials such a... more Charge collection is critical in any photodetector or photovoltaic device. Novel materials such as quantum dots (QDs) have extraordinary light absorption properties, but their poor mobility and short diffusion length limit efficient charge collection using conventional top/bottom contacts. In this work, a novel architecture based on multiple intercalated chemical vapor deposition graphene monolayers distributed in an orderly manner inside a QD film is studied. The intercalated graphene layers ensure that at any point in the absorbing material, photocarriers will be efficiently collected and transported. The devices with intercalated graphene layers have superior quantum efficiency over single‐bottom graphene/QD devices, overcoming the known restriction that the diffusion length imposes on film thickness. QD film with increased thickness shows efficient charge collection over the entire λ ≈ 500–1000 nm spectrum. This architecture could be applied to boost the performance of other low...
We report an AlGaAsOI quantum photonic circuit with multiple pair sources and tunable interferome... more We report an AlGaAsOI quantum photonic circuit with multiple pair sources and tunable interferometers. We demonstrate Hong-Ou-Mandel interference between two microring resonators and a tunable Bell state generator producing Ψ+ and Φ − bi-photon entangled states.
Aluminum gallium arsenide-on-insulator (AlGaAsOI) exhibits large χ2 and χ3 optical nonlinearities... more Aluminum gallium arsenide-on-insulator (AlGaAsOI) exhibits large χ2 and χ3 optical nonlinearities, a wide tunable bandgap, low waveguide propagation loss, and a large thermo-optic coefficient, making it an exciting platform for integrated quantum photonics. With ultrabright sources of quantum light established in AlGaAsOI, the next step is to develop the critical building blocks for chip-scale quantum photonic circuits. Here we expand the quantum photonic toolbox for AlGaAsOI by demonstrating edge couplers, 3 dB splitters, tunable interferometers, and waveguide crossings with performance comparable to or exceeding silicon and silicon-nitride quantum photonic platforms. As a demonstration, we de-multiplex photonic qubits through an unbalanced interferometer, paving the route toward ultra-efficient and high-rate chip-scale demonstrations of photonic quantum computation and information applications.
Advances in intelligent systems and computing, 2020
Over the last few years, establishments in the Philippines have slowly moved towards full utiliza... more Over the last few years, establishments in the Philippines have slowly moved towards full utilization of automated car parking ticket machines that have been employed all over the world. However, because this is new to the Philippine setting, there have been issues and complaints from users in operating the current machines, resulting to establishments reverting to hiring personnel to manually manage parking fee payments. A physical and cognitive usability study was conducted on a parking ticket machine in a shopping mall in the National Capital Region through observing users as they performed the process of paying through the machine. Task completion rates and errors were recorded for 100 users of the machine, who also answered a System Usability Scale (SUS) questionnaire. Three key metrics were measured: (1) the average time spent by new and experienced users, (2) the relative efficiency of manual and automated payment modes, and (3) overall user satisfaction. Results of the study showed a significant difference between average completion times of new and experienced users. SUS survey results showed that users found the machine to be fairly easy to learn, and that transactions through the machine can be faster than that of a cashier. However, a wide range in task completion times was observed for the automated process. This can be attributed to several errors and issues encountered during the payment process of some customers, primarily with the cash inlet rejecting certain bills and new users having difficulty identifying the appropriate slots of the machine. It was also observed that users encountered problems due to a mismatch between machine dimensions and their anthropometric measurements, particularly height. The study proved that poor parking ticket machine utilization was due to problems in human-machine interaction as well as mismatches between physical dimensions and user population anthropometry. Recommendations were provided in order to improve machine dimensions, layout and overall usability.
Runoff from glacierised Andean river basins is essential for sustaining the livelihoods of millio... more Runoff from glacierised Andean river basins is essential for sustaining the livelihoods of millions of people. By running a high-resolution climate model over the two most glacierised regions of Peru we unravel past climatic trends in precipitation and temperature. Future changes are determined from an ensemble of statistically downscaled global climate models. Projections under the high emissions scenario suggest substantial increases in temperature of 3.6 °C and 4.1 °C in the two regions, accompanied by a 12% precipitation increase by the late 21st century. Crucially, significant increases in precipitation extremes (around 75% for total precipitation on very wet days) occur together with an intensification of meteorological droughts caused by increased evapotranspiration. Despite higher precipitation, glacier mass losses are enhanced under both the highest emission and stabilization emission scenarios. Our modelling provides a new projection of combined and contrasting risks, in a...
Within the past decade, the aerospace engineering industry has evolved outside the constraints of... more Within the past decade, the aerospace engineering industry has evolved outside the constraints of using single, large, custom satellites. Due to increased reliability and robustness of commercial off the shelf (COTS) printed circuit board (PCB) components, missions instead have transitioned towards deploying swarms of smaller satellites. This approach significantly decreases the mission cost by reducing custom engineering and deployment expenses. Nanosatellites are able to be quickly developed with a more modular design at lowered risk. The Alpha mission at Cornell Space Systems Studio is fabricated in this manner. However, for the purpose of this mission, only one satellite was initially developed. This manuscript will discuss a systems engineering approach to the development of this satellite. As a disclaimer, this manuscript is written from a systems perspective. Therefore it will follow many subsystems from a wide range of functionalities. The research in this manuscript was kep...
<p>The Sibinacocha catchment is located in the southern region of Peru, ins... more <p>The Sibinacocha catchment is located in the southern region of Peru, inside the Vilcanota Urubamba Basin (VUB) system, and provides a range of important ecosystem services that local people depend on in their daily lives. Mapping highland ecosystems such as these is challenging because of cloud cover, and thus large-scale mapping activities are frequently applied. For this reason, there is a lack of studies focused on annual-scale land cover changes that may reveal sudden changes, or expose the interaction of changes between ecosystems. In this study, we identify five different land covers comprising the Sibinacocha catchment, namely glaciers, water bodies, wetlands, pastures, and low-vegetation areas. The evolution of the land cover of these ecosystems is mapped using a Random Forest classification model, which is a supervised machine-learning algorithm developed in Google Earth Engine. We apply it to a 36 year-long stack of Landsat images (Landsat 5, 7, and 8) from 1984 to 2020, using five classification criteria such as different normalized indices and a slope discrimination criteria obtained from SRTM information. Overall results were validated using the Kappa coefficient (K; 0.97) and overall accuracy analysis (97%) both based on collected field data, highlighting a good performance of the Random Forest model at classifying highland ecosystems. The results of the land cover evolution from 1984 and 2020, show significant area changes mainly on glaciers (-35%), wetlands (-17%), and water bodies (+14%) with noticeable trends, and low changes in pastures (+2%) and low-vegetation areas (+8%). For the time period of analysis, we identify an increase less than +0.8ºC in the annual temperature and 20 mm in annual precipitation. Using simple linear regression and correlation analysis, the changes we observe can be explained by the ecosystem responding to a warming climate. As glaciers recede, they are replaced by water bodies and low-vegetation ecosystems, low-vegetation ecosystems have generally become wetter, and wetlands and pastures transition backward and forward depending on their management. With these results, it is possible to understand the ecosystem’s natural evolution, enhanced by external factors, and to observe that it is ultimately conditioned by accelerated glacier retreat in the catchment headwaters.</p>
<p>Precipitation, snow and ice melt from Andean river basins provide a cruc... more <p>Precipitation, snow and ice melt from Andean river basins provide a crucial water source to mountain and downstream communities equally. Precipitation and temperature changes due to global climate change are likely to affect agriculture, hydropower generation and hazard risks, but are poorly constrained, especially in future projections.</p><p>Here we focus on two heavily glacierised regions of the Peruvian Andes, the Cordillera Blanca, and the Cordillera Vilcanota-Urubamba, to assess projected changes in extreme meteorological events and droughts. Previous work suggests increasing temperatures in both regions in the 21<sup>st</sup> century, with contrasting projections of precipitation trends. There has been little focus, however, on how extremes in precipitation and temperature might vary in the future. Having created a bias-corrected regional climate model from 1980-2018, we use empirical quantile mapping to statistically downscale 30 CMIP5 models. This ensemble is analysed to determine future changes in climate extremes.  </p><p>Both minimum and maximum daily temperatures are projected to increase in the from 2018 to 2100. This leads to a large reduction in the number of frost days in both regions, and suggests that under a high-emissions scenario, almost every day in the late 21<sup>st</sup> century will be in the 90<sup>th</sup> percentile of temperatures experienced during 1980-2018. The number of wet and dry days is not projected to change, but precipitation falling on very wet days (in the 95<sup>th</sup> percentile of the 1980-2018 period) is projected to increase significantly.</p><p>Lastly, we consider changes in future meteorological droughts using the standardised precipitation evapotranspiration index (SPEI) which considers potential evapotranspiration, as well as precipitation. We estimate potential evapotranspiration from temperature projections, using the Hargreaves method. Despite projected precipitation increases, temperature increases leading to an increase in evaporation may be large enough to increase meteorological droughts in the future, with the total number of drought months projected to almost double under high emission scenarios by the end of the 21<sup>st</sup> century. In a region that already experiences water stress and hazards, these changes to both extreme rainfall and drought could have a significant impact for communities in the Peruvian Andes, and for the downstream urban areas and industry that rely on mountain river flow.</p><p> </p>
<p>Glacier meltwater is a vital component of river discharge in the... more <p>Glacier meltwater is a vital component of river discharge in the Peruvian Andes, providing an important source of dry season runoff for communities, agriculture and fragile mountain ecosystems. Previous hydrochemical and modelling studies have identified the importance of glacier meltwater to downstream runoff and analysis of runoff records suggest ‘peak water’ has passed already. These studies, however, have been confined to the Rio Santa basin and the models applied have simplifications in their treatment of glacier melt and evolution. Our objectives are to i) determine the past glacier contribution to streamflow, determining when peak water passed and quantifying the recession of the glacier contribution to runoff; ii) predict future glacier evolution and its consequent impacts on water resources; and iii) to compare the hydrological response of catchments in central and southern Peru and establish their future response to glacier recession.</p><p>To meet these objectives we have applied the hourly physically-oriented, glacio-hydrological model TOPKAPI-ETH to two catchments in the Peruvian Andes: the Rio Santa in the Cordillera Blanca (4953 km<sup>2</sup>) and the Rio Urubamba draining the Cordilleras Vilcanota, Urubamba and Vilcabamba (11048 km<sup>2</sup>), the two most glacierised catchments in Peru. Past glacier recession has been substantial and future temperature rise is likely to lead to further glacier retreat, threatening water security in both regions. The model is forced with hourly atmospheric inputs from high-resolution (4 km), bias-corrected Weather Research and Forecasting (WRF) model outputs, which are downscaled to the TOPKAPI-ETH model resolution (100 m), using temperature and precipitation lapse rates defined from the WRF data for all sub-catchments of each domain. To reduce equifinality in model parameters we calibrate the model in a stepwise manner, using a combination of in-situ and remotely sensed data. Melt model parameters are calibrated based on full energy balance simulations at five sites across the two domains, with albedo parameters also derived from calibration with measured data. We calibrate the temperature decrease over glacier ice in an iterative manner using the WRF air temperatures, observed weather station data and the energy balance model outputs. Precipitation undercatch is a key unknown but it is constrained by careful comparison of modelled glacier surface mass balances with those inverted from remotely sensed data, while hydrological routing parameters are identified through calibration against hourly runoff records collected within the catchments. </p><p>We use the model outputs to unravel the water balance characteristics of both catchments, their main drivers, including the relative importance of glacier and snow melt components within catchment runoff, and how they vary seasonally, inter-annually and through time due to glacier recession. By applying the model to two catchments with contrasting climatologies and glacier characteristics we are also able to disentangle the reasons for their distinct future trajectories. </p>
Around 70% of the world’s tropical glaciers are located in Peru, and they are melting rapidly in ... more Around 70% of the world’s tropical glaciers are located in Peru, and they are melting rapidly in response to climate change. The glaciers of the data-sparse Southern Peruvian Andes, comprising the Cordilleras Vilcanota, Vilcabamba, and Urubamba, are a primary water source for thousands of people living in the rural foothills, and support people throughout the wider Cusco region. Here, we calculate geodetic mass balance for the Cordillera Vilcanota (−0.48 ± 0.07 m w.e. yr−1) using the ASTER satellite archive and derive a total loss of 3.18 ± 0.44 Gt ice between 2000 and 2020. Glacierised area has shrunk rapidly since the 1970s (losses of 54, 56, and 64% for the Cordilleras Vilcanota, Vilcabamba, and Urubamba respectively) as a consequence of changing climatic patterns, with low-lying glaciers receding the most across all regions. We calculate a rise in the median elevation of glaciers ranging from 15.9 m per decade over the Quelccaya ice cap in the Cordillera Vilcanota, to 32.8 m per...
This paper presents an orbit-to-ground model for the atmospheric entry of ChipSats, gram-scale sp... more This paper presents an orbit-to-ground model for the atmospheric entry of ChipSats, gram-scale spacecraft that offer unique advantages over their conventionally larger counterparts. ChipSats may prove particularly useful for in-situ measurements in the upper atmosphere, where spatially and temporally varying phenomena are especially difficult to characterize. Globally distributed ChipSats would enable datasets of unprecedented detail, assuming they could survive. The model presented is used to assess the survival and dispersion of a swarm of ChipSats when deployed over the Earth, Moon, Mars, and Titan. These planetary exploration case studies focus on the Monarch, the newest-generation ChipSat developed at Cornell University, in order to evaluate technology readiness for such missions. A parametric study is then conducted to inform future ChipSat design, highlighting the role of the ballistic coefficient in both peak entry temperature and mission duration.
Over the last few years, establishments in the Philippines have slowly moved towards full utiliza... more Over the last few years, establishments in the Philippines have slowly moved towards full utilization of automated car parking ticket machines that have been employed all over the world. However, because this is new to the Philippine setting, there have been issues and complaints from users in operating the current machines, resulting to establishments reverting to hiring personnel to manually manage parking fee payments. A physical and cognitive usability study was conducted on a parking ticket machine in a shopping mall in the National Capital Region through observing users as they performed the process of paying through the machine. Task completion rates and errors were recorded for 100 users of the machine, who also answered a System Usability Scale (SUS) questionnaire. Three key metrics were measured: (1) the average time spent by new and experienced users, (2) the relative efficiency of manual and automated payment modes, and (3) overall user satisfaction. Results of the study...
Charge collection is critical in any photodetector or photovoltaic device. Novel materials such a... more Charge collection is critical in any photodetector or photovoltaic device. Novel materials such as quantum dots (QDs) have extraordinary light absorption properties, but their poor mobility and short diffusion length limit efficient charge collection using conventional top/bottom contacts. In this work, a novel architecture based on multiple intercalated chemical vapor deposition graphene monolayers distributed in an orderly manner inside a QD film is studied. The intercalated graphene layers ensure that at any point in the absorbing material, photocarriers will be efficiently collected and transported. The devices with intercalated graphene layers have superior quantum efficiency over single‐bottom graphene/QD devices, overcoming the known restriction that the diffusion length imposes on film thickness. QD film with increased thickness shows efficient charge collection over the entire λ ≈ 500–1000 nm spectrum. This architecture could be applied to boost the performance of other low...
We report an AlGaAsOI quantum photonic circuit with multiple pair sources and tunable interferome... more We report an AlGaAsOI quantum photonic circuit with multiple pair sources and tunable interferometers. We demonstrate Hong-Ou-Mandel interference between two microring resonators and a tunable Bell state generator producing Ψ+ and Φ − bi-photon entangled states.
Aluminum gallium arsenide-on-insulator (AlGaAsOI) exhibits large χ2 and χ3 optical nonlinearities... more Aluminum gallium arsenide-on-insulator (AlGaAsOI) exhibits large χ2 and χ3 optical nonlinearities, a wide tunable bandgap, low waveguide propagation loss, and a large thermo-optic coefficient, making it an exciting platform for integrated quantum photonics. With ultrabright sources of quantum light established in AlGaAsOI, the next step is to develop the critical building blocks for chip-scale quantum photonic circuits. Here we expand the quantum photonic toolbox for AlGaAsOI by demonstrating edge couplers, 3 dB splitters, tunable interferometers, and waveguide crossings with performance comparable to or exceeding silicon and silicon-nitride quantum photonic platforms. As a demonstration, we de-multiplex photonic qubits through an unbalanced interferometer, paving the route toward ultra-efficient and high-rate chip-scale demonstrations of photonic quantum computation and information applications.
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Papers by Joshua Castro