A recent study examined the use of virtual reality imagery in conjunction with MADYMO computation... more A recent study examined the use of virtual reality imagery in conjunction with MADYMO computational modeling to facilitate prototype development and existing-design optimization of crashworthy child restraint systems (CRS). A postprocessing tool called ...
Most current anomaly detection methods suffer from the curse of dimensionality when dealing with ... more Most current anomaly detection methods suffer from the curse of dimensionality when dealing with high-dimensional data. We propose an anomaly detection algorithm that can scale to high-dimensional data using concepts from the theory of large deviations. The proposed Large Deviations Anomaly Detection (LAD) algorithm is shown to outperform state of art anomaly detection methods on a variety of large and high-dimensional benchmark data sets. Exploiting the ability of the algorithm to scale to high-dimensional data, we propose an online anomaly detection method to identify anomalies in a collection of multivariate time series. We demonstrate the applicability of the online algorithm in identifying counties in the United States with anomalous trends in terms of COVID-19 related cases and deaths. Several of the identified anomalous counties correlate with counties with documented poor response to the COVID pandemic.
Computer-aided design and finite element methods (FEM) have interested dental researchers because... more Computer-aided design and finite element methods (FEM) have interested dental researchers because of its use in the computer simulation and design of dental implants, a process greatly facilitated by the development of new computer technology and more accurate modeling technologies. FEM allows for a better understanding of stresses along the surfaces of an implant and in surrounding bone. This will aid in the optimization of implant design and placement of the implant into the bone; it will also help when designing the final prostheses to minimize stresses. The purpose of this review is to elucidate the role of FEM and the impact of this technology in clinical dentistry in the new millennium.
International Journal for Uncertainty Quantification, 2015
This paper presents a novel approach to assessing the hazard threat to a locale due to a large vo... more This paper presents a novel approach to assessing the hazard threat to a locale due to a large volcanic avalanche. The methodology combines: (i) mathematical modeling of volcanic mass flows; (ii) field data of avalanche frequency, volume, and runout; (iii) large-scale numerical simulations of flow events; (iv) use of statistical methods to minimize computational costs, and to capture unlikely events; (v) calculation of the probability of a catastrophic flow event over the next T years at a location of interest; and (vi) innovative computational methodology to implement these methods. This unified presentation collects elements that have been separately developed, and incorporates new contributions to the process. The field data and numerical simulations used here are subject to uncertainty from many sources, uncertainties that must be properly accounted for in assessing the hazard. The methodology presented here will be demonstrated with data from the Soufrière Hills Volcano on the island of Montserrat, where there is a relatively complete record of volcanic mass flows from the past 15 years. This methodology can be transferred to other volcanic sites with similar characteristics and where sparse historical data have prevented such high-quality analysis. More generally, the core of this methodology is widely applicable and can be used for other hazard scenarios, such as floods or ash plumes.
In this paper, we present new ideas to greatly enhance the quality of uncertainty quantification ... more In this paper, we present new ideas to greatly enhance the quality of uncertainty quantification in the DDDAS framework. We build on ongoing work in large scale transport of geophysical mass of volcanic origin-a danger to both land based installations and airborne vehicles. The principal new idea introduced is the concept of a localized Bayes linear model as a surrogate for the expensive simulator. Probability of ash presence is compared to earlier work.
This paper describes XSEDE Metrics on Demand, a comprehensive auditing framework for use by highp... more This paper describes XSEDE Metrics on Demand, a comprehensive auditing framework for use by highperformance computing centers, which provides metrics regarding resource utilization, resource performance, and impact on scholarship and research. This role-based framework is designed to meet the following objectives: (1) provide the user community with a tool to manage their allocations and optimize their resource utilization; (2) provide operational staff with the ability to monitor and tune resource performance; (3) provide management with a tool to monitor utilization, user base, and performance of resources; and (4) provide metrics to help measure scientific impact. Although initially focused on the XSEDE program, XSEDE Metrics on Demand can be adapted to any high-performance computing environment. The framework includes a computationally lightweight application kernel auditing system that utilizes performance kernels to measure overall system performance. This allows continuous resource auditing to measure all aspects of system performance including filesystem performance, processor and memory performance, and network latency and bandwidth. Metrics that focus on scientific impact, such as publications, citations and external funding, will be included to help quantify the important role high-performance computing centers play in advancing research and scholarship.
Particle transport models can be divided into two broad categories: those intended to calculate e... more Particle transport models can be divided into two broad categories: those intended to calculate eruption column characteristics based on tephra fall deposits, as in [1], and those intended to predict long-range atmospheric and deposit distributions based on the scale of the eruption, as in [2]. Both types of models rely on the existence of an explicit relationship between the eruption and atmospheric dynamics and the resulting fall deposit. This relationship is complicated by a number of factors, including plume mechanics, variable ...
Numerical models for simulation of mass flows are typically focussed upon accurately predicting t... more Numerical models for simulation of mass flows are typically focussed upon accurately predicting the paths, travel times and inundation from a single flow or collapse event. When considering catchment-based hazards from a volcano, this is complicated by often being faced with several possible scenarios. Over the last 800 years at Mt. Taranaki/ Egmont, a number of dome growth and collapse events have resulted in the genesis and emplacement of block-and-ash flows (BAFs). Each BAF was directed northwestward by a breach in the crater rim. The latest dome collapse events in the AD 1880s and AD 1755 inundated the northwestern flank and had run-out lengths 10 km from source. Future activity of this type could have a devastating effect on the Taranaki region's communities, infrastructure and economy. Hazard planning has involved constructing volcanic hazard maps based upon the areas inundated by past volcanic flows, with little consideration of present-day topography. Here, a numerical geophysical mass flow modelling approach is used to forecast the hazards of future comparable BAF events on NW Mt. Taranaki. The Titan2D programme encompasses a ''shallow water'', continuum solution-based, granular flow model. Flow mechanical properties needed for this approach include estimates of internal and basal friction as well as the physical dimensions of the initial collapse. Before this model can be applied to Taranaki BAFs, the input parameters must be calibrated by simulating a range of past collapse events. By using AD 1860 and AD 1755 scenarios, initial collapse volumes can be well constrained and internal and basal friction angles can be evaluated through an iterative approach from previous run-out lengths. A range of possible input parameters was, therefore, determined to produce a suite of potentially inundated areas under present-day terrain. A suite of 10 forecasts from a uniformly distributed range were combined to create a map of relative probabilities of inundation by future BAF events. These results were combined in a GIS package to produce hazard zones
... In its simplest form, it is the tangent of the angle (α) connecting the top of the source are... more ... In its simplest form, it is the tangent of the angle (α) connecting the top of the source area to the most distal part of the flow (Heim, 1932): (7)H max /L max =μ=tanαwhere H max is the fall height and L max is the horizontal distance travelled. ...
... In its simplest form, it is the tangent of the angle (α) connecting the top of the source are... more ... In its simplest form, it is the tangent of the angle (α) connecting the top of the source area to the most distal part of the flow (Heim, 1932): (7)H max /L max =μ=tanαwhere H max is the fall height and L max is the horizontal distance travelled. ...
The eruption of Eyjafjalla, Iceland, began wreaking havoc on European aviation with ash emissions... more The eruption of Eyjafjalla, Iceland, began wreaking havoc on European aviation with ash emissions from 14 April 2010 onward. Peak ash emissions occurred in the period 15-20 April. To make predictions of the likely position of the ash cloud and issue advisories to the airline industry, London VAAC (Volcanic Ash Advisory Center) solved mathematical models of advection and dispersion. These models incorporate data with stochastic variability, such as a varying windfield. The models also require input data that are not ...
The eruption of Eyjafjalla, Iceland, began wreaking havoc on European aviation with ash emissions... more The eruption of Eyjafjalla, Iceland, began wreaking havoc on European aviation with ash emissions from 14 April 2010 onward. Peak ash emissions occurred in the period 15-20 April. To make predictions of the likely position of the ash cloud and issue advisories to the airline industry, London VAAC (Volcanic Ash Advisory Center) solved mathematical models of advection and dispersion. These models incorporate data with stochastic variability, such as a varying windfield. The models also require input data that are not ...
ABSTRACT In explosive volcanic eruptions, a large amount of ash may be injected into the atmosphe... more ABSTRACT In explosive volcanic eruptions, a large amount of ash may be injected into the atmosphere. The ash clouds extend over large areas and can travel thousands of kilometers from the source volcano, disrupting air traffic and posing a significant hazard to air travel. To predict the likely position of the ash cloud, mathematical models of advection and dispersion are used. These models require input data on source conditions such as eruption plume height, as well as the windfield. In this contribution, we extend a previous work on uncertainty quantification in the volcanic input parameters by considering the variability in the windfields. The puff trajectory model is used to hindcast the motion of the ash cloud for the eruption of Eyjafjallajokull, Iceland which had a peak ash emission in the period 14-18 April 2010. Windfields along with source parameters (vent radius, vent velocity, mean grain size and grain size variance) represent major sources for uncertainties in ash transport and dispersion simulations. Based on our lack of knowledge of the exact conditions of the source, probability distributions are assigned to the parameters which are later sampled in a Monte Carlo fashion. For windfields, ensemble methods are considered to be an effective way to estimate the probability density function of future states of the atmosphere by addressing uncertainties present in initial conditions and in model approximations. We are using the Global Ensemble Forecast System (GEFS) generated by the National Centers for Environmental Prediction (NCEP), which is a weather forecast model made up of 21 separate ensemble members. Output statistics are then computed by properly summing the weighted values of the output parameters of interest. The results are presented as forecast envelope and show how volcanic source term uncertainty and windfield stochastic variability can affect the forecast. Thus, we produce a complete probabilistic forecast of ash cloud position.
ABSTRACT Computational methods used in modeling geophysical mass flows assume that parameters (fr... more ABSTRACT Computational methods used in modeling geophysical mass flows assume that parameters (friction angles) and initial data (volume/starting location) are known exactly, when often they are only known in a probabilistic sense. For example, if the bed friction angle is known to lie between 15 and 25 degrees, with insufficient data to say which values within the range are more likely than others, proper treatment requires the input for bed friction to be a uniform probability distribution function (PDF) over that range. During the generation of hazard maps from numerical models, geologists need a tool to quantify the effect of this input uncertainty on specific output quantities of interest. Monte Carlo (MC) sampling is prohibitively expensive for sufficient accuracy; for three significant figures of accuracy approximately 106 MC runs are required, for 20 minute single processor runs on 64 processors this would take 217 days. The relative expense of first principle based models like the Savage-Hutter type avalanche model's governing PDEs (which require the solution of a set of nonlinear hyperbolic equations) rules out using the currently popular Stochastic Galerkin method of uncertainty propagation. In this contribution, we discuss the use of an intelligent sampling methodology to propagate the input uncertainty through the TITAN geophysical flow solver. The stochastic output is displayed as a map of the depth that the flow will not exceed at each (X,Y) point for an arbitrary confidence level.
A recent study examined the use of virtual reality imagery in conjunction with MADYMO computation... more A recent study examined the use of virtual reality imagery in conjunction with MADYMO computational modeling to facilitate prototype development and existing-design optimization of crashworthy child restraint systems (CRS). A postprocessing tool called ...
Most current anomaly detection methods suffer from the curse of dimensionality when dealing with ... more Most current anomaly detection methods suffer from the curse of dimensionality when dealing with high-dimensional data. We propose an anomaly detection algorithm that can scale to high-dimensional data using concepts from the theory of large deviations. The proposed Large Deviations Anomaly Detection (LAD) algorithm is shown to outperform state of art anomaly detection methods on a variety of large and high-dimensional benchmark data sets. Exploiting the ability of the algorithm to scale to high-dimensional data, we propose an online anomaly detection method to identify anomalies in a collection of multivariate time series. We demonstrate the applicability of the online algorithm in identifying counties in the United States with anomalous trends in terms of COVID-19 related cases and deaths. Several of the identified anomalous counties correlate with counties with documented poor response to the COVID pandemic.
Computer-aided design and finite element methods (FEM) have interested dental researchers because... more Computer-aided design and finite element methods (FEM) have interested dental researchers because of its use in the computer simulation and design of dental implants, a process greatly facilitated by the development of new computer technology and more accurate modeling technologies. FEM allows for a better understanding of stresses along the surfaces of an implant and in surrounding bone. This will aid in the optimization of implant design and placement of the implant into the bone; it will also help when designing the final prostheses to minimize stresses. The purpose of this review is to elucidate the role of FEM and the impact of this technology in clinical dentistry in the new millennium.
International Journal for Uncertainty Quantification, 2015
This paper presents a novel approach to assessing the hazard threat to a locale due to a large vo... more This paper presents a novel approach to assessing the hazard threat to a locale due to a large volcanic avalanche. The methodology combines: (i) mathematical modeling of volcanic mass flows; (ii) field data of avalanche frequency, volume, and runout; (iii) large-scale numerical simulations of flow events; (iv) use of statistical methods to minimize computational costs, and to capture unlikely events; (v) calculation of the probability of a catastrophic flow event over the next T years at a location of interest; and (vi) innovative computational methodology to implement these methods. This unified presentation collects elements that have been separately developed, and incorporates new contributions to the process. The field data and numerical simulations used here are subject to uncertainty from many sources, uncertainties that must be properly accounted for in assessing the hazard. The methodology presented here will be demonstrated with data from the Soufrière Hills Volcano on the island of Montserrat, where there is a relatively complete record of volcanic mass flows from the past 15 years. This methodology can be transferred to other volcanic sites with similar characteristics and where sparse historical data have prevented such high-quality analysis. More generally, the core of this methodology is widely applicable and can be used for other hazard scenarios, such as floods or ash plumes.
In this paper, we present new ideas to greatly enhance the quality of uncertainty quantification ... more In this paper, we present new ideas to greatly enhance the quality of uncertainty quantification in the DDDAS framework. We build on ongoing work in large scale transport of geophysical mass of volcanic origin-a danger to both land based installations and airborne vehicles. The principal new idea introduced is the concept of a localized Bayes linear model as a surrogate for the expensive simulator. Probability of ash presence is compared to earlier work.
This paper describes XSEDE Metrics on Demand, a comprehensive auditing framework for use by highp... more This paper describes XSEDE Metrics on Demand, a comprehensive auditing framework for use by highperformance computing centers, which provides metrics regarding resource utilization, resource performance, and impact on scholarship and research. This role-based framework is designed to meet the following objectives: (1) provide the user community with a tool to manage their allocations and optimize their resource utilization; (2) provide operational staff with the ability to monitor and tune resource performance; (3) provide management with a tool to monitor utilization, user base, and performance of resources; and (4) provide metrics to help measure scientific impact. Although initially focused on the XSEDE program, XSEDE Metrics on Demand can be adapted to any high-performance computing environment. The framework includes a computationally lightweight application kernel auditing system that utilizes performance kernels to measure overall system performance. This allows continuous resource auditing to measure all aspects of system performance including filesystem performance, processor and memory performance, and network latency and bandwidth. Metrics that focus on scientific impact, such as publications, citations and external funding, will be included to help quantify the important role high-performance computing centers play in advancing research and scholarship.
Particle transport models can be divided into two broad categories: those intended to calculate e... more Particle transport models can be divided into two broad categories: those intended to calculate eruption column characteristics based on tephra fall deposits, as in [1], and those intended to predict long-range atmospheric and deposit distributions based on the scale of the eruption, as in [2]. Both types of models rely on the existence of an explicit relationship between the eruption and atmospheric dynamics and the resulting fall deposit. This relationship is complicated by a number of factors, including plume mechanics, variable ...
Numerical models for simulation of mass flows are typically focussed upon accurately predicting t... more Numerical models for simulation of mass flows are typically focussed upon accurately predicting the paths, travel times and inundation from a single flow or collapse event. When considering catchment-based hazards from a volcano, this is complicated by often being faced with several possible scenarios. Over the last 800 years at Mt. Taranaki/ Egmont, a number of dome growth and collapse events have resulted in the genesis and emplacement of block-and-ash flows (BAFs). Each BAF was directed northwestward by a breach in the crater rim. The latest dome collapse events in the AD 1880s and AD 1755 inundated the northwestern flank and had run-out lengths 10 km from source. Future activity of this type could have a devastating effect on the Taranaki region's communities, infrastructure and economy. Hazard planning has involved constructing volcanic hazard maps based upon the areas inundated by past volcanic flows, with little consideration of present-day topography. Here, a numerical geophysical mass flow modelling approach is used to forecast the hazards of future comparable BAF events on NW Mt. Taranaki. The Titan2D programme encompasses a ''shallow water'', continuum solution-based, granular flow model. Flow mechanical properties needed for this approach include estimates of internal and basal friction as well as the physical dimensions of the initial collapse. Before this model can be applied to Taranaki BAFs, the input parameters must be calibrated by simulating a range of past collapse events. By using AD 1860 and AD 1755 scenarios, initial collapse volumes can be well constrained and internal and basal friction angles can be evaluated through an iterative approach from previous run-out lengths. A range of possible input parameters was, therefore, determined to produce a suite of potentially inundated areas under present-day terrain. A suite of 10 forecasts from a uniformly distributed range were combined to create a map of relative probabilities of inundation by future BAF events. These results were combined in a GIS package to produce hazard zones
... In its simplest form, it is the tangent of the angle (α) connecting the top of the source are... more ... In its simplest form, it is the tangent of the angle (α) connecting the top of the source area to the most distal part of the flow (Heim, 1932): (7)H max /L max =μ=tanαwhere H max is the fall height and L max is the horizontal distance travelled. ...
... In its simplest form, it is the tangent of the angle (α) connecting the top of the source are... more ... In its simplest form, it is the tangent of the angle (α) connecting the top of the source area to the most distal part of the flow (Heim, 1932): (7)H max /L max =μ=tanαwhere H max is the fall height and L max is the horizontal distance travelled. ...
The eruption of Eyjafjalla, Iceland, began wreaking havoc on European aviation with ash emissions... more The eruption of Eyjafjalla, Iceland, began wreaking havoc on European aviation with ash emissions from 14 April 2010 onward. Peak ash emissions occurred in the period 15-20 April. To make predictions of the likely position of the ash cloud and issue advisories to the airline industry, London VAAC (Volcanic Ash Advisory Center) solved mathematical models of advection and dispersion. These models incorporate data with stochastic variability, such as a varying windfield. The models also require input data that are not ...
The eruption of Eyjafjalla, Iceland, began wreaking havoc on European aviation with ash emissions... more The eruption of Eyjafjalla, Iceland, began wreaking havoc on European aviation with ash emissions from 14 April 2010 onward. Peak ash emissions occurred in the period 15-20 April. To make predictions of the likely position of the ash cloud and issue advisories to the airline industry, London VAAC (Volcanic Ash Advisory Center) solved mathematical models of advection and dispersion. These models incorporate data with stochastic variability, such as a varying windfield. The models also require input data that are not ...
ABSTRACT In explosive volcanic eruptions, a large amount of ash may be injected into the atmosphe... more ABSTRACT In explosive volcanic eruptions, a large amount of ash may be injected into the atmosphere. The ash clouds extend over large areas and can travel thousands of kilometers from the source volcano, disrupting air traffic and posing a significant hazard to air travel. To predict the likely position of the ash cloud, mathematical models of advection and dispersion are used. These models require input data on source conditions such as eruption plume height, as well as the windfield. In this contribution, we extend a previous work on uncertainty quantification in the volcanic input parameters by considering the variability in the windfields. The puff trajectory model is used to hindcast the motion of the ash cloud for the eruption of Eyjafjallajokull, Iceland which had a peak ash emission in the period 14-18 April 2010. Windfields along with source parameters (vent radius, vent velocity, mean grain size and grain size variance) represent major sources for uncertainties in ash transport and dispersion simulations. Based on our lack of knowledge of the exact conditions of the source, probability distributions are assigned to the parameters which are later sampled in a Monte Carlo fashion. For windfields, ensemble methods are considered to be an effective way to estimate the probability density function of future states of the atmosphere by addressing uncertainties present in initial conditions and in model approximations. We are using the Global Ensemble Forecast System (GEFS) generated by the National Centers for Environmental Prediction (NCEP), which is a weather forecast model made up of 21 separate ensemble members. Output statistics are then computed by properly summing the weighted values of the output parameters of interest. The results are presented as forecast envelope and show how volcanic source term uncertainty and windfield stochastic variability can affect the forecast. Thus, we produce a complete probabilistic forecast of ash cloud position.
ABSTRACT Computational methods used in modeling geophysical mass flows assume that parameters (fr... more ABSTRACT Computational methods used in modeling geophysical mass flows assume that parameters (friction angles) and initial data (volume/starting location) are known exactly, when often they are only known in a probabilistic sense. For example, if the bed friction angle is known to lie between 15 and 25 degrees, with insufficient data to say which values within the range are more likely than others, proper treatment requires the input for bed friction to be a uniform probability distribution function (PDF) over that range. During the generation of hazard maps from numerical models, geologists need a tool to quantify the effect of this input uncertainty on specific output quantities of interest. Monte Carlo (MC) sampling is prohibitively expensive for sufficient accuracy; for three significant figures of accuracy approximately 106 MC runs are required, for 20 minute single processor runs on 64 processors this would take 217 days. The relative expense of first principle based models like the Savage-Hutter type avalanche model's governing PDEs (which require the solution of a set of nonlinear hyperbolic equations) rules out using the currently popular Stochastic Galerkin method of uncertainty propagation. In this contribution, we discuss the use of an intelligent sampling methodology to propagate the input uncertainty through the TITAN geophysical flow solver. The stochastic output is displayed as a map of the depth that the flow will not exceed at each (X,Y) point for an arbitrary confidence level.
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