A multivariate approach to the analysis of average evoked potentials.
Quantitative multivariate statistical analysis of average evoked potentials and application to visual stimulus intensity and duration
STATISTICAL CORRELATION↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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A sequential approach to multivariable stability robustness analysis
In sequential loop closure, the importance of evaluating the stability and stability robustness at the intermediate loop closures is well known, yet how the stability and stability robustness evaluated at the intermediate steps contribute to the stability and stability robustness of the overall feedback system must be developed. An analysis of the complete feedback system reveals the multivariable Nyquist contributions from the intermediate loop closures. It is also shown that the results greatly simplify if frequency separation exists between the intermediate loops. The analysis is presented with a two-step loop closure procedure using 'inner' and 'outer' loops which can be generalized to multi-step situations. The control of the longitudinal dynamics of an aircraft is addressed to further clarify and demonstrate the results.
Newman, Brett↗
Multivariate space - time analysis of PRE-STORM precipitation
This paper presents the methodologies and results of the multivariate modeling and two-dimensional spectral and correlation analysis of PRE-STORM rainfall gauge data. Estimated parameters of the models for the specific spatial averages clearly indicate the eastward and southeastward wave propagation of rainfall fluctuations. A relationship between the coefficients of the diffusion equation and the parameters of the stochastic model of rainfall fluctuations is derived that leads directly to the exclusive use of rainfall data to estimate advection speed (about 12 m/s) as well as other coefficients of the diffusion equation of the corresponding fields. The statistical methodology developed here can be used for confirmation of physical models by comparison of the corresponding second-moment statistics of the observed and simulated data, for generating multiple samples of any size, for solving the inverse problem of the hydrodynamic equations, and for application in some other areas of meteorological and climatological data analysis and modeling.
Polyak, Ilya↗
Metastatic Melanoma Induced Metabolic Changes in C57BL/6J Mouse Stomach Measured by 1H NMR Spectroscopy
Melanoma is a malignant tumor of melanocytes with high capability of invasion and rapid metastasis to other organs. Malignant melanoma is the most common metastatic malignancy found in gastrointestinal tract (GI). To the best of our knowledge, previous studies of melanoma in gastrointestinal tract are all clinical case reports. In this work, 1H NMR-based metabolomics approach is used to investigate the metabolite profiles differences of stomach tissue extracts of metastatic B16-F10 melanoma in C57BL/6J mouse and search for specific metabolite biomarker candidates. Principal Component Analysis (PCA), an unsupervised multivariate data analysis method, is used to detect possible outliers, while Orthogonal Projection to Latent Structure (OPLS), a supervised multivariate data analysis method, is employed to evaluate important metabolites responsible for discriminating the control and the melanoma groups. Both PCA and OPLS results reveal that the melanoma group can be well separated from its control group. Among the 50 identified metabolites, it is found that the concentrations of 19 metabolites are statistically and significantly changed with the levels of O-phosphocholine and hypoxanthine down-regulated while the levels of isoleucine, leucine, valine, isobutyrate, threonine, cadaverine, alanine, glutamate, glutamine, methionine, citrate, asparagine, tryptophan, glycine, serine, uracil, and formate up-regulated in the melanoma group. These significantly changed metabolites are associated with multiple biological pathways and may be potential biomarkers for metastatic melanoma in stomach.
59 BASIC BIOLOGICAL SCIENCES↗
Multivariate interactive digital analysis system /MIDAS/ - A new fast multispectral recognition system
The MIDAS system is a prototype, multiple-pipeline digital processor mechanizing the multivariate-Gaussian, maximum-likelihood decision algorithm operating at 200,000 pixels/second. It incorporates displays and film printer equipment under control of a general purpose midi-computer and possesses sufficient flexibility that operational versions of the equipment may be subsequently specified as subsets of the system.
Kriegler, F.↗
Fractionation of Palliative Radiation Therapy for Bone Metastases in Ontario: Do Practice Guidelines Guide Practice?
Purpose: To evaluate the effect of a provincial practice guideline on the fractionation of palliative radiation therapy for bone metastases (PRT.B) in Ontario. Methods and Materials: The present retrospective study used electronic treatment records linked to Ontario's population-based cancer registry. Hierarchical multivariable regression analysis was used to evaluate temporal trends in the use of single fractions (SFs), controlling for patient-related factors associated with the use of SFs. Results: From 1984 to 2012, 43.9% of 161,835 courses of PRT.B were administered as SFs. The percentage of SF courses was greater for older patients (age <50 years, 39.8% vs age >80 years, 52.5%), those with a shorter life expectancy (survival >12 months, 36.9% vs < 1 month, 53.6%), and those who lived farther from a radiation therapy center (<10 km, 42.1% vs > 50 km, 47.3%). The percentage of SFs to spinal fields was lower than that to other skeletal sites (31.5% vs 57.1%). The percentage of SFs varied among the cancer centers (range, 26.0%-67.8%). These differences were all highly significant in the multivariable analysis (P<.0001). In 2004, Cancer Care Ontario released a practice guideline endorsing the use of SFs for uncomplicated bone metastases. The rate of use of SFs increased from 42.3% in the pre-guideline period (1999-2003) to 52.6% in the immediate post-guideline period (2004-2007). However, it subsequently decreased again to 44.0% (2009-2012). These temporal trends were significant after controlling for patient-related factors in the multivariable analysis (P<.0001). Large intercenter variations in the use of SFs persisted after publication of the guideline. Conclusions: The publication of an Ontario practice guideline endorsing the use of SF PRT.B was associated with only a transient increase in the use of SFs in Ontario and did little to reduce intercenter variations in fractionation.
62 RADIOLOGY AND NUCLEAR MEDICINE↗
Dynamic piezoresponse force microscopy: Spatially resolved probing of polarization dynamics in time and voltage domains
An approach for probing dynamic phenomena during hysteresis loop measurements in piezoresponse force microscopy (PFM) is developed. Dynamic PFM (D-PFM) necessitates development of 5-dimensional (5D) data acquisition protocols and associated methods for analysis and visualization of multidimensional data. Using a combination of multivariate statistical analysis and phenomenological fitting, we explore dynamic behavior during polarization switching in model ferroelectric films with dense ferroelastic domain structures and in ferroelectric capacitors. In polydomain films, multivariate analysis of the switching data suggests that ferroelectric and ferroelastic components can be decoupled and time dynamics can be explored. In capacitors, a strong correlation between polarization dynamics and microstructure is observed. The future potential of D-PFM for probing time-dependent hysteretic phenomena in ferroelectrics and ionic systems is discussed.
Dynamic piezoresponse force microscopy↗
Breast Cancer Laterality Does Not Influence Survival in a Large Modern Cohort: Implications for Radiation-Related Cardiac Mortality
Objectives: Radiation therapy for left-sided breast cancer has been associated with an elevated risk of cardiac mortality, based on studies predating treatment planning based on computed tomography. This study assessed the impact of tumor laterality on overall survival (OS) in a large cohort treated with modern techniques, to indirectly determine whether left-sided treatment remains associated with increased cardiac mortality. Methods and Materials: Patients treated for breast cancer with breast conserving surgery and adjuvant external beam radiation therapy were identified in the National Cancer Database, and OS was compared based on tumor laterality using Kaplan-Meier analysis. Separate analyses were performed for noninvasive and invasive carcinoma and for breast-only and breast plus regional nodal radiation therapy. Multivariate regression analysis of OS was performed with demographic, pathologic, and treatment variables as covariates to adjust for factors associated with breast cancer–specific survival. Results: We identified 344,831 patients whose cancer was diagnosed from 1998 to 2006 with a median follow-up time of 6.04 years (range, 0-14.17 years). Clinical, tumor, and treatment characteristics were similar between laterality groups. Regional nodal radiation was used in 14.2% of invasive cancers. No OS difference was noted based on tumor laterality for patients treated with breast-only (hazard ratio [HR] 0.984, P=.132) and breast plus regional nodal radiation therapy (HR 1.001, P=.957). In multivariate analysis including potential confounders, OS was identical between left and right sided cancers (HR 1.002, P=.874). No significant OS difference by laterality was observed when analyses were restricted to patients with at least 10 years of follow-up (n=27,725), both in patients treated with breast-only (HR 0.955, P=.368) and breast plus regional nodal radiation therapy (HR 0.859, P=.155). Conclusions: Radiation therapy for left-sided breast cancer does not appear to increase the risk of death in this national database relative to right-sided tumors. Consequently, radiation therapy–induced cardiac disease may be less prominent than previously demonstrated.
62 RADIOLOGY AND NUCLEAR MEDICINE↗
MIDAS, prototype Multivariate Interactive Digital Analysis System, phase 1. Volume 1: System description
The MIDAS System is described as a third-generation fast multispectral recognition system able to keep pace with the large quantity and high rates of data acquisition from present and projected sensors. A principal objective of the MIDAS program is to provide a system well interfaced with the human operator and thus to obtain large overall reductions in turnaround time and significant gains in throughput. The hardware and software are described. The system contains a mini-computer to control the various high-speed processing elements in the data path, and a classifier which implements an all-digital prototype multivariate-Gaussian maximum likelihood decision algorithm operating at 200,000 pixels/sec. Sufficient hardware was developed to perform signature extraction from computer-compatible tapes, compute classifier coefficients, control the classifier operation, and diagnose operation.
Kriegler, F. J.↗
MIDAS, prototype Multivariate Interactive Digital Analysis System, phase 1. Volume 3: Wiring diagrams
The Midas System is a third-generation, fast, multispectral recognition system able to keep pace with the large quantity and high rates of data acquisition from present and projected sensors. A principal objective of the MIDAS Program is to provide a system well interfaced with the human operator and thus to obtain large overall reductions in turn-around time and significant gains in throughput. The hardware and software generated in Phase I of the overall program are described. The system contains a mini-computer to control the various high-speed processing elements in the data path and a classifier which implements an all-digital prototype multivariate-Gaussian maximum likelihood decision algorithm operating at 2 x 100,000 pixels/sec. Sufficient hardware was developed to perform signature extraction from computer-compatible tapes, compute classifier coefficients, control the classifier operation, and diagnose operation. The MIDAS construction and wiring diagrams are given.
Kriegler, F. J.↗
MIDAS, prototype Multivariate Interactive Digital Analysis System, Phase 1. Volume 2: Diagnostic system
The MIDAS System is a third-generation, fast, multispectral recognition system able to keep pace with the large quantity and high rates of data acquisition from present and projected sensors. A principal objective of the MIDAS Program is to provide a system well interfaced with the human operator and thus to obtain large overall reductions in turn-around time and significant gains in throughout. The hardware and software generated in Phase I of the over-all program are described. The system contains a mini-computer to control the various high-speed processing elements in the data path and a classifier which implements an all-digital prototype multivariate-Gaussian maximum likelihood decision algorithm operating 2 x 105 pixels/sec. Sufficient hardware was developed to perform signature extraction from computer-compatible tapes, compute classifier coefficients, control the classifier operation, and diagnose operation. Diagnostic programs used to test MIDAS' operations are presented.
Kriegler, F. J.↗
MIDAS, prototype Multivariate Interactive Digital Analysis System for large area earth resources surveys. Volume 1: System description
A third-generation, fast, low cost, multispectral recognition system (MIDAS) able to keep pace with the large quantity and high rates of data acquisition from large regions with present and projected sensots is described. The program can process a complete ERTS frame in forty seconds and provide a color map of sixteen constituent categories in a few minutes. A principle objective of the MIDAS program is to provide a system well interfaced with the human operator and thus to obtain large overall reductions in turn-around time and significant gains in throughput. The hardware and software generated in the overall program is described. The system contains a midi-computer to control the various high speed processing elements in the data path, a preprocessor to condition data, and a classifier which implements an all digital prototype multivariate Gaussian maximum likelihood or a Bayesian decision algorithm. Sufficient software was developed to perform signature extraction, control the preprocessor, compute classifier coefficients, control the classifier operation, operate the color display and printer, and diagnose operation.
Christenson, D.↗
Spatio-temporal multivariate cluster evolution analysis for detecting and tracking climate impacts
Recent years have seen a growing concern about climate change and its impacts. While Earth System Models (ESMs) can be invaluable tools for studying the impacts of climate change, the complex coupling processes encoded in ESMs and the large amounts of data produced by these models, together with the high internal variability of the Earth system, can obscure important source-to-impact relationships. Here, this paper presents a novel and efficient unsupervised data-driven approach for detecting statistically-significant impacts and tracing spatio-temporal source-impact pathways in the climate through a unique combination of ideas from anomaly detection, clustering and Natural Language Processing (NLP). Using as an exemplar the 1991 eruption of Mount Pinatubo in the Philippines, we demonstrate that the proposed approach is capable of detecting known post-eruption impacts/events. We additionally describe a methodology for extracting meaningful sequences of post-eruption impacts/events by using NLP to efficiently mine frequent multivariate cluster evolutions, which can be used to confirm or discover the chain of physical processes between a climate source and its impact(s).
Anomaly detection↗
Assessing Intra-arterial Complications of Planning and Treatment Angiograms for Y-90 Radioembolization
PurposeTo report hepatic arterial-related complications encountered during planning and treatment angiograms for radioembolization and understand any potential-associated risk factors.Materials and Methods518 mapping or treatment angiograms for 180 patients with primary or metastatic disease to the liver treated by Yttrium-90 radioembolization between 2/2010 and 12/2015 were retrospectively reviewed. Intra-procedural complications were recorded per SIR guidelines. Patient demographics, indication for treatment, prior exposure to chemotherapeutic agents, operator experience, and disease burden were reviewed. Technical variables including type of radioembolic (glass vs. resin microspheres), indication for angiography (mapping vs. treatment), variant anatomy, and attempts at coil embolization were also assessed.ResultsThirteen (13/518, 2.5%) arterial-related complications occurred in 13 patients. All but two complications resulted during transcatheter coil embolization to prevent non-target embolization. Complications included coil migration (n = 6), arterial dissection (n = 2), focal vessel perforation (n = 2), arterial thrombus (n = 2), and vasospasm prohibiting further arterial sub-selection (n = 1). Transarterial coiling was identified as a significant risk factor of complications on both univariate and multivariate regression analysis (odds ratio 7.8, P = 0.004). Usage of resin microspheres was also a significant risk factor (odds ratio 9.5, P = 0.042). No other technical parameters or pre-procedural variables were significant after adjusting for confounding on multivariate analysis (P > 0.05).ConclusionIntra-procedural hepatic arterial complications encountered during radioembolization were infrequent but occurred mainly during coil embolization to prevent non-target delivery to extra-hepatic arteries.
62 RADIOLOGY AND NUCLEAR MEDICINE↗
Multivariate singular spectrum analysis and the road to phase synchronization
Not Available
Groth, Andreas↗
Assessment of Critical Events Corridors through Multivariate Cascading Outages Analysis
Massive blackouts of electrical power systems in North America over the past decade has focused increasing attention upon ways to identify and simulate network events that may potentially lead to widespread network collapse. This paper summarizes a method to simulate power-system vulnerability to cascading failures to a supplied set of initiating events synonymously termed as Extreme Events. The implemented simulation method is currently confined to simulating steady state power-system response to a set of extreme events. The outlined method of simulation is meant to augment and provide a new insight into bulk power transmission network planning that at present remains mainly confined to maintaining power system security for single and double component outages under a number of projected future network operating conditions. Although one of the aims of this paper is to demonstrate the feasibility of simulating network vulnerability to cascading outages, a more important goal has been to determine vulnerable parts of the network that may potentially be strengthened in practice so as to mitigate system susceptibility to cascading failures. This paper proposes to demonstrate a systematic approach to analyze extreme events and identify vulnerable system elements that may be contributing to cascading outages. The hypothesis of critical events corridors is proposed to represent repeating sequential outages that can occur in the system for multiple initiating events. The new concept helps to identify system reinforcements that planners could engineer in order to 'break' the critical events sequences and therefore lessen the likelihood of cascading outages. This hypothesis has been successfully validated with a California power system model.
24 POWER TRANSMISSION AND DISTRIBUTION↗
A State-Space Model of an Inverter-Based Microgrid for Multivariable Feedback Control Analysis and Design
In this work, a synchronous model for grid-connected and islanded microgrids is presented. The grid-connected model is based on the premise that the reference frame is synchronized with the AC bus. The quadrature component of the AC bus voltage can be cancelled, which allows to express output power as a linear equation for nominal values in the AC bus amplitude voltage. The model for the islanded microgrid is developed by integrating all the inverter dynamics using a state-space model for the load currents. This model is presented in a comprehensive way such that it could be scalable to any number of inverter-based generators using inductor–capacitor–inductor (LCL) output filters. The use of these models allows designers to assess microgrid stability and robustness using modern control methods such as eigenvalue analysis and singular value diagrams. Both models were tested and validated in an experimental setup to demonstrate their accuracy in describing microgrid dynamics. In addition, three scenarios are presented: non-controlled model, Linear-Quadratic Integrator (LQI) power control, and Power-Voltage (PQ/Vdq) droop–boost controller. Experimental results demonstrate the effectiveness of the control strategies and the accuracy of the models to describe microgrid dynamics.
24 POWER TRANSMISSION AND DISTRIBUTION↗