Showing papers by "General Electric published in 2008"

The Alzheimer's Disease Neuroimaging Initiative (ADNI): MRI methods.

Abstract: Dementia, one of the most feared associates of increasing longevity, represents a pressing public health problem and major research priority. Alzheimer's disease (AD) is the most common form of dementia, affecting many millions around the world. There is currently no cure for AD, but large numbers of novel compounds are currently under development that have the potential to modify the course of the disease and slow its progression. There is a pressing need for imaging biomarkers to improve understanding of the disease and to assess the efficacy of these proposed treatments. Structural magnetic resonance imaging (MRI) has already been shown to be sensitive to presymptomatic disease (1-10) and has the potential to provide such a biomarker. For use in large-scale multicenter studies, however, standardized methods that produce stable results across scanners and over time are needed. The Alzheimer's Disease Neuroimaging Initiative (ADNI) study is a longitudinal multisite observational study of elderly individuals with normal cognition, mild cognitive impairment (MCI), or AD (11,12). It is jointly funded by the National Institutes of Health (NIH) and industry via the Foundation for the NIH. The study will assess how well information (alone or in combination) obtained from MRI, (18F)-fludeoyglucose positron emission tomography (FDG PET), urine, serum, and cerebrospinal fluid (CSF) biomarkers, as well as clinical and neuropsychometric assessments, can measure disease progression in the three groups of elderly subjects mentioned above. At the 55 participating sites in North America, imaging, clinical, and biologic samples will be collected at multiple time points in 200 elderly cognitively normal, 400 MCI, and 200 AD subjects. All subjects will be scanned with 1.5 T MRI at each time point, and half of these will also be scanned with FDG PET. Subjects not assigned to the PET arm of the study will be eligible for 3 T MRI scanning. The goal is to acquire both 1.5 T and 3 T MRI studies at multiple time points in 25% of the subjects who do not undergo PET scanning [R2C1]. CSF collection at both baseline and 12 months is targeted for 50% of the subjects. Sampling varies by clinical group. Healthy elderly controls will be sampled at 0, 6, 12, 24, and 36 months. Subjects with MCI will be sampled at 0, 6, 12, 18, 24, and 36 months. AD subjects will be sampled at 0, 6, 12, and 24 months. Major goals of the ADNI study are: to link all of these data at each time point and make this repository available to the general scientific community; to develop technical standards for imaging in longitudinal studies; to determine the optimum methods for acquiring and analyzing images; to validate imaging and biomarker data by correlating these with concurrent psychometric and clinical assessments; and to improve methods for clinical trials in MCI and AD. The ADNI study overall is divided into cores, with each core managing ADNI-related activities within its sphere of expertise: clinical, informatics, biostatistics, biomarkers, and imaging. The purpose of this report is to describe the MRI methods and decision-making process underlying the selection of the MRI protocol employed in the ADNI study.

Damage propagation modeling for aircraft engine run-to-failure simulation

Abstract: This paper describes how damage propagation can be modeled within the modules of aircraft gas turbine engines. To that end, response surfaces of all sensors are generated via a thermo-dynamical simulation model for the engine as a function of variations of flow and efficiency of the modules of interest. An exponential rate of change for flow and efficiency loss was imposed for each data set, starting at a randomly chosen initial deterioration set point. The rate of change of the flow and efficiency denotes an otherwise unspecified fault with increasingly worsening effect. The rates of change of the faults were constrained to an upper threshold but were otherwise chosen randomly. Damage propagation was allowed to continue until a failure criterion was reached. A health index was defined as the minimum of several superimposed operational margins at any given time instant and the failure criterion is reached when health index reaches zero. Output of the model was the time series (cycles) of sensed measurements typically available from aircraft gas turbine engines. The data generated were used as challenge data for the prognostics and health management (PHM) data competition at PHMpsila08.

Distribution System Voltage Performance Analysis for High-Penetration PV

Abstract: Distributed generation can have an impact on distribution feeder voltage regulation, and distributed solar photovoltaics (PV) are no exception As the penetration level of solar PV rises over the coming decades, reverse power flow on the distribution feeder will happen more frequently and the associated voltage rise might lead to violations of voltage boundaries defined by ANSI C841 The severity of possible voltage problems depends on the relative size and location of distributed PV generation and loads, distribution feeder topology, and method of voltage regulation In this paper, an illustrative distribution system feeder is assumed, and various case studies are conducted The performance of the commonly used distribution voltage regulation methods under reverse power flow are investigated and presented Voltage performance of the feeder, and the flow of active and reactive power are studied under different loading assumptions, and different assumptions of PV inverters' participation The paper also explores the system performance using coordinated controls of inverters and utility equipment

An outlook on x-ray CT research and development.

Abstract: Over the past decade, computed tomography (CT) theory, techniques and applications have undergone a rapid development. Since CT is so practical and useful, undoubtedly CT technology will continue advancing biomedical and non-biomedical applications. In this outlook article, we share our opinions on the research and development in this field, emphasizing 12 topics we expect to be critical in the next decade: analytic reconstruction, iterative reconstruction, local/interior reconstruction, flat-panel based CT, dual-source CT, multi-source CT, novel scanning modes, energy-sensitive CT, nano-CT, artifact reduction, modality fusion, and phase-contrast CT. We also sketch several representative biomedical applications.

Nanostructures for photovoltaics

Abstract: The use of various nanostructures in new solar cell designs and modes of enhancing conventional solar cells are described. The cell designs and enhancements are categorized by the type of nanostructure utilized. These include: (a) bulk nanostructured materials [3D]; (b) quantum wells [2D]; (c) nanowires [1D]; and (d) quantum dots/nanoparticles [0D]. The methods of fabricating such structures are first described, followed by examples from the literature of how they have been utilized in a photovoltaic application. Scientific challenges associated with nanostructured photovoltaic devices are also discussed, followed by the prospects for use in real applications.

Overview of PI-Based Solutions for the Control of DC Buses of a Single-Phase H-Bridge Multilevel Active Rectifier

Abstract: The H-bridge-based multilevel active rectifier is an attractive topology that allows feeding of multiple dc loads. The main control problem is to manage state variables (one current plus dc voltages) with only switching functions. In this paper, three PI-based solutions are discussed, and the tuning of the best solution is addressed in case resonant controllers are used instead of classical integrators. Moreover, practical problems such as the implementation and the influence of phase-locked-loop systems and of analog filters (first order and Butterworth) on the measurements are discussed.

Hybrid Model Predictive Control of the Step-Down DC–DC Converter

Abstract: DC-DC converters pose challenging hybrid control problems, since the semiconductor switches induce different modes of operation and several constraints (on the duty cycle and the inductor current) are present. In this paper, we propose a novel approach to the modeling and controller design problem for fixed-frequency DC-DC converters, using a synchronous step-down DC-DC converter as an illustrative example. We introduce a hybrid converter model that is valid for the whole operating regime. Based on this model, we formulate and solve a constrained optimal control problem. To make the scheme implementable, we derive offline the explicit state-feedback control law, which can be easily stored and implemented in a lookup table. A Kalman filter is added to account for unmeasured load variations and to achieve zero steady-state output voltage error. An a posteriori analysis proves, by deriving a piecewise-quadratic Lyapunov function, that the closed-loop system is exponentially stable. Simulation results demonstrate the potential advantages of the proposed control methodology.

System and method for electric vehicle charging and billing using a wireless vehicle communication service

Abstract: A vehicle charging station for use in transmitting charging power to an electric vehicle for use in charging the vehicle is configured to communicatively couple to the electric vehicle via a network connection to a wireless network provider and electrically couple to the electric vehicle via a connector. Vehicle charging station is further configured to receive a unique identifier from the electric vehicle via the network connection, deliver a quantity of electrical charging power to the electric vehicle via the connector, and meter the quantity of electrical charging power delivered to the electric vehicle.

Development and Implementation of a Synchrophasor Estimator Capable of Measurements Under Dynamic Conditions

Abstract: The classical two-parameter Fourier algorithm for computing synchrophasors is appropriate when the underlying voltage and current waveforms are sinusoids with constant amplitude and phase angle and with a frequency equal to the assumed value. Synchrophasor measurements, however, are applied in power systems to track dynamic conditions where, by definition, currents and voltages, though resembling sine-waves, exhibit changes in their magnitudes and vectorial positions. This paper presents a novel algorithm for estimating synchrophasors under such dynamic conditions. In contrast to the classical Fourier algorithm, our model is a complex Taylor expansion, yielding several parameters in the model to be estimated. Four- and six-parameter models are presented corresponding to first and second order Taylor expansions. This paper derives a compensation method for canceling the error in the classical Fourier algorithm that arises under dynamic conditions, shows comparative simulation and test results and describes an efficient implementation. Application of the error cancellation method to other phasor algorithms and extending the technique to higher order Taylor expansions, are discussed. Implementation of synchrophasor measurements on protection and control intelligent electronic devices (IEDs) is discussed, and solutions are presented that allow for secure integration.

Dynamics of Laminar Premixed Flames Forced by Harmonic Velocity Disturbances

Abstract: This paper describes the dynamics of constant-burning-velocity premixed flames responding to harmonic velocity disturbances. Results are derived from analytical and computational solutions of the nonlinear G equation and compared with available experimental data. It is shown that the flame dynamics are controlled by the superposition of two waves propagating along the flame sheet: those originating at the flame-anchoring point and from flow nonuniformities along the flame. They may either constructively or destructively superpose, and so the overall linear flame response depends upon two Strouhal numbers, St 2 and Stc, related to the amount of time taken for a flow (St c ) and flame-front (St 2 ) disturbance to propagate the flame length, normalized by the acoustic period. The nonlinear flame response is controlled by flame propagation normal to itself, which smoothens out the wrinkles induced by the forcing at an amplitude-dependent rate. The flame's nonlinear response is shown to exhibit two qualitatively different behaviors. For parameter values at which these disturbances constructively interfere, the nonlinear flame response saturates. When the flame disturbances destructively interfere, the nonlinear transfer function may actually exceed its linear value before saturating. This result explains experimentally observed variations of the nonlinear flame response with frequency.

A very high frequency dc-dc converter based on a class Φ 2 resonant inverter

Abstract: This paper introduces a new dc-dc converter suitable for operation at very high frequencies under on-off control. The converter power stage is based on a resonant inverter (the Phi2 inverter) providing low switch voltage stress and fast settling time. A new multi-stage resonant gate driver suited for driving large, high-voltage rf MOSFETS at VHF frequencies is also introduced. Experimental results are presented from a prototype dc-dc converter operating at 30 MHz at input voltages up to 200 V and power levels above 200 W. These results demonstrate the high performance achievable with the proposed design.

Simple and robust image-based autofocusing for digital microscopy

Abstract: A simple image-based autofocusing scheme for digital microscopy is demonstrated that uses as few as two intermediate images to bring the sample into focus. The algorithm is adapted to a commercial inverted microscope and used to automate brightfield and fluorescence imaging of histopathology tissue sections.

Predicting Controller Capacity in Supervisory Control of Multiple UAVs

Abstract: In the future vision of allowing a single operator to remotely control multiple unmanned vehicles, it is not well understood what cognitive constraints limit the number of vehicles and related tasks that a single operator can manage. This paper illustrates that, when predicting the number of unmanned aerial vehicles (UAVs) that a single operator can control, it is important to model the sources of wait times (WTs) caused by human-vehicle interaction, particularly since these times could potentially lead to a system failure. Specifically, these sources of vehicle WTs include cognitive reorientation and interaction WT (WTI), queues for multiple-vehicle interactions, and loss of situation awareness (SA) WTs. When WTs were included, predictions using a multiple homogeneous and independent UAV simulation dropped by up to 67%, with a loss of SA as the primary source of WT delays. Moreover, this paper demonstrated that even in a highly automated management-by-exception system, which should alleviate queuing and WTIs, operator capacity is still affected by the SA WT, causing a 36% decrease over the capacity model with no WT included.

System and method for advanced condition monitoring of an asset system

Abstract: A method for advanced condition monitoring of an asset system includes sensing actual values of an operating condition for an operating regime of the asset system using at least one sensor; estimating sensed values of the operating condition by using an auto-associative neural network; determining a residual vector between the estimated sensed values and the actual values; and performing a fault diagnostic on the residual vector. In another method, an operating space of the asset system is segmented into operating regimes; the auto-associative neural network determines estimates of actual measured values; a residual vector is determined from the auto-associative neural network; a fault diagnostic is performed on the residual vector; and a change of the operation of the asset system is determined by analysis of the residual vector. An alert is provided if necessary. A smart sensor system includes an on-board processing unit for performing the method of the invention.

Automated healthcare information composition and query enhancement

Abstract: Certain embodiments of the present invention provide systems and methods for information composition and query enhancement. Certain embodiments provide an information composition and query enhancement system. The system includes a query generation and enhancement engine generating and conducting a query of one or more data sources based on user input and a data context to produce query results. The system also includes an information composition engine assembling the query results to provide a bundle of documents meaningful to the particular user. The system further includes a document summarization engine clustering and summarizing the bundle of documents to provide a content summary in addition to the bundle of documents for output in a presentation to a user.

Dry 3-way catalytic reduction of gas turbine NOX

Abstract: A power generation system capable of eliminating NOxcomponents in the exhaust gas by using a 3-way catalyst, comprising a gas compressor to increase the pressure of ambient air fed to the system; a combustor capable of oxidizing a mixture of fuel and compressed air to generate an expanded, high temperature exhaust gas; a turbine that uses the force of the high temperature gas; an exhaust gas recycle (EGR) stream back to the combustor; a 3-way catalytic reactor downstream of the gas turbine engine outlet which treats the exhaust gas stream to remove substantially all of the NOx components; a heat recovery steam generator (HRSG); an EGR compressor feeding gas to the combustor and turbine; and an electrical generator.

Predicting hospitalization due to worsening heart failure using daily weight measurement: analysis of the Trans-European Network-Home-Care Management System (TEN-HMS) study

Abstract: Aims We sought to test the utility of weight gain algorithms to predict episodes of worsening heart failure (WHF) using home-telemonitoring data collected as part of the TEN-HMS study. Methods and results Simple rule-of-thumb (RoT) algorithms (i.e. 3 lbs in 1 day and 5 lbs in 3 days) and a moving average convergence divergence (MACD) algorithm were compared. WHF was defined as hospitalization for WHF or worsening of breathlessness or leg oedema. Of 168 patients, 45 were hospitalized with WHF and 76 were hospitalized for other reasons. On average, weight gain occurred in the 14 days prior to WHF hospitalizations but not in the 14 days prior to non-WHF hospitalizations [1.9 ± 4.7 lbs (0.9 ± 2.1 kg) vs. −0.4 ± 2.5 lbs (−0.2 ± 1.1 kg), P < 0.0001]. The true alerts rate was higher for the RoT algorithms compared with the MACD (58 and 65% vs. 20%). However, the RoT algorithms had much higher false alert rates (54 and 58% vs. 9%) rendering them of little practical use for predicting WHF events. Conclusion A MACD algorithm is more specific but less sensitive than RoT when trying to predict episodes of WHF based on daily weight measurements. However, many episodes of WHF do not appear to be associated with weight gain and therefore telemonitoring of weight alone may not have great value for heart failure management.

Designing multichannel, multidimensional, arbitrary flip angle RF pulses using an optimal control approach.

Abstract: The vast majority of parallel transmission RF pulse designs so far are based on small-tip-angle (STA) approximation of the Bloch equation. These methods can design only excitation pulses with small flip angles (e.g., 30 degrees ). The linear class large-tip-angle (LCLTA) method is able to design large-tip-angle parallel transmission pulses through concatenating a sequence of small-excitation pulses when certain k-space trajectories are used. However, both STA and LCLTA are linear approximations of the nonlinear Bloch equation. Therefore, distortions from the ideal magnetization profiles due to the higher order terms can appear in the final magnetization profiles. This issue is addressed in this work by formulating the multidimensional multichannel RF pulse design as an optimal control problem with multiple controls based directly on the Bloch equation. Necessary conditions for the optimal solution are derived and a first-order gradient optimization algorithm is used to iteratively solve the optimal control problem, where an existing pulse is used as an initial "guess." A systematic design procedure is also presented. Bloch simulation and phantom experimental results using various parallel transmission pulses (excitation, inversion, and refocusing) are shown to illustrate the effectiveness of the optimal control method in improving the spatial localization or homogeneity of the magnetization profiles.

Integrated system and method for producing fuel composition from biomass

Abstract: A method of producing a fuel composition from a bio-oil feedstock is provided, wherein the bio-oil feedstock is subjected to a step of oil extraction to produce a bio-oil and deoiled residue. At least a portion of the deoiled residue is gasified to produce a hydrogen-containing gas. The bio-oil is subjected to an upgrading process to ultimately produce a fuel composition. At least a part of the hydrogen-containing gas produced in the gasification of deoiled residue is used in the upgrading process of producing a fuel composition. The upgrading process, which can involve hydro-treating, hydroisomerization and at least one separation step, produces light hydrocarbons in addition to the product fuel composition. The light hydrocarbons can be used in the gasification operation, e.g., to reduce tar formation.

128‐channel body MRI with a flexible high‐density receiver‐coil array

Abstract: Purpose To determine whether the promise of high-density many-coil MRI receiver arrays for enabling highly accelerated parallel imaging can be realized in practice. Materials and Methods A 128-channel body receiver-coil array and custom MRI system were developed. The array comprises two clamshells containing 64 coils each, with the posterior array built to maximize signal-to-noise ratio (SNR) and the anterior array design incorporating considerations of weight and flexibility as well. Phantom imaging and human body imaging were performed using a variety of reduction factors and 2D and 3D pulse sequences. Results The ratio of SNR relative to a 32-element array of similar footprint was 1.03 in the center of an elliptical loading phantom and 1.7 on average in the outer regions. Maximum g-factors dropped from 5.5 (for 32 channels) to 2.0 (for 128 channels) for 4 × 4 acceleration and from 25 to 3.3 for 5 × 5 acceleration. Residual aliasing artifacts for a right/left (R/L) reduction factor of 8 in human body imaging were significantly reduced relative to the 32-channel array. Conclusion MRI with a large number of receiver channels enables significantly higher acceleration factors for parallel imaging and improved SNR, provided losses from the coils and electronics are kept negligible. J. Magn. Reson. Imaging 2008;28:1219–1225. © 2008 Wiley-Liss, Inc.

American Institute of Ultrasound in Medicine consensus report on potential bioeffects of diagnostic ultrasound: executive summary.

Abstract: The continued examination of potential biological effects of ultrasound and their relationship to clinical practice is a key element in evaluating the safety of diagnostic ultrasound. Periodically, the American Institute of Ultrasound in Medicine (AIUM) sponsors conferences bringing experts together to examine the literature on ultrasound bioeffects and to develop conclusions and recommendations related to diagnostic ultrasound. The most recent effort included the examination of effects whose origins were thermal or nonthermal, with separate evaluations for potential effects related to fetal ultrasound. In addition, potential effects due to the introduction of ultrasound contrast agents were summarized. This information can be used to assess risks in comparison to the benefits of diagnostic ultrasound. The conclusions and recommendations are organized into 5 broad categories, with a comprehensive background and evaluation of each topic provided in the corresponding articles in this issue. The following summary is not meant as a substitute for the detailed examination of issues presented in each of the articles but rather as a means to facilitate further study of this consensus report and implementation of its recommendations. The conclusions and recommendations are the result of several rounds of deliberations at the consensus conference, subsequent review by the Bioeffects Committee of the AIUM, and approval by the AIUM Board of Governors.

Effects of Hydrogen on Stress Corrosion Crack Growth Rate of Nickel Alloys in High-Temperature Water

Abstract: Stress corrosion cracking (SCC) of Alloy 600 (UNS N06600) and Alloys 182 (UNS W86182), 132 (UNS W86132), and 82 (UNS N06082) weld metals in high-temperature water is important because thes...

Refrigerator with a convertible compartment

Abstract: A refrigerator includes a first compartment, a second compartment and a multi-functional compartment that is disposed between the first compartment and the second compartment and is adjustable between temperature modes selected from the group consisting of a fresh food temperature mode, a soft freeze mode, a freezer mode and a chiller temperature mode.

Intra-area master reactive controller for tightly coupled windfarms

Abstract: A wind turbine generator control system is provided for controlling output of a plurality of tightly-coupled windfarms 10, 15, 20 connected at a point of common 25 coupling with a power system grid 30. A master reactive control device 75 employs algorithms 295, 380 whose technical effect is to coordinate the real power, reactive power and voltage output of the multiple windfarms. The master reactive control device 75 incorporates a reactive power regulator 100A that can be used to regulate reactive power, power factor or voltage at the point of common coupling 25 and an active power regulator 300 that can be used to regulate real power at the point of common coupling 25, such that each windfarm 10, 15, 20 is not asked to contribute or violate its own operating capability.