The Experts below are selected from a list of 21390 Experts worldwide ranked by ideXlab platform
Jerry L. Sanders - One of the best experts on this subject based on the ideXlab platform.
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Modeling Operator workstation interference in asynchronous automatic assembly systems
Discrete Event Dynamic Systems, 1992Co-Authors: Manjunath Kamath, Jerry L. SandersAbstract:In several instances ofdiscrete event dynamic systems (DEDS), jobs sometimes require service from two or more resources at the same time. When queueing network models are used to study DEDS, this feature ofsimultaneous resource possession is often ignored because it is difficult for the models to handle. In some DEDS, this feature of a job demanding several resources simultaneously can have a significant effect on system performance, especially if there is a limited amount of one or more of these resources. For example, in an asynchronous automatic assembly system, an assembly at a workstation needs an Operator when it experiences a jam (a random phenomenon) in order to clear the jam. Due to the presence of a limited (small) number of Operators, an assembly may have to wait for an Operator. This waiting orinterference time has a significant effect on the system production rate. This paper develops an analytical approximation method that can be used to determine the steady-state performance of automatic assembly systems for a given assignment of Operators. The analytical method involves the simultaneous solution of two “coupled” queueing models; one of the models calculates the waiting time for an Operator resource, while the other computes the waiting time for a workstation resource. The solution technique developed can be adapted to study instances of simultaneous resource possession in other DEDS, such as flexible manufacturing systems and computer/communication networks.
Becky L Hooey - One of the best experts on this subject based on the ideXlab platform.
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Modeling Operator workload for the resource prospector lunar rover mission
International Conference on Applied Human Factors and Ergonomics, 2017Co-Authors: Becky L Hooey, Jason J N T Toy, Robert E Carvalho, Terrence Fong, Brian F GoreAbstract:NASA’s Resource Prospector mission is an unmanned lunar exploration mission currently in the concept development stage. Early tests have shown that the unique mission characteristics may combine to create the potential for very high workload for Operators. This paper applies a taxonomy of workload drivers to identify the contextual variables expected to contribute to Operator workload during the mission. Specifically, workload drivers attributed to the environment, task demands, equipment, and Operator characteristics are reviewed. This research is intended to support the development of predictive models of Operator workload to support the design and evaluation of workload countermeasures for the mission.
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Modeling Operator performance and cognition in robotic missions
Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 2011Co-Authors: Marquis A Gacy, Brian F Gore, Christopher D Wickens, Angelia Sebok, Becky L HooeyAbstract:Control of the robotic arm on the International Space Station is a challenging endeavor, not only due to the high consequence of failure, but also because the limited number and arrangement of came...
Manjunath Kamath - One of the best experts on this subject based on the ideXlab platform.
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Modeling Operator workstation interference in asynchronous automatic assembly systems
Discrete Event Dynamic Systems, 1992Co-Authors: Manjunath Kamath, Jerry L. SandersAbstract:In several instances ofdiscrete event dynamic systems (DEDS), jobs sometimes require service from two or more resources at the same time. When queueing network models are used to study DEDS, this feature ofsimultaneous resource possession is often ignored because it is difficult for the models to handle. In some DEDS, this feature of a job demanding several resources simultaneously can have a significant effect on system performance, especially if there is a limited amount of one or more of these resources. For example, in an asynchronous automatic assembly system, an assembly at a workstation needs an Operator when it experiences a jam (a random phenomenon) in order to clear the jam. Due to the presence of a limited (small) number of Operators, an assembly may have to wait for an Operator. This waiting orinterference time has a significant effect on the system production rate. This paper develops an analytical approximation method that can be used to determine the steady-state performance of automatic assembly systems for a given assignment of Operators. The analytical method involves the simultaneous solution of two “coupled” queueing models; one of the models calculates the waiting time for an Operator resource, while the other computes the waiting time for a workstation resource. The solution technique developed can be adapted to study instances of simultaneous resource possession in other DEDS, such as flexible manufacturing systems and computer/communication networks.
Brian F Gore - One of the best experts on this subject based on the ideXlab platform.
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Modeling Operator workload for the resource prospector lunar rover mission
International Conference on Applied Human Factors and Ergonomics, 2017Co-Authors: Becky L Hooey, Jason J N T Toy, Robert E Carvalho, Terrence Fong, Brian F GoreAbstract:NASA’s Resource Prospector mission is an unmanned lunar exploration mission currently in the concept development stage. Early tests have shown that the unique mission characteristics may combine to create the potential for very high workload for Operators. This paper applies a taxonomy of workload drivers to identify the contextual variables expected to contribute to Operator workload during the mission. Specifically, workload drivers attributed to the environment, task demands, equipment, and Operator characteristics are reviewed. This research is intended to support the development of predictive models of Operator workload to support the design and evaluation of workload countermeasures for the mission.
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Modeling Operator performance and cognition in robotic missions
Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 2011Co-Authors: Marquis A Gacy, Brian F Gore, Christopher D Wickens, Angelia Sebok, Becky L HooeyAbstract:Control of the robotic arm on the International Space Station is a challenging endeavor, not only due to the high consequence of failure, but also because the limited number and arrangement of came...
Gerard T Schuster - One of the best experts on this subject based on the ideXlab platform.
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attenuation compensation for least squares reverse time migration using the viscoacoustic wave equation
Geophysics, 2014Co-Authors: Gaurav Dutta, Gerard T SchusterAbstract:Strong subsurface attenuation leads to distortion of amplitudes and phases of seismic waves propagating inside the earth. Conventional acoustic reverse time migration (RTM) and least-squares reverse time migration (LSRTM) do not account for this distortion, which can lead to defocusing of migration images in highly attenuative geologic environments. To correct for this distortion, we used a linearized inversion method, denoted as Qp-LSRTM. During the leastsquares iterations, we used a linearized viscoacoustic Modeling Operator for forward Modeling. The adjoint equations were derived using the adjoint-state method for back propagating the residual wavefields. The merit of this approach compared with conventional RTM and LSRTM was that Qp-LSRTM compensated for the amplitude loss due to attenuation and could produce images with better balanced amplitudes and more resolution below highly attenuative layers. Numerical tests on synthetic and field data illustrated the advantages of Qp-LSRTM over RTM and LSRTM when the recorded data had strong attenuation effects. Similar to standard LSRTM, the sensitivity tests for background velocity and Qp errors revealed that the liability of this method is the requirement for smooth and accurate migration velocity and attenuation models.
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least squares migration of incomplete reflection data
Geophysics, 1999Co-Authors: Tamas Nemeth, Gerard T SchusterAbstract:A least-squares migration algorithm is presented that reduces the migration artifacts (i.e., recording footprint noise) arising from incomplete data. Instead of migrating data with the adjoint of the forward Modeling Operator, the normal equations are inverted by using a preconditioned linear conjugate gradient scheme that employs regularization. The Modeling Operator is constructed from an asymptotic acoustic integral equation, and its adjoint is the Kirchhoff migration Operator. We tested the performance of the least-squares migration on synthetic and field data in the cases of limited recording aperture, coarse sampling, and acquisition gaps in the data. Numerical results show that the least-squares migrated sections are typically more focused than are the corresponding Kirchhoff migrated sections and their reflectivity frequency distributions are closer to those of the true model frequency distribution. Regularization helps attenuate migration artifacts and provides a sharper, better frequency distribution of estimated reflectivity. The least-squares migrated sections can be used to predict the missing data traces and interpolate and extrapolate them according to the governing Modeling equations. Several field data examples are presented. A ground-penetrating radar data example demonstrates the suppression of the recording footprint noise due to a limited aperture, a large gap, and an undersampled receiver line. In addition, better fault resolution was achieved after applying least-squares migration to a poststack marine data set. And a reverse vertical seismic profiling example shows that the recording footprint noise due to a coarse receiver interval can be suppressed by least-squares migration.