摘要 :
The aerodynamic loads exerted on a cylindrical platform model at high angles of attack (35° < α < 55°) are manipulated in wind tunnel experiments using distributed bleed actuation on its forebody. The asymmetry of the counter rotating forebody vortex pair that forms over the forebody and leads to asymmetric side forces and yawing moment at high incidences is exploited for control of these loads using azimuthally segmented bleed effected over the forebody. In the present investigations, bleed actuation is effected either for suppression or enhancement of these asymmetric loads. It is demonstrated that by direct control of the forebody vortices, segmented bleed can effectively attenuate the randomly evolving loads and/or effect prescribed side load. It is shown that over the present range of angles of incidence segmented bleed configurations can lead to significant changes in controlled side force of up to ΔCs = ±3.5 with minimal changes in lift and drag (for reference C_l≈4.5)....
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The aerodynamic loads exerted on a cylindrical platform model at high angles of attack (35° < α < 55°) are manipulated in wind tunnel experiments using distributed bleed actuation on its forebody. The asymmetry of the counter rotating forebody vortex pair that forms over the forebody and leads to asymmetric side forces and yawing moment at high incidences is exploited for control of these loads using azimuthally segmented bleed effected over the forebody. In the present investigations, bleed actuation is effected either for suppression or enhancement of these asymmetric loads. It is demonstrated that by direct control of the forebody vortices, segmented bleed can effectively attenuate the randomly evolving loads and/or effect prescribed side load. It is shown that over the present range of angles of incidence segmented bleed configurations can lead to significant changes in controlled side force of up to ΔCs = ±3.5 with minimal changes in lift and drag (for reference C_l≈4.5).
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A lumped parameter model of a friction tester is used to show that the dynamic response of the transducer can corrupt the measurement of friction. The corruption can be minimized by using a transducer which has a stiffness at leas...
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A lumped parameter model of a friction tester is used to show that the dynamic response of the transducer can corrupt the measurement of friction. The corruption can be minimized by using a transducer which has a stiffness at least two orders ofmagnitude higher than that of sliding system. A friction tester was designed to provide this stiffness difference. The slopes of friction-velocity curves of polymer-polymer sliding systems are shown to influence the stability of the sliding system. Largenegative slopes were observed for polymer pairs which exhibited multiple stick-slip cycles during sliding.
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The flow over an inclined slender axisymmetric cylinder (L/D = 11) with an ogive forebody is investigated experimentally at high angles of attack up to a = 65°. Of particular interest is the evolution and control of net side forc...
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The flow over an inclined slender axisymmetric cylinder (L/D = 11) with an ogive forebody is investigated experimentally at high angles of attack up to a = 65°. Of particular interest is the evolution and control of net side forces that are associated with asymmetries of the forebody vortices. It is shown that the interactions of the forebody vortices with the near-wake vortices of the cylinder leads to the formation of a vertical stack of counter-rotating streamwise vortices whose order depends on the dominant asymmetry of the forebody vortex pair. Synthetic jet actuation applied at the juncture of the forebody leads reversal of the order of the vortex stack in the wake and consequently alters the net side force. The present investigations also demonstrated that unsteady coupling between the cylindrical body and its near wake can lead to strong yaw-roll instabilities. The manipulation of the body vortex system and the side force by flow control actuation can be used for bi-directional control of the body's trajectory and suppress this instability.
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摘要 :
The flow over an inclined slender axisymmetric cylinder (L/D = 11) with an ogive forebody is investigated experimentally at high angles of attack up to a = 65°. Of particular interest is the evolution and control of net side forc...
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The flow over an inclined slender axisymmetric cylinder (L/D = 11) with an ogive forebody is investigated experimentally at high angles of attack up to a = 65°. Of particular interest is the evolution and control of net side forces that are associated with asymmetries of the forebody vortices. It is shown that the interactions of the forebody vortices with the near-wake vortices of the cylinder leads to the formation of a vertical stack of counter-rotating streamwise vortices whose order depends on the dominant asymmetry of the forebody vortex pair. Synthetic jet actuation applied at the juncture of the forebody leads reversal of the order of the vortex stack in the wake and consequently alters the net side force. The present investigations also demonstrated that unsteady coupling between the cylindrical body and its near wake can lead to strong yaw-roll instabilities. The manipulation of the body vortex system and the side force by flow control actuation can be used for bi-directional control of the body's trajectory and suppress this instability.
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Aerodynamic instabilities of a slender cylinder with an ogive forebody inclined at high incidence (45° < α< 60°) in a uniform stream is investigated in wind tunnel experiments. At these inclination angles the rollup of the counter-rotating forebody vortex pair becomes asymmetric and their subsequent interactions with the wire-mounted cylinder and its wake induce a nominally-stable side force whose sense depends on and varies with the azimuthal orientation of the forebody. The present investigations have shown that at some orientation of the forebody the tip vortices develop strong azimuthal oscillations that are manifested in bimodal migration in the near wake. Furthermore, the coupling to the model leads to time-varying side forces and unstable oscillations. Azimuthal actuation effected by an embedded synthetic jet at the juncture of the forebody is used to stabilize the vortex pair and thereby suppress the model oscillations. The unstable oscillations can be suppressed during pitch up/down maneuvers either ahead or following the onset of the instability....
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Aerodynamic instabilities of a slender cylinder with an ogive forebody inclined at high incidence (45° < α< 60°) in a uniform stream is investigated in wind tunnel experiments. At these inclination angles the rollup of the counter-rotating forebody vortex pair becomes asymmetric and their subsequent interactions with the wire-mounted cylinder and its wake induce a nominally-stable side force whose sense depends on and varies with the azimuthal orientation of the forebody. The present investigations have shown that at some orientation of the forebody the tip vortices develop strong azimuthal oscillations that are manifested in bimodal migration in the near wake. Furthermore, the coupling to the model leads to time-varying side forces and unstable oscillations. Azimuthal actuation effected by an embedded synthetic jet at the juncture of the forebody is used to stabilize the vortex pair and thereby suppress the model oscillations. The unstable oscillations can be suppressed during pitch up/down maneuvers either ahead or following the onset of the instability.
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摘要 :
A lumped parameter model of a friction tester is used to show that the dynamic response of the transducer can corrupt the measurement of friction. The corruption can be minimized by using a transducer which has a stiffness at leas...
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A lumped parameter model of a friction tester is used to show that the dynamic response of the transducer can corrupt the measurement of friction. The corruption can be minimized by using a transducer which has a stiffness at least two orders of magnitude higher than that of sliding system. A friction tester was designed to provide this stiffness difference. The slopes of friction-velocity curves of polymer-polymer sliding systems are shown to influence the stability of the sliding system. Large negative slopes were observed for polymer pairs which exhibited multiple stick-slip cycles during sliding.
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The Offshore Operators Committee (OOC), which is comprised of 110 companies, awarded Walk Haydel a contract to collect and evaluate aerometric (meteorological and air quality) monitoring and emission inventory data in the Gulf of ...
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The Offshore Operators Committee (OOC), which is comprised of 110 companies, awarded Walk Haydel a contract to collect and evaluate aerometric (meteorological and air quality) monitoring and emission inventory data in the Gulf of Mexico within 200 kilometers (km) of the Breton National Wilderness Area (BNWA). The wilderness area, a Class I string of barrier islands off the coast of Louisiana and Mississippi, is a federally protected bird and wildlife sanctuary. The Minerals Management Service (MMS) is requiring that all oil and gas companies operating on the Outer Continental Shelf within 100 km (200 km for the BAMP study) of BNWA gather relevant meteorological data. The OOC expanded the scope to include air quality and emission data. This presentation focuses on the emission inventory portion of the project and how the emission data will be used to evaluate the atmospheric dispersion modeling. Nitrogen oxides and sulfur dioxide are the parameters of interest from offshore sources because of their contribution to the increment consumption of BNWA.
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New field-effect electro-optic modulators (EOM) have been investigated and demonstrated. The new EOM has inherently attractive characteristics of broad spectral bandwidth, insensitivity of polarization, controllable waveguide prof...
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New field-effect electro-optic modulators (EOM) have been investigated and demonstrated. The new EOM has inherently attractive characteristics of broad spectral bandwidth, insensitivity of polarization, controllable waveguide profile, high power-handling capability, low loss, and a simplified fabrication process which can lead to mass producibility and low cost. A LiNbO$-3$/ device has experimentally demonstrated an extinction ratio of 25 dB.
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Mining histopathological and genetic data provides a unique avenue to deepen our understanding of cancer biology. However, extensive cancer heterogeneity across image- and molecular-scales poses technical challenges for feature ex...
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Mining histopathological and genetic data provides a unique avenue to deepen our understanding of cancer biology. However, extensive cancer heterogeneity across image- and molecular-scales poses technical challenges for feature extraction and outcome prediction. In this study, we propose a feature-enhanced graph network (FENet) for genetic mutation prediction using histopathological images in colon cancer. Unlike conventional approaches analyzing patch-based feature alone without considering their spatial connectivity, we seek to link and explore non-isomorphic topological structures in histopathological images. Our FENet incorporates feature enhancement in convolutional graph neural networks to aggregate discriminative features for capturing gene mutation status. Specifically, our approach could identify both local patch feature information and global topological structure in histopathological images simultaneously. Furthermore, we introduced an ensemble strategy by constructing multiple subgraphs to boost the prediction performance. Extensive experiments on the TCGA-COAD and TCGA-READ cohort including both histopathological images and three key genes' mutation profiles (APC, KRAS, and TP53) demonstrated the superiority of FENet for key mutational outcome prediction in colon cancer.
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Mining histopathological and genetic data provides a unique avenue to deepen our understanding of cancer biology. However, extensive cancer heterogeneity across image- and molecular-scales poses technical challenges for feature ex...
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Mining histopathological and genetic data provides a unique avenue to deepen our understanding of cancer biology. However, extensive cancer heterogeneity across image- and molecular-scales poses technical challenges for feature extraction and outcome prediction. In this study, we propose a feature-enhanced graph network (FENet) for genetic mutation prediction using histopathological images in colon cancer. Unlike conventional approaches analyzing patch-based feature alone without considering their spatial connectivity, we seek to link and explore non-isomorphic topological structures in histopathological images. Our FENet incorporates feature enhancement in convolutional graph neural networks to aggregate discriminative features for capturing gene mutation status. Specifically, our approach could identify both local patch feature information and global topological structure in histopathological images simultaneously. Furthermore, we introduced an ensemble strategy by constructing multiple subgraphs to boost the prediction performance. Extensive experiments on the TCGA-COAD and TCGA-READ cohort including both histopathological images and three key genes' mutation profiles (APC, KRAS, and TP53) demonstrated the superiority of FENet for key mutational outcome prediction in colon cancer.
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