171 research outputs found
Parallel Implementation of Katsevich's FBP Algorithm
For spiral cone-beam CT, parallel computing is an effective
approach to resolving the problem of heavy computation burden. It
is well known that the major computation time is spent in the
backprojection step for either filtered-backprojection (FBP) or
backprojected-filtration (BPF) algorithms. By the cone-beam cover
method [1], the backprojection procedure is driven by cone-beam
projections, and every cone-beam projection can be backprojected
independently. Basing on this fact, we develop a parallel
implementation of Katsevich's FBP algorithm. We do all the
numerical experiments on a Linux cluster. In one typical
experiment, the sequential reconstruction time is 781.3 seconds,
while the parallel reconstruction time is 25.7 seconds with 32
processors
Theoretical Model Construction of Deformation-Force for Soft Grippers Part I: Co-rotational Modeling and Force Control for Design Optimization
Compliant grippers, owing to adaptivity and safety, have attracted
considerable attention for unstructured grasping in real applications, such as
industrial or logistic scenarios. However, accurately modeling the
bidirectional relationship between shape deformation and contact force for such
grippers, the Fin-Ray grippers as an example, remains stagnant to date. To
address this research gap, this article devises, presents, and experimentally
validates a universal bidirectional force-displacement mathematical model for
compliant grippers based on the co-rotational concept, which endows such
grippers with an intrinsic force sensing capability and offers a better insight
into the design optimization. In Part I of the article, we introduce the
fundamental theory of the co-rotational approach, where arbitrary large
deformation of beam elements can be modeled. Its intrinsic principle allows
taking materials with varying stiffness, various connection types, and key
design parameters into consideration with few assumptions. Further, the
force-displacement relationship is numerically derived, providing accurate
displacement estimations of the gripper under external forces with minor
computational loads. The performance of the proposed method is experimentally
verified through comparison with Finite Element Analysis (FEA) in simulation,
obtaining a fair degree of accuracy (6%), and design optimization of Fin-Ray
grippers is systematically investigated. Part II of this article demonstrating
the force sensing capabilities and the effects of representative co-rotational
modeling parameters on model accuracy is released in Arxiv
Pragmatic Conventions Influencing Children's Use of Causal Constructions in Natural Discourse
Proceedings of the Sixteenth Annual Meeting of the Berkeley Linguistics Society (1990), pp. 205-21
Theoretical Model Construction of Deformation-Force for Soft Grippers Part II: Displacement Control Based Intrinsic Force Sensing
Force-aware grasping is an essential capability for most robots in practical
applications. Especially for compliant grippers, such as Fin-Ray grippers, it
still remains challenging to build a bidirectional mathematical model that
mutually maps the shape deformation and contact force. Part I of this article
has constructed the force-displacement relationship for design optimization
through the co-rotational theory. In Part II, we further devise a
displacement-force mathematical model, enabling the compliant gripper to
precisely estimate contact force from deformations sensor-free. The presented
displacement-force model elaborately investigates contact forces and provides
force feedback for a force control system of a gripper, where deformation
appears as displacements in contact points. Afterward, simulation experiments
are conducted to evaluate the performance of the proposed model through
comparisons with the finite-element analysis (FEA) in Ansys. Simulation results
reveal that the proposed model accurately estimates contact force, with an
average error of around 3% and 4% for single or multiple node cases,
respectively, regardless of various design parameters (Part I of this article
is released in Arxiv1
Characterization of four vaccine-related polioviruses including two intertypic type 3/type 2 recombinants associated with aseptic encephalitis
Temperature sensitivity of 4 poliovirus type 3 isolates. (DOC 31 kb
Autoencoding a Soft Touch to Learn Grasping from On-land to Underwater
Robots play a critical role as the physical agent of human operators in
exploring the ocean. However, it remains challenging to grasp objects reliably
while fully submerging under a highly pressurized aquatic environment with
little visible light, mainly due to the fluidic interference on the tactile
mechanics between the finger and object surfaces. This study investigates the
transferability of grasping knowledge from on-land to underwater via a
vision-based soft robotic finger that learns 6D forces and torques (FT) using a
Supervised Variational Autoencoder (SVAE). A high-framerate camera captures the
whole-body deformations while a soft robotic finger interacts with physical
objects on-land and underwater. Results show that the trained SVAE model
learned a series of latent representations of the soft mechanics transferrable
from land to water, presenting a superior adaptation to the changing
environments against commercial FT sensors. Soft, delicate, and reactive
grasping enabled by tactile intelligence enhances the gripper's underwater
interaction with improved reliability and robustness at a much-reduced cost,
paving the path for learning-based intelligent grasping to support fundamental
scientific discoveries in environmental and ocean research.Comment: 17 pages, 5 figures, 1 table, submitted to Advanced Intelligent
Systems for revie
A Chinese Herbal Preparation Containing Radix Salviae Miltiorrhizae, Radix Notoginseng and Borneolum Syntheticum Reduces Circulating Adhesion Molecules
Circulating adhesion molecules (CAMs), surface proteins expressed in the vascular endothelium, have emerged as risk factors for cardiovascular disease (CVD). CAMs are involved in intercellular communication that are believed to play a role in atherosclerosis. A Chinese medicine, the “Dantonic Pill” (DP) (also known as the “Cardiotonic Pill”), containing three Chinese herbal material medica, Radix Salviae Miltiorrhizae, Radix Notoginseng and Borneolum Syntheticum, has been used in China for the prevention and management of CVD. Previous laboratory and animal studies have suggested that this preparation reduces both atherogenesis and adhesion molecule expression. A parallel double blind randomized placebo-controlled study was conducted to assess the effects of the DP on three species of CAM (intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 and endothelial cell selectin (E-selectin)) in participants with mild-moderate hypercholesterolemia. Secondary endpoints included biochemical and hematological variables and clinical effects. Forty participants were randomized to either treatment or control for 12 weeks. Treatment with DP was associated with a statistically significant decrease in ICAM-1 (9% decrease, P = .03) and E-Selectin (15% decrease, P = .004). There was no significant change in renal function tests, liver function tests, glucose, lipids or C-reactive protein levels and clinical adverse effects did not differ between the active and the control groups. There were no relevant changes in participants receiving placebo. These results suggest that this herbal medicine may contribute to the development of a novel approach to cardiovascular risk reduction
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