56 research outputs found
Trajectory Planning with Pose Feedback for a Dual-Arm Space Robot
In order to obtain high precision path tracking for a dual-arm space robot, a trajectory planning method with pose feedback is proposed to be introduced into the design process in this paper. Firstly, pose error kinematic models are derived from the related kinematics and desired pose command for the end-effector and the base, respectively. On this basis, trajectory planning with pose feedback is proposed from a control perspective. Theoretical analyses show that the proposed trajectory planning algorithm can guarantee that pose error converges to zero exponentially for both the end-effector and the base when the robot is out of singular configuration. Compared with the existing algorithms, the proposed algorithm can lead to higher precision path tracking for the end-effector. Furthermore, the algorithm renders the system good anti-interference property for the base. Simulation results demonstrate the effectiveness of the proposed trajectory planning algorithm
A Secure Authentication Framework to Guarantee the Traceability of Avatars in Metaverse
Metaverse is a vast virtual environment parallel to the physical world in
which users enjoy a variety of services acting as an avatar. To build a secure
living habitat, it's vital to ensure the virtual-physical traceability that
tracking a malicious player in the physical world via his avatars in virtual
space. In this paper, we propose a two-factor authentication framework based on
chameleon signature and biometric-based authentication. First, aiming at
disguise in virtual space, we propose a chameleon collision signature algorithm
to achieve the verifiability of the avatar's virtual identity. Second, facing
at impersonation in physical world, we construct an avatar's identity model
based on the player's biometric template and the chameleon key to realize the
verifiability of the avatar's physical identity. Finally, we design two
decentralized authentication protocols based on the avatar's identity model to
ensure the consistency of the avatar's virtual and physical identities.
Security analysis indicates that the proposed authentication framework
guarantees the consistency and traceability of avatar's identity. Simulation
experiments show that the framework not only completes the decentralized
authentication between avatars but also achieves the virtual-physical tracking.Comment: 12 pages, 9 figure
An interface-enriched generalized finite-element method for efficient electromagnetic analysis of composite materials
An interface-enriched generalized FEM is presented for analyzing electromagnetic problems involving composite materials. To avoid of generating conformal meshes in highly inhomogeneous domains, enriched vector basis functions are introduced over the intersections of material interfaces and the nonconforming elements to capture the normal derivative discontinuity of the tangential field component. These enrichment functions are directly constructed from a linear combination of the vector basis functions of the subelements. Several numerical examples are presented to verify the algorithm with analytical solutions and demonstrate its h-refinement convergence rate. Finally, two illustrative examples, involving multiple microvascular channels and circular inclusions, are solved
Portable wireless electrocorticography system with a fexible microelectrodes array for epilepsy treatment
In this paper, we present a portable wireless electrocorticography (ECoG) system. It uses a high
resolution 32-channel fexible ECoG electrodes array to collect electrical signals of brain activities and to
stimulate the lesions. Electronic circuits are designed for signal acquisition, processing and transmission
using Bluetooth Low Energy 4 (LTE4) for wireless communication with cell phone. In-vivo experiments
on a rat show that the fexible ECoG system can accurately record electrical signals of brain activities
and transmit them to cell phone with a maximal sampling rate of 30 ksampling/s per channel. It
demonstrates that the epilepsy lesions can be detected, located and treated through the ECoG system.
The wireless ECoG system has low energy consumption and high brain spatial resolution, thus has great
prospects for future application
4-Nonylphenol induces autophagy and attenuates mTOR-p70S6K/4EBP1 signaling by modulating AMPK activation in Sertoli cells
The estrogenic chemical 4-nonylphenol (NP) is known to impair testicular devolopment and spermatogenesis in rodents. The objective of this study was to explore the effects of NP on autophagy induction and AMPK-mTOR signaling pathway in Sertoli cells (SCs), which are the ānursemaid cellsā for meiosis of spermatocytes. In this study we exposed 7-week-old male rats to NP by intra-peritoneal injection at 0, 20, 50 or 100 mg/kg body weight/2 days for 20 consecutive days. Our results showed that exposure to NP dose-dependently induces the formation of autophagosomes in SCs, increases the expression of Beclin-1, the conversion of LC3-I to LC3-II and the mRNA expression of Atg3, Atg5, Atg7 and Atg12 in testis, and these effects are concomitant with the activation of AMPK, and the suppression of TSC2-mTOR-p70S6K/4EBP1 signaling cascade in testis. Furthermore, 10 ĀµM Compound C or AMPKĪ±1 siRNA pre-treatment effectively attenuated autophagy and reversed AMPK-mTOR-p70S6K/4EBP1 signaling in NP-treated SCs. Co-treatment with 1 mM AICAR remarkably strengthened NP-induced autophagy and mTOR inhibition in SCs. Together, these data suggest that NP stimulates Sertoli cell autophagy and inhibits mTOR-p70S6K/4EBP1 activity through AMPK activation, which is the potential mechanism responsible for the regulation of testis function and differentiation following NP exposure
Advanced finite-element techniques for simulation of composite materials and large-scale scattering problems
This dissertation aims at developing sophisticated finite-element based numerical algorithms for efficient electromagnetic modeling and design of composite materials, fast frequency-domain scattering analysis of electrically large problems on massive parallelized computers, and efficient broadband analysis of resonant waveguide structures. To these ends, first, an interface-enriched generalized finite-element method (IGFEM) is introduced for electromagnetic analysis of heterogeneous materials. To avoid using conformal meshes, the method assigns generalized degrees of freedom at material interfaces to capture the discontinuities of the field and its derivatives, and maintains the same level of solution accuracy and computational complexity as the standard FEM based on conformal meshes. The fixed mesh nature combined with an analytical sensitivity analysis significantly reduces the computational cost in gradient-based shape optimization. Second, an efficient parallelization strategy is proposed for the domain decomposition based dual-primal finite-element tearing and interconnecting (FETI-DP) algorithm. Load balancing, global, neighboring, inter-processor communication minimization, and preconditioning techniques are adopted to improve the computational and parallel efficiency. An inhomogeneous truncation boundary condition is presented to enable the FETI-DP simulation of a stratified medium. The parallel FETI-DP algorithm is also combined with a fast near- to far-field transformation and a linear interpolation technique for efficient vectorial field imaging of electrically large objects. Finally, a hybrid technique that consists of the time- and frequency-domain computations and model-order reduction strategy is developed for the efficient simulations of resonant waveguide structures. Numerous results are presented to demonstrate the accuracy, efficiency, and capability of the proposed methods
Advanced finite-element techniques for simulation of composite materials and large-scale scattering problems
This dissertation aims at developing sophisticated finite-element based numerical algorithms for efficient electromagnetic modeling and design of composite materials, fast frequency-domain scattering analysis of electrically large problems on massive parallelized computers, and efficient broadband analysis of resonant waveguide structures. To these ends, first, an interface-enriched generalized finite-element method (IGFEM) is introduced for electromagnetic analysis of heterogeneous materials. To avoid using conformal meshes, the method assigns generalized degrees of freedom at material interfaces to capture the discontinuities of the field and its derivatives, and maintains the same level of solution accuracy and computational complexity as the standard FEM based on conformal meshes. The fixed mesh nature combined with an analytical sensitivity analysis significantly reduces the computational cost in gradient-based shape optimization. Second, an efficient parallelization strategy is proposed for the domain decomposition based dual-primal finite-element tearing and interconnecting (FETI-DP) algorithm. Load balancing, global, neighboring, inter-processor communication minimization, and preconditioning techniques are adopted to improve the computational and parallel efficiency. An inhomogeneous truncation boundary condition is presented to enable the FETI-DP simulation of a stratified medium. The parallel FETI-DP algorithm is also combined with a fast near- to far-field transformation and a linear interpolation technique for efficient vectorial field imaging of electrically large objects. Finally, a hybrid technique that consists of the time- and frequency-domain computations and model-order reduction strategy is developed for the efficient simulations of resonant waveguide structures. Numerous results are presented to demonstrate the accuracy, efficiency, and capability of the proposed methods.U of I OnlyAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD syste
Genomeāwide comparative identification and analysis of membraneāFADSālike superfamily genes in freshwater economic fishes
Membrane fatty acid desaturase (FADS)ālike superfamily proteins (FADSs) are essential for the synthesis of unsaturated fatty acids (UFAs). Recently, studies on FADS in fishes have mostly focused on marine species, and a comprehensive analysis of the FADS superfamily, including the FADS, stearoylāCoA desaturase (SCD), and sphingolipid delta 4ādesaturase (DEGS) families, in freshwater economic fishes is urgently required. To this end, we conducted a thorough analysis of the number, gene/protein structure, chromosomal location, gene linkage map, phylogeny, and expression of the FADS superfamily. We identified 156 FADSs genes in the genome of 27 representative species. Notably, FADS1 and SCD5 were lost in most freshwater fish and other teleosts. All FADSs proteins contain 4 transmembrane helices and 2ā3 amphipathic Ī±āhelices. FADSs in the same family are often linked on the same chromosome; moreover, FADS and SCD or DEGS are frequently collocated on the same chromosome. In addition, FADS, SCD, and DEGS family proteins share similar evolutionary patterns. Interestingly, FADS6, as a member of the FADS family, exhibits a similar gene structure and chromosome location to that of SCD family members, which may be the transitional form of FADS and SCD. This study shed light on the type, structure, and phylogenetic relationship of FADSs in freshwater fishes, offering a new perspective into the functional mechanism analysis of FADSs
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