2,102 research outputs found
A Fast Integrated Planning and Control Framework for Autonomous Driving via Imitation Learning
For safe and efficient planning and control in autonomous driving, we need a
driving policy which can achieve desirable driving quality in long-term horizon
with guaranteed safety and feasibility. Optimization-based approaches, such as
Model Predictive Control (MPC), can provide such optimal policies, but their
computational complexity is generally unacceptable for real-time
implementation. To address this problem, we propose a fast integrated planning
and control framework that combines learning- and optimization-based approaches
in a two-layer hierarchical structure. The first layer, defined as the "policy
layer", is established by a neural network which learns the long-term optimal
driving policy generated by MPC. The second layer, called the "execution
layer", is a short-term optimization-based controller that tracks the reference
trajecotries given by the "policy layer" with guaranteed short-term safety and
feasibility. Moreover, with efficient and highly-representative features, a
small-size neural network is sufficient in the "policy layer" to handle many
complicated driving scenarios. This renders online imitation learning with
Dataset Aggregation (DAgger) so that the performance of the "policy layer" can
be improved rapidly and continuously online. Several exampled driving scenarios
are demonstrated to verify the effectiveness and efficiency of the proposed
framework
Two Rapid Power Iterative DOA Estimators for UAV Emitter Using Massive/Ultra-massive Receive Array
To provide rapid direction finding (DF) for unmanned aerial vehicle (UAV)
emitter in future wireless networks, a low-complexity direction of arrival
(DOA) estimation architecture for massive multiple input multiple output (MIMO)
receiver arrays is constructed. In this paper, we propose two strategies to
address the extremely high complexity caused by eigenvalue decomposition of the
received signal covariance matrix. Firstly, a rapid power-iterative rotational
invariance (RPI-RI) method is proposed, which adopts the signal subspace
generated by power iteration to gets the final direction estimation through
rotational invariance between subarrays. RPI-RI makes a significant complexity
reduction at the cost of a substantial performance loss. In order to further
reduce the complexity and provide a good directional measurement result, a
rapid power-iterative Polynomial rooting (RPI-PR) method is proposed, which
utilizes the noise subspace combined with polynomial solution method to get the
optimal direction estimation. In addition, the influence of initial vector
selection on convergence in the power iteration is analyzed, especially when
the initial vector is orthogonal to the incident wave. Simulation results show
that the two proposed methods outperform the conventional DOA estimation
methods in terms of computational complexity. In particular, the RPIPR method
achieves more than two orders of magnitude lower complexity than conventional
methods and achieves performance close to CRLB. Moreover, it is verified that
the initial vector and the relative error have a significant impact on the
performance of the computational complexity
The chloride channel cystic fibrosis transmembrane conductance regulator (CFTR) controls cellular quiescence by hyperpolarizing the cell membrane during diapause in the crustacean Artemia
Cellular quiescence, a reversible state in which growth, proliferation, and other cellular activities are arrested, is important for self-renewal, differentiation, development, regeneration, and stress resistance. However, the physiological mechanisms underlying cellular quiescence remain largely unknown. In the present study, we used embryos of the crustacean Artemia in the diapause stage, in which these embryos remain quiescent for prolonged periods, as a model to explore the relationship between cell-membrane potential (V-mem) and quiescence. We found that V-mem is hyperpolarized and that the intracellular chloride concentration is high in diapause embryos, whereas V-mem is depolarized and intracellular chloride concentration is reduced in postdiapause embryos and during further embryonic development. We identified and characterized the chloride ion channel protein cystic fibrosis transmembrane conductance regulator (CFTR) of Artemia (Ar-CFTR) and found that its expression is silenced in quiescent cells of Artemia diapause embryos but remains constant in all other embryonic stages. Ar-CFTR knockdown and GlyH-101-mediated chemical inhibition of Ar-CFTR produced diapause embryos having a high V-mem and intracellular chloride concentration, whereas control Artemia embryos released free-swimming nauplius larvae. Transcriptome analysis of embryos at different developmental stages revealed that proliferation, differentiation, and metabolism are suppressed in diapause embryos and restored in postdiapause embryos. Combined with RNA sequencing (RNA-Seq) of GlyH-101-treated MCF-7 breast cancer cells, these analyses revealed that CFTR inhibition down-regulates the Wnt and Aurora Kinase A (AURKA) signaling pathways and up-regulates the p53 signaling pathway. Our findings provide insight into CFTR-mediated regulation of cellular quiescence and V-mem in the Artemia model
Influence of ground-Rydberg coherence in two-qubit gate based on Rydberg blockade
For neutral atom qubits, the two-qubit gate is typically realized via the
Rydberg blockade effect, which hints about the special status of the Rydberg
level besides the regular qubit register states. Here, we carry out
experimental and theoretical studies to reveal how the ground-Rydberg coherence
of the control qubit atom affects the process of two-qubit Controlled-Z ()
gate, such as the commonly used ground-Rydberg -gap- pulse sequence
originally proposed in Phys. Rev. Lett. \textbf{85}, 2208 (2000). We measure
the decoherence of the control qubit atom after the -gap- pulses and
make a direct comparison with the typical decoherence time
extracted from Ramsey fringes of the ground-Rydberg transition. In particular,
we observe that the control qubit atom subject to such pulse sequences
experiences a process which is essentially similar to the ground-Rydberg Ramsey
interference. Furthermore, we build a straightforward theoretical model to link
the decoherence process of control qubit subject to gate -gap-
pulse sequence and the , and also analyze the typical origins of
decoherence effects. Finally, we discuss the gate fidelity loss due to
the limits imposed by the ground-Rydberg coherence properties and prospective
for improving fidelity with new gate protocols.Comment: 8 figure
Exploring scale invariance in the expansion of a spherical unitary Fermi gas
A unitary Fermi gas in an isotropic harmonic trap is predicted to show scale
and conformal symmetry that have important consequences in its thermodynamic
and dynamical properties. By experimentally realizing an isotropic harmonic
trap, we study the expansion of a unitary Fermi gas and demonstrate its
universal expansion dynamics along different directions and at different
temperatures. We show that as a consequence of SO(2,1) symmetry, the measured
release energy is equal to that of the trapping energy. In addition, away from
resonance when scale invariance is broken, we determine the effective exponent
that relates the chemical potential and average density along the
BEC-BCS crossover, which qualitatively agrees with the mean field predictions.
This work opens the possibility of studying non-equilibrium dynamics in a
conformal invariant system in the future.Comment: 15 pages and 8 figur
Diffusion basis spectrum imaging detects axonal loss after transient dexamethasone treatment in optic neuritis mice
Optic neuritis is a frequent first symptom of multiple sclerosis (MS) for which corticosteroids are a widely employed treatment option. The Optic Neuritis Treatment Trial (ONTT) reported that corticosteroid treatment does not improve long-term visual acuity, although the evolution of underlying pathologies is unclear. In this study, we employed non-invasive diffusion basis spectrum imaging (DBSI)-derived fiber volume to quantify 11% axonal loss 2 months after corticosteroid treatment (vs. baseline) in experimental autoimmune encephalomyelitis mouse optic nerves affected by optic neuritis. Longitudinal DBSI was performed at baseline (before immunization), after a 2-week corticosteroid treatment period, and 1 and 2 months after treatment, followed by histological validation of neuropathology. Pathological metrics employed to assess the optic nerve revealed axonal protection and anti-inflammatory effects of dexamethasone treatment that were transient. Two months after treatment, axonal injury and loss were indistinguishable between PBS- and dexamethasone-treated optic nerves, similar to results of the human ONTT. Our findings in mice further support that corticosteroid treatment alone is not sufficient to prevent eventual axonal loss in ON, and strongly support the potential of DBSI as a
帕金森病认知功能损害的中医药治疗
Parkinson’s disease (PD) is a degenerative disease of the central nervous system that involves many other systems. Cognitive impairment is one of the major presentations of non-motor symptoms of PD. Mild cognitive impairment in Parkinson’s disease (PD-MCI), a predictive factor of the transformation of PD to dementia is a common cognitive defect in PD patients. The effects of traditional Chinese Medicine on cognitive impairment in Parkinson’s disease were valued at home and abroad. Traditional Chinese Medicine has less toxic and side effects, treatment based on syndrome differentiation, and adjustment the balance of Yin and Yang for patients. Combination of Chinese and western medicine treatment could not only reduce the amount of dopamine agents but also counteract the toxic and side effects induced by dopamine agents. Meanwhile, combination of Chinese and western medicine treatment could delay the occurrence and development of cognitive impairment, and has broad application prospect.帕金森病(PD)是一种累及多系统的中枢神经系统变性病。认知功能障碍是PD非运动症状的重要表现形式,大多数PD患者均伴有认知功能损害并最终发展成为痴呆。中医药在帕金森病治疗中的作用越来越受到国内外的重视。中药具有毒副作用小且通过辨证论治、从整体调节患者阴阳平衡的特点,中西医结合治疗既能减少多巴胺制剂用量,又能有效拮抗和治疗西药所引起的毒副作用,延缓认知障碍的发生和发展,具有广阔应用前景
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