80 research outputs found
Properties of recoverable region and semi-global stabilization in recoverable region for linear systems subject to constraints
This paper investigates time-invariant linear systems subject to input and state constraints. It is shown that the recoverable region (which is the largest domain of attraction that is theoretically achievable) can be semiglobally stabilized by continuous nonlinear feedbacks while satisfying the constraints. Moreover, a reduction technique is presented which shows, when trying to compute the recoverable region, that we only need to compute the recoverable region for a system of lower dimension which generally leads to a considerable simplification in the computational effort
Internal stabilization and external stabilization of linear systems subject to constraints
Having studied during the last decade several aspects of several control design problems for linear systems subject to magnitude and rate constraints on control variables, during the last two years the research has broadened to include magnitude constraints on control variables as well as state variables. Recent work by Han et al. (2000), Hou et al. (1998) and Saberi et al. (2002) considered linear systems in a general framework for constraints including both input magnitude constraints as well as state magnitude constraints. In particular, Saberi et al. consider internal stabilization while Han et al. consider output regulation in different frameworks, namely a global, semiglobal, and regional framework. These problems require very strong solvability conditions. Therefore, a main focus for future research should focus on finding a controller with a large domain of attraction and some good rejection properties for disturbances restricted to some bounded se
A Fast Symbolic Computation Approach to Statistical Analysis of Mesh Networks with Multiple Sources *
Abstract-Mesh circuits typically consist of many resistive links and many sources. Accurate analysis of massive mesh networks is demanding in the current integrated circuit design practice, yet their computation confronts numerous challenges. When variation is considered, mesh analysis becomes a much harder task. This paper proposes a symbolic computation technique that can be applied to the moment-based analysis of mesh networks with multiple sources. The variation issues are easily taken care of by a structured computation mechanism, which can naturally facilitate sensitivity based analysis. Applications are addressed by applying the computation technique to a set of mesh circuits with varying sizes
Implementation of a Symbolic Circuit Simulator for Topological Network Analysis
Abstract- Many topological approaches to symbolic network analysis have been proposed in the literature, but none are implemented ultimately as a simulator for large network analysis due to their complexity and exponentially increasing number of terms. A novel methodology adopted in this paper uses a graph reduction approach based on a set of graph reduction rules developed recently. Furthermore, a Binary Decision Diagram is used in the implementation of a symbolic simulator that is capable of analyzing large analog circuit blocks. Implementation details and experimental results are reported. Keywords-admissible term, BDD, graph reduction, symbolic analysis I
Atomistic simulations of thermodynamic properties of liquid gallium from first principles
In the research of condensed matter, atomistic dynamic simulations play a
crucial role, particularly in revealing dynamic processes, phase transitions
and thermodynamic statistics macroscopic physical properties in systems such as
solids and liquids. For a long time, simulating complex and disordered liquids
has been a challenge compared to ordered crystalline structures. The primary
reasons for this challenge are the lack of precise force field functions and
the neglect of nuclear quantum effects. To overcome these two limits in
simulation of liquids, we use a deep potential (DP) with quantum thermal bath
(QTB) approach. DP is a machine learning model are sampled from density
functional theory and able to do large-scale atomic simulations with its
precision. QTB is a method which incorporates nuclear quantum effects by
quantum fluctuation dissipation. The application of this first principles
approach enable us to successfully describe the phase transition processes in
solid and liquid Gallium (Ga) as well as the associated dynamic phenomena. More
importantly, we obtain the thermodynamic properties of liquid Ga, such as
internal energy, specific heat, enthalpy change, entropy and Gibbs free energy,
and these results align remarkably well with experiments. Our research has
opened up a new paradigm for the study of dynamics and thermodynamics in
liquids, amorphous materials, and other disordered systems, providing valuable
insights and references for future investigations.Comment: 7 pages, 11 figures for maintext; 6pages, 8 figures for supplementary
material
A review of phase change heat transfer in shape-stabilized phase change materials (ss-PCMs) based on porous supports for thermal energy storage
Latent heat thermal energy storage (LHTES) uses phase change materials (PCMs) to store and release heat, and can effectively address the mismatch between energy supply and demand. However, it suffers from low thermal conductivity and the leakage problem. One of the solutions is integrating porous supports and PCMs to fabricate shape-stabilized phase change materials (ss-PCMs). The phase change heat transfer in porous ss-PCMs is of fundamental importance for determining thermal-fluidic behaviours and evaluating LHTES system performance. This paper reviews the recent experimental and numerical investigations on phase change heat transfer in porous ss-PCMs. Materials, methods, apparatuses and significant outcomes are included in the section of experimental studies and it is found that paraffin and metal foam are the most used PCM and porous support respectively in the current researches. Numerical advances are reviewed from the aspect of different simulation methods. Compared to representative elementary volume (REV)-scale simulation, the pore-scale simulation can provide extra flow and heat transfer characteristics in pores, exhibiting great potential for the simulation of mesoporous, microporous and hierarchical porous materials. Moreover, there exists a research gap between phase change heat transfer and material preparation. Finally, this review outlooks the future research topics of phase change heat transfer in porous ss-PCMs
Methylprednisolone as Adjunct to Endovascular Thrombectomy for Large-Vessel Occlusion Stroke
Importance
It is uncertain whether intravenous methylprednisolone improves outcomes for patients with acute ischemic stroke due to large-vessel occlusion (LVO) undergoing endovascular thrombectomy.
Objective
To assess the efficacy and adverse events of adjunctive intravenous low-dose methylprednisolone to endovascular thrombectomy for acute ischemic stroke secondary to LVO.
Design, Setting, and Participants
This investigator-initiated, randomized, double-blind, placebo-controlled trial was implemented at 82 hospitals in China, enrolling 1680 patients with stroke and proximal intracranial LVO presenting within 24 hours of time last known to be well. Recruitment took place between February 9, 2022, and June 30, 2023, with a final follow-up on September 30, 2023.InterventionsEligible patients were randomly assigned to intravenous methylprednisolone (n = 839) at 2 mg/kg/d or placebo (n = 841) for 3 days adjunctive to endovascular thrombectomy.
Main Outcomes and Measures
The primary efficacy outcome was disability level at 90 days as measured by the overall distribution of the modified Rankin Scale scores (range, 0 [no symptoms] to 6 [death]). The primary safety outcomes included mortality at 90 days and the incidence of symptomatic intracranial hemorrhage within 48 hours.
Results
Among 1680 patients randomized (median age, 69 years; 727 female [43.3%]), 1673 (99.6%) completed the trial. The median 90-day modified Rankin Scale score was 3 (IQR, 1-5) in the methylprednisolone group vs 3 (IQR, 1-6) in the placebo group (adjusted generalized odds ratio for a lower level of disability, 1.10 [95% CI, 0.96-1.25]; P = .17). In the methylprednisolone group, there was a lower mortality rate (23.2% vs 28.5%; adjusted risk ratio, 0.84 [95% CI, 0.71-0.98]; P = .03) and a lower rate of symptomatic intracranial hemorrhage (8.6% vs 11.7%; adjusted risk ratio, 0.74 [95% CI, 0.55-0.99]; P = .04) compared with placebo.
Conclusions and Relevance
Among patients with acute ischemic stroke due to LVO undergoing endovascular thrombectomy, adjunctive methylprednisolone added to endovascular thrombectomy did not significantly improve the degree of overall disability.Trial RegistrationChiCTR.org.cn Identifier: ChiCTR210005172
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