109 research outputs found
The Sliding Mode Control about ASR of Vehicle with Four Independently Driven In-Wheel Motors Based on the Exponent Approach Law
AbstractAcceleration slip regulation control system is a new active safety technology. In this paper, through the research of the four-wheel independent drive electric vehicle, a sliding mode variable structure control algorithm based on exponent approach law is proposed, which is applied to the ASR system. This paper establishes a seven DOFs vehicle dynamics model, tests whether the ASR control strategy is efficient on the poor condition road. The simulation results show that the vehicle acceleration performance improvement rate increases by 43.5% and 58.5% with the control strategy. During the two simulation processes, the results indicate that the sliding mode variable structure control algorithm applied to ASR system has a good adaptation to good and slippery roads. The algorithm can greatly improve the four-wheel independent drive electric vehicle's acceleration performance
Learning Image-Conditioned Dynamics Models for Control of Under-actuated Legged Millirobots
Millirobots are a promising robotic platform for many applications due to
their small size and low manufacturing costs. Legged millirobots, in
particular, can provide increased mobility in complex environments and improved
scaling of obstacles. However, controlling these small, highly dynamic, and
underactuated legged systems is difficult. Hand-engineered controllers can
sometimes control these legged millirobots, but they have difficulties with
dynamic maneuvers and complex terrains. We present an approach for controlling
a real-world legged millirobot that is based on learned neural network models.
Using less than 17 minutes of data, our method can learn a predictive model of
the robot's dynamics that can enable effective gaits to be synthesized on the
fly for following user-specified waypoints on a given terrain. Furthermore, by
leveraging expressive, high-capacity neural network models, our approach allows
for these predictions to be directly conditioned on camera images, endowing the
robot with the ability to predict how different terrains might affect its
dynamics. This enables sample-efficient and effective learning for locomotion
of a dynamic legged millirobot on various terrains, including gravel, turf,
carpet, and styrofoam. Experiment videos can be found at
https://sites.google.com/view/imageconddy
Evaluation of polymyxin B AUC/MIC ratio for dose optimization in patients with carbapenem-resistant Klebsiella pneumoniae infection
Polymyxin B has been used as a last-line therapy for the treatment of carbapenem-resistant gram-negative bacterial infection. The pharmacokinetic/pharmacodynamic index (AUC/MIC) of polymyxin B has not been clinically evaluated, given that the broth microdilution method for polymyxin susceptibility testing is rarely used in hospitals. This study analyzed data from 77 patients with carbapenem-resistant Klebsiella pneumoniae infections. Among the samples, 63 K. pneumoniae isolates had MIC values of 1.0 mg/L as measured by broth microdilution but 0.5 mg/L as measured using the Vitek 2 system. Polymyxin B AUC/MIC was significantly associated with clinical response (p = 0.002) but not with 30-day all-cause mortality (p = 0.054). With a target AUC/MIC value of 50, Monte Carlo simulations showed that a fixed dose of 100 mg/12 h and three weight-based regimens (1.25 mg/kg/12 h for 80 kg and 1.5 mg/kg/12 h for 70 kg/80 kg) achieved a cumulative fraction of response >90% regardless of renal function, but the risk of nephrotoxicity was high. For patients with carbapenem-resistant K. pneumoniae infections, the underestimation of polymyxin resistance in automated systems need to be taken into account when optimizing polymyxin B dosing based on pharmacokinetic/pharmacodynamic principles
Oxide perovskite BaSnO3: A promising high-temperature thermoelectric material for transparent conducting oxides
The new technology of energy conversion must be developed to ensure energy
sustainability. Thermoelectric (TE) materials provide an effective means to
solve the energy crisis. As a potential TE candidate, the TE properties of
perovskite have received extensively attention. We here investigate the TE
transport properties of the transparent conducting oxide (TCO) BaSnO3 by
first-principles calculations. We find that the BaSnO3 perovskite exhibits
outstanding dynamic and thermal stabilities, which provide excellent electronic
and thermal transport properties simultaneously. These properties contribute to
the remarkable Seebeck coefficient and power factor, which gives rise to the ZT
of n-1.03 and p-3.64 at 900 K. Additionally, doping and nanostructure open
prospects for effectively improving the TE properties of BaSnO3. Our work
provides a basis for further optimizing the TE transport properties of cubic
BaSnO3 and may have worthwhile practical significance for applying cubic
perovskite to the high-temperature thermoelectric field.Comment: 29 pages,6 figures,1 tabl
Superfolded configuration induced low thermal conductivity in two-dimensional carbon allotropes revealed via machine learning force constant potential
Understanding the fundamental link between structure and functionalization is
crucial for the design and optimization of functional materials, since
different structural configurations could trigger materials to demonstrate
diverse physical, chemical, and electronic properties. However, the correlation
between crystal structure and thermal conductivity (\k{appa}) remains
enigmatic. In this study, taking two-dimensional (2D) carbon allotropes as
study cases, we utilize phonon Boltzmann transport equation (BTE) along with
machine learning force constant potential to thoroughly explore the complex
folding structure of pure sp2 hybridized carbon materials from the perspective
of crystal structure, mode-level phonon resolved thermal transport, and atomic
interactions, with the goal of identifying the underlying relationship between
2D geometry and \k{appa}. We propose two potential structure evolution
mechanisms for targeted thermal transport properties: in-plane and out-of-plane
folding evolutions, which are generally applicable to 2D carbon allotropes. It
is revealed that the folded structure produces strong symmetry breaking, and
simultaneously produces exceptionally strongly suppressed phonon group
velocities, strong phonon-phonon scattering, and weak phonon hydrodynamics,
which ultimately lead to low \k{appa}. The insight into the folded effect of
atomic structures on thermal transport deepens our understanding of the
relationship between structure and functionalization, which offers
straightforward guidance for designing novel nanomaterials with targeted
\k{appa}, as well as propel developments in materials science and engineering
2D Janus Niobium Oxydihalide NbO: Multifunctional High-Mobility Piezoelectric Semiconductor for Electronics, Photonics and Sustainable Energy Applications
Two-dimensional (2D) niobium oxydihalide NbOI has been recently
demonstrated as an excellent in-plane piezoelectric and nonlinear optical
materials. Here we show that Janus niobium oxydihalide, NbO (X, Y = Cl, Br,
I and XY), is a multifunctional anisotropic semiconductor family with
exceptional piezoelectric, electronic, photocatalytic and optical properties.
NbO are stable and mechancially flexible monolayers with band gap around
the visible light regime of eV. The anisotropic carrier mobility of
NbO lies in the range of cmVs, which
represents some of the highest among 2D semiconductors of bandgap
eV. Inversion symmetry breaking in Janus NbO generates sizable out-of-plane
piezoelectric response while still retaining a strong in-plane
piezoelectricity. Remarkably, NbO exhibits an additional out-of-plane
piezoelectric response, as large as 0.55 pm/V. GW-BSE
calculation further reveals the strong linear optical dichroism of NbO in
the visible-to-ultraviolet regime. The optical absorption peaks with
\% in the deep UV regime ( eV), outperforming the vast majority of
other 2D materials. The high carrier mobility, strong optical absorption,
sizable built-in electric field and band alignment compatible with overall
water splitting further suggest the strengths of NbO in energy conversion
application. We further propose a directional stress sensing device to
demonstrate how the out-of-plane piezoelectricity can be harnessed for
functional device applications. Our findings unveil NbO as an exceptional
multifunctional 2D semiconductor for flexible electronics, optoelectronics, UV
photonics, piezoelectric and sustainable energy applications.Comment: 16 Pages, 7 Figures, 3 Table
Impact of Minor Alloy Components on the Electrocapillarity and Electrochemistry of Liquid Metal Fractals
Exploring and controlling surface tension-driven phenomena in liquid metals may lead to unprecedented possibilities for next-generation microfluidics, electronics, catalysis, and materials synthesis. In pursuit of these goals, the impact of minor constituents within liquid alloys is largely overlooked. Herein, it is showed that the presence of a fraction of solute metals such as tin, bismuth, and zinc in liquid gallium can significantly influence their electrocapillarity and electrochemistry. The instability-driven fractal formation of liquid alloy droplets is investigated with different solutes and reveals the formation of distinctive non-branched droplets, unstable fractals, and stable fractal modes under controlled voltage and alkaline solution conditions. In their individually unique fractal morphology diagrams, different liquid alloys demonstrate significantly shifted voltage thresholds in transition between the three fractal modes, depending on the choice of the solute metal. Surface tension measurements, cycle voltammetry and surface compositional characterizations provide strong evidence that the minor alloy components drastically alter the surface tension, surface electrochemical oxidation, and oxide dissolution processes that govern the droplet deformation and instability dynamics. The findings that minor components are able to regulate liquid alloys’ surface tensions, surface element distributions and electrochemical activities offer great promises for harnessing the tunability and functionality of liquid metals.</p
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