RISE-Based Integrated Motion Control of Autonomous Ground Vehicles With Asymptotic Prescribed Performance

This article investigates the integrated lane-keeping and roll control for autonomous ground vehicles (AGVs) considering the transient performance and system disturbances. The robust integral of the sign of error (RISE) control strategy is proposed to achieve the lane-keeping control purpose with rollover prevention, by guaranteeing the asymptotic stability of the closed-loop system, attenuating systematic disturbances, and maintaining the controlled states within the prescribed performance boundaries. Three contributions have been made in this article: 1) a new prescribed performance function (PPF) that does not require accurate initial errors is proposed to guarantee the tracking errors restricted within the predefined asymptotic boundaries; 2) a modified neural network (NN) estimator which requires fewer adaptively updated parameters is proposed to approximate the unknown vertical dynamics; and 3) the improved RISE control based on PPF is proposed to achieve the integrated control objective, which analytically guarantees both the controller continuity and closed-loop system asymptotic stability by integrating the signum error function. The overall system stability is proved with the Lyapunov function. The controller effectiveness and robustness are finally verified by comparative simulations using two representative driving maneuvers, based on the high-fidelity CarSim-Simulink simulation

Variation in brain connectivity during motor imagery and motor execution in stroke patients based on electroencephalography

ObjectiveThe objective of this study was to analyze the changes in connectivity between motor imagery (MI) and motor execution (ME) in the premotor area (PMA) and primary motor cortex (MA) of the brain, aiming to explore suitable forms of treatment and potential therapeutic targets.MethodsTwenty-three inpatients with stroke were selected, and 21 right-handed healthy individuals were recruited. EEG signal during hand MI and ME (synergy and isolated movements) was recorded. Correlations between functional brain areas during MI and ME were compared.ResultsPMA and MA were significantly and positively correlated during hand MI in all participants. The power spectral density (PSD) values of PMA EEG signals were greater than those of MA during MI and ME in both groups. The functional connectivity correlation was higher in the stroke group than in healthy people during MI, especially during left-handed MI. During ME, functional connectivity correlation in the brain was more enhanced during synergy movements than during isolated movements. The regions with abnormal functional connectivity were in the 18th lead of the left PMA area.ConclusionLeft-handed MI may be crucial in MI therapy, and the 18th lead may serve as a target for non-invasive neuromodulation to promote further recovery of limb function in patients with stroke. This may provide support for the EEG theory of neuromodulation therapy for hemiplegic patients

Aluminate red phosphor in light-emitting diodes : theoretical calculations, charge varieties and high-pressure luminescence analysis

This work was supported by the Ministry of Science and Technology of Taiwan (Contract Nos. MOST 104-2113-M- 002-012-MY3 and MOST 104-2923-M-002-007-MY3). This research was also supported by National Centre for Re- search and Development, Poland (Grant No. PL- TW2/8/2015).Searching for a non-rare earth-based oxide red-emitting phosphor is crucial for phosphor-converted light- emitting diodes (LEDs). In this study, we optimized a blue and UV-light excited Sr4Al14O25:Mn phosphor exhibiting red emission peaked at ~653 nm, which was successfully synthesized by solid-state reaction. The crystal structure, micromorphology, and luminescent properties of Sr4Al14O25:Mn phosphors were characterized by X-ray Rietveld refinement, high-resolution transmission electron microscopy, and photoluminescence spectra. The band gap and electronic structure of Sr4Al14O25 were analyzed by density functional theory calculation using the hybrid exchange- correlation functional. The crystal field environment effect of Al sites from introducing activator Mn ions was investigated with the aid of Raman 27Al nuclear magnetic resonance spectra and electron spin resonance. The pressure dependent on the luminescent properties and decay time of this compound were presented. The tricolor display spectrum by combining blue InGaN chips, commercial β-SiAlON:Eu2+ green phosphor, and Sr4Al14O25:Mn red phosphor were evaluated for commercial applications: using the present Sr4Al14O25:Mn red phosphor converted LED as backlighting source.PostprintPeer reviewe

Two-Stage DEA Analysis of Water Resource Use Efficiency

This paper presents an extended two-stage data envelopment analysis (DEA) method for analyzing water resource use efficiency (WRUE) and related WRUE issues, which was developed by introducing regional water resource metabolic theory into the two-stage DEA method. It has the following advantages: (1) it has the ability to reflect the inner difference and connection of the regional water resource consumption process, which developed the corresponding physical model instead of making it a “black box”; (2) the built physical model for WRUE divided the main body of water resource consumption into social and economic subsystems, which can thus elaborate WRUE; (3) it can analyze not only WRUE but also related WRUE issues. The proposed method was applied to a real-case study in Gansu Province, China. Results show that decision makers can determine the comprehensive and accurate WRUE and negative factors of WRUE in Gansu Province. Moreover, the results offer recommendations for decision makers to plan for efficient use of water resources in different cities

Broad-Scope Thermometry Based on Dual-Color Modulation up-Conversion Phosphor Ba₅Gd₈Zn₄O₂₁:Er³⁺/Yb³⁺

Yb³⁺/Er³⁺ codoped Ba₅Gd₈Zn₄O₂₁ up-conversion (UC) phosphors with tunable emission were synthesized using a facile sol–gel method. UC spectra are composed of green emission from ²H_11/2/⁴S_3/2 → ⁴I_15/2 transitions and red emission from ⁴F_9/2 → ⁴I_15/2 transition of Er³⁺ ion with the excitation of 980 nm laser diodes. Modulation of emitting color from green to red could be achieved by adjusting dopant concentrations or pulse width of 980 nm laser. The mechanism of the former strategy was figured out through analyzing visible and near-infrared (NIR) down-conversion emission spectra together with the corresponding green level (⁴S_3/2) lifetimes under excitation of 490 nm light, and the latter method was explained by the non-steady-state up-converison process. Temperature detection range was expanded to low temperature region by utilizing red-emitting stark levels of Er³⁺ ion as thermally coupled levels. Thermal sensing performances based on green-emitting levels (²H_11/2/⁴S_3/2) and red emitting stark levels (⁴F_9/2(1)/ ⁴F_9/2(2)) of Er³⁺ ion were estimated and the maximum sensitivity are 0.0032 K^–1 at 490 and 0.0029 K^–1 at 200 K in our experimental range, respectively. Moreover, the effects of UC emission color from different dopant concentrations and pulse widths of lasers on sensor sensitivity were also investigated in detail. Results imply that the present phosphor Ba₅Gd₈Zn₄O₂₁:Er³⁺/Yb³⁺ exhibits high and stable sensitivity in a wide temperature detection scope, which makes it an excellent candidate for an optical thermometer

Sensitivity modulation of upconverting thermometry through engineering phonon energy of a matrix

Investigation of the unclear influential factors to thermal sensing capability is the only way to achieve highly sensitive thermometry, which is greatly needed to meet the growing demand for potential sensing applications. Here, the effect from the phonon energy of a matrix on the sensitivity of upconversion (UC) microthermometers is elaborately discussed using a controllable method. Uniform truncated octahedral YF₃:Er³⁺/Yb³⁺ microcrystals were prepared by a hydrothermal approach, and phase transformation from YF₃ to YOF and Y₂O₃ with nearly unchanged morphology and size was successfully realized by controlling the annealing temperature. The phonon energies of blank matrixes were determined by FT-IR spectra and Raman scattering. Upon 980 nm excitation, phonon energy-dependent UC emitting color was finely tuned from green to yellow for three samples, and the mechanisms were proposed. Thermal sensing behaviors based on the TCLs (²H₁₁/₂/⁴S₃/₂) were evaluated, and the sensitivities gradually grew with the increase in the matrix's phonon energy. According to chemical bond theory and first-principle calculations, the most intrinsic factors associated with thermometric ability were qualitatively demonstrated through analyzing the inner relation between the phonon energy and bond covalency. The exciting results provide guiding insights into employing appropriate host materials with desired thermometric ability while offering the possibility of highly accurate measurement of temperature.8 page(s

Abnormal annealing-induced strengthening in Ni39.3Al15.7Fe45 eutectic medium entropy alloy

Cold-working combined with annealing is frequently used to enhance strength of traditional alloy materials. However, this thermal-mechanical processing is not adapted to the preparation for some near net shape parts. In this paper, a dual-phase Ni39.3Al15.7Fe45 eutectic medium entropy alloy (EMEA) was prepared by vacuum arc melting and abnormal annealing-induced strengthening is demonstrated and analyzed via XRD, SEM, EDS, TEM and room temperature tensile testing. It is found that the Ni39.3Al15.7Fe45 EMEA is composed of FCC solid solution phase and BCC phase. After annealing, ordered L12 phase precipitated from FCC solid solution, which induces a significant increment of tensile strength and a weak decrease of tensile plasticity. The tensile strength and elongation are 991 MPa and 24.1 % at as-cast state, the tensile strength and elongation are 1279 MPa and 22.4 % after annealing at 700 °C for 1 h