Improved Model-Free Sliding Mode Control of Linear Motor Based on Time-Varying Gain Model-Assisted Linear Extended State Observer

Aiming at the effects of motor parameter ingress and load mutation on the speed control of permanent magnet synchronous linear motor (PMSLM) motors, this paper designs a PMSLM improved model-free sliding-mode speed control strategy based on the variable-gain model-assisted linear expansion observer (TMLESO). First, time-varying gain-based model-assisted linear expansion observer (MLESO) is designed to improve the accuracy of LESO generalized perturbation estimation. Next, the TMLESO is constructed by combining the MLESO and the time-varying function to solve the problem of large initial peaks. Finally, a model-free sliding-mode velocity controller with adaptable boundary layer thickness is constructed to reduce the effect of sliding-mode jitter on velocity tracking and improve the dynamic performance of the system. The effectiveness of the proposed control strategy is analyzed through simulations and experiments

A Statistical Stt-Ram Retention Model For Fast Memory Subsystem Designs

Spin-transfer torque random access memory (STT-RAM) is a promising nonvolatile memory (NVM) solution to implement on-chip caches and off-chip main memories for its high integration density and short access time, but it suffers from considerable write latency and energy overhead. Aggressively relaxing its non-volatility for write fast and write energy efficient memory subsystems has been quite debatable, due to the unclear retention behavior on a timescale of microseconds-to-seconds. Moreover, recent studies project that retention failure will eventually dominate the cell reliability as STT-RAM scales. As a result, a comprehensive understanding of the thermal noise induced STT-RAM retention mechanism has become a must. In this work, we develop a compact semi-analytical model for fast retention failure analysis. We then systematically analyze critical factors (e.g., initial angle, device dimension etc.) and their impacts on the STT-RAM retention behavior through our model. Our experimental results show that STT-RAM suffers from a soft-error style retention failure, which may happen instantly just after the last write finishes and is totally different from that of DRAM and Flash, i.e., the gradual charge loss process. Our model offers an excellent agreement with the results from golden macro-magnetic simulations in the region of interest without conducting expensive Monte-Carlo runs. At last, we demonstrate our model can enable architectural designers to rethink STT-RAM based memory designs by emphasizing its probabilistic retention property

DIC-Based Hydration Absorption Detection and Displacement Field Evolution of Outcrop Porous Sandstone

In order to study the hydration absorption behaviors and characteristics of sandstone in Mogao Grottoes in China, the pressure-less hydration absorption experiment on the outcrop porous sandstone of Mogao Grottoes was carried out by using the self-developed real-time monitoring experimental system. The hydration absorption was measured and the curve of hydration absorption with time was drawn. At the same time, the digital image correlation method (DIC) was used to measure the full-field deformation, and the speckle pattern of the sample was analyzed using Match ID, and the displacement field and strain field of the sandstone sample at different hydration absorption moments were computed. Moreover, the sparse area and dense area of sandstone are used as regions of interest (ROI) for DIC analysis. According to the test results, it is concluded that the hydration absorption of sandstone increases rapidly in the initial stage, and gradually tends to be stable with the change of time. This corresponds well with the deformation characteristics of sandstone analyzed using DIC. In the initial stage, the deformation of sandstone increases rapidly. With the change in time, the deformation of sandstone samples gradually slows down. When the hydration adsorption reaches saturation, the sandstone continues to deform for a period of time before stopping hydration absorption. The results of the mercury injection test and the XRD test show that the porosity of the sparse area is larger than that of the dense area and the particle content of the dense area is lower. When the sandstone is saturated with water, the liquid is immersed in the pores between the solid particles, which makes the sparse area more prone to stress concentration, and the deformation in the sparse area is larger. Therefore, when analyzing the hydration absorption deformation of sandstone, the porosity should be considered

Identification and functional characterization of intermediate-size non-coding RNAs in maize

Abstract Background The majority of eukaryote genomes can be actively transcribed into non-coding RNAs (ncRNAs), which are functionally important in development and evolution. In the study of maize, an important crop for both humans and animals, aside from microRNAs and long non-coding RNAs, few studies have been conducted on intermediate-size ncRNAs. Results We constructed a homogenized cDNA library of 50–500 nt RNAs in the maize inbred line Chang 7–2. Sequencing revealed 169 ncRNAs, which contained 58 known and 111 novel ncRNAs (including 70 snoRNAs, 27 snRNAs, 13 unclassified ncRNAs and one tRNA). Forty of the novel ncRNAs were specific to the Panicoideae, and 24% of them are located on sense-strand of the 5′ or 3′ terminus of protein coding genes on chromosome. Target site analysis found that 22 snoRNAs can guide to 38 2’-O-methylation and pseudouridylation modification sites of ribosomal RNAs and small nuclear RNAs. Expression analysis showed that 43 ncRNAs exhibited significantly altered expression in different tissues or developmental stages of maize seedlings, eight ncRNAs had tissue-specific expression and five ncRNAs were strictly accumulated in the early stage of leaf development. Further analysis showed that 3 of the 5 stage-specific ncRNAs (Zm-3, Zm-18, and Zm-73) can be highly induced under drought and salt stress, while one snoRNA Zm-8 can be repressed under PEG-simulated drought condition. Conclusions We provided a genome-wide identification and functional analysis of ncRNAs with a size range of 50–500 nt in maize. 111 novel ncRNAs were cloned and 40 ncRNAs were determined to be specific to Panicoideae. 43 ncRNAs changed significantly during maize development, three ncRNAs can be strongly induced under drought and salt stress, suggesting their roles in maize stress response. This work set a foundation for further study of intermediate-size ncRNAs in maize

Well-Dispersed Ruthenium in Mesoporous Crystal TiO₂ as an Advanced Electrocatalyst for Hydrogen Evolution Reaction

TiO₂ mesoporous crystal has been prepared by one-step corroding process via an oriented attachment (OA) mechanism with SrTiO₃ as precursor. High resolution transmission electron microscopy (HRTEM) and nitrogen adsorption–desorption isotherms confirm its mesoporous crystal structure. Well-dispersed ruthenium (Ru) in the mesoporous nanocrystal TiO₂ can be attained by the same process using Ru-doped precursor SrTi_1–<i>x</i>Ru_<i>x</i>O₃. Ru is doped into lattice of TiO₂, which is identified by HRTEM and super energy dispersive spectrometer (super-EDS) elemental mapping. X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance spectroscopy (EPR) suggest the pentavalent Ru but not tetravalent, while partial Ti in TiO₂ accept an electron from Ru and become Ti³⁺, which is observed for the first time. This Ru-doped TiO₂ performs high activity for electrocatalytic hydrogen evolution reaction (HER) in alkaline solution. First-principles calculations simulate the HER process and prove TiO₂:Ru with Ru⁵⁺ and Ti³⁺ holds high HER activity with appropriate hydrogen-adsorption Gibbs free energies (Δ<i>G</i>_H)