In this paper a novel adaptive sliding mode control method has been designed and applied to the load frequency control. Firstly, a novel adaptive sliding mode control method is designed. Secondly, ...the stability of this method has been proved mathematically. Finally, one numerical simulation example is presented to verify the effectiveness of the proposed control scheme. At the same time, the proposed new adaptive sliding mode control method is compared with the classical adaptive sliding mode control method. From the simulation results, it is confirmed the validity of the proposed adaptive sliding mode control method in terms of external disturbances and parameter variation. It is also verified the superiority of the proposed adaptive sliding mode control method in terms of chattering, overshoot and response time in comparison with classical adaptive sliding mode control method.
Sliding mode control (SMC) has the attractiveness of robustness to the system model uncertainties and disturbance, which has wide applications in power system, power electronics, and vehicle ...suspension system. However, it also has a drawback of chattering. To decrease the chattering phenomenon, this study develops a novel adaptive high-order sliding mode control (HOSMC), which has the benefit of parameterizable unmodeled dynamics compared with the HOSMC method. The proposed method can be employed for load frequency control with nonlinearities. The simulations are based on two and three areas of the power system with load frequency control. From the simulation results, it is apparent that the frequency deviation and ACE (area control error) converge to zero when using the proposed method. In addition, the simulation results validate the robustness of the proposed method in the case of parameters change. The oscillation and chattering can be attenuated more by the raised adaptive HOSMC compared to the super-twisting (ST) algorithm, which verifies the advantages of the proposed adaptive HOSMC scheme.
Ammonia is essential for food and energy. Industrial ammonia synthesis via Haber–Bosch process is energy-intensive and releases large amount of CO2. Increasing research efforts are devoted to “green” ...ammonia synthesis. The present article reviews the recent progress in the fields of thermocatalytic, electrocatalytic, photocatalytic and chemical looping processes for dinitrogen reduction towards ammonia formation and discusses the challenges borne for mild-condition synthesis.
This work reviewed the current progress in thermocatalysis, electrocatalysis, photocatalysis and chemical looping process for mild-condition NH3 synthesis, aiming to employ renewable energy to minimize the fossil fuel consumption and CO2 emission. Display omitted
Rice (
Oryza sativa
) is both a vital source of food and a key model cereal for genomic research. Insect pests are major factors constraining rice production. Here, we provide an overview of recent ...progress in functional genomics research and the genetic improvements of insect resistance in rice. To date, many insect resistance genes have been identified in rice, and 14 such genes have been cloned via a map-based cloning approach. The proteins encoded by these genes perceive the effectors of insect and activate the defense pathways, including the expression of defense-related genes, including mitogen-activated protein kinase, plant hormone, and transcription factors; and defense mechanism against insects, including callose deposition, trypsin proteinase inhibitors (TryPIs), secondary metabolites, and green leaf volatiles (GLVs). These ongoing functional genomic studies provide insights into the molecular basis of rice–insect interactions and facilitate the development of novel insect-resistant rice varieties, improving long-term control of insect pests in this crucial crop.
An output-capacitorless low-dropout regulator (LDO) compensated by a single Miller capacitor is implemented in a commercial 90-nm CMOS technology. The proposed LDO makes use of the small transistors ...realized in nano-scale technology to achieve high stability, fast transient performance and small voltage spikes under rapid load-current changes without the need of an off-chip capacitor connected at the LDO output. Experimental result verifies that the proposed LDO is stable for a capacitive load from 0 to 50 pF (estimated equivalent parasitic capacitance from load circuits) and with load capability of 100 mA. Moreover, the gain-enhanced structure provides sufficient loop gain to improve line regulation to 3.78 mV/V and load regulation to 0.1 mV/mA, respectively. The embedded voltage-spike detection circuit enables pseudo Class-AB operation to drive the embedded power transistor promptly. The measured power consumption is only 6 μW under a 0.75-V supply. The maximum overshoot and undershoot under a 1.2-V supply are less than 66 mV for full load current changes within 100-ns edge time, and the recovery time is less than 5 μs.
Ammonia synthesis under mild conditions is a goal that has been long sought after. Previous investigations have shown that adsorption and transition-state energies of intermediates in this process on ...transition metals (TMs) scale with each other. This prevents the independent optimization of these energies that would result in the ideal catalyst: one that activates reactants well, but binds intermediates relatively weakly. Here we demonstrate that these scaling relations can be broken by intervening in the TM-mediated catalysis with a second catalytic site, LiH. The negatively charged hydrogen atoms of LiH act as strong reducing agents, which remove activated nitrogen atoms from the TM or its nitride (TMN), and as an immediate source of hydrogen, which binds nitrogen atoms to form LiNH
. LiNH
further splits H
heterolytically to give off NH
and regenerate LiH. This synergy between TM (or TMN) and LiH creates a favourable pathway that allows both early and late 3d TM-LiH composites to exhibit unprecedented lower-temperature catalytic activities.
This study evaluates the long-term Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 6.1 (C6.1) Level 3 atmospheric aerosol products over land. For this purpose, three ...monthly aerosol optical depth (AOD) datasets, including Dark Target (DT), Deep Blue (DB) and combined DT and DB (DTB) during 2003–2017, are collected. Aerosol Robotic Network (AERONET) Version 2 Level 2.0 (cloud-screened and quality-assured) monthly measurements at 431 sites around the world are selected for comparison. This study attempts to provide a better understanding of the different MODIS products for their applicability at multiple spatial scales and their suitability for representing the long-term trend of aerosol characteristics. Experiments are performed with direct comparisons between MODIS retrievals and AERONET measurements at global, local to site scales. Meanwhile, the spatial and temporal variations are also compared and discussed. Our results illustrate that C6.1 MODIS AOD retrievals are well correlated with AERONET AOD measurements globally, while the DTB product performs best at most regions, yet the DB product is superior at the site scale. In general, Terra AOD products always overestimate while Aqua AOD products are more accurate in describing the annual mean AOD loadings over land. For long-term aerosol trends, there are small differences between Terra and Aqua aerosol products. Among the three aerosol datasets, neither one can consistently outperform the others in both spatial and temporal aerosol variations over land. In general, DTB products can more accurately capture the correct aerosol changes and are strongly recommended for selection in related aerosol studies at the global scale.
•Noticeable differences are observed for multiple MODIS monthly AOD products.•Aqua products can describe the annual mean AODs more accurately than Terra's.•Terra and Aqua AODs show similar performance in capturing the aerosol trends.•DTB product is generally recommended for long-term AOD studies over land.
Abstract
Severe events of wintertime particulate air pollution in Beijing (winter haze) are associated with high relative humidity (RH) and fast production of particulate sulfate from the oxidation ...of sulfur dioxide (SO
2
) emitted by coal combustion. There has been considerable debate regarding the mechanism for SO
2
oxidation. Here we show evidence from field observations of a haze event that rapid oxidation of SO
2
by nitrogen dioxide (NO
2
) and nitrous acid (HONO) takes place, the latter producing nitrous oxide (N
2
O). Sulfate shifts to larger particle sizes during the event, indicative of fog/cloud processing. Fog and cloud readily form under winter haze conditions, leading to high liquid water contents with high pH (>5.5) from elevated ammonia. Such conditions enable fast aqueous-phase oxidation of SO
2
by NO
2
, producing HONO which can in turn oxidize SO
2
to yield N
2
O.This mechanism could provide an explanation for sulfate formation under some winter haze conditions.
Aberrant activation of AKT disturbs the proliferation, survival and metabolic homeostasis of various human cancers. Thus, it is critical to understand the upstream signalling pathways governing AKT ...activation. Here, we report that AKT undergoes SETDB1-mediated lysine methylation to promote its activation, which is antagonized by the Jumonji-family demethylase KDM4B. Notably, compared with wild-type mice, mice harbouring non-methylated mutant Akt1 not only exhibited reduced body size but were also less prone to carcinogen-induced skin tumours, in part due to reduced AKT activation. Mechanistically, the interaction of phosphatidylinositol (3,4,5)-trisphosphate with AKT facilitates its interaction with SETDB1 for subsequent AKT methylation, which in turn sustains AKT phosphorylation. Pathologically, genetic alterations, including SETDB1 amplification, aberrantly promote AKT methylation to facilitate its activation and oncogenic functions. Thus, AKT methylation is an important step, synergizing with PI3K signalling to control AKT activation. This suggests that targeting SETDB1 signalling could be a potential therapeutic strategy for combatting hyperactive AKT-driven cancers.
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