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An adaptive super-twisting multivariable fast terminal sliding mode control scheme based on time delay estimation (TDE) and asymmetric error constraints are proposed to guarantee high-precision trajectory tracking control of cable-driven manipulators under complicated unknown uncertainties. The control system is constrained by joint position errors, which are asymmetric and time-varying. First, the error range of the joints is designed to ensure that the deviation of the joint position from the desired profile is not too large while ensuring the safety performance of the manipulator, and the remaining set-total system dynamics are estimated and compensated using time-delay estimation. Secondly, the design analysis of the angular false expectation using safety constraint functions allows the constraints of different cross sections to be handled in a unified system architecture; the problem of robotic arm motion trajectories with output constraints and uncertainties is addressed through rigorous analysis. The super-twisting adaptive control effectively ensures fast, accurate and robust convergence of the algorithm in satisfying all constraints in operation, and the stability of the closed-loop control system is analyzed using the Lyapunov method. Finally, the effectiveness and superiority of the proposed adaptive hyper-torsional non-singular terminal sliding mode control scheme are verified by simulations and experiments in 2-DOF.

The performance of a hemispherical resonant gyroscope (HRG) is directly affected by the sphericity error of the thin-walled spherical shell of the hemispherical shell resonator (HSR). In the production process of the HSRs, high-speed, high-accuracy, and high-robustness requirements are necessary for evaluating sphericity errors. We designed a sphericity error evaluation method based on the minimum zone criterion with an adaptive number of subpopulations. The method utilizes the global optimal solution and the subpopulations’ optimal solution to guide the search, initializes the subpopulations through clustering, and dynamically eliminates inferior subpopulations. Simulation experiments demonstrate that the algorithm exhibits excellent evaluation accuracy when processing simulation datasets with different sphericity errors, radii, and numbers of sampling points. The uncertainty of the results reached the order of 10−9 mm. When processing up to 6000 simulation datasets, the algorithm’s solution deviation from the ideal sphericity error remained around −3 × 10−9 mm. And the sphericity error evaluation was completed within 1 s on average. Additionally, comparison experiments further confirmed the evaluation accuracy of the algorithm. In the HSR sample measurement experiments, our algorithm improved the sphericity error assessment accuracy of the HSR’s inner and outer contour sampling datasets by 17% and 4%, compared with the results given by the coordinate measuring machine. The experiment results demonstrated that the algorithm meets the requirements of sphericity error assessment in the manufacturing process of the HSRs and has the potential to be widely used in the future.

The sphericity error is a critical form and position tolerance for spheres. We explored the distribution of sphericity errors within the solution space to achieve a high-precision evaluation using the minimum zone criteria. Within local solution spaces, we propose treating the evaluation of sphericity errors as a unimodal function optimization task. And computational geometric methods are employed to achieve highly accurate solutions within the local solution spaces. Subsequently, we integrated the computational geometric method with the differential evolution algorithm (DE algorithm). By centering on individual population members of the DE algorithm, we partitioned the local solution spaces and utilized the best solutions within them to optimize the population. With the gradual convergence of the DE algorithm, we successfully achieved the high-precision resolution of sphericity errors. The experimental results demonstrate a significant order-of-magnitude improvement in precision compared to traditional algorithms in the field of sphericity error evaluation, with uncertainty levels reaching magnitudes of 10−14 mm. Moreover, this method enhances the accuracy of sphericity error evaluation by approximately 10% for three-coordinate measuring machines. Additionally, we conducted ablation experiments to validate the effectiveness of the proposed computational geometric method. In summary, this approach enables the high-precision evaluation of sphericity errors and provides a practical methodology for applying ultra-precision spheres in precision engineering.

The spatial and temporal environmental conditions in the southern coastal waters of Korea (SCWK) as a complex area, which is influenced by both ocean currents and anthropogenic nutrient inputs, are highly variable. The impacts of environmental factors on the distribution of phytoplankton community structure in the SCWK remain unclear. Based on high-performance liquid chromatography (HPLC) analysis of a variety of photosynthetic pigments, spatial and temporal variations in phytoplankton community compositions were investigated in the SCWK. Cluster analysis, correlation analysis, and generalized additive models (GAMs) were used to explore the major phytoplankton groups and their response patterns to temperature, salinity, depth, and macronutrients. The results indicated that diatoms were the absolute dominant groups in the SCWK for all seasons, especially in cold seasons. Diatoms mainly concentrated at 1% light depths, while high chlorophyll-a concentrations (>3 µg/L) occurred at 100% and 30% light depths with good light conditions. Both clustering and correlation analyses showed that diatoms had a strong positive correlation with macronutrients such as dissolved inorganic nitrogen (DIN), dissolved inorganic phosphate (DIP), and dissolved silica (DSi). The temperature and salinity discrepancy between surface and bottom layers in summer caused a strong water stratification resulting in blocking nutrient-rich bottom water upwelling and leading cyanobacteria to become the dominant groups at 100% and 30% light depths in summer. Consistently, the cyanobacteria were highly associated with high temperature and low salinity in the correlation analysis and GAM results. Compared with diatom-predominant sites, cryptophytes and diatom-dominated sites are characterized by higher average excess nitrate (ExN). Further research on the responses of small-sized prokaryotic phytoplankton especially cyanobacteria to environmental variations and their primary production contributions would warrant a better understanding of the SCWK ecosystem.

The physical properties, group composition, stable carbon isotope, and biomarker compound distribution characteristics of crude oil in the Archean buried hill were studied and compared with the geochemical characteristics of Paleogene crude oil, in order to discuss the geochemical characteristics and sources of crude oil from the Archean buried hill JZ25-1S in the Liaoxi Low Uplift. The crude oil from the second member of the Paleogene Shahejie Formation and the Archean buried hill in this area are mainly light and medium crude oil. The oil has medium saturated hydrocarbon, high aromatic hydrocarbon, high non-hydrocarbon and asphaltene contents. The carbon isotopes of the crude oil are distributed between -26.2‰ and -24.4‰, and the isotopic fractionation among group components is small. The chromatographic curve clearly shows the "bulge" formed by biodegradation, the single peak and post-kurtosis state is dominant, the Pr/Ph value is generally around 1.3, and the Pr/nC17, Ph/nC18 values are both high. The sterane characteristics of crude oil show a high gammacerane abundance, the C27 rearranged sterane and 4-methyl sterane contents are medium, the dinostane content is low, and the regular sterane C27, C28, C29 fingerprints are partial"V" or "L" shaped. However, the characteristics of Archean crude oil from wells JZ25-1S-4D and JZ25-1-10D are quite different from the above-mentioned crude oil. Comprehensive analysis suggests that the main body of crude oil from the Paleogene and Archean buried hills in the JZ25-1S area is a mixture from the Es3 member of the Liaoxi Sag and the Es1 member of the Liaozhong Sag. Its parent material comes from a weakly reducing environment with moderate salinity and is mainly derived from algae and other phytoplankton. The crude oil has a high degree of maturity and is severely biodegraded. The Archean buried hill crude oil from wells JZ25-1S-4D and JZ25-1-10D is derived from the Es3 member source rock in the Liaoxi Sag, which was deposited in a weakly reducing freshwater environment with high maturity and weak biodegradation.

The relative importance of interannual environmental changes in shaping phytoplankton community structure remains unclear in the East China Sea (ECS), which is the largest marginal sea in the western North Pacific Ocean. Based on high-performance liquid chromatography (HPLC) analysis of a variety of photosynthetic pigments, we investigated spatiotemporal variations in the phytoplankton community in the northern East China Sea (NECS) from 2018 to 2020 to understand biomass and compositional responses to environmental conditions in a complex current system. Correlation heatmaps and generalized additive models (GAMs) were used to explore the variations in major phytoplankton groups and their relationships to temperature, salinity, depth, and nutrients. The results indicated that the phytoplankton community structure was significantly different between 2018/2019 and 2020. Under the conditions of high dissolved inorganic nitrogen (DIN) and low dissolved inorganic phosphate (DIP) concentrations in winter 2020, cryptophytes replaced diatoms as the dominant species and were observed for the first time in this study area. Dinoflagellates predominated throughout the euphotic zone in spring 2020, and statistical analysis showed that dinoflagellates tended to prevail at low DIP and high DIN conditions compared with diatoms. Summer was the only season with strong water stratification that reoccurred every year, and diatoms were mainly concentrated at nutrient-enriched 1% light depths in the summers of 2018/2019. However, a large amount of Changjiang River Diluted Water (CDW) from the surface and western part of the study area affected all sampling sites eastward to 126°E in 2020, allowing diatoms to be dominant at 100% and 30% light depths in the westernmost stations in the NECS. In autumn 2020, diatoms decreased significantly because of DIP-limited environmental conditions and were replaced by small phytoplankton. Under expected warming ocean scenarios with human-induced nutrient inputs, small phytoplankton will become dominant, while spring dinoflagellate blooms will occur more frequently in the NECS. International monitoring programs for marine ecosystems are currently needed in the ECS.

Abstract Background Endoglucanase has been extensively employed in industrial processes as a key biocatalyst for lignocellulosic biomass degradation. Thermostable endoglucanases with high catalytic activity at elevated temperatures are preferred in industrial use. To improve the activity and thermostability, site-directed mutagenesis was conducted to modify the N-glycosylation sites of the thermostable β-1,4-endoglucanase CTendo45 from Chaetomium thermophilum. Results In this study, structure-based rational design was performed based on the modification of N-glycosylation sites in CTendo45. Eight single mutants and one double mutant were constructed and successfully expressed in Pichia pastoris. When the unique N-glycosylation site of N88 was eliminated, a T90A variant was active, and its specific activity towards CMC-Na and β-d-glucan was increased 1.85- and 1.64-fold, respectively. The mutant R67S with an additional N-glycosylation site of N65 showed a distinct enhancement in catalytic efficiency. Moreover, T90A and R67S were endowed with extraordinary heat endurance after 200 min of incubation at different temperatures ranging from 30 to 90 °C. Likewise, the half-lives (t 1/2) indicated that T90A and R67S exhibited improved enzyme thermostability at 80 °C and 90 °C. Notably, the double-mutant T90A/R67S possessed better hydrolysis activity and thermal stability than its single-mutant counterparts and the wild type. Conclusions This study provides initial insight into the biochemical function of N-glycosylation in thermostable endoglucanases. Moreover, the design approach to the optimization of N-glycosylation sites presents an effective and feasible strategy to improve enzymatic activity and thermostability.

The novel cellobiohydrolase gene ctcel7 was identified from Chaetomium thermophilum, and its recombinant protein CtCel7, a member of glycoside hydrolase family 7, was heterologously expressed in Pichia pastoris and biochemically characterized. Compared with commercial hydrolases, purified CtCel7 exhibited superior bifunctional cellobiohydrolase and xylanase activities against microcrystalline cellulose and xylan, respectively, under optimal conditions of 60°C and pH 4.0. Moreover, CtCel7 displayed remarkable thermostability with over 90% residual activity after heat (60°C) treatment for 180 min. CtCel7 was insensitive to most detected cations and reagents and preferentially cleaved the β-1,4-glycosidic bond to generate oligosaccharides through the continuous saccharification of lignocellulosic substrates, which are crucial for various practical applications. Notably, the hydrolysis effect of a commercial cellulase cocktail on pretreated wheat straw was substantively improved by its combination with CtCel7. Taken together, these excellent properties distinguish CtCel7 as a robust candidate for the biotechnological production of biofuels and biobased chemicals.