Sliding mode sensorless control of wind turbine pitch motor with ESO feedforward compensation in the offshore wind power system

In order to improve the dynamic performance of the control system, a variable frequency sliding mode sensorless control strategy based on Extended State Observer (ESO) feedforward compensation was proposed in order to improve the disturbance and jitter problems of pitch motors in offshore wind power generation systems. The fast exponential reaching law is designed in the velocity loop, and the integrated sliding surface is adopted, which reduces the steady-state error of the traditional sliding surface and weakens the jitter phenomenon of the moving point on the sliding surface. The traditional sliding mode observer is improved, and the variable cut-off frequency filter is used instead of the low-pass filter in the filtering process to filter the signals of each speed band. At the same time, in order to estimate the disturbances in the system, the Linear Extended State Observer (LESO) is designed to observe and compensate for the unknown disturbances, which improves the robustness of the system. The simulation results show that the control strategy in this paper solves the problems of traditional Sliding Mode Control (SMC), which not only shortens the response time of the system, but also significantly improves the anti-disturbance performance of the system, and the overall effect is significantly improved

Non-equilibrium behaviour in coacervate-based protocells under electric-field-induced excitation

Although numerous strategies are now available to generate rudimentary forms of synthetic cell-like entities, minimal progress has been made in the sustained excitation of artificial protocells under non-equilibrium conditions. Here we demonstrate that the electric field energization of coacervate microdroplets comprising polylysine and short single strands of DNA generates membrane-free protocells with complex, dynamical behaviours. By confining the droplets within a microfluidic channel and applying a range of electric field strengths, we produce protocells that exhibit repetitive cycles of vacuolarization, dynamical fluctuations in size and shape, chaotic growth and fusion, spontaneous ejection and sequestration of matter, directional capture of solute molecules, and pulsed enhancement of enzyme cascade reactions. Our results highlight new opportunities for the study of non-equilibrium phenomena in synthetic protocells, provide a strategy for inducing complex behaviour in electrostatically assembled soft matter microsystems and illustrate how dynamical properties can be activated and sustained in microcompartmentalized media.</p

Improving winter wheat yield estimation by assimilation of the leaf area index from Landsat TM and MODIS data into the WOFOST model

To predict regional-scale winter wheat yield, we developed a crop model and data assimilation framework that assimilated leaf area index (LAI) derived from Landsat TM and MODIS data into the WOFOST crop growth model. We measured LAI during seven phenological phases in two agricultural cities in China’s Hebei Province. To reduce cloud contamination, we applied Savitzky–Golay (S–G) filtering to the MODIS LAI products to obtain a filtered LAI. We then regressed field-measured LAI on Landsat TM vegetation indices to derive multi-temporal TM LAIs. We developed a nonlinear method to adjust LAI by accounting for the scale mismatch between the remotely sensed data and the model’s state variables. The TM LAI and scale-adjusted LAI datasets were assimilated into the WOFOST model to allow evaluation of the yield estimation accuracy. We constructed a four-dimensional variational data assimilation (4DVar) cost function to account for the observations and model errors during key phenological stages. We used the shuffled complex evolution–University of Arizona algorithm to minimize the 4DVar cost function between the remotely sensed and modeled LAI and to optimize two important WOFOST parameters. Finally, we simulated winter wheat yield in a 1-km grid for cells with at least 50% of their area occupied by winter wheat using the optimized WOFOST, and aggregated the results at a regional scale. The scale adjustment substantially improved the accuracy of regional wheat yield predictions (R2 = 0.48; RMSE= 151.92 kg ha−1) compared with the unassimilated results (R2 = 0.23;RMSE= 373.6 kg ha−1) and the TM LAI results (R2 = 0.27; RMSE= 191.6 kg ha−1). Thus, the assimilation performance depends strongly on the LAI retrieval accuracy and the scaling correction. Our research provides a scheme to employ remotely sensed data, ground-measured data, and a crop growth model to improve regional crop yield estimates

Joint retrieval of growing season corn canopy LAI and leaf chlorophyll content by fusing Sentinel-2 and MODIS images

Continuous and accurate estimates of crop canopy leaf area index (LAI) and chlorophyll content are of great importance for crop growth monitoring. These estimates can be useful for precision agricultural management and agricultural planning. Our objectives were to investigate the joint retrieval of corn canopy LAI and chlorophyll content using filtered reflectances from Sentinel-2 and MODIS data acquired during the corn growing season, which, being generally hot and rainy, results in few cloud-free Sentinel-2 images. In addition, the retrieved time series of LAI and chlorophyll content results were used to monitor the corn growth behavior in the study area. Our results showed that: (1) the joint retrieval of LAI and chlorophyll content using the proposed joint probability distribution method improved the estimation accuracy of both corn canopy LAI and chlorophyll content. Corn canopy LAI and chlorophyll content were retrieved jointly and accurately using the PROSAIL model with fused Kalman filtered (KF) reflectance images. The relation between retrieved and field measured LAI and chlorophyll content of four corn-growing stages had a coefficient of determination (R2) of about 0.6, and root mean square errors (RMSEs) ranges of mainly 0.1-0.2 and 0.0-0.3, respectively. (2) Kalman filtering is a good way to produce continuous high-resolution reflectance images by synthesizing Sentinel-2 and MODIS reflectances. The correlation between fused KF and Sentinel-2 reflectances had an R2 value of 0.98 and RMSE of 0.0133, and the correlation between KF and field-measured reflectances had an R2 value of 0.8598 and RMSE of 0.0404. (3) The derived continuous KF reflectances captured the crop behavior well. Our analysis showed that the LAI increased from day of year (DOY) 181 (trefoil stage) to DOY 236 (filling stage), and then increased continuously until harvest, while the chlorophyll content first also increased from DOY 181 to DOY 236, and then remained stable until harvest. These results revealed that the jointly retrieved continuous LAI and chlorophyll content could be used to monitor corn growth conditions

[1,5]-Hydride Shift-Cyclization versus C(sp2)-H Functionalization in the Knoevenagel-Cyclization Domino Reactions of 1,4- and 1,5-Benzoxazepines

Domino cyclization reactions of N-aryl-1,4- and 1,5-benzoxazepine derivatives involving [1,5]-hydride shift or C(sp2)-H functionalization were investigated. Neuroprotective and acetylcholinesterase activities of the products were studied. Domino Knoevenagel-[1,5]-hydride shift-cyclization reaction of N-aryl-1,4-benzoxazepine derivatives with 1,3-dicarbonyl reagents having active methylene group afforded the 1,2,8,9-tetrahydro-7bH-quinolino [1,2-d][1,4]benzoxazepine scaffold with different substitution pattern. The C(sp3)-H activation step of the tertiary amine moiety occurred with complete regioselectivity and the 6-endo cyclization took place in a complete diastereoselective manner. In two cases, the enantiomers of the chiral condensed new 1,4-benzoxazepine systems were separated by chiral HPLC, HPLC-ECD spectra were recorded, and absolute configurations were determined by time-dependent density functional theory- electronic circular dichroism (TDDFT-ECD) calculations. In contrast, the analogue reaction of the regioisomeric N-aryl-1,5-benzoxazepine derivative did not follow the above mechanism but instead the Knoevenagel intermediate reacted in an SEAr reaction [C(sp2)-H functionalization] resulting in a condensed acridane derivative. The AChE inhibitory assays of the new derivatives revealed that the acridane derivative had a 6.98 uM IC50 value

Robotic versus laparoscopic right hemicolectomy with complete mesocolic excision: a retrospective multicenter study with propensity score matching

ObjectiveDuring the past decade, the concept of complete mesocolic excision (CME) has been developed in an attempt to minimize recurrence for right-sided colon cancer. This study aims to compare outcomes of robotic versus laparoscopic right hemicolectomy with CME for right-sided colon cancer.MethodsWe performed a retrospective multicenter propensity score matching study. From July 2016 to July 2021, 382 consecutive patients from different Chinese surgical departments were available for inclusion out of an initial cohort of 412, who underwent robotic or laparoscopic right hemicolectomy with CME. Data of all patients were retrospectively collected and reviewed. Of these, 149 cases were performed by a robotic approach, while the other 233 cases were done by laparoscopy. Propensity score matching was applied at a ratio of 1:1 to compare perioperative, pathologic, and oncologic outcomes between the robotic and the laparoscopic groups (n = 142).ResultsBefore propensity score matching, there were no statistical differences regarding the sex, history of abdominal surgery, body mass index (BMI), American Joint Committee on Cancer (AJCC) staging system, tumor location, and center between groups (p &gt; 0.05), while a significant difference was observed regarding age (p = 0.029). After matching, two comparable groups of 142 cases were obtained with equivalent patient characteristics (p &gt; 0.05). Blood loss, time to oral intake, return of bowel function, length of stay, and complications were not different between groups (p &gt; 0.05). The robotic group showed a significantly lower conversion rate (0% vs. 4.2%, p = 0.03), but a longer operative time (200.9 min vs. 182.3 min, p &lt; 0.001) and a higher total hospital cost (85,016 RMB vs. 58,266 RMB, p &lt; 0.001) compared with the laparoscopic group. The number of harvested lymph nodes was comparable (20.4 vs. 20.5, p = 0.861). Incidence of complications, mortality, and pathologic outcomes were similar between groups (p &gt; 0.05). The 2-year disease-free survival rates were 84.9% and 87.1% (p = 0.679), and the overall survival rates between groups were 83.8% and 80.7% (p = 0.943).ConclusionDespite the limitations of a retrospective analysis, the outcomes of robotic right hemicolectomy with CME were comparable to the laparoscopic procedures with fewer conversions to open surgery. More clinical advantages of the robotic surgery system need to be further confirmed by well-conducted randomized clinical trials with large cohorts of patients

Neighborhood Aggregation Collaborative Filtering Based on Knowledge Graph

In recent years, the research of combining a knowledge graph with recommendation systems has caused widespread concern. By studying the interconnections in knowledge graphs, potential connections between users and items can be discovered, which provides abundant and complementary information for recommendation of items. However, most existing studies have not effectively established the relation between entities and users. Therefore, the recommendation results may be affected by some unrelated entities. In this paper, we propose a neighborhood aggregation collaborative filtering (NACF) based on knowledge graph. It uses the knowledge graph to spread and extract the user&rsquo;s potential interest, and iteratively injects them into the user features with attentional deviation. We conducted a large number of experiments on three public datasets; we verifyied that NACF is ahead of the most advanced models in top-k recommendation and click-through rate (CTR) prediction

TARCS: A Topology Change Aware-Based Routing Protocol Choosing Scheme of FANETs

The rapid change of topology is one of the most important factors affecting the performance of the routing protocols of flying ad hoc networks (FANETs). A routing scheme suitable for highly dynamic mobile ad hoc networks is proposed for the rapid change of topology in complex scenarios. In the scheme moving nodes sense changes of the surrounding network topology periodically, and the current mobile scenario is confirmed according to the perceived result. Furthermore, a suitable routing protocol is selected for maintaining network performances at a high level. The concerned performance metrics are packet delivery ratio, network throughput, average end-to-end delay and average jitter. The experiments combine the random waypoint model, the reference point group mobility model and the pursue model to a chain scenario, and simulate the large changes of the network topology. Results show that an appropriate routing scheme can adapt to rapid changes in network topology and effectively improve network performance

Fault Segment Location for MV Distribution System Based on the Characteristic Voltage of LV Side

The voltage and current measurement of the medium-voltage (MV) side are used for the traditional fault location method, which leads to a high installation cost of the measurement and complicated post-operational and maintenance work. A fault location method is proposed based on the distributed measurement at the low-voltage (LV) side. On the analysis of voltage distribution rules and the influence of the distribution transformer on voltage transmission, obvious differences are found in the variation of voltage (phase voltage and sequence voltage) at the LV side for different faults—specifically, the detection sensitivity of the voltage to different faults varies. Therefore, a fault location method for the MV distribution network based on characteristic voltage at the LV side is proposed. Firstly, the characteristic voltage is selected adaptively according to the fault type. The suspected fault path is then determined by the characteristic voltage amplitude of measuring points. Finally, the fault segment is located via the characteristic current of each segment. This method can be applied in combination with the widely used LV measurement equipment such as the power consumption information acquisition system and the intelligent fusion terminal to acquire LV side voltage without adding new measurement devices. The distribution difference of the characteristic voltage at the LV side is applied for accurate fault finding, which is an economical and practical new idea for the fault location of the distribution network. The correctness and effectiveness of the method were verified by the simulation of the IEEE 34 system built in PSCAD/EMTDC and a real distribution network