With the ever‐increasing penetration of wind power into power systems, wind turbine generators (WTGs) are required to provide frequency regulation services to maintain the system frequency stability. ...For variable‐speed WTGs, the adaptability of dissimilar frequency control strategies to different operating regions is distinct, which impacts the system frequency response. However, existing under‐frequency load shedding (UFLS) schemes do not take that impact into account, causing improper load shedding after a loss of generation. To this end, this paper proposes an adaptive UFLS scheme for power systems with high wind power penetration considering operating regions. Based on the WTG operating characteristics in different operating regions, the appropriate frequency control strategy for each operating region is elaborated. The simplified frequency response model of the power system considering WTGs participating in frequency regulation is then established. According to the WTG active power response characteristics in different operating regions, the impact of WTGs participating in frequency regulation on UFLS is analysed. Accordingly, the method of accurately estimating the magnitude of the power deficiency and calculating the amount of load to be shed is proposed. Finally, the feasibility and effectiveness of the proposed UFLS scheme are verified through simulations on the IEEE 39‐bus test system.
A portable colorimetric aptasensor was constructed based on the dual catalytic performance of CeO
2
nanozyme to determine carbohydrate antigen 125 (CA125). Firstly, CeO
2
nanozyme was synthesized by ...calcination and ultrasonically dispersed in a macroporous silica foam (MSF) to form CeO
2
@MSF. Then the aptamer of CA125 (apt) and complementary DNA (c-DNA) were successively assembled on the CeO
2
@MSF to construct a CeO
2
@MSF/apt/c-DNA colorimetric aptasensor, which exhibited excellent oxidase-mimic performance and phosphatase-mimic activity simultaneously. In the presence of CA125, the apt specifically binds to target CA125, and the single-strand c-DNA leaves the CeO
2
@MSF/apt surface, which is catalytically hydrolyzed by exonuclease I. The produced phosphate ions inhibit the phosphatase-mimic activity of CeO
2
nanozyme. Thus, the absorbance at 652 nm of 3,3′,5,5′-tetramethylbenzidine solution containing ascorbic acid-2-phosphate increases with the concentration of CA125. The response is linearly related to the logarithm of CA125 concentration from 1.0 to 10.0 U/mL under optimal experimental conditions. Based on this, the constructed colorimetric aptasensor has a high sensitivity, good selectivity, and high accuracy for CA125 determination in real human serum sample.
Graphical Abstract
Developing low-energy input route for conversion of methane (CH
4
) to value-added methanol (CH
3
OH) at room temperature is important in environment and industry. Bonding in electron donor-acceptor ...hybrid can potentially promote charge transfer and photocatalytic efficiency of CH
4
conversion. Herein, bonding in electron donor rhodamine B (RhB)-acceptor (TiO
2
) hybrid (RhB/TiO
2
) significantly promotes the selectivity of photocatalytic oxidation of CH
4
to CH
3
OH and utilization of visible light (low-energy photons) at ambient condition. Even under green light irradiation (
λ
= 550 nm), the noble-metal-free RhB/TiO
2
hybrid synthesized presents enhanced oxidation of CH
4
to CH
3
OH with a generation rate of 143 µmol·g
−1
·h
−1
and selectivity of 94%. This work demonstrates the possibility and feasibility of noble-metal-free catalysts for activating CH
4
under visible light at room temperature.
Scanning tunneling microscope observations show a geometrical transition from a planar structure to a 3D structure at n = 8. This geometrical transition resulted in a significant decrease in the ...activation energy of the CO oxidation reaction. The upper-layer Pt atoms of the 3D cluster structure that starts to form at n = 8 are low-coordinated Pt atoms, and they may play an important role in the CO oxidation reaction.
In this work, a systematic study on laser-assisted glass frit bonding process was carried out by response surface methodology (RSM). Laser power, sealing speed and spot diameter were considered as ...key bonding parameters. Combined with a central rotatable experimental design, RSM was employed to establish mathematical model to predict the relationship between the shear force after bonding and the bonding process parameters. The model was validated experimentally. Based on the model, the interaction effects of the process parameters on the shear force were analyzed and the optimum bonding parameters were achieved. The results indicate that the model can be used to illustrate the relationship between the shear force and the bonding parameters. The predicted results obtained under the optimized parameters by the models are consistent with the experimental results.
•We have studied the influence of multi-factors on laser-assisted glass frit bonding.•We established a mathematical model to predict the shear strength of laser bonding.•The predicted values are in agreement with the experiment values.
Represented by wind turbines and ultra high-voltage DC (UHVDC), the power-electronic interfaced power sources participate in fast frequency control, which has a significant impact on the power system ...frequency. However, the conventional under-frequency load shedding (UFLS) scheme doesn’t take into account the impact above, resulting in unreasonable load shedding after a large loss of generation. To this end, this article proposes an adaptive UFLS control strategy of power systems with wind turbines and UHVDC participating in frequency regulation. Firstly, based on the virtual inertia control model and the primary frequency control model of wind turbines and UHVDC, the study establishes the simplified frequency response model of the power system considering the participation of wind turbines and UHVDC in frequency regulation. Furthermore, the impact of the active power response characteristics of wind turbines and UHVDC participating in frequency regulation on the magnitude of the active power deficiency is comprehensively analyzed. Thus the precise estimation of the magnitude of the power deficiency can be achieved, which provides technical guidance for multi-stage UFLS. Finally, simulation results demonstrate that the proposed UFLS strategy is capable of reflecting the power system frequency more objectively after a large loss of generation event. In addition, the proposed UFLS strategy outperforms the conventional UFLS strategy in terms of shedding less amount of load when the same desired effect of frequency recovery is achieved.
We aimed to explore the impact of using virtual reality technology to intervene in and encourage the developmental behavior areas of cognition, imitation, and social interaction in children with ...autism spectrum disorder.
Forty-four children with autism spectrum disorder were divided randomly into an intervention group and a control group, with each group consisting of 22 participants. Incorporating conventional rehabilitation strategies, virtual reality technology was used with the intervention group to conduct rehabilitation training in areas including cognition, imitation, and social interaction. The control group was provided conventional/routine clinical rehabilitation training. The children's cognitive development was evaluated before and 3 months after intervention.
After intervention, the developmental abilities of both groups of children in the areas of cognition, imitation, and social interaction were improved over their abilities measured before the intervention (
< 0.05). However, post-intervention score differences between the two groups demonstrated that the intervention group levels were better than the control group levels only in the areas of cognition and social interaction (
< 0.05).
Combining virtual reality with conventional rehabilitation training improved the cognitive and social development of children with autism spectrum disorder and supported the goal of improving the rehabilitation effect.
In recent years, with the rapid development of computer technology, continual optimization of various learning algorithms and architectures, and establishment of numerous large databases, artificial ...intelligence (AI) has been unprecedentedly developed and applied in the field of ophthalmology. In the past, ophthalmological AI research mainly focused on posterior segment diseases, such as diabetic retinopathy, retinopathy of prematurity, age-related macular degeneration, retinal vein occlusion, and glaucoma optic neuropathy. Meanwhile, an increasing number of studies have employed AI to diagnose ocular surface diseases. In this review, we summarize the research progress of AI in the diagnosis of several ocular surface diseases, namely keratitis, keratoconus, dry eye, and pterygium. We discuss the limitations and challenges of AI in the diagnosis of ocular surface diseases, as well as prospects for the future.
Objective, accurate, and efficient measurement of exophthalmos is imperative for diagnosing orbital diseases that cause abnormal degrees of exophthalmos (such as thyroid-related eye diseases) and for ...quantifying treatment effects.
To address the limitations of existing clinical methods for measuring exophthalmos, such as poor reproducibility, low reliability, and subjectivity, we propose a method that uses deep learning and image processing techniques to measure the exophthalmos. The proposed method calculates two vertical distances; the distance from the apex of the anterior surface of the cornea to the highest protrusion point of the outer edge of the orbit in axial CT images and the distance from the apex of the anterior surface of the cornea to the highest protrusion point of the upper and lower outer edges of the orbit in sagittal CT images.
Based on the dataset used, the results of the present method are in good agreement with those measured manually by clinicians, achieving a concordance correlation coefficient (CCC) of 0.9895 and an intraclass correlation coefficient (ICC) of 0.9698 on axial CT images while achieving a CCC of 0.9902 and an ICC of 0.9773 on sagittal CT images.
In summary, our method can provide a fully automated measurement of the exophthalmos based on orbital CT images. The proposed method is reproducible, shows high accuracy and objectivity, aids in the diagnosis of relevant orbital diseases, and can quantify treatment effects.
A technique for detecting gaseous products in an air atmosphere was achieved based on a quadrupole mass spectrometer and a space-minimized sliding unit settled in a vacuum chamber for the purpose of ...controlling the flow of sample gas and increasing the concentration of products. The test results showed that when a hydrogenated DLC film was rubbed in a dry air environment, carbons were oxidized to form CO
2
. However, in a humid air atmosphere, water molecules competitively reacted with carbons to form hydrocarbons, so the oxidization of carbons by oxygen was inhibited. The different tribochemistry is thought to play an important role in the tribological behaviors of DLC films.
