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Remote sensing of chlorophyll-a (Chl-a) concentrations in coastal waters is of great importance for the assessment of the marine ecological conditions. However, due to the complex water body optical properties, accurate selection of optimal feature bands is limited, which poses a great challenge for high-precision retrieval. The purpose of this research is to address the problem of high-precision retrieval of the Chl-a concentration in small coastal waters. In this article, a singular value decomposition and deep neural network (SVD-DNN) Chl-a inversion model for Hong Kong coastal waters were constructed. Other machine learning methods, such as random forest (RF) and the support vector machine (SVM) are also used to establish the inversion models for the comparison. At the same time, a comparative analysis was performed with Chl-a retrieval models created using a feature selection method based on the correlation of band combinations. These models are validated using the Landsat 8 OLI and synchronously measured Chl-a dataset (N = 149 samples). Results show that the developed SVD-DNN model has the best retrieval accuracy [mean R = 0.90, root mean square error (RMSE) = 1.21, mean absolute error (MAE) = 1.05], outperforming the SVD-RF and SVD-SVM models. The SVD-DNN model shows superior retrieval performance when the Chl-a concentration is below 6 micrograms per liter (RMSE = 0.66, MAE = 0.67). The proposed model also shows better temporal generalization ability in 2013, 2014, and 2016 compared to the other models. This study demonstrates that the developed and validated SVD-DNN model has excellent robustness and generalization ability and can be used in combination with Landsat data for long-term retrieval of Chl-a across different time series.

Abstract To study the effect of different sizes and speeds of coal gangue falling on hydraulic supports for top‐coal caving discharge hydraulic support on the bearing characteristics of the hydraulic support, the ADAMS hydraulic support rigid‐flexible coupling analysis model was established. HyperMesh is used to flexibly process the hydraulic support, and the column and jack are equivalently replaced by spring damping system. By applying step loads of different sizes and speeds to simulate the impact force generated when the coal gangue falls on different positions of the cover beam, the dynamic response characteristics of the column, balance jack and other articulation points are obtained. Analyses show that: when the impact load is closer to the roof beam, the articulation point of the roof beam‐cover beam and the balancing jack are easy to be damaged. When the same impact load is applied to the cover beam, the faster the load is applied, the hydraulic support column and balancing jack may not be able to absorb and disperse the pressure effectively in time, resulting in the articulation points being subjected to a larger impact force, which is easy to cause damage or destruction. When different sizes and speeds of impact loads are applied to the cover beam, the latter has a greater impact on the dynamic response of the front and rear connecting rod articulation points and the cover beam‐roof beam articulation point than the former, and the hydraulic bracket will be more prone to vibration, deformation, and stress concentration, thus affecting the stability and safety of the bracket. The article is of guiding significance for designing and optimizing the structure and parameters of the hydraulic support, and improving the support performance and stability of the hydraulic support in the comprehensive release working face.

Abstract To solve the problems of poor top coal drawing, lagging collapse, and difficulty in parallel operation of mining and drawing in extra-thick coal seams, considering the 8222 working face of the Tashan Mine as the engineering background, we first investigate the basic problems of fully mechanized top coal drawing mining in extra-thick coal seams using the single-round group drawing method (GDM). We then analyze the drawing law of top coal with different thicknesses under the single-round GDM from the aspects of top coal recovery (TCR) and drawing efficiency, coal loss mechanism, and the relation between TCR and gangue content (GC), providing a basis for determining the process parameters of GDM. Results indicate that as the top coal thickness increases, the number of drawing openings considerably influences drawing efficiency and top coal loss. And there is a notable thickness effect of the number of drawing openings on the top coal loss. There is a quantitative relationship among TCR, cumulative GC (CGC) and instantaneous GC (IGC), and CGC and TCR can be predicted based on the IGC. Consequently, theoretical analysis and numerical simulation results indicate that the optimal IGC threshold at the coal drawing openings between 31.2 and 40%. Through optimizing the coal drawing method and strictly controlling the IGC at the coal drawing openings on-site, the measured working face TCR increased from 75.25 to 90.12%, and CGC was controlled at approximately 9%. Meanwhile, the average coordination efficiency of mining and drawing time reaches 68.2%, effectively ensuring the construction of a coal mine with an annual output of 15 million tons.

The utilization of compression garments (CGs) has demonstrated the potential to improve athletic performance; however, the specific mechanisms underlying this enhancement remain a subject of further investigation. This study aimed to examine the impact of CGs on running mechanics and muscle synergies from a neuromuscular control perspective. Twelve adult males ran on a treadmill at 12 km/h, while data pertaining to lower limb kinematics, kinetics, and electromyography were collected under two clothing conditions: whole leg compression garments and control. The Non-negative matrix factorization algorithm was employed to extract muscle synergy during running, subsequently followed by cluster analysis and correlation analysis. The findings revealed that the CGs increased knee extension and reduced hip flexion at foot strike compared with the control condition. Moreover, CGs were found to enhance stance-phase peak knee extension, while diminishing hip flexion and maximal hip extension during the stance-phase, and the ankle kinematics remained unaltered. We extracted and classified six synergies (SYN1-6) during running and found that only five SYNs were observed after wearing CGs. CGs altered the structure of the synergies and changed muscle activation weights and durations. The current study is the first to apply muscle synergy to discuss the effect of CGs on running biomechanics. Our findings provide neuromuscular evidence for the idea of previous studies that CGs alter the coordination of muscle groups, thereby affecting kinematic characteristics during running.

The origin and tectonic regime responsible for the inland Jurassic granites in Southeast (SE) China remain controversial. This study presents zircon secondary ion mass spectrometry (SIMS) U-Pb ages, in situ zircon Hf-O isotopes, and whole-rock geochemical and Sr-Nd isotopic data for the Fogang and Xinxing Batholiths in central Guangdong. Mineralogical and geochemical features indicate that these granites are high-K (>4.8 wt% K2O at 72 wt% SiO2), calc-alkaline I-type granites. SIMS U-Pb analyses on magmatic zircons yield consistent ages ranging from 158 to 163 Ma, suggesting that the Fogang and Xinxing granites were emplaced in the period of 163–158 Ma. In addition, these granites have whole-rock initial Sr87/Sr86 ratios of 0.6802–0.7072 and negative εNd(t) values of −9.5 to −8.2, zircon negative εHf(t) values of −12.34 to −0.56, and high δ18O values of 7.64‰–10.08‰. The above features imply that the granites were most likely generated through the mixture of supracrustal sedimentary components with minor addition of mantle-derived magmas. Granites from the Fogang and Xinxing Batholiths in SE China should be derived from the Proterozoic crustal reworking due to asthenosphere upwelling or underplating and intrusion of mafic magmas. These Jurassic granites reflect anorogenic magmatism probably formed in an intraplate extensional setting resulted from the foundering of the flat slab beneath SE China.

Abstract Objective This study aimed to examine the effects of combining transcranial direct current stimulation (tDCS) and foot core exercise (FCE) on the sensorimotor function of the foot (i.e., toe flexor strength and passive ankle kinesthesia) and static balance. Methods In this double-blinded and randomized study, 30 participants were randomly assigned into two groups: tDCS combined with FCE and sham combined with FCE (i.e., control group). The participants received 2 mA stimulation for 20 min concurrently with FCE over 4 weeks (i.e., three sessions per week). After the first two groups completed the intervention, a reference group (FCE-only group) was included to further explore the placebo effects of sham by comparing it with the control group. Foot muscle strength, passive ankle kinesthesia, and static balance were assessed at baseline and after the intervention. Results Compared with the control group and baseline, tDCS combined with FCE could increase toe flexor strength (p

Study region: The Sanjiang Plain (SJP), located at the confluence reaches of the Heilong, Songhua, and Wusuli Rivers in Northeast China. Study focus: This study aimed to quantify the effects of varying climate and land-use/land-cover (LULC) dynamics on green water (GW) over the SJP during two distinctive periods (i.e., pre-2000 and post-2000), when synergetic effects of increased precipitation and temperature and rapid development of agriculture occurred. This assessment used the distributed eco-hydrological model ESSI-3. Multivariable and multi-objective calibration approaches (i.e., discharge, evapotranspiration, and terrestrial water storage anomaly) were used to ensure the high accuracies of the model outputs. New hydrological insights for the region: This research concluded that GW flow and GW storage in the SJP evidently increased after 2000 compared with before. Across the SJP, GW flow and GW storage responded differently to climate changes and LULC dynamics during pre-2000 and post-2000 period. Our results demonstrated that GW storage changes were predominately affected by climatic changes, especially variations in precipitation, whose contribution accounted for more than 56% after 2000. However, GW flow changes were mainly governed by LULC changes, especially the influence of cropland transformation, whose contribution increased over 20% in the post-2000 period. This study posed a deep insight regarding impacts of regional climatic and LULC changes on GW dynamics, which may benefit decision-making for planting structure optimization and adjustment over the region.

This paper demonstrates a C-band 25G colorless passive optical network (PON) based on semiconductor optical amplifier (SOA) and 10G electro-absorption modulator (EAM). The experimental results show that the SOA in the optical network unit (ONU) can erase the downlink signal by taking advantage of the gain saturation feature, realizing the reuse of downstream wavelength. Meanwhile, the SOA gain can compensate for the EAM loss by optimizing the current and injection power. Apart from this, equalization algorithms at the optical line terminal are investigated for linear and nonlinear impairments compensation. Besides, the system robustness to the ASE and the maximum transmission speed are also evaluated. Finally, the system capacity can reach up to 25 Gbps with NRZ format at a bit-error ratio threshold of 2 × 10−2, proving that this system is a promising technology for future high-speed colorless 2 × 25G or 4 × 25G Wavelength division Multiplexing (WDM) PON system.

Semiconductor photocatalysis technology is an environmentally friendly and efficient emerging technology. This method can use sunlight as a driving force to quickly decompose organic pollutants in water bodies. Zinc oxide (ZnO) and tungsten oxide (WO3) photocatalysts can absorb sunlight and participate in photocatalytic degradation reactions due to their relatively narrow band gap. Highly photosensitive WO3 nanofibers and ZnO/WO3 composite nanofibers were fabricated via the electrospinning method. When 100 mg/L of rhodamine B (Rh B) solution was used as the degradation substrate, the degradation efficiencies of WO3 and ZnO/WO3 for Rh B dye were 70% and 90%, respectively, after a photocatalytic reaction of 120 min. The surface morphology, crystal structure, and optical properties of ZnO/WO3 composite nanofibers and WO3 nanofibers were characterized by SEM, XRD, XPS, and UV-vis absorption spectra, and the experimental results were analyzed and explained using different mechanisms. The results show that ZnO/WO3 composite nanofibers have better UV-visible light absorption performance, and the sample has a higher UV-visible light utilization rate. This was mainly due to the fact that a P-N heterojunction was formed in the semiconductor composite, and the electron–hole pair could realize rapid separation under the drive of a built-in electric field force, which promoted the migration of carrier. Therefore, the photocatalytic activity of the ZnO/WO3 catalyst was significantly higher than that of the WO3 catalyst, which promoted rapid improvement of the photocatalytic degradation efficiency of the Rh B dye.

Heavy-metal pollution of soils has become a major environmental concern around the world presently. Soil washing provides an effective measure of removing contaminants from soil permanently, of which washing reagent plays a vital role in the process. This article reviews the current knowledge acquired on the main aspects concerning washing reagents of soil washing for remediation of heavy-metal-contaminated soil based on more than 150 published studies over a period from 1990 to 2021. The review identifies and discusses the types of washing reagents with their associated characteristics. Based on the factors influencing washing remediation, multi-criteria decision-analysis, together with an integrated four-step procedure, is put forward to manage the selection and prioritizing of washing reagents. It crops out from the literature survey that the selection of the washing reagents is a balanced process by considering washing effect, environmental impact, and cost-effectiveness. On the basis of such observation and evaluation, it is recommended that further study should be focused on developing new washing reagents or compound washing reagents that possess the advantage over heavy-metal removal ability, eco-friendliness, and cost-effectiveness as well. Selecting washing agents that are capable of being recovered from waste such as dissolved organic matter would be a promising trend in washing remediation. Artificial intelligence is expected to assist in the selection of washing reagents.

Snowsport athletes face a high injury risk both during training and in competitions. Reducing injury incidence is crucial for athletes to achieve breakthroughs. This narrative review aimed to summarize and analyze injury data of elite athletes in snowsports and provide references for injury prevention and health security for these athletes and their coaches. A total of 39 studies that investigated snowsport injury were analyzed in the present study. On the basis of injury data of elite athletes in snowsports events, this narrative review focused on four aspects, namely, injury incidence, severity, location and causes. The findings of this review were as follows. (1) The highest injury incidence was recorded in freestyle skiing, followed by alpine skiing and snowboarding, the majority of which were moderate and severe injuries. (2) The proportion of injury in competitions and during training was similar. However, more injuries occurred in official training during the Winter Olympic Games; by contrast, injury proportion was higher in competitions during World Cup/World Championships. (3) The most commonly and severely injured body parts were the knees (29.9%), head and face (12.1%), shoulders and clavicula (10.5%), and lower back (8.9%). The most common injury types were joint and ligament injury (41.5%), fracture and bone stress (24.4%), concussion (11.1%), and muscle/tendon injury (10.7%). (4) The main causes of snowsport injury were collisions, falls, and non-contact injuries. Snowsport injury was also influenced by the skill level of the athletes, gender, course setup and equipment. Future studies should further explore the influence of event characteristics and intrinsic and extrinsic risk factors on snowsport injury. An injury or trauma reconstruction may be developed to predict athletic injuries and provide effective prevention strategies.

Nowadays, compression garments (CGs) are widely used in winter racing sports, such as speed skating, short-track speed skating, alpine skiing, and cross-country skiing. However, the effect of wearing CGs on athletic performance in these specific sports is still not fully examined. Thus, the aim of this narrative review is to summarize the research and application of CGs in winter racing sports and to discuss how the CGs help athletes improve their performance in an integrative manner (i.e., physiology, aerodynamics, and biomechanics). A total of 18 experimental studies dedicated to CGs in winter racing sports were identified from the peer-review scientific literature. The main findings are as follows. (1) Currently, CG studies have mainly focused on drag reduction, metabolism, muscle function, strength performance, and fatigue recovery. (2) The results of most studies conducted in wind tunnels showed that, for cylindrical structures similar to the human body, clothing with rough surfaces can reduce air drag. Notably, the effect of CGs on drag reduction in real competition has not been fully explored in the literature. (3) Compression can reduce muscle vibrations at high impact and help athletes control the center of pressure movement, a function that is important for alpine skiing. Future studies are needed to improve current understanding of the effects of compression clothing microstructure on drag reduction and their stretching in different parts of the body. Furthermore, the design of experimental protocol must be consistent with those during the competition, thus providing a full discussion on energy metabolism, fatigue, and recovery affected by CGs.

Since the initial publication of Kelly et al.'s seminal paper on resource allocation in wired networks, many studies based on the cross-layer design philosophy have been conducted in both wired and wireless networks. The Lagrangian duality technique has been widely adopted to solve the cross-layer optimization problem, but it is slowly convergent and sensitive to the iterative step size, especially for large networks. In this paper, a joint congestion control and power allocation second-order algorithm (JCCPA) is proposed, in which the joint optimization problem is modeled as a network utility maximization (NUM) framework, and the primal-dual interior-point method is used to solve the NUM problem. The JCCPA updates the primal variables and dual variables simultaneously according to their Newton directions; as a result,resulting in a faster convergence speed is reached. Moreover, the matrix-splitting technology is utilized to decompose the computation of the Hessian matrix and its inverse into different nodes and links so that the distributed update of source rate and node power can be implemented. The simulation results demonstrate that the JCCPA not only significantly improves energy efficiency but also has a faster convergence speed and is insensitive to step size.

This paper proposes a low-power fractional-N all-digital PLL (ADPLL) for the narrow-band Internet-of-Things applications. Multi-step lock controlling and oscillator tuning word coarse prediction algorithms help to accelerate the locking process to less than $20~\mu \text{s}$ . A digital-to-time converter (DTC) is used with a phase prediction algorithm to minimize the detection range of the time-to-digital converter for low power consumption. The $\Sigma \Delta $ dither block is designed to improve the nonlinearity of DTC resulting in a −40-dBc in-band spur suppression. A low supply of 0.6-V digitally controlled oscillator has the frequency coverage of 1.5–2.05 GHz. Fabricated in a 55-nm CMOS, the ADPLL occupies an active area of 0.88 mm2 and consumes 4 mW at 1.8 GHz. With a 24-MHz reference clock, the measurement results show that this work achieves better than −94-dBc/Hz in-band phase noise and −120.5 dBc/Hz at 1-MHz offset of 1.83-GHz carrier frequency. The FoM value is −233.4 dB, and the reference spur is −76.3 dBc.

During freeze–thaw periods, the transformation between phreatic water and soil water will change the soil hydrothermal properties and affect the soil freezing and thawing in shallow groundwater areas. The purpose of this study was to determine the effect of four different groundwater table depths (GTDs) and two soil textures on the process of soil freezing and thawing during two successive freeze–thaw periods using the Simultaneous Heat and Water (SHAW) model. The results show that the frost depth was the maximum when the GTD was 1.0 m, and the maximum frost depths of sandy loam and fine sand were 97.6 and 98.9 cm, respectively. When the GTD was larger than 1.5 m, the maximum frost depth decreased with an increase in GTD, and the maximum frost depth of the soil profile was more sensitive to changes in the air temperature. The frost depth of the soil profile was linear with the square root of the accumulated negative soil surface temperature (ANST) under different GTDs. The ANST was influenced by the phreatic evaporation, and the soil freezing rate increased with an increase in GTD under the same ANST. This research is significant for the rational development of soil water and heat resources and the study of soil water–heat transfer in shallow groundwater areas.