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Temperature-program strategy was used to regulate the chemical behaviors of species, enrich unsaturated silicon species in liquor, promote the disintegration of metal particles, and achieve the encapsulation of ultra-small metal oxide nanoclusters.

To better understand how fish communities respond to environmental changes under extreme climate events, we examine changes in fish communities in Beibu Gulf during strong El Niño and La Niña events. Strong La Niña and El Niño events affect the composition, abundance, and distribution of fish communities in Beibu Gulf. Fish community distribution and composition change before and after La Niña and El Niño events, and dominant species within them change with stable fishing intensity. The abundance and distribution of small pelagic fish such as Japanese jack mackerel (Trachurus japonicus) and Japanese scad (Decapterus maruadsi) are the most affected. Using a generalized additive model (GAM), we explore relationships between the abundance of T. japonicus and D. maruadsi and a suite of environmental variables. The GAM results revealed that sea surface salinity and sea surface temperature best explain changes in catch per unit effort of these two species during a La Niña event; depth, sea surface temperature, and mixed layer depth during an El Niño event. The results obtained in this study will offer support for implementing more-accurate, scientific fisheries management measures.

Improving prediction of ecological responses to climate variability requires understanding how local fish population dynamics are impacted by climate events. The present study was conducted in the Beibu Gulf of the northwestern South China Sea where the fisheries are characterized by high ecological and commercial value. We evaluated the relationship between major commercial fish population dynamics (abundance and distribution) and climate periods, using survey data from 2006–2020. The analysis using random forest and GAM models show that climate events are not the best predictors for the variations of fish abundance, because abundance of most fish stocks decreases significantly with the year, and the increasing fishing pressure over time can better explain the overall downward trend in fishery stocks. However, environmental variables that correlate significantly with interannual variation in ONI may impact fish abundance in short terms. Our research suggests that climate events leading to higher surface seawater salinity in winter favors pelagic fishes by improving habitat availability, and higher near-surface chlorophyll-α concentration during La Niña events provides better food condition for overwintering fish. In addition, there is no clear evidence that climatic events have a significant impact on gravity center of fish distribution, whereas climate change has caused most fishes to move to cooler coastal waters in the north.

In this study, the effect of channel baffles and louver baffles on the flow pattern in the large-scale industrial fluidized beds was studied by computational fluid dynamics (CFD) methods. Then, the effect of flow pattern on the chemical reaction performance was studied for the first time. Simulation results showed that the gas velocity distributed more uniformly, solid particles dispersed more homogeneously and aggregation scarcely occurred in the fluidized bed with louver baffles than that with channel baffles. The residence time distribution indicated that louver baffles remarkably suppressed gas back-mixing in comparison with channel baffles. The reasonable agreements of pressure distribution and reaction results between the simulation in the bed with channel baffles and the data on a large-scale industrial apparatus demonstrated the accuracy of the CFD model. The predicted conversion of SiCl4 in the bed with louver baffles (27.44%) was higher than that with channel baffles (22.69%), indicating that louver baffles markedly improved the performance of the fluidized bed. This study could provide useful information for future structural improvements of baffles in large-scale fluidized beds.

The lower the minimum surface electrostatic potential of the ligand, the better the modification effect on Ru-based catalysts. The modification effect of HMTA and DABCO on Ru-based catalysts is greatly improved when they are prepared into organic chlorine salts.

Largehead hairtail Trichiurus japonicus is a major commercial fish species in the Beibu Gulf of the northwestern South China Sea. Despite much effort to protect the fishery resource, the current stock of T. japonicus is overexploited. As the impacts of climate change unfold globally, seasonal changes in the distribution of largehead hairtail in the Beibu Gulf have not yet been clarified. Maximum entropy model based on mixed layer depth and salinity were projected onto seasonal habitat changes of T. japonicus in the Beibu Gulf under a current scenario and three different Representative Concentration Pathways (126, 370, 585) to evaluate geographic distribution changes under the different climate-change scenarios. The current geographic distribution results showed variation with seasonality, as the wintering population shifts toward the northeast. Under each of three SSP scenarios, there is higher risk to habitat suitability in the 2090s as compared with that in the 2050s. The disadvantage to T. japonicus distribution is greatest in winter under each of the three climate change scenarios, both in the short- and long-term. Potential suitable habitat distributions have a minor range extension in Representative Concentration Pathway 370–2050 winter, but in the rest of the scenes and years they contract to south of the Beibu Gulf. The overall results indicate that seasonal differences in suitable habitat should be considered to ensure effective planning of future management strategies for T. japonicus.

Accurate information on the temporal and spatial distribution of fish stocks is necessary for informed management and conservation of fisheries resources. We report on the temporal and spatial variation in biomass and density of a hitherto little-studied species of commercial importance, the threadfin porgy Evynnis cardinalis, it was listed as endangered (EN) in a recent International Union for Conservation of Nature (IUCN) red list, on the northern South China Sea continental shelf, using data collected during fisheries surveys from 2014 to 2015. Seasonal variation in the frequency of occurrence of E. cardinalis in trawl samples on this shelf was highest during summer (68.57%) and lowest during winter (31.43%). Average biomass was highest in autumn (33.05 kg·km−2) and density was highest in spring (936 ind·km−2). The highest annual average biomass (41.6 kg·km−2) and density (1021 ind·km−2) occurred off Shantou, and the lowest occurred off Zhanjiang (7.2 kg·km−2 and 165 ind·km−2, respectively); seasonal patterns in density are more similar in waters off Yangjiang and Shantou than elsewhere. The highest annual average biomass occurred at 40 m depth (56.9 kg·km−2), and the highest annual average density (1084 ind·km−2) occurred at 30 m depth. Density of E. cardinalis varied with depth, with lower densities occurring in shallow and deeper waters, and higher densities at intermediate depths.

The Beibu Gulf in the northwestern South China Sea is one of the world’s most productive fishing grounds, yet its biotic resources appear to be in rapid decline because of overexploitation. Assessments of the health status of the fisheries’ resources in the gulf provide a foundation for their conservation and management. As fish accounted for 84% to 97% of the total catch in the Beibu Gulf in the period 1962–2017, a Fish-based Index of Biotic Integrity (F-IBI) was developed for the Beibu Gulf, and data from otter trawl surveys during the period 1962–2017 were used to measure variations in the fish community. The assessment revealed a generally downward trend in total fish catch density (kg/km2), catch density of 12 traditional commercial demersal fish species, and percentage of nektonic-feeding species, but an upward trend for the percentage of fishes with a planktivorous or detritus diet, percentage of pelagic species, and percentage of the dominant species. The dominant species varied greatly over the 50 year period and showed a tendency towards small-sized species. The synthetic F-IBI variable showed a downward trend and has indicated a ‘fair’ state since 1998. The decline in the F-IBI over the last three decades suggests that anthropogenic disturbances, especially overfishing, have had a serious impact on the fish community of the Beibu Gulf. The F-IBI is currently at risk of becoming ‘poor.’ Consequently, we suggest that rigid and enforceable fishery management measures should be taken by both China and Vietnam to prevent further deterioration of the fisheries’ resources in the gulf.

In the world, more than 80% of the fisheries by numbers and about half of the catches have not been formally analyzed and evaluated due to limited data. It has led to the fast growth of data-poor evaluation methods. There have been various studies carried out on the comparative performance of data-poor and data-moderate methods in evaluating fishery exploitation status. However, most studies to date have focused on coastal fish stocks with simple data sources. It is important to pay attention to high sea fisheries because they are exploited by multiple countries, fishing gears and data may be divrsified and inconsistent. Furthermore, a comparison of the performance of catch-based, length-based, and abundance-based methods to estimate fishery status is needed. This study is the first attempt to apply catch-based, length-based, and abundance-based data-poor methods to stock assessment for an oceanic tuna fishery and to compare the performance with a data-moderate model. Results showed that the three data-poor methods with various types of data did not produce an entirely consistent stock status of the southern Atlantic albacore (Thunnus alalunga) fishery in 2005, as the estimated B2005/BMSY ranged from 0.688 to 1.3 and F2005/FMSY ranged from 0.708 to 1.6. The Monte Carlo Catch maximum sustainable yield model (CMSY) produced a similar time series of B/BMSY and F/FMSY and stock status (recovering) to the Bayesian state-space Schaefer model (BSM). The abundance-based method (AMSY) gave the most conservative condition (overfished) of this fishery. Sensitivity analysis showed the results of the length-based Bayesian biomass estimation method (LBB) are sensitive to Linf settings, and the results with higher Linf were similar to those of other models. However, the LBB results with setting Linf at lower levels produced more optimistic conditions (healthy). Our results highlight that attention should be paid to the settings of model parameter priors and different trends implied in various types of data when using these data-poor methods.

To explore the role of substituents on ligands in the modification of metal catalysts, a series of Ru–amide/AC catalysts are synthesized with various amide ligands derived from formamide and assessed for acetylene hydrochlorination. Activity evaluation reveals a rule that replacing a hydrogen on formamide with an electron donor substituent can enhance the catalytic performance, while electron withdrawing substituents have the opposite effect. However, formanilide, which violates this law, shows the best modification effect, which is proved to be the effect of steric hindrance by characterization and DFT calculation. Therefore, another rule is concluded that the electron donor ability and steric hindrance of substituents on amide ligands jointly affect the modification effect. Finally, benzanilide, with a superior modification effect, which searched based on the above results, gives strong evidence for the correction of these rules. This work provides a theoretical basis for the search for efficient ligands for acetylene hydrochlorination.

The objective of this research is to explore the relationships among various multidimensional factor groups and the density of fishery resources of ecosystems in offshore waters and to expand the application of deep machine learning algorithm in this field. Based on XGBoost and random forest algorithms, we first conducted regulatory importance ranking analysis on the time factor, space factor, acoustic technology factor, abiotic factor, and acoustic density of offshore fishery resources in the South China Sea. Based on these analyses, data slicing is carried out for multiple factors and acoustic density, and the relationship between multidimensional factor group and the density of marine living resources in the ecosystem of offshore waters is elaborately compared and analyzed. Importance ranking shows that the concentration of active silicate at 20 m depth, water depth, moon phase perfection, and the number of pulses per unit distance (Ping) are the first-order factors with a cumulative contribution rate of 50%. The comparative analysis shows that there are some complex relationships between the multidimensional factor group and the density of marine biological resources. Within a certain range, one factor strengthens the influence of another factor. When Si20 is in the range of 0–0.1, and the moon-phase perfection is in the range of 0.3–1, both Si20 and moon-phase perfection strengthened the positive influence of water depth on the density of fishery biological resources.

Sharks occupy an important ecological niche in marine ecosystems. As top predators, they can restrict and control the behavior, numbers and composition of other species through downward effects, and play an essential role in ecosystem stability. Shark fishery data are limited, and for most Chondrichthyes species there is no formal fishery resource assessment at a global level. In this study, we applied the length-based Bayesian biomass (LBB) estimation method to assess the stock status of four common shark bycatch species of which more than 100 samples were collected in coastal waters of the northern South China Sea. Estimates of the length of 50% of individuals captured by gear/the length at first capture that maximized the catch and biomass (Lc/Lc_opt) of a species ranged from 0.49 to 1.4; the draughtsboard shark Cephaloscyllium sarawakensis had the highest value, and the shortnose dogfish Squalus brevirostris had the lowest. Estimates of the collected biomass/biomass of the maximum sustainable yield (B/BMSY) ranged from 0.86 to 1.9. Both C. sarawakensis and the spadenose shark Scoliodon laticaudus were fully exploited, while the spatulasnout catshark Apristurus platyrhynchus and S. brevirostris were in good condition. To verify the stability of the LBB, length frequency data for the most common species S. laticaudus were divided into different size-class intervals; simulations revealed estimated parameters based on these to be insensitive to differences in intervals, except for the smallest (10 mm), which did not affect evaluation results. These results can be used to provide a scientific basis on which shark fisheries in this region can be managed and prior parameters for related resource assessment methods can be determined.

Surface mechanical attrition treatment (SMAT) was employed to produce gradient structures in AZ31B Mg alloy samples with two different initial textures. The structure of both samples can be regarded as an integration of two main layers: the severely deformed layer exhibited dramatic grain refinement to nano- and submicron-scale with weakened and randomized textures; the less deformed layer exhibited the inherited coarse grains with increased dislocation density, possessing the similar texture with the sample prior to SMAT. All the samples containing different layer constituents cut from the SMAT alloys showed remarkable increase of strength compared to the original Mg alloy. However, the two integral SMAT samples with different initial textures exhibited marked difference in uniform elongation (UE) during tension. That was attributed to the different strain hardening behaviors influenced by the deformation coordination and strain partitioning between layers with different orientation relationships. The 0° oriented SMAT sample showed no macroscopic strain transfer or slip transmission across layers, which was hard to cause dislocation accumulation throughout the whole thickness of the layered sample. That resulted in a limited strain hardening and UE. However, the favored orientation relationship between layers of the 45° oriented SMAT sample facilitated the strain transfer and slip continuity across the layers. That generated a dynamically migrating interface during tension, which allowed the dislocations accumulating over the whole sample volume. This caused a pronounced strain hardening and sustained UE to an appreciable value.

The sensor-perceived vibration signals of multistage wind turbine gearboxes have more complex frequency features than that of single-stage gearboxes since there are more meshing vibration sources and more complicated transmission paths inside them, which lead to difficulties in condition monitoring and fault diagnosis. Aiming to understand the vibration frequency features of multistage wind turbine gearboxes, a mathematical vibration model of healthy wind turbine gearboxes is developed and the spectral structure of the model is deduced by adopting Fourier series analysis. In the vibration model, the time-varying transmission paths from all the meshing vibration sources to the fixed sensor are considered, and the equivalent transmission path functions of the time-varying transmission paths are proposed for the first time. The theoretical derivations are validated by both simulations and engineering tests using two cases of 2.0MW industrial wind turbine gearboxes. The findings in this work are not only applicable to the gearboxes studied in this paper, but also to other similar multistage gearboxes, which can provide a priori spectral structure for the multistage gearbox to assist its condition monitoring and fault diagnosis.

A highly dispersed and stable PdC phase supported on α-Al2O3 for semi-hydrogenation of acetylene was prepared using N-containing silane coupling agent as a modifier. The catalyst exhibited as much as 15% higher ethylene selectivity than traditional PdAg alloy with full acetylene conversion under 240 °C and performed longer stability within 200 h tolerance test. Characterization results reveal that the excellent ethylene selectivity is mainly derived from the special PdC phase nanoparticle structure with lattice relaxation and distortion. This unique structure makes the catalyst perform weaker adsorption of ethylene, have more abundant spillover hydrogen on the carrier surface and lead a strong interaction between the Pd nanoparticles and surface. Experimental results and DFT calculations have shown the PdC phase is a more promising structure than the commonly used PdAg alloy.

Interfacial interaction in the core-shell hybrid materials makes a great influence for the enhanced electrochemical performances. In this paper, to explore the essential role of the interfacial interaction in the core-shell hybrid electrodes, we prepare a simple mutually-coupled 3D heterogeneous core/shell electrode by NiFe PBAs (Prussian blue analogues) (shell) depositing on the surface of NiFe LDH (layered double hydroxides) (core). The elements of Fe and Ni in NiFe LDH can partly replace the original connections in the NiFe PBAs thus forming a strong interfacial coordination bonding between LDH and PBAs (Fe/Ni(LDH)–CN–Fe/Ni(PBAs) or O–Fe/Ni(PBAs)). Electrochemical tests show that the hybridization present excellent electrochemical performances with a high capacity of 1351 F g−1 at 1 A g−1, which is much higher than that of PBAs-based electrodes recently report. In-situ Raman spectroscopic analysis shows that NiFe LDH@NiFe PBAs present enhanced Faradic redox reaction during charging/discharging process, which is owing to the strong interfacial interaction between two phases. The density functional theory (DFT) calculations results demonstrate that the strong connection bonding can improve the electrical conductivities greatly. This work underscores the crucial role of interface coupling interaction between core and shell and give a new perspective to design core-shell hybrid electrode with excellent electrochemical performance.

In this study, we designed and synthesized a novel battery-type electrode featuring three-dimensional (3D) hierarchical ZnO@Ni x Co1−x(OH) y core/shell nanowire/nanosheet arrays arranged on Ni foam substrate via a two-step protocol including a wet chemical process followed by electro-deposition. We then characterized its composition, structure and surface morphology by X-ray diffraction, energy-dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy, EDS elemental mapping. Our electrochemical measurements show that the ZnO@Ni0.67Co0.33(OH) y electrode material exhibited a noticeably high specific capacity of as much as 255 (mA·h)/g at 1 A/g. Additionally, it demonstrated a superior rate capability, as well as an excellent cycling stability with 81.6% capacity retention over 2000 cycles at 5 A/g. This sample delivered a high energy density of 64 W·h/kg and a power density of 250 W/kg at a current density of 1 A/g. With such remarkable electrochemical properties, we expect the 3D hierarchical hybrid electrode material presented in this work to have promising applications for the next generation of energy storage systems.

Herein, experiments and DFT calculations were co-researched on high-performance catalysts for acetylene hydrochlorination. Firstly, the mesoporous carbon materials with adjustable N-doping content (MC-xN, x = 0, 0.5, 1, 2) were successfully synthesized. And the oxidized Ru species were further loaded (Ru-MC-xN) through simple hydrothermal method. Under the experimental condition of T = 170 °C, GHSV(C2H2) = 360 h−1, V(HCl)/V(C2H2) = 1.15, Ru-MC-2N shows excellent catalytic activity, with the acetylene conversion of 98.0 %. Characterized by various techniques, N-doping is confirmed to relatively inhibit the coke deposition and increase the percentage of oxidized Ru species which is attributed to regulation of the adsorption energy. Catalytic pathways of Ru in different valences are also revealed by DFT method. Results show that oxidized Ru species own higher catalytic activities than Ru0 species and manifest the molecular mechanism for HCl activation of RuO2. These findings provide theoretical basis for designs and applications of Ru-based catalysts in acetylene hydrochlorination.

Faced with the problems of poor activity and inferior selectivity, highly dispersed Pd catalysts pre-modified by minimal 3-aminopropyltriethoxysilane (APTES) were prepared via impregnation reduction method. The amount of APTES was adjusted according to molar ratios of the APTES to Pd (APTES/Pd). The catalytic hydrogenation efficiency exhibited a volcano-shape trend with the amount of APTES. Grafting of suitable amount of APTES improved the dispersion of the Pd, increased the weak acid content of the γ-Al2O3 and regulated the reducibility of the catalysts. The catalyst having APTES/Pd = 2 with 0.192 wt% Pd showed the highest catalytic activity and selectivity, with 100 % in the selectivity and the improvement of 27.3 % in the hydrogenation efficiency and 104.8 % in the H2O2 productivity compared with the commercial catalyst (0.298 wt%). Furthermore, the APTES aggregated with the amount of APTES, which provided intense anchoring sites for the Pd and resulted in the increase in larger palladium nanoparticles.

Real-time volume flow rate of gas component for slowly changing composition mixtures is of chief importance for some special research applications. However, it is always difficult for us to achieve the goal by sophisticated gas flowmeter. In this study, we demonstrate two methods for the problem solution by the flow measurement of acetylene in unsteady gas flow based on online gas chromatography accompanying with a gas mass-flowmeter. For Method 1, high purity methane is applied as an internal standard and the volume flow rate of acetylene is obtained via coherent equations. Method 2 makes fully use of the online gas chromatography automated integration under fixed gas chromatography work conditions. Results have shown that both methods are feasible and effective, and Method 2 is more accurate than Method 1 with relative error less than 0.7%.

A series of reduced graphene oxide–mesoporous silica nanoflakes (rGO–MSN) with adjustable surface wettability were developed. Detailed SEM, TEM, XRD, BET, and TGA analyses demonstrated that morphologies, structures, porosities of the obtained composite materials were greatly influenced by rGO content. Moreover, micrographs and conductivity measurements were conducted to investigate the performance of rGO–MSN as emulsifier in stabilizing paraffin/water two-phase system. Furthermore, anchored with –SO3H, the modified hybrid nanoflakes SO3H–rGO–MSN-x% were employed as solid emulsifier and catalyst (Pickering interfacial catalyst) at solvent free oil–oil interface for acetal reaction and showed excellent dodecyl aldehyde conversion more than 90%.