This paper studies the oscillation and asymptotic properties of delay differential equations with damping and sub-linear neutral terms using the generalized Riccati transformation technique and the mean value theorem. After analyzing the function of the cross-link between the condition $\int^\infty_{t_0}(\frac{1}{R(t)})^{\frac{1}{\gamma}}{\rm{d}}t=\infty$ and the relationship of parameters $\gamma$ and $\beta$ in the differential equations oscillation, the sufficient conditions for the existence of vibration solutions are provided to extend the existing results in the cited literature. Lastly, some applications are given to illustrate the significance of these results.
This study builds on the method developed by Wang for images of multilinear polynomials on algebra of upper triangular $ 2\times2$ matrices. The main goal of the paper is to give a description of the images of multilinear polynomials on algebra of upper triangular $ 3\times 3$ matrices, thereby partly solving the Fagundes and Mello conjecture, a variation of the famous Lvov-Kaplansky conjecture.
In this paper, we study the long-time dynamic behavior of solutions for the non-autonomous classical reaction-diffusion equation with nonlinear boundary conditions and fading memory, where the internal nonlinearity and boundary nonlinearity adheres to polynomial growth of arbitrary order as well as the balance condition. In addition, the forcing term is translation bounded, rather than translation compact, by use of contractive function method and process theory. The existence and the topological structure of uniform attractors in $L^{2}(\Omega)\times L_\mu^2(\mathbb R^+; H_{0}^1(\Omega))$ are proven. This result extends and improves existing research in the literature.
In this paper, we investigate the uniqueness and distribution of zeros of a class of difference polynomials by using Nevanlinna’s value distribution theory. We obtain results about the uniqueness of the difference polynomials $P(f)\sum_{i=1}^{k}t_{i}f(z+c_{i})$ and the distribution of zeros of the difference polynomials $P(f)(\sum_{i=1}^{k}b_{i}(z)f(z+c_{i}))^s-b_0(z)$ , where $f(z)$ is a transcendental entire function of finite order, $c_i, t_i\;(i=1, 2, \cdots,k)$ are non-zero constants, and $b_i(z)\;(i=0, 1, \cdots,k)$ are small functions with respect to $f(z)$ .
The development of wireless communication has made spectrum resources increasingly scarce. Existing spectrum resources, however, are not currently used in an efficient way. This contradiction can usually be attributed to the problem created by static spectrum allocation strategies. Cognitive radio (CR) is widely regarded as a feasible solution to solve the problem of static spectrum allocation. In recent years, deep learning, an emerging field of machine learning, has contributed to a number of notable research and application achievements. It has become one of the driving technologies behind artificial intelligence. In this paper, we investigated the application of deep learning to CR; this includes the development of cognitive radio and deep learning as well as the usage of deep learning models in key technologies for CR (such as spectrum prediction, spectrum environment sensing, signal analysis, etc.). Lastly, we summarize and discuss conclusions from this review.
Modified Newtonian dynamics is a major competitor of dark matter theory and contains not only a gravitational constant but also an acceleration constant. Based on a circular orbit solution for a two-body problem, this paper is devoted to studying a plane circular restricted three-body problem using modified Newtonian dynamics. We work out the Lagrangian points and the Hill curves akin to those observed in Newtonian dynamics. In contrast, however, the location and number of Lagrangian points, as well as the profile of the Hill region, are dependent on both the acceleration constant and the mass ratio of the main celestial bodies. These findings reveal a new avenue for testing modified Newtonian dynamics.
Quantum theory has the characteristics of superposition, entanglement, incompatibility, and interference, which make it an excellent modeling framework. For the purpose of sentence matching, we explore the ability of quantum theory as a framework to capture sentence meaning and model semantic processes. We use quantum states to construct the semantic Hilbert space and calculate the fidelity of information during sentence transformation. The similarity of sentences is subsequently determined by using word embedding technology to represent words or concepts in semantic vector spaces. Simulation data showed that the proposed method achieved better results than traditional methods for sentence matching datasets constructed on real business scenarios. Hence, this paper provides a new idea for similarity research of multiple sentences and introduces a breakthrough in interdisciplinary research between computer science and quantum theory, in line with current research trends.
There is an inconsistency between the Hubble parameter obtained from local measurements and model-based parameters obtained from cosmic microwave background (CMB) measurements. This inconsistency motivated us to consider new cosmological models based on $\Lambda {\rm{CDM}}$ (Lambda Cold Dark Matter Model), such as a large-scale Lorentz violation model with non-vanishing spatial curvature. The degeneracy among the spatial curvature, cosmological constant, and cosmological contortion distribution makes the model viable for interpretation of the observation data. By comparing the luminosity distance modulus and redshift with the model prediction and calculating the change in matter density as well as the cosmological constant over time, we limit the spatial curvature density to a certain range. Accordingly, we discuss the performance of the large-scale Lorentz violation model with non-vanishing spatial curvature under these constraints.
In this study, the low-energy effective field theory approach is used to analyze nuclear matter and a zero-temperature Fermi system. By solving the Bethe-Goldstone equation (BGE) in the 1S0 channel, we obtain the closed-form Brückner G matrix and derive its renormalized non-perturbative form. Upon selecting values for relevant parameters, a number of physical issues are analyzed with the Brückner G matrix, such as pairing and single particle energy of a Fermi system in the density background. Lastly, the framework and results are compared with those published in the literature.
In this paper, we use time-resolved Kerr rotation(TRKR) spectroscopy to study the electron spin coherence dynamics of a wurtzite (0001) plane n-CdS single crystal at different temperatures and wavelengths. Two types of electronic spin signals are observed in this material at low temperatures. One is a long-lived spin signal at relatively long pump probe wavelengths, where the spin dephasing time exceeds 4.8 ns at 5 K and decreases with increasing temperature. The other is a short-lived spin signal at relatively short pump probe wavelengths, where the spin dephasing time is about 40 ps and persists up to room temperature; in this case, the spin signal is largely independent of temperature. Studies have shown that long-lived spin signals can be attributed to localized electrons, while short-lived spin signals can be attributed to conduction delocalized electrons.
High-order harmonic generation (HHG) may occur during the interaction between an intense laser field and an atom or molecule; HHG has become an important xtreme utility vehicle(XUV) light source which can be used to probe atomic and molecular structures. In this paper, we investigate the effect of the radial distribution of electric density on the HHG spectra by calculating the HHG spectrum of noble atomic gases in a polarized laser field using s and p orbital functions as ground state wave functions. The results show that the form of the wave function does not influence the cutoff value of the harmonic spectrum, which is determined by the ionization threshold energy and the laser intensity. However, different types of orbital wave functions do lead to different envelopes for the HHG spectrum. In particular, there is an additional dip in the plateau area for the p orbital case compared with the spectrum for the s orbital case. By analyzing the formula for the HHG spectrum, we attributed the dip position on the HHG spectrum to the density distribution of the ground state wave function in momentum space. This work may shed light on applications for using the HHG spectrum to visualize atomic orbitals.
In this paper, we study the strong and weak coupling between excitons of a WSe2 monomolecular thin film and a light field in a self-made Fabry–Pérot semiconductor microcavity at 300 K. The optical properties of the sample were studied using a micro-fluorescence / white light reflection spectroscopy system with integrated angular resolution; the formation of exciton polaritons was observed in the strong coupling region, corresponding to a Rabi splitting energy of 46.7 meV. The theoretical fitting results agree with the experimental phenomena. This lays the foundation for further research on the coherent properties of exciton polaritons, and the study also provide ideas for the application of industrial optoelectronic devices in the future..
In this paper, whispering gallery mode (WGM) excited in a two-dimensional electromagnetic Helmholtz cavity are studied using a rigorous, generalized dual series approach. The excitation wavelengths of several whispering gallery modes are given, and the dependence of electromagnetic whispering gallery modes on the angle of incidence and the angular width of opening cavities is investigated. It was found that WGM are very sensitive to slight changes in wavelength or the angular width of the opening; at the same time, WGM can be excited across a wide range of incident angles given a fixed orientation angle of the cavity. This shows that the angular width of the opening has a significant influence on the performance of Helmholtz cavities and hence is a key parameter in their design. On the other hand, given the lack of sensitivity to the incident angle, no particular specification is needed when designing an artificially structured electromagnetic material using these Helmholtz cavities; accordingly, the fabrication difficulty is relatively low.
The square potential barrier is an ideal model for investigation of quantum tunneling. We simulate the square potential barrier by using the dipole potential for the interaction between an atom and a blue-detuned far-off-resonant super-Gaussian beam, as well as the ponderomotive potential for the interaction between an electron and a super-Gaussian beam. A comparison between the numerical results for scattering by the super-Gaussian potential barrier and the analytical results for scattering by a square potential barrier shows that a super-Gaussian beam with an order exceeding 20 could simulate a square potential barrier accurately. We also show that two super-Gaussian beams could be used to study the resonant quantum tunneling effect. In summary, our results could be applied to an experimental investigation of quantum tunneling through a square potential barrier.
Two-dimensional materials have been used in applications across a variety of fields; transition metal dichalcogenides(TMDCs), in particular, are a candidate for use in the field of optoelectronics due to the presence of a band gap. In this paper, WS2 monolayers prepared by micro-mechanical exfoliation are transferred to two micro-period electrode structures. We found that the photoluminescence of the material is modulated by external bias. We studied the effects of bias on the photoluminescence of the WS2 monolayer at room temperature and low temperature. The corresponding characteristics and physical mechanisms of the photoluminescence(PL) spectra, moreover, are analyzed and discussed. With the application of bias to modulate the optical properties of the WS2 monolayer, it is expected that the technology can be applied to many photoelectric products, including field effect transistors, photodetectors, flexible electronic devices, and heterojunction devices.
The objective of this paper is to propose a mathematical theory that can describe the non-Markovian characteristics of the network spreading process, thereby establishing theoretical support for controlling the propagation of diseases or rumors in the real world. According to the second-order mean-field approximation method and the concept of idle edges, a series of partial differential equations are presented that can be used to solve the non-Markovian spreading dynamics of a susceptible-infected (SI) model in complex networks. By comparing the simulation outputs with the theoretical results, this mathematical method can accurately predict the spreading process of the SI model on complex networks. The theory, moreover, can be used to predict the average time for a single node to be infected. The correctness and accuracy of the theory is verified by experimental simulation results.
Intonation is the tone of speech, which is formed by variations in pitch and emphasis; it is one of the characteristics of human emotion transmission. By adjusting the intonation parameters to change the length and height of certain words in discourse, the controlled intonation can mimic the effect of singing; this approach, in turn, can be used to address the lack of research on voice synthesis in singing. The cepstrum method is used to extract the pitch frequency, the LPC (linear predictive coding) method is used to estimate the formant, and a high-order polynomial is used to fit the pitch of the voice; the fitting function is then adjusted in real time to form the tone required to achieve the objective of singing. Given two basic speech parameters, pitch frequency and formant, combined with the mathematical nature of pronunciation, this paper uses an intuitive mathematical method to synthesize the effect of singing; using this method, the original voice and the synthetic voice reach an overall recognition rate of 87.6%. The result of this synthesis shows that by adjusting the parameters of speech synthesis, we can achieve greater control over voice singing.
The photoanode of I-doped TiO2 nanotube arrays (ITNA) prepared by anodization exhibited better degradation performance than TNA. The planar photocatalytic fuel cell (p-PFC) obtained by combining ITNA and Pt electrodes achieved a maximum decolorization rate of 93.1% when the concentration of methylene blue (MB) was 6 mg·L–1and the electrode plate spacing was 1.0 cm. The degradation of MB occurred on the surface of ITNA, which was a rate-limiting step. Compared to other structures, p-PFC had a higher photocatalytic performance and better production of h+ and ·OH, while degrading MB and other organics.
In this study, four typical typhoons that significantly affected Shanghai were selected based on their respective intensity and the water level along the Shanghai Coast. The RMW (Radius of Maximum Winds) formula, moreover, was determined using in-situ data from recent typhoons. The typhoon model was built and validated using in-situ wind speeds from the four typhoons selected. The peak wind speed and the forward peak wind speed along the Shanghai Coast were calculated, case by case, during all typhoons over the period from 1949 to 2014 as well as the four typical typhoons selected. Finally, the range and distribution of the peak (forward peak) wind speed were quantitatively studied.
In this study, we analyzed the spatial and temporal variations in the residual water level of the Changjiang Estuary and evaluated the respective causes. To achieve this objective, we used data from the hourly water level at the Chongxi, Nanmen, and Baozhen hydrological stations in the Changjiang Estuary; daily river discharge levels at the Datong hydrological station; and wind speed and direction at the Chongming eastern shoal weather station in 2016 and 2017. The results showed that the residual water level was the highest at Chongxi station and the lowest at Baozhen station among the three hydrological stations in each month. The drops in residual water level among the hydrological stations became smaller during low river discharge and tended to become larger during high river discharge. Higher levels of river discharge were associated with a larger drop in the residual water level. In 2016, the residual water levels at the Chongxi, Nanmen, and Baozhen hydrological stations were lowest in February with values of 2.09, 1.96, and 1.93 m, respectively; similarly, the residual water levels were the highest in July with values of 2.91, 2.62, and 2.50 m, respectively. The residual water level was mainly affected by river discharge, while the wind was also an important influencing factor in the variations observed. Southerly wind made the residual water level decrease, and northerly wind made it increase. In 2017, the minimum monthly mean residual water level occurred in December with values of 2.04, 1.91, and 1.87 m at the Chongxi, Nanmen, and Baozhen hydrological stations, respectively; this coincided with the lowest annual river discharge observed during the same period. The maximum monthly mean residual water level occurred in October with values of 2.79, 2.58, and 2.49 m at the Chongxi, Nanmen, and Baozhen hydrological stations, respectively. Although the river discharge was lower in October than the one in July by 24214 m3/s, the residual water level was higher in October than that in July. The explanation for this phenomenon is the persistent strong northerly wind observed in middle to late October, which produced strong landward Ekman water transport, and resulted in the water level rise. The spatial and temporal variation in the residual water level of the Changjiang Estuary is remarkable, and should be considered in engineering design and theoretical research.
Qingcaosha Reservoir is the main water source for Shanghai, providing approximately 55% of its high-quality raw water needs, and effectively guarantees the safety of water supply for Shanghai. The waters near the Qingcaosha Reservoir experience saltwater spillover from the North Branch into the South Branch; the nearby waters, moreover, suffer from direct saltwater intrusion from the open sea. In this study, a large number of measured salinity data in the upstream and downstream sluice was used to statistically analyze the characteristics of direct saltwater intrusion near the Qingcaosha Reservoir waters in recent decades. The analysis results show that direct saltwater intrusion neat the Qingcaosha Reservoir waters in recent decades was closely related to the river discharge, tide, and wind. There were a total of 16 instances of direct saltwater intrusion at the upstream sluice that occurred from September to March of the following year; likewise, there were a total of 41 instances of direct saltwater intrusion at the downstream sluice that occurred from September to May of the following year. The direct saltwater intrusions at the upstream and downstream sluices appeared primarily in December, January, and February of each year. We found that saltwater intrusions occurred most commonly when the river discharge was less than 18 000 m3/s during neap tide and middle tide (after neap tide) accompanied by persistent northerly or northwesterly winds. We found that the strength and duration of the northerly or northwesterly winds in the days preceding saltwater intrusion had an important role on direct saltwater intrusion.
Twenty-two surface sediments collected from the Changjiang Estuary and neighboring shelf were subjected to particle-size measurements, with the intent of understanding the implications for provenance, transport, and depositional dynamics. The results showed that Changjiang River-derived sediments, relict sands, and Yellow River-derived sediments were the primary sources controlling the magnetic properties of sediments in the study area. The three areas, however, exhibited different spatial distributions. Spatial variations of magnetic parameters, including magnetic susceptibility (χ), saturation isothermal remanent magnetization (SIRM), hard isothermal remanent magnetization (HIRM), and anhysteretic susceptibility (χARM), suggest that sediments from the Changjiang River are transported towards the south and southeast when they move out of the river mouth. According to bi-plots of SIRM versus χ and S-ratio (S–100) versus SIRM, the > 63 μm fraction is roughly bounded by the 30 m isobaths that separates the Changjiang River sediment from the relict sands on the shelf. The < 16 μm fraction is derived mainly from the modern fluvial sources of the Changjiang and Yellow Rivers; in particular, the Changjiang River-derived sediment dominates the inner estuary and the Yellow River-derived sediment dominates the northern coast of the shelf. The other areas of the shelf are characterized by mixed sources of the < 16 μm fraction, with a majority being Changjiang River-derived sediment. Spatial variations of particle size compositions and magnetic properties reflect the role of hydrodynamic sorting on particle size as well as mineral density; this results in differences in magnetic properties among the sedimentary units as well as the contribution of different sized fractions to the bulk SIRM values. Particle size separation could reduce the effect of particle size on bulk magnetic properties and lead to more precise provenance discrimination. Our results have great potential in the study of geomorphological changes and quantitative source identification in delta environments.
Flux footprint analysis is an important step in studying the carbon, water vapor, and heat flux exchange of land-atmosphere interactions based on the eddy covariance (EC) method. In this research, we used the flux source area model (FSAM) to investigate seasonal flux footprints with different wind directions and atmospheric conditions on the basis of half-hourly EC measurements throughout 2018. The results showed that: ① The flux footprint area changes with the seasons. The largest flux footprint area, ordered highest to lowest, was found in autumn, summer, spring, and winter under stable stratification; meanwhile, under unstable stratification, the flux footprint area did not change significantly between seasons. The daily variation in the footprint, moreover, was obvious and the footprint was found to be larger comparatively at nighttime than that observed during the daytime. ② The flux source area under non-prevailing wind conditions was larger than that under the prevailing wind condition. ③ The flux source area was much larger under stable stratification. The distance between the location of the maximum value of the flux footprint and the station was also found to be much larger under stable stratification.
Surface sediments were collected from five representative areas—the floodgate entrance, the north and south sides of the reclamation area, and the central and downstream sections—of Qingcaosha Reservoir; the pollution characteristics and potential ecological risk of seven heavy metals (Cu, Zn, Pb, Cr, Cd, As and Hg) in these sediments were subsequently investigated. Results showed that the heavy metal content in the surface sediments showed spatial variations: the content was relatively higher in the center of the reservoir and was low in the north and south sides of the reclamation area. Heavy metals in the surface sediments, in addition, were mainly in the residual fraction; the content of heavy metals in the exchangeable fraction was extremely low. A potential ecological risk assessment indicated that the comprehensive potential ecological risk index (ERI) of the investigated heavy metals ranged from 55 to 113. The maximum ERI value was observed around the floodgate of the reservoir entrance, and low ERI values were observed at the north and south sides of the reclamation area. The ERI was lower than the threshold for low ecological risk, indicating that heavy metals in the surface sediments of the Qingcaosha Reservoir have low potential ecological risk.
The biological filtering effect of reservoirs has become an area of focus for environmental science. We conducted an in situ survey, with different upstream retention times, of chlorophyll-a (Chl.a) and nutrients at the Zhexi, Zhelin, Hualiangting, and Yahekou reservoirs. We found that: ① In the vertical direction, Chl.a in each reservoir had the largest subsurface layer and generally decreased downward, resulting in upper nutrients assimilated by algae and an average vertical retention rate of DIN, DIP, and DSi of the reservoirs at 6.29%, 14.92%, and 8.60%, respectively. ② The concentration of Chl.a and the biomass of phytoplankton generally decreased from upstream to downstream, resulting in lots of nutrients assimilated by algae upstream, and the average horizontal retention rate of DIN, DIP, and DSi of the reservoirs at 26.53%, 39.89%, and 31.70%, respectively. ③ The total average retention rate of DIN, DIP, and DSi of the four reservoirs were 32.82%, 54.80%, and 40.30%, respectively. ④ The concentration of DIP decreased gradually with increases in the reservoir’s retention time; in fact, the concentration of DIP even decreased to 0.1 μmol/L, i.e. the growth of phytoplankton was fully limited by DIP.
The concentrations and relative ratios of alkaline earth metals, such as Sr, Ba, and Ca, in sediments are widely used to discriminate marine and terrestrial environments in paleoenvironmental research. However, geochemical elements occur mostly in mineral crystal lattices (namely, the residual phase after acid extraction), which is not linked to the physical, biological, or chemical environments of the deposition processes. Hence, only selective extraction of phases can be used to interpret changes in the sedimentary environment. In this study, we collected surficial sediments from the present-day saltmarsh-tidal flat, alluvial plain, and tidal river (Yaojiang River) in Ningbo Plain and used a plasma spectrometer to measure the concentrations of Sr, Ba, and Ca in: the leachates extracted by diluted acetic acid (HAc) and diluted hydrochloric acid (HCl), the residues after acid extraction, and the bulk samples. The results showed that alkaline earth metals in the HAc-leachates were most sensitive to changes in the sedimentary environment, followed by the HCl-leachates. No variation in Sr/Ba (molar ratio) could be distinguished in the bulk samples of surficial sediments collected from different sedimentary settings. Furthermore, consistent results were obtained by using different sample amounts and measuring instruments when applying the HAc method. Significant variations in alkaline earth metals in the HAc-leachates were observed for the surficial sediments in this study. Ca and Sr showed the highest concentrations in the saltmarsh-tidal flat sediments and the lowest concentrations in the alluvial sediments; Ba concentration showed the opposite trend. We thus suggest that end-member analyses of the alkaline earth metals in HAc leachates can be used to effectively identify transgression/regression recorded in sedimentary stratigraphy in the coastal zone.
Laoyehai is a lagoon located on the east coast of Hainan and is impacted heavily by human activities (especially those related to aquaculture). Laoyehai is characterized by its eutrophic and hypoxic waters. During previous dry and flood seasons (specifically, April 2010 and August 2011), when hypoxia occurred, field work was conducted to observe the dissolved oxygen (DO) and to collect organic matter. Hypoxia was significant in the spring season with surface DO as low as 50%, while the bottom hypoxic water prevailed in both seasons. In the spring season, the C/N ratio of particulate organic matter was higher than that observed in the summer season (C/N in the spring: 9.7, C/N in the summer: 7.7). Organic matter composition indicated by amino acids showed that there was strong in situ production in the spring relative to that in the summer. Lower C/N values and higher carbon and nitrogen yields of amino acids (AA C yield, AA N yield) in the summer showed active in situ production, suggesting that organic matter was mainly derived from phytoplankton. This also explains the sufficient surface DO in the summer. The degradation of particulate organic matter increased with the decrease of dissolved oxygen, indicating that the particulate organic matter and its degradation were the key driving factors for oxygen consumption in the lagoon. Meanwhile, we found that the relationship between dissolved organic matter components and DO was not significant.
Urban greenspace is an important part of the urban green system and urban landscape, with important ecological, social, psychological, and economic functions. The evolutionary trajectories and change patterns of urban greenspaces are of great significance to the sustainable development of urban green space systems and the optimization of the urban ecological network. There is ongoing emphasis on urban greenspace research; most previous research studies on greenspace changes have used landscape indices and spatial analysis methods, which struggle to accurately reflect the change process, change types, and spatial distribution patterns of greenspace. In our paper, seven types of greenspace evolution were defined, including continuous, expansion, contraction, dissipation, creation, merging, and splitting. Then, an evolution graph was constructed by defining greenspace patches as nodes and greenspace evolution relations as edges. Based on the greenspace evolution graph, the greenspace evolution process and its corresponding evolutionary trajectory were further extracted and visualized. Taking the Shanghai city center as a case study area, the spatial distribution pattern and change process of the urban greenspace for 2008, 2012, and 2016 were extracted. Results indicated that the most dominant greenspace evolution types were creation and dissipation. The newly added urban greenspace patches were more evenly distributed compared with those patches involved with an evolution type of dissipation. Small patches were more likely to be located in the urban center, while large patches tended to be concentrated in rural areas. The location of greenspace patches that disappeared were mostly concentrated in non-central areas, particularly in the Pudong New Area. Compared with the urban greenspace changes between 2008 and 2012, locations where new greenspace appeared between 2012 and 2016 were more evenly distributed, while locations where greenspace disappeared were more concentrated.
Using a combination of 0.25 m resolution aerial remote sensing data and topographic maps, the land use data for the Shanghai Huangpu River Water Source Protection Area in 2000, 2005, 2010, and 2015 were evaluated by means of manual visual interpretation. With the growth of industrial land from 2000 to 2015, there has been a relative decline in the proportion of agricultural land and water areas and a relative increase in the proportion of urban land areas. In the past 15 years, the areas used for farming and cultivating livestock and poultry have decreased by 44.17% and 71.65%, respectively. The area of water reduction has decreased by 6.44%. The area of green land forests, in contrast, has increased by 645.94%. The area of urban land has increased by 53.53%. All types of urban land use have increased, with the area used for industrial storage increasing the most at 21.77%. From the perspective of land transfer, the area of cultivated land transferred outward was the largest in the past 15 years, accounting for 22,839.96 hectares, and the transfer-outward rate of livestock and poultry farming land was the highest at 91.23%. The area of green land forests transferred inward was the largest at 16190.32 hectares; the transfer of industrial storage land inward was the second largest at 7979.12 hectares. Based on an analysis of development in the region, population changes, policy impacts, and other factors, our results indicate that urbanization and industrialization drove the increases in urban land areas; moreover, environmental policies affected green land areas as well as livestock and poultry farming land areas, market regulations affected aquaculture land areas, and environmental policies and urbanization affected water source protection areas.
With the ongoing urbanization process in Hangzhou, we investigated the species composition and structure of ruderal communities across eight urban habitat types. Habitat factors such as light intensity, soil pH, soil electrical conductivity, soil compaction, soil total nitrogen, soil total phosphorus, soil organic matter, and interference types were measured; we subsequently analyzed the relationship between species composition and habitat factors of the ruderal communities. The results indicated that forest gap and lawn were the most common habitat types, and these community types covered 20.1% and 16.3%, respectively, of the total 1665 sampling plots surveyed. In all seven habitats except tree pool, moreover, dwarf-growth annual ruderals were the dominant species within the community. There were 30 ruderal species distributed across eight habitats. Environmental factors varied across the different habitats. The light intensity was the lowest in the forest gap, the soil conductivity value was the highest in the shrub-grassland gap, and the light intensity and soil compactness were the highest in soil abandoned land.
In this study, we investigated the plant species composition of three types of abandoned farmland and compared with cultivated farmland in the Chongqing suburban area. We analyzed dynamic changes in species composition and community type as well as trends in plant diversity. The results showed that a total of 99 species, 90 genera, and 39 families were recorded in the spring and autumn. At the second level of the TWINSPAN classification, the cultivated farmland, early abandoned farmland, and late abandoned farmland could all be distinguished. As the number of years since abandonment of the farmland increased, the dominant life form of the plant community gradually transitioned from annual to perennial, and woody plants began to become the dominant species. Plant diversity gradually increased from the early to middle stage of abandonment, but declined during the later stage.
In this study, we measured the branch xylem structure of 85 woody plant species at the Shanghai Chenshan Botanical Garden to compare vessel characteristics among different life forms and check their phylogenetic signals. The trade-off between vessel density and vessel size was subsequently compared among different life forms. The results showed that: ① The vessel diameter ((28.55 ± 8.84) μm) and vessel ratio (8.7% ± 2.89%) of evergreen woody plants were significantly smaller than the vessel diameter ((35.81 ± 13.92) μm) and vessel ratio (12.7% ± 4.82%) of deciduous woody plants; meanwhile, there was no significant difference observed in the vessel density between evergreen plants ((149.3 ± 75.62) N/mm2) and deciduous plants ((164.5 ± 154.28) N/mm2). The vessel diameter of trees ((35.86 ± 13.5) μm) was significantly larger than that of shrubs ((26.24 ± 8.84) μm), but there was no significant difference observed in the vessel ratio and vessel density between trees (12.09% ± 5.01%; (151.9 ± 142.73) N/mm2) and shrubs (10.59% ± 2.99%; (208.7 ± 126.37) N/mm2). ② There were significant phylogenetic signals observed in vessel diameter and vessel density, and the signal of vessel density was larger than that of vessel diameter. There was, however, no obvious phylogenetic signal in the vessel ratio. ③ The standardized major axis test indicated that the trade-off between vessel density and vessel size existed in all life forms, with a common slope coefficient of –0.89 and a 95% confidence interval (–0.98 ~ –0.79). However, the intercept of evergreen trees was significantly smaller than that of deciduous trees, suggesting that deciduous trees have a larger vessel diameter than evergreen trees for a given vessel density.
In this study, we evaluated the variation patterns of air anions in nine plant communities with different structures in Zhongshan Park of the central city of Shanghai; the air anion concentration was monitored continuously over the course of a year. In addition, we analyzed the influence of different factors—community structure, canopy density, and the level of surrounding water—on air anion concentration. The results showed that the air anion concentration within different community types was mostly between 200 cm3 and 700 cm3, and the daily variation showed a single peak. Air anion concentration remained at a high level but fluctuated significantly from July to October. The relationship between community structure and air anion concentration was roughly as follows: herbage > arbor with shrubs ≈ arbor with herbage > arbor with shrubs and herbage; in general, the more complex the community structure, the less the air anion variability. There was a negative correlation between the mean variation of the air anion concentration and the canopy density, implying that higher canopy density values were associated with lower mean variation of the air anion concentration throughout the community. This negative correlation became more significant in the daytime, between 7:00 to 19:00, when photosynthesis was ongoing. In addition, the impact of static water on the anion concentration was not found to be significant. The conclusion of this paper can provide basic data and a scientific basis for the construction of healthy plant communities in urban parks.
This study investigated the distribution characteristics and influencing factors of crabs and crab burrows in Fengxian coastal wetland to reveal the main influencing factors in crabs’ and crab burrows’ distribution and deepen the understanding of crabs’ living habits. The results showed that: ① The abundance of Helice tientsinesis in the high-marsh Phragmites australis habitat is higher than that in the middle-marsh Phragmites australis -Spartina alterniflora mixed habitat and low-marsh Spartina alterniflora habitat (p < 0.01). However, there is no significant difference in the abundance of Sesarma plicate between habitats (p > 0.05). ② The density of crab burrows in the high-marsh Phragmites habitat is significantly higher than that in the middle-marsh Phragmites-Spartina mixed habitat and the low-marsh Spartina habitat (p < 0.05), while the average opening diameter of crab burrows is significantly lower than that in the middle-marsh Phragmites -Spartina mixed habitat and the low-marsh Spartina habitat (p < 0.05). ③ There is no significant linear relationship between crab abundance and the density of crab burrows( p > 0.05), while there is a significant positive correlation between the density of crab burrows and the abundance of Helice tientsinesis ( p < 0.01). ④ Crab abundance is negatively correlated with plant underground biomass ( p < 0.01). ⑤ There is a negative correlation between the density of crab burrows and vegetation coverage and plant density. The relative elevation, water content, conductivity, total organic carbon content, and total nitrogen content are positively correlated with the density of crab burrows. Among these factors, the relative elevation is the habitat factor with the highest correlation with the density of crab burrows.
Let ${\mathfrak{g}}$ be the Witt algebra over an algebraically closed field of characteristic $p>3$ , and $r\in\mathbb{Z}_{\geqslant 2}$ . The commuting variety ${{\cal{C}}_{r}}\left( \mathfrak{g} \right)$ of $r$ -tuples over ${\mathfrak{g}}$ is defined as the collection of all $r$ -tuples of pairwise commuting elements in ${\mathfrak{g}}$ . In contrast with Ngo’s work in 2014, for the case of classical Lie algebras, we show that the variety ${{\cal{C}}_{r}}\left( \mathfrak{g} \right)$ is reducible, and there are a total of $\frac{p-1}{2}$ irreducible components. Moreover, the variety $ {{\cal{C}}_{r}}\left( \mathfrak{g} \right) $ is not equidimensional. All irreducible components and their dimensions are precisely determined. In particular, the variety ${{\cal{C}}_{r}}\left( \mathfrak{g} \right)$ is neither normal nor Cohen-Macaulay. These results are different from those for the case of classical Lie algebra, $\mathfrak{sl}_2$ .
For the infinite dimensional simple 3-Lie algebra $A_{\omega}^{\delta}$ over a field $\mathbb F$ of characteristic zero, we construct two infinite dimensional intermediate series modules $(V, \rho_{\lambda, 0})=T_{\lambda, 0}$ and $(V, \rho_{\lambda, 1})=T_{\lambda, 1}$ of $A_{\omega}^{\delta}$ as well as a class of infinite dimensional modules $(V, \psi_{\lambda,\mu})$ of ad $(A_{\omega}^{\delta})$ , where $\lambda, \mu\in \mathbb F$ . The relation between 3-Lie algebra $A_{\omega}^{\delta}$ -modules and induced modules of ad $(A_{\omega}^{\delta})$ are discussed. It is shown that only two of infinite dimensional modules, namely $(V, \psi_{\lambda, 1})$ and $(V, \psi_{\lambda, 0})$ , are induced modules.
Let $ G $ be a connected reductive algebraic group over an algebraically closed field $ k $ of prime characteristic $ p $ , and let $ {\frak {g}} = {\rm{Lie}}(G) $ , $U_{\chi}({\frak {g}}) $ be the reduced enveloping algebra. In this paper, when $ p $ -character $ \chi $ has the standard Levi form, we prove that a $ U_{\chi}({\frak {g}}) $ -module $ Q $ is a tilting module if and only if it is projective.
中国综合性科技类核心期刊(北大核心)
