In this paper, a stationary problem for the reaction-diffusion equation with a discontinuous right-hand side is considered. Based on ideas from contrast structure theory, the asymptotic representations for eigenvalues and eigenfunctions are constructed by solving a Sturm-Liouville problem and an estimation of the remainder is obtained. Moreover, a sufficient condition which guarantees the stability of the solution to this task is established.
This paper explores the neighbor sum distinguishing list total coloring of graphs $G$ with maximum degree $\varDelta \left( G \right) \geqslant 8$ and maximum average degree ${\rm{mad}}\left( G \right) < \frac{{14}}{3}$ . By applications of the Combinatorial Nullstellensatz and discharge method, moreover, it is shown that the neighbor sum distinguishing total choice number of the graphs does not exceed $\varDelta \left( G \right) + 3$ .
Let $G = (V, E)$ be a simple graph. For any vertex set $S$ of V, if $G - S$ is acyclic, then $S$ is a decycling set of G; the minimum size of a decyling set is called the decycling number of G, denoted by $\phi \left( G \right)$ . In this paper, we consider the decycling problem of join graphs and obtain the exact value for the decycling number of some types of join graphs. Let ${G_m}$ and ${G_n}$ be simple connected graphs of the order m and n, respectively. Then the decycling number of the join graph ${G_m} \vee {G_n}$ satisfies: $\min \{ m,n\} \leqslant \phi ({G_m} \vee {G_n}) \leqslant $ $ \min \{ m + \phi ({G_n}),n + \phi ({G_m})\}$ . The results presented in this paper confirm that the upper bound for the above inequality is tight. In particular, if ${G_m}$ and ${G_n}$ are trees, then we can obtain the exact value for the decycling number of ${G_m} \vee {G_n}$ .
Using resorcinol-formaldehyde resin as the carbon source, melamine as the nitrogen source, and NaOH as the etchant, a nitrogen-doped carbon-coated silicon (Si@void@N-C) anode material with a yolk-shell structure was synthesized. The samples were characterized and tested by XRD, SEM and X-ray photoelectron spectroscopy, TEM, and electrochemical tests; the results confirmed that a Si@void@NC composite anode material with a yolk-shell structure was successfully synthesized. The material was found to have excellent electrochemical performance. The initial capacity reached 1282.3 mA/g after charging and discharging at a current density of 0.1 A/g. After 100 cycles, its specific capacity was as high as 994.2 mAh/g with a capacity retention of 77.5%, demonstrating good cycle performance. The nitrogen-doped carbon shell of the Si@void@N-C material helps with the electrical conductivity of the composite material. Meanwhile, the yolk-shell structure effectively alleviates the volume effect of silicon; this feature is beneficial to the formation of a stable SEI film and improves the cycle stability of the battery.
In this study, we used negative ion photoelectron spectroscopy (NIPES) combined with quantum chemical calculation to explore the electronic structures, micro-solvation effect, and stabilization mechanism of two compounds, SO3– and HSO3–, that are readily abundant in the atmosphere. Vertical detachment energies of (3.31 ± 0.02) and (3.91 ± 0.02) eV and adiabatic detachment energies of (3.02 ± 0.05) and (3.56 ± 0.05) eV were measured for SO3– and HSO3–, respectively. These results are reproduceable when using a nuclear ensemble approach and Dyson orbitals in the calculation. The typical density of states method, however, cannot demonstrate the nuclear vibration effect, ionization probability, and orbital relaxation effect during the ionization process. We studied the micro-solvation effect of HSO3–·(H2O)n (n = 0 ~ 5) and found that system stability was enhanced by an increase in the surrounding water molecules, whereby electrostatic interaction played a dominant role and the induction effect made an increasingly important contribution. We believe this work will help improve the modeling of atmospheric sulfate aerosols and provide a scientific basis for the effective control of haze formation.
Ag nanoparticles were first prepared using a seed-based thermal synthetic procedure. The monometallic particles were then transformed into bimetallic particles via a galvanic replacement reaction. A transmission electron microscope (TEM), scanning transmission electron microscope (STEM), and absorption spectrum were subsequently used for characterization. By controlling the amount of seed added, the ultrasonic exposure, and the centrifugal time, we can effectively tune the size of the particles and the localized surface plasmon resonance peak positions. The TDBC film can be wrapped on the surface of the metallic nanostructures by a ligand exchange reaction to achieve strong coupling between surface plasmon and molecular excitons.
Porous silicon/hard carbon composite (Si@CTS) was successfully fabricated using liquidphase encapsulation and a low-temperature pyrolysis process, in which silicon particles from cutting waste in the manufacturing of crystalline silicon solar cells was used as a raw material and chitosan as carbon source. In this paper, the electrochemical performance of Si@CTS and a mixture of Si@CTS and graphite (Si@CTS/G) as anode materials of a lithium-ion battery was studied. The Si@CTS electrode showed a high discharge specific capacity of 1672.8 mAh/g and a high initial coulombic efficiency of 84.45%. After 100 cycles, the Si@CTS retained a reversible capacity of 626.4 mAh/g. The discharge specific capacity of the Si@CTS/G composite was 698.1 mAh/g; hence, the discharge specific capacity of the Si@CTS/G composite was higher than that of Si@CTS and offered better stability. The findings are critical for mass manufacture and deployment of silicon/carbon anodes with high capacity and stability in lithium-ion batteries.
To better understand the diversity of bryophytes in East China, bryophytes were systematically investigated and collected in the Huangshan - Tianmu Mountain range and Xianxia - Wuyi Mountain range in the region. In the course of field investigation, eighteen new records of liverwort species were found in Zhejiang Province, belonging to 10 families and 13 genera, respectively. Notably, Hattoria is a new genus record for Zhejiang Province. In this paper, the habitats, geographical distributions, and main identifying features of these new records are provided. Moreover, illustrations of rare and endemic liverwort species in China are presented. These new findings further enrich the bryophyte flora of Zhejiang Province and provide new basic information about the flora of the province.
Two epiphyllous species, namely Cheilolejeunea chenii and C. obtusilobula, were newly recorded in Zhejiang Province. The specimens were collected from Gaoshanwan Village, Yushang Township, Qingyuan County, Zhejiang Province. It is worth noting that C. chenii has a very narrow distribution range in China and is a particularly rare species that should be protected as soon as possible. In this paper, the morphological characteristics, distribution, and habitats of the two species are briefly described and discussed. Given that the two species are not currently within the protection scope of the nature reserve, we also propose new ideas for in-situ conservation of epiphyllous liverworts.
In this study, the Shengli Coal Mine—a representative coal mine in the semi-arid grassland of Inner Mongolia—and the adjacent Beizi Temple, Botanical Garden, and Nanshan Reservoir were selected as the study areas. By studying the correlation between the characteristics of the bryophyte community and the physical and chemical properties of the soil, the influence of soil on the distribution of bryophytes was analyzed during the reclamation process. The results showed that there were 4 families, 6 genera, and 7 species of bryophytes in the Shengli mining area. The total coverage of bryophytes in each habitat could be ranked according to the following order: Beizi Temple > Botanical Garden > south dump of the mining area > Nanshan Reservoir > plantation in the mining area > north dump of the mining area. An analysis of the diversity index, moreover, showed that the Shannon-Wiener index at the south dump was the highest, indicating that the species complexity of the moss community at the south dump was relatively high. An analysis of the correlation between the coverage of the bryophyte community and the physical and chemical properties of the soil showed that the soil pH value, silt content, sand content, and gravel content all had significant effects on the distribution of bryophytes. Multivariate analysis of the bryophyte community structure and soil physical and chemical properties showed that the differences in bryophyte community structure between different study areas was related to the cumulative influence of environmental factors.
Spatial accessibility is an important reference index to determine whether the layout of various types of facilities is reasonable. Scientific evaluation of the spatial accessibility of service facilities is an important basis for judging regional service differences and optimizing the spatial allocation of resources. Using the basic potential model as a basis for our analysis, we introduced a demand-side threshold, designed a three-level service radius based on the scale requirements for elderly care institutions, and implemented regional priority matching principles. Taking Fengxian District of Shanghai as an example, we analyzed the spatial accessibility of elderly care institutions in the region based on the actual driving time between supply and demand points and ArcGIS spatial analysis technology. The results show that the spatial accessibility of nursing homes in Fengxian District is uneven, and the spatial accessibility in some areas of Nanqiao Town, Zhuanghang Town, and Jinhui Town is significantly higher. A trend of gradually decreasing accessibility can be observed from the city center to the periphery. In some towns and villages of the central region, there are dense elderly care institutions and relatively concentrated elderly resources. The improved potential model considers the influence of factors such as the service capacity of elderly care institutions and the needs of the elderly, which can evaluate the spatial accessibility of institutions more effectively. The research results provide a reference point and offer suggestions for scientific planning and decision-making of elderly care institutions.
In this study, we used the geographic weighted regression (GWR) method to explore the impact of compulsory education quality on housing prices. For the purpose of this analysis, we considered Wuhan in Hubei Province as the study area and collected school and housing price data from websites such as Sofang.com, Jzb.com, Whjyj.gov.cn, etc. We also used the inverse distance weighted (IDW) method for visual analysis. The results showed that: ① The quality of compulsory education has a positive impact on housing prices, and provincial demonstration schools, in particular, create a relatively high price premium on housing prices; ② The capitalization effect of the quality of junior high school is higher than that of elementary school; ③ The quality of primary and junior high school education in new urban areas has the greatest impact on housing prices. The quality of the combination of primary and junior high schools in the central and northern areas of Jiangan District had a significant impact on housing prices, while the quality of schools in the Wuchang, Qiaokou, and Jianghan districts had relatively less impact on housing prices as a whole.
A supply network is an important carrier for the spatial flow of industrial elements, and its structure and evolution can reflect the spatial clustering characteristics of related industries. In this study, we used thermal analysis, network analysis, and other methods to understand and analyze China’s automobile parts supply network at the national and regional levels in 2009, 2014, and 2019; in addition, we explored the evolution of spatiotemporal pattern characteristics of the network’s structure. The study found that: ① Automobile parts companies are primarily distributed across the eastern part of China, followed by the central and western regions. The companies form six clusters centered on the Yangtze River Delta region, Beijing-Tianjin-Hebei region, Northeast region, Pearl River Delta region, Central China region, and Chengdu-Chongqing region. ② The density of the network continues to increase. In 2019, the network density reached 0.5017, showing strong connectivity. Changchun had the highest extroversion in 2009, and Wuhan had the highest in 2014 and 2019. Shanghai has always maintained the highest introversion and continues to increase. More than 50% of the top ten cities are located in the Yangtze River Delta, and the remaining cities are located in the Beijing-Tianjin-Hebei, Northeast, Chengdu-Chongqing, and Central China regions. In addition, the automobile parts supply network has obvious hierarchical characteristics. The first-level links included Shanghai-Changchun in 2009, Shanghai-Changchun and Shiyan-Wuhan in 2014, and Shanghai-Changchun and Shanghai-Wuhan in 2019. ③ If we analyze the spatiotemporal characteristics of the supply network of China’s six major clusters with OEMs and automobile parts factories as nodes, we find that the Northeast region forms a vehicle-parts concentric inward supply network structure, the Yangtze River Delta and Chengdu-Chongqing regions form vehicle-parts concentric outbound supply network structures, the Beijing-Tianjin-Hebei and Pearl River Delta regions form vehicle-parts eccentric outbound supply network structures, and Central China forms a vehicle-parts eccentric inward supply network structure.
Three-dimensional vegetation volume is a comprehensive index that can be used to represent the ecological benefits of urban vegetation. However, the challenge of how to accurately and quickly carry out three-dimensional vegetation volume monitoring in highly heterogeneous urban habitats is an urgent problem that requires attention. In this paper, we used Shanghai Botanical Garden as a case study. We acquired low-altitude, high-resolution images of Shanghai Botanical Garden through a UAV aerial photography system; after extracting the data, we calculated the surface elevation and canopy height models, estimated the three-dimensional vegetation volume, and analyzed the spatial distribution pattern. The results showed that: ① The overall plane and elevation accuracy of UAV images was better than 0.1 m, and the average error and standard deviation of the canopy height model accuracy was 0.27 m and 0.58 m, respectively. ② The vegetation volume of Shanghai Botanical Garden was distributed in a pattern from northeast low to southwest high, with a total vegetation volume of 3538944.50 m3. The average green density of the botanical garden was 6.51 m3/m2. The three gardens with the highest vegetation volume were: Peony Garden (289491.00 m3), Pinetum Garden (338322.10 m3), and the Green Space Attached to The Greenhouse (360587.50 m3). The three gardens with the lowest vegetation volume were: Recreational Green Space (24761.50 m3), Monocotyledon Botanical Garden (31621.40 m3), and Rose Garden (74607.30 m3). The three gardens with the highest vegetation volume density were: Tropical Orchid Room (9.23 m3/m2), Fern Garden (11.30 m3/m2), and Magnolia and Camphor Avenue (13.11 m3/m2). The three gardens with the lowest vegetation volume density were Recreational Green Space (1.57 m3/m2), Scientific Research Center Green Space (1.81 m3/m2), and Rose Garden (2.58 m3/m2). ③ The vegetation volume of each specialized garden was significantly related to the distribution area of the arbor community, the height of the constructive species, and the product thereof. The vegetation volume density of each specialized garden was significantly related to the proportion of the area of the arbor community in the specialized garden, the height of the constructive species, and the product thereof. This research can serve as a methodology reference for the quick estimation of urban vegetation volume, and provide basic data vegetation volume estimates and spatial pattern optimization for Shanghai Botanical Garden.
Estuarine cities are heavily influenced by anthropogenic activities. In turn, their water bodies often face serious eutrophication and pollution problems, thereby exerting significant pressure on the urban production and living environment. This study focuses on the water bodies in the city of Shanghai, an important estuarine megacity in China. Using the Sentinel-2 satellite and in situ measured water spectrum data, we built an inversion model for rapid identification of two critical parameters for eutrophication assessment, namely chlorophyll-a concentration and turbidity. We subsequently analyzed the spatial and temporal variability of these two parameters using time-series satellite data. Our results showed that the correlation coefficient (R2) of turbidity and chlorophyll-a concentration inversion based on remote sensing was 0.95 and 0.87, respectively; the root mean square error (RMSE) was 4.33 μg/L and 8.93 NTU, respectively. Time-series analysis from 2019 showed that both chlorophyll-a concentration and turbidity in different urban water bodies were highest in the summer and lowest in the winter in Shanghai. Specifically, chlorophyll-a concentrations across water bodies decreased in the following sequence: aqua-culture/planting ponds, permanent freshwater lakes, reservoir ponds, permanent rivers, and canals/transportation rivers. In the case of turbidity, the water bodies ordered from highest to the lowest followed the sequence: aqua-culture/planting ponds, permanent rivers, canals/water delivery rivers, permanent freshwater lakes, and reservoir ponds. Time series analysis of chlorophyll-a concentrations and turbidity from 2019 showed that in water bodies with less human disturbance, the correlation between chlorophyll-a concentration and turbidity was stronger than those that were heavily influenced by anthropogenic activities. The use of Sentinel-2 satellite images to retrieve the chlorophyll-a concentration and turbidity in water bodies can generally provide information on the eutrophication status of water bodies in Shanghai; the data, moreover, can serve as a reference for aquatic environmental monitoring of inland water bodies in other cities.
In this paper, the presence of the Tianzhuang fault was confirmed using a combination of petroleum geophysical exploration, geology, remote sensing, and other data. The study concluded that the fault originated from the west of Tiancun, Jinyuan District, Taiyuan City with a total length of about 35 km from Houjiazhai to Tianzhuang. The fault trends from west to east with the pattern EW-NEE-NE, and tends to the SE as a high-angle normal fault. The Tianzhuang fault is a concealed fault associated with the piedmont fault of the East and West Mountains of the Taiyuan Basin. Through the joint drilling exploration across the Tianzhuang fault, near the Ma Lianying Road, there were three distinct sedimentary cycles of river lake swamp facies found in the strata: in the 80 ~ 60 m section, the sedimentary environment tends to frequent gradually, and the sedimentary facies is lake→swamp; in the 60 ~ 30 m section, the sedimentary environment tends to be stable and frequent twice, and the sedimentary facies is river→swamp→river→lake→swamp→river; in the 30 ~ 0 m section, the sedimentary environment tends to be stable gradually, and the sedimentary facies is swamp→lake→swamp. The Quaternary strata in the site gradually thickens from north to south in the horizontal direction, and the coarse-grained deposits become thinner. There is a magnitude change in the borehole, ZK3←→ZK4←→ZK7, and the first layer is thick in the vertical direction. Particle deposition occurs at 20 ~ 30 m, and the floating is not large; the sedimentation cycle number is roughly “M” from deep to shallow, and the sedimentation number reaches a peak at 30 ~ 40 m and 50 ~ 60 m. From the perspective of detecting the strata, all the boreholes in the silty layer of the Holocene boundary were exposed, and the depth was relatively small. It is believed that the sampling rate of the bored sand layer is not the same and hence it is expected that the fault of the Tianzhuang fault is not broken. There are three primary sets of fault-breaking strata in the Tianzhuang fault, all of which are from the Late Pleistocene strata; these did not penetrate the Upper Pleistocene, and thus the target fault was determined to be the late Pleistocene active fault. From top to bottom, the offset of faulted strata increases gradually: 0.4 m, 3.5 m, and 7.2 m, in turn. There are two coseismic displacements of about 3 meters in the exposed depth of the borehole, which can be used to judge the occurrence of two main dislocation events in the identified layer. This provides reliable geological evidence for analyzing the seismic risk of the Tianzhuang fault.
Constructing 3-Pre-Lie algebras has always been a difficult problem; until now, there have been very few examples of 3-Pre-Lie algebras. In this paper, we use homogenous Rota-Baxter operators of weight zero on the infinite dimensional 3-Lie algebra $A_{\omega}=\langle L_m | m\in {\mathbb{Z}}\rangle$ to construct 3-Pre-Lie algebras $B_k,~0\leqslant k\leqslant 4$ , and we subsequently discuss the structure. It is shown that $B_2$ and $B_4$ are non-isomorphic simple 3-Pre-Lie algebras, $B_1$ is an indecomposable 3-Pre-Lie algebra with infinitely many one-dimensional ideals, and $B_3$ is an indecomposable 3-Pre-Lie algebra with finitely many ideals.
The discounted Hamilton-Jacobi equation (H-J equation) is a special form of the contact Hamilton-Jacobi equation; hence, study of the discounted H-J equation is important. In this article, we first study an expression of the viscosity solution $u_{\lambda}(x,t)$ for the discounted H-J equation in non-compact space. Then, we explore the convergence of the viscosity solution $u_{\lambda}(x,t)$ for a specific discounted H-J equation with $\lambda >0$ in non-compact space for the initial value in different cases.
Let $G$ be a simple graph. A total coloring $f$ of $G$ is called an IE-total coloring if $f(u)\neq f(v)$ for any two adjacent vertices $u$ and $v$ , where $V(G)$ denotes the set of vertices of $G$ . For an IE-total coloring $f$ of $G$ , the set of colors $C(x)$ (non-multiple sets) of vertex $x$ under $f$ of $G$ is the set of colors of vertex $x$ and of the edges incident with $x$ . If any two distinct vertices of $G$ have distinct color sets, then $f$ is called a vertex-distinguishing IE-total coloring of $G$ . We explore the vertex distinguishing IE-total coloring of complete tripartite graphs $K_{5,5,p}$ $(p \geqslant 2\;028)$ through the use of multiple methods, including distributing the color sets in advance, constructing the colorings, and contradiction. The vertex-distinguishing IE-total chromatic number of $K_{5,5,p}$ $(p \geqslant 2\;028)$ is determined.
By generalizing and using the normal form theory and center manifold theorem of delay differential equations, a class of high-codimension bifurcation problems of predator-prey systems with delay and Allee effect are investigated. Firstly, sufficient conditions for the existence of the positive equilibrium and the codimension 3 bifurcation at this positive equilibrium are established. Subsequently, the normal form of the system at the positive equilibrium is deduced. Finally, from the topological equivalence of the normal form and the original system, the bifurcation phenomenon of the original system at the positive equilibrium is analyzed.
Homotopy analysis method is an effective method for constructing approximate analytical solutions to strongly nonlinear problems. The technique has been widely applied to solve important problems in scientific research and engineering technology. Compared with other existing techniques, this method leverages auxiliary parameters and functions to adjust and control the convergence region and convergence speed of approximate analytical solutions. In this paper, we present a parameter selection algorithm based on machine learning techniques to determine the optimal values of convergence control parameters for homotopy analysis solutions. This marks the first time that homotopy analysis method and machine learning techniques have been combined to obtain approximate analytical method with better convergence for strongly nonlinear mathematical and physical equations. By applying the method to several examples, we show that the convergence of solutions using the proposed method is better than those obtained from existing homotopy analysis methods. In addition, our algorithm is both more universal and flexible.
Using double-layer networks, we constructed a coupled propagation model (Noisy Voter - Susceptible-Infected-Recovery) with different time evolution scales. This coupled spreading process can be characterized by numerical analysis method of microscopic Markov chain theory. We verified the accuracy of the proposed numerical analysis method using a large number of Monte Carlo simulation experiments. We found a crossover phenomenon of the phase transition type in the coupled model. Specifically, when the noise in the opinion formation process is relatively small, the information propagation scale and the proportion of positive opinions change discontinuously with the information transmission rate. At the same time, the hysteresis loop and bistability phenomenon appear, in which the phenomenon of global consensus can be observed. When the noise is large, the order parameters of these two dynamic processes vary continuously with the transmission rate.
As a result of ongoing advances in artificial intelligence technology, the potential for learning analysis in teaching evaluation and educational data mining is gradually being recognized. In classrooms, artificial intelligence technology can help to enable automated student behavior analysis, so that teachers can effectively and intuitively grasp students’ learning behavior engagement; the technology, moreover, can provide data to support subsequent improvements in learning design and implementation of teaching interventions. The main scope of the research is as follows: Construct a classroom student behavior dataset that provides a basis for subsequent research; Propose a behavior detection method and a set of feasible, high-precision behavior recognition models. Based on the global features of the human posture extracted from the Openpose algorithm and the local features of the interactive objects extracted by the YOLO v3 algorithm, student behavior can be identified and analyzed to help improve recognition accuracy; Improve the model structure, compress and optimize the model, and reduce the consumption of computing power and time. Four behaviors closely related to the state of learning engagement: listening, turning sideways, bowing, and raising hands are recognized. The accuracy of the detection and recognition method on the verification set achieves 95.45%. The recognition speed and accuracy of common behaviors, such as playing with mobile phones and writing, are greatly improved compared to the original model.
In this paper, we propose the construction of a bi-directional fully connected structure for better extraction of context information. We also propose the construction of a bi-directional attention structure for compressing matrices containing rich text features into a vector. The bi-directional fully connected structure and the gated structure are then combined. This research demonstrates that the proposed combined structure has a net positive effect on text classification accuracy. Finally, by combining these three structures and a bi-direction long short-term memory, we propose a new text classification model. Using this model, we obtained competitive results on seven commonly used text classification datasets and achieved state-of-the-art results on five of them. Experiments showed that the combination of these structures can significantly reduce classification errors.
By combining information extraction technology, data matching technology, and one-time manual processing, mathematical subjective questions can be transformed into tree-shaped multiple-choice questions. In this study, an automatic correction system for college mathematics assignments was developed by combining modern information and network technology; the system was subsequently trialed in the teaching of entry-level college mathematics courses. The proposed system solves bottlenecks related to automatic grading of subjective mathematics questions, including multiple-choice questions, fill-in-the-blank questions, judgment questions, quiz questions, calculation questions, and proof questions. The system can correct routine exercises for mathematics courses of primary schools, middle schools, and universities so as to achieve more efficient completion. The idea, furthermore, can be applied to various aspects of mathematics teaching, such as previews before class, classroom exercises, reviews after class, preparations for examinations, online examinations, etc. The electronic data collected in the process of automatic correction can subsequently be used for data analysis, teaching guidance, teaching research, and the construction of educational informatization.
In this paper, the atomic structure, stability, electronic structure, and magnetism of two-dimensional transition metal phosphide MnTn+1 (M = V, Cr; T = P, As, and Sb) slices were systematically studied using the first-principles calculations based on density functional theory. By calculating the formation energy and phonon spectrum, it was determined that only V4As5, Cr2P3, Cr3P4, Cr4P5, Cr2As3, and Cr3As4 are stable two-dimensional magnetic multilayers. The results show that these stable two-dimensional magnetic materials are antiferromagnetic metals. In addition, the electronic structure and the magnetic coupling mechanism of these materials were further analyzed.
This paper explores a method for generating optically mediated entanglement between Bose-Einstein condensates (BECs). Using a quantum nondemolition Hamiltonian with BECs placed in a Mach-Zehnder configuration, it is shown that entangled states can be induced by performing measurement on light. In particular, the effects of the entangled state in the presence of decoherence were analyzed. The behavior of the entangled state was found to be sensitive to the atom-light interaction time. The entangled state is relatively stable when the dimensionless interaction time $ \tau \lesssim \frac{1}{\sqrt{N}} $ and relatively fragile when the time is greater.
In this paper, the motion trajectory of micro-nanoparticles is calculated based on the Euler-Richardson algorithm after the optical force exerted on the particles is determined using Mie scattering theory. The Euler-Richardson algorithm has better calculation accuracy and faster convergence speed than the Euler algorithm and the Euler-Kromer algorithm, and thus is an appropriate approach to describe the trajectory of particles. Hence, the motion trajectory of a nanoparticle in a periodic conservative optical force field is calculated based on the Euler-Kromer algorithm; the results confirm consistency with the physical analysis, further verifying the effectiveness and stability of the approach. The calculation method shown in this paper provides a high-efficiency approach to study optical trapping, transport, sorting of colloidal particles, and biological macromolecules as well as the cooling of macroscopic particles in optical micro-manipulation.
In this paper, the exterior solution for a spherically symmetric black hole surrounded by plasma is studied in detail. After deriving the fundamental governing equations, the analytic solutions under two approximate conditions, ${g_{tt}}{g_{rr}} = - 1$ and $p = 0$ , are investigated. Comparing the two results with the accurate numerical solution, we find that the former approximation offers superior accuracy. This provides a basis for studying the quasinormal modes of perturbations as well as the shadow and ring when the black hole is surrounded by plasma.
In this study, ultrafast spin dynamics on FM-AFM (ferromagnetism-antiferromagnetism) thin film were explored using pump-probe technology with circularly polarized and linear pump beams. Circularly polarized light generates an effective inducting magnetic field, which is called the inverse Faraday effect. The direction of the transient Kerr peak only depends on the angular momentum of photons. The amplitude of the Kerr peak depends on the thickness of the MnIr film. This may be attributed to the fact that the transient Kerr peak originates from the magnetization of paramagnetic electrons. This study may help further the understanding of spin dynamics in HD-AOS (Helicity-Dependent All Optical Switching).
In recent years, a new laser cooling method—named bichromatic adiabatic cooling—has been developed; however, the method offers low cooling efficiency. In this paper, numerical optimization of the bichromatic adiabatic cooling process has been performed. It is shown that there is an optimal pulse time for the optical fields to achieve the highest cooling efficiency. Moreover, a comparison of the cooling efficiency with the Gaussian light pulse and square pulse shows that the cooling efficiency is insensitive to the pulse shape. Because this cooling method relies on adiabatic evolution of the light field-atom system, it is shown that it is better to slow the speed of the atomic beam to maintain the adiabatic condition. Finally, the effect of spontaneous emission on bichromatic adiabatic cooling is studied. The results show that use of a long pulse significantly reduces cooling efficiency.
In this paper, the phase estimation limits of an active-related Mach-Zehnder interferometer with three port inputs and two different input states was studied using quantum Fisher information and quantum Fisher information matrix theory. In the case of an arbitrary light field input to a single port, the effect of the input field fluctuation on the limit of phase estimation is eliminated by the theory of phase averaging and the quantum Fischer information matrix. In the case of a dual port input coherent state, the effect of the fluctuating light field on the estimation limit cannot be eliminated, and the phase estimation limit depends on the initial phase of the two input coherent states.
Recently, research on multi-mode, multi-band transceivers has garnered significant interest; in this context, the Software-Define Radio (SDR) system is considered a good candidate. To reduce the negative influence of out-of-band interference on transceiver performance of the SDR system, a high out-of-band rejection IF (intermediate frequency) filter with tunable bandwidth and programable gain is proposed. The proposed filter consists of a biquadratic Gm-C filter, a gain-boosting stage, and a 5th-order elliptic filter. In the proposed filter, the variable gain is achieved using a biquadratic Gm-C filter and a gain-boosting stage, and the tunable bandwidth is achieved using capacitor arrays. In addition, a 5th-order elliptic filter is added to improve out-of-band rejection. The post-layout simulation shows that the bandwidth is tuned over a range of 1 MHz–30 MHz, and the minimum out-of-band rejection at twice the bandwidth reaches 44.56 dB. The gain control range is from –20 dB to 20 dB, and the power consumption and active area for the analog counterpart is 5.1 mW and 1.23 mm2, respectively. The proposed filter is suitable for the analog front-end of multi-mode communication terminals.
In recent years, white pollution caused by waste plastics has attracted widespread attention. Microplastics, which are smaller than 5 mm, are widely distributed in the marine environment. The organisms attached to microplastic surfaces include potential pathogenic bacteria that are harmful to marine life and even human health, as well as plastic-degrading bacteria that can reduce their pollution. Microplastics are difficult to degrade, so they can exist in the aquatic environment for a long time, and the microorganisms attached to their surface can also live stably. In addition, microplastics may pass through the food chain to organisms at higher nutritional levels, and may be eaten by fish and affect fish growth. This paper reviews the distribution of microplastics in the ocean and the potential effects of harmful substances contained or attached to the microplastic surface on organisms. The ecological effects of pathogenic microorganisms attached to the surface of microplastics and plastic decomposition microorganisms, as well as the potential of microplastic transmission to high nutritional levels through the food chain were discussed. The ecological risk of microplastic distribution and surface-attached organisms was analyzed. Furtherly, it is still necessary to understand the impact of plastic waste and microplastics on the marine ecosystem, so as to fully understand the ecological effects of marine microplastics and their attachments, and provide a scientific basis for marine plastic pollution control.
In this study, we analyzed the diversity of microbes across 45 collected soil samples using meta-barcoding. The analysis showed similar α diversity of soil microbes in a vertical forest (VF) building and the surrounding green area, but a high level of differentiation in the microbe community composition and β diversity between these two types of habitats. The results indicated that a VF can accommodate a large number of microbe species and provided evidence for the contribution of VFs to the conservation of urban biodiversity.
Based on the classical theory of island biogeography, thirteen remnant forest patches of fragmented urban habitats were chosen as islands, and the Lao Mountain as the mainland. Then, canonical correspondence analysis (CCA) was used to analyze the relationship between species composition and four factors — namely, patch area, distance to species pool, human disturbance intensity, and isolation degree. The lengths of vectors in CCA biplots were used as weights for each influencing factor to calculate the overall sum, named the isolated island index (III); an isolated island index evaluation system of forest patches in fragmented urban habitats was subsequently designed. The results indicated that the relationship between III and richness was significantly negative for native species, but not significant for alien species richness. There was a significant relationship found for bird dispersal and wind dispersal species. The linear function was determined to be the best simulating model.
In this study, an ecological survey of the lake water in Luxun Park from January to October 2019 was conducted to determine the community structure characteristics and health of phytoplankton in the water. In particular, the community composition, density, biomass, diversity, uniformity, and dominant species of phytoplankton were analyzed. A total of 83 genera of 8 phyla of phytoplankton were identified; of these, Cyanophyta, Chlorophyta, and Diatoms had the largest number of species. The annual average cell density was 14.17×106 ind/L, and the annual average biomass was 3.57 mg/L. Density and biomass typically increase with seasonal changes. The dominant phyla were the Cyanophyta, Chlorophyta, and Diatom phylum; meanwhile, Pseudo-Anabaena, Platychophyta, Scenedesmus, and Cyclotella were the major dominant species. Redundant analysis was used to further analyze the environmental factors in the lake water of Luxun Park. The results showed that pH, nitrate nitrogen, nitrous nitrogen, and permanganate index are the key factors affecting the structure of the phytoplankton community.
Using a combination of mechanical and representative sampling, plots in 13 cities of the Yangtze River Delta Region were surveyed in 2015—2016; the survey consisted of 449 plots across 76 urban parks, roads, and waterfront greenbelt areas. As part of this study, we analyzed the factors and drivers for species composition, distribution, size, coverage, and growth vigor of the predominant trees located in the urban plots; the data provides a scientific basis for the future construction of forest cities and the improvement of urban human settlements. The results show that: ① In total, 157 tree species were recorded in the surveyed plots, which belonged to 115 genera and 54 families. The dominant families belonged to the Rosaceae group (20 species across 12 genera), with a high proportion of single families and relatively dispersed species composition. ② The plots were characterized by significant temperate features (73 genera), showing that the tree species have typical temperate properties in application. ③ The main tree species of the urban man-made forests were Cinnamomum camphora and Platanus × acerifolia, with coverage reaching 27.45%; specifically, Cinnamomum camphora was the dominant species. The utilization of trees across different types of urban plots varied considerably. ④ It was found that tree species with 10 cm ≤ D≤ 30 cm constituted the majority of tall trees in the urban plots, including many species of native trees such as Sapindus saponaria, Koelreuteria bipinnata 'Integrifoliola', and Liquidambar formosana. The quantity and distribution of the trees, however, was found to be extremely unbalanced. The coverage of Cinnamomum camphora and Platanus × acerifolia in the area was as high as 45.18%, and the relative species diversity and community stability were found to be weak. We recommend that the coverage of other tree species is gradually increased in the future construction of urban plots.
Based on daily monitoring data of the Qingcaosha Reservoir water intake from 2010 to 2019, this paper analyzes the interannual and seasonal variation trends in the main physical and chemical water quality indicators, and explores the correlation between these indicators. The results show that: ① The dissolved oxygen at the intake of Qingcaosha Reservoir was consistently high, and the pH value was slightly alkaline. ② The concentration of ammonia nitrogen was low at the intake of Qingcaosha Reservoir, the concentration of nitrate-nitrogen was between 1.2 and 2.0 mg/L, the concentration of total phosphorus was between 0.1 and 0.2 mg/L, and the permanganate index was between 2.0 and 4.0 mg/L. These indexes, furthermore, all showed a downward trend after 2015, suggesting that the quality of incoming water subsequently improved. ③ Dissolved oxygen concentration, water temperature, and pH exhibited obvious seasonal variations, while total hardness, permanent hardness, conductivity, and chloride showed consistent variations under the influence of seawater intrusion. There was no significant seasonal variation in the other indicators. ④ The concentration of total phosphorus and the permanganate index increased with turbidity. The concentration of total phosphorus and nitrate nitrogen, moreover, decreased with an increase in water discharge at Datong.
In this study, follow-up monitoring over the course of two and a half years was carried out to analyze the long-term impact of sediment dredging on water quality, new sediments, benthos, and microorganisms of a river reach in Shandong Province. The results showed that the contents of CODCr and TP could be effectively removed by dredging, but little effect was observed on the contents of TN and NH4+-N. The C/N ratio in the new sediments decreased gradually over the observation period, which was beneficial to the recovery of microbial and benthic communities. Dredging can reduce the average biomass and density of tremididae in surface sediments to a certain extent, while Chironomidae density is less affected by dredging. Dredging did not change the microbial community structure significantly, which may be related to the depth of dredging. Exogenous pollutants and man-made drainage can affect the water quality and sediment pollutant content of the dredged river section; this effect, however, may recover in a short time after completion of the microbial community construction. In conclusion, the overall engineering effects of dredging were observed during the study period (2–4 years after dredging); in this time, the water quality and sediment pollution improved, which was conducive to the restoration of benthos and microbial diversity. However, with the passage of time and human interference, the net effect on water quality maintenance weakened.
中国综合性科技类核心期刊(北大核心)
