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Normal families of meromorphic functions and omitted functions

YANG Qi, YANG Jinhua

Journal of East China Normal University(Natural Science) 2020, 2020 (1): 1-6. DOI: 10.3969/j.issn.1000-5641.201811043

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In this paper, we study the normal criterion of meromorphic functions concerning omitted functions. By using P-Z lemma and the method of proof by contradiction, we obtain a new normal criterion: if the zeros of the families of meromorphic functions are all have multiplicity at least 3, then the families of meromorphic functions concerning omitted functions are normal.

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Analysis and application of exponential degradation paths with random failure thresholds

GUAN Qiang, FU Zhiliang

Journal of East China Normal University(Natural Science) 2020, 2020 (1): 7-15. DOI: 10.3969/j.issn.1000-5641.201811040

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In a classical degradation experiment, the performance of a product is reduced or raised to a certain threshold value, which is regarded as a product failure; this is often refereed to as single-point degradation. Although this definition is widely used, it is not sufficiently comprehensive and cannot be used alone to describe the full product degradation process. In this study, we improve the single-point degradation model and propose the interval degradation model; in this context, the previously fixed threshold value will be generalized to a random value at a specified interval. We discuss the lifetime distributions for a variety of interval degradation models when the degradation path is an exponential function. Numerical integration and Monte Carlo simulation are used to calculate the lifetime distribution for interval degradation models and single-point degradation models; in addition, we determine the relationship between the respective models. The simulation results reveal that the performance of the interval degradation model is more reasonable and effective than that of single-point degradation model.

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The polar form of hyperbolic commutative quaternions

KONG Xiangqiang

Journal of East China Normal University(Natural Science) 2020, 2020 (1): 16-23. DOI: 10.3969/j.issn.1000-5641.201911001

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Firstly, this paper presents the e₁-e₂ representation and matrix representation of hyperbolic commutative quaternions. Secondly, the polar form theorem of hyperbolic commutative quaternion is presented; the existence and uniqueness of the respective polar form are proven, and a series of properties for the hyperbolic commutative quaternion polar form are obtained. Lastly, the relationship between the polar form, e₁-e₂ representation and matrix representation of hyperbolic commutative quaternions are discussed. Hence, the paper provides a theoretical basis for further research on the application of hyperbolic commutative quaternions.

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An algorithm for finding all polynomial solutions of nonlinear difference equations

Jiangtao YU, Yinping LIU

Journal of East China Normal University(Natural Science) 2020, 2020 (1): 24-39. DOI: 10.3969/j.issn.1000-5641.201811037

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Difference equations are a major aspect of computer algebra; yet, there are currently few studies on solving general nonlinear difference equations. Inspired by the homogeneous balance principle that works well for solving nonlinear differential equations, we use it to find polynomial solutions for a wide range of nonlinear difference equations, in which a new n-order expansion method is proposed to process the powerless cases of the homogeneous balance principle. They are combined together as an algorithm that can be used to find all polynomial solutions of nonlinear difference equations. The algorithm is implemented in Maple, and the experiments show that it is effective and efficient.

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I-convexity and Q-convexity of Orlicz-Bochner function spaces with the Luxemburg norm

DONG Xiaoli, GONG Wanzhong

Journal of East China Normal University(Natural Science) 2020, 2020 (1): 40-50. DOI: 10.3969/j.issn.1000-5641.201811042

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There are some equivalent definitions for I-convexity and Q-convexity. In this context, if (Ω, Σ, μ) is a finite measure space, the Orlicz-Bochner function space L_(M)(μ, X) endowed with the Luxemburg norm is I-convex if and only if M ∈ △₂(∞) ∩ ▽₂(∞) and X is I-convex; similarly, L_(M)(μ, X) is Q-convex if and only if M ∈ △₂(∞) ∩ ▽₂(∞) and X is Q-convex.

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Topological graph passwords based on the gracefulness of disconnected graphs with circles

MU Yarong, LIU Xinsheng, YAO Bing

Journal of East China Normal University(Natural Science) 2020, 2020 (1): 51-57. DOI: 10.3969/j.issn.1000-5641.201811045

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Graph labeling is an important branch of graph theory. We use disconnected graphs to start our study, and show that disconnected graphs G = (C₄, K_r)∪∪_t=1^kK_m,n^t and G = (C₄, K_r)∪K_1,n∪∪_t=1^kT^t allow graceful labelings. Algorithms can be used to provide a theoretical basis for proving the application of disconnected graphs to networks.

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Atomic distortion in CrN: A first-principle investigation

WANG Qianqian, ZHAO Zhenjie, LI Xin, XIE Wenhui

Journal of East China Normal University(Natural Science) 2020, 2020 (1): 58-66. DOI: 10.3969/j.issn.1000-5641.201922002

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First principle calculations indicate that Cr and N atoms in the orthorhombic phase of CrN (Chromium Nitride) tend to shift from their ideal positions along the [100] direction. This shift can induce zigzag Cr-N-Cr chains in the orthorhombic phase; these atomic distortions have not been taken into account in previous studies. The atomic distortions may decrease the total energy of the orthorhombic phase by 0.125 eV/formula unit and make the structure more stable. Lattice constants, moreover, may also be in better agreement with experiment results when considering these atomic distortions. Further, the bulk modulus K₀ decreases significantly when considering the atomic distortions and is closer to the experimental value. The atomic distortions are induced by the asymmetric magnetic forces between asymmetric magnetic layers in the special antiferromagnetic order of the orthorhombic phase, which compensates for the magnetic forces between the layers. The atomic distortions would not change the Mott-insulator property of the orthorhombic phase but may reduce the band gap slightly.

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Study on the covariant chiral effective field theory of vector meson

WANG Yan, YANG Jifeng

Journal of East China Normal University(Natural Science) 2020, 2020 (1): 67-75. DOI: 10.3969/j.issn.1000-5641.201922007

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In this paper, we employ covariant chiral effective field theory to explore the prescriptions in the loops involving spin 1 vector fields. The self-energy diagram for a Goldstone boson containing a vector meson line is studied, and consistent results are obtained in two representations of the vector field. Our calculation shows that the EOMS^[1](Extended On-Mass Shell) proposed indeed removes the terms that violate chiral power counting. Closer examination, however, shows that the problematic sources are actually localized; thus, we propose a simpler EMS (extended MS) cheme, which is further validated using a vertex diagram. Compared to EOMS, this scheme eliminates the localized terms that violate chiral power counting without additional manipulation or modification of the non-local terms. This feature would bring about better convergence of the chiral expansion and is more suitable for studying heavy hadrons with chiral effective theory.

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The complexity of Kerr-AdS black holes

DING Yuchen, WANG Tao

Journal of East China Normal University(Natural Science) 2020, 2020 (1): 76-82. DOI: 10.3969/j.issn.1000-5641.201922004

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Gauge/gravity duality has shed light on physics research. It reveals that conformal field theory on the boundary is equivalent to the bulk of anti-de Sitter space-time, which brings us great convenience for studying the conformal field on the boundary. Recently, Susskind et al. proposed a conjecture for complexity/action duality, which states that the quantum computational complexity of the boundary state of a black hole is equivalent to the action in a Wheeler-DeWitt patch. The complexity represents the difficulty of performing quantum computing, which means that black holes may be linked to quantum computing. This provides us with deeper insights on black holes. Based on this conjecture and taking the contribution of null joints into consideration, we improve the original method of Susskind et al., and recalculate the action growth rate of the Wheeler-DeWitt patch of Kerr-AdS black holes more accurately. Finally, we get the complexity of the state on the boundary of Kerr-AdS black hole space-time.

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Novel polymer semiconductor films and related field effect transistor devices

YE Jianchun, ZHOU Lizhao, LI Wenwu, OU-YANG Wei

Journal of East China Normal University(Natural Science) 2020, 2020 (1): 83-92. DOI: 10.3969/j.issn.1000-5641.201922006

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Thin films using a novel organic polymer semiconductor (DPPTTT(poly(3,6-di(2-thien-5-yl)-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione) thieno [3,2-b] thiophene)) were prepared by a solution process and characterized through different techniques. It was found that the thickness, surface roughness, and Raman peak strength of the semiconductor films changed with the solution concentration and rotation rate. The polymer semiconductor was used to prepare the active layer for p-type organic field effect transistors; with these, the influence of channel length on critical transistor parameters (i.e., carrier mobility and threshold voltage) was studied. It was found that the effective carrier mobility was the highest at 0.12 cm²/Vs when the channel length was reduced to 50 μm. With a decrease in channel length, both carrier mobility and threshold voltage tended to increase, which was contrary to the short channel effect. This paper may provide new perspectives for better understanding the physics of field effect transistor devices.

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Application of TiO₂ nanotube arrays for bipolar photocatalytic fuel cells

WANG Jianqiao, LIU dong, ZHOU Jun, XI Qinghua, NIE Er, SUN Zhuo

Journal of East China Normal University(Natural Science) 2020, 2020 (1): 93-102. DOI: 10.3969/j.issn.1000-5641.201922005

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Photocatalytic fuel cell (PFC) technology is a combination of photocatalytic technology and fuel cell technology, which can degrade wastewater and generate electricity at the same time. The influence of the preparation process for photoanodes of TiO₂ Nanotube Arrays (TNAs) on its morphology and structure was explored; a positive correlation between the electrolysis time and the tube length of TNAs was confirmed by a Field Emission Scanning Electron Microscope (FESEM). We can combine TNAs with Cu₂O photoelectrodes to obtain a system with stronger photocatalytic activity, confirming the existence of a PFC synergistic effect. The optimal electrolysis process was 4 h, and the photocatalytic degradation rate of the electrode prepared by this process was more than 79% within 2 h. Analysis of the three standards showed an excellent linear correlation between the photocurrent of PFC and the chemical oxygen demand (COD); as the degradation proceeds, the mass transfer process is reduced and the correlation between the two is weakened.

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Performance of lime-based algae control in urban landscape water

ZHOU Yunchang, HE Yan, CHEN Jinghan, HUANG Minsheng

Journal of East China Normal University(Natural Science) 2020, 2020 (1): 103-109. DOI: 10.3969/j.issn.1000-5641.201831012

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In this research, we studied the effect of lime dosages on algae control as well as the dynamic changes in nitrogen and phosphorus nutrients in urban landscape water based on the growth and decline of algae blooms at Guhua Park in Shanghai. The results showed clear seasonal variations in algae biomass in Guhua Park. The growth of algae could be inhibited by the addition of lime, and the inhibition performance improved with increases in lime dosage. Specifically, the algal inhibition rate ranged from 20% to 46% when the applied lime dosage increased from 0.02 g/L to 0.2 g/L. When the lime dosage increased from 0.2 g/L to 0.5 g/L, however, there was no significant increase in inhibition efficiency observed. Therefore, considering both algal inhibition efficiency and economic cost, the optimum dosage of lime is 0.2 g/L. Meanwhile, nitrogen and phosphorus nutrients in water initially increased and then decreased, reaching a final dynamic equilibrium. This study offers a new approach for algae control of urban landscape water.

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Health assessment of transboundary rivers based on the PSR and matter-element extension models: A case study of Taipu River

XIE Yihan, LI Gen, YANG Mengjie, CHU Xiaoye

Journal of East China Normal University(Natural Science) 2020, 2020 (1): 110-122. DOI: 10.3969/j.issn.1000-5641.201831013

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Taking Taipu River as an example, a multi-index assessment system for the water body and riparian zone is constructed based on the PSR model. Index weights are calculated with the entropy weight method, and the Taipu River is evaluated using the PSR and matter-element extension models. The results show that the Wujiang segment is classified as “high pressure-good state-low response ability”, the Jiashan segment is classified as “low pressure-medium state-low response ability”, and Qingpu segment is classified as “low pressure-medium state-high response ability”. The result of the health assessment of Wujiang is Grade Ⅲ (poor). Meanwhile, Jiashan and Qingpu are both Grade Ⅱ (medium), but leaning towards Grade I (good); this indicates that although the current health status of the river is medium, the health status of the water source area could be gradually restored by further increasing protection of the water source given that the policy is to some extent already effective. The results can provide decision support for river management and ecological construction of the riparian zone in Taipu River.

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Journal of East China Normal University(Natural Science) 2020, 2020 (1): 123-125. DOI: 10.3969/j.issn.1000-5641.202049001

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Analysis of water and sediment characteristics in the main tributaries of the Yangtze River and their associated influence factors

WANG Zhengcheng, MAO Haitao, SHEN Jiwei, TANG Xin, CHEN Xiang

Journal of East China Normal University(Natural Science) 2020, 2020 (1): 126-138. DOI: 10.3969/j.issn.1000-5641.201841031

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Water and sediment characteristics of Yalong River, Minjiang River, Jialing River, and Wujiang River are one of the defining aspects of variation in Yangtze River sediment; they have influence on the operation of the Three Gorges Reservoir, which is related to utilization of water resources in the Yangtze River Valley and equilibrium of the water ecosystem. This article is based on hydrological and sediment monitoring data from 2002—2016 of four important hydrological control stations set up in the main tributaries of the Yangtze River, which are Tongzilin, Gaochang, Beibei, and Wulong. Variation characteristics of hydrology and sediment parameters and their associated influence factors were studied systematically; correlations between hydrological and sediment parameters were subsequently analyzed by SPSS. The results showed that over time: the annual average sediment concentration, annual sediment load, and modulus of sediment transport of the tributaries of the Yangtze River decreased 22.57%~91.54%; the annual runoff of Yalong River, Minjiang River, and Wujiang River increased 3.28%~17.96%, but that of Jialing River decreased 1.58%; and the median size of sediment of the Jialing and Wujiang Rivers increased 50%~80%. Furthermore, cascade hydro power stations were built, which led to annual average sediment concentration, annual sediment load, median size of sediment, and modulus of sediment transport to decrease by 5%~79.34%. Natural disasters such us heavy rainfall, landslide, collapse, debris flow, dam-break, landslide under artificial conditions, and dumping earth rock into a river lead to annual average sediment concentration, annual sediment load, and modulus of sediment transport to increase by 20%~702.94%. Correlations between the parameters ranked from strong to weak are: annual average sediment concentration and annual sediment load/annual average sediment transport modulus, annual runoff and annual average sediment concentration, annual runoff and annual sediment load/annual average sediment transport modulus, annual average sediment concentration and median size of sediment, median size of sediment and annual sediment load/annual average sediment transport modulus, and annual runoff and median size of sediment. The research results will provide theoretical support for the planning and design of cascade hydropower stations in tributaries of the Yangtze River as well as operation of the Three Gorges Reservoir.

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Water transfer plan for the Ecological Restoration Project Area in Chongming Dongtan National Nature Reserve

LU Peiyi, ZHU Jianrong, YUAN Lin, TIAN Bo, PAN Jialin

Journal of East China Normal University(Natural Science) 2020, 2020 (1): 139-149. DOI: 10.3969/j.issn.1000-5641.201841035

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The Ecological Restoration Project Area in Chongming Dongtan National Nature Reserve is located in the East Asian-Australasian Flyway. Different bird species have their own unique requirements for habitat water depth. Water depths for bird habitats can be managed via habitat blocks; the blocks are divided based on the feeding characteristics and spatial distributions of the respective target bird species. Accordingly, the key to effective water depth management is to maintain a suitable water depth in each block. For internal habitat blocks in the southern C zone of the Ecological Restoration Project Area, when a block’s water depth is greater than the maximum critical depth, water is drained to the Suitang River, which sits outside the blocks and inside the coastal levee. Conversely, when the water depth decreases below the minimum critical depth, water is drawn from the Suitang River into the habitat blocks through the sluice gate from the outer Chongming Dongtan. Water level variations in the habitat blocks and the Suitang River and changes in mean water depth of each block are calculated according to water balance principles. These principles take into consideration evaporation, precipitation, plant evapotranspiration, and soil infiltration; moreover, the time and amount of water drained from the habitat blocks or the water drawn from the outer Chongming eastern shoal were also calculated and analyzed. The research results enable a scientific water replenishment plan for ecological water regulation at Chongming Dongtan National Nature Reserve and guidance for building favorable habitats for migratory birds.

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Spatiotemporal variations and influencing factors of organic carbon content in the urban rivers of Shanghai

ZHU Kun, WU Ying, Qi Lijun

Journal of East China Normal University(Natural Science) 2020, 2020 (1): 150-158. DOI: 10.3969/j.issn.1000-5641.201841032

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Surface water samples were collected monthly from four sites in Suzhou River and Huangpu River from December 2015 to December 2016. We analyzed the concentration of dissolved organic carbon (DOC) and particulate organic carbon (POC) along with total suspended matter (TSM) and stable carbon isotope (δ¹³C) to understand the spatial and temporal variations in Suzhou River and Huangpu River. During the dry season, the DOC concentration of upstream sections of Suzhou River (4.52 ±0.48 mg·L^-1) was higher than the downstream sections (3.66 ±0.32 mg·L^-1), while there was no significant difference between the upstream and downstream sections during the flood season. Different retention times for DOC transportation for the upstream sections relative to the downstream sections might be a major factor for the spatial distribution of DOC. The δ¹³C (-29.1‰ ±1.0‰) during the flood season was more negative than the dry season (-28.1‰ ±0.6‰), indicating the significant contribution from plankton in the flood season. The mass fraction of POC (POC%) showed no significant differences between the flood and dry seasons, but the POC% in the dry season (6.01% ±2.27%) was still higher than the flood season (4.10% ±0.99%). The DOC concentration and POC% in Huangpu River showed no obvious differences the upstream and downstream sections; however, DOC showed higher concentration during the winter and lower concentration during the summer. The lower TSM (79.1 ±26.4 mg·L^-1) and more negative δ¹³C (-28.1‰ ±0.9‰) in the flood season suggested that the Huangpu River was affected mainly by the water discharge from Taihu Lake during the flood season; POC% in the flood season was higher than the dry season. DOC was the dominant fraction of organic carbon in the two rivers, and the difference in the water self-purification capacity between two urban rivers resulted in the difference of DOC/POC variation range. The gradual decrease in the DOC concentration of the Huangpu River during the period from 2005-2016 indicates that the third phase of sewage treatment projects achieved initial effectiveness in controlling organic pollution of the Huangpu River, but the high concentration of total organic carbon (TOC) indicates that the organic pollution in Huangpu River was still at a relative high level.

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Review of estuarine and coastal environmental monitoring technologies

GU Jinghua, GE Zhenpeng, WANG Jie

Journal of East China Normal University(Natural Science) 2020, 2020 (1): 159-170. DOI: 10.3969/j.issn.1000-5641.201841037

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Estuaries and coasts are the most sensitive zones in land-sea interaction-these zones have now become the core of earth system science research. In recent years, estuarine and coastal environments are facing serious challenges from rises in both sea level and high-intensity human activities. Strengthening the capacity of estuarine coastal environmental monitoring technology is essential for understanding the process and change mechanisms of the estuarine and coastal environments and improving our prediction of future changes. In this paper, monitoring elements, methods, common instruments, and equipment for estuarine and coastal monitoring are discussed holistically based on five aspects: meteorology, hydrology, topography, geology, and environment. Given the uniqueness of estuarine and coastal locations, we show that current monitoring of extreme weather and long time series data is particularly inadequate and needs to be improved holistically.

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Property of the consistent Fredholm index and property (ω₁)

DAI Lei

Journal of East China Normal University(Natural Science) 2020, 2020 (2): 1-7. DOI: 10.3969/j.issn.1000-5641.201911004

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In this paper, a new spectrum is defined according to the property of the consistent Fredholm index. We establish the sufficient and necessary conditions for a bounded linear operator defined on a Hilbert space that satisfies the property (ω₁). In addition, the paper explores the relationship between the property (ω₁) and hypercyclic operators (or supercyclic operators). Meanwhile, new conditions for hypercyclic operators and supercyclic operators are given.

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Rigidity of submanifolds with parallel mean curvature in a hyperbolic space

ZHOU Jundong

Journal of East China Normal University(Natural Science) 2020, 2020 (2): 8-14. DOI: 10.3969/j.issn.1000-5641.201911009

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Let M be a complete submanifold with parallel mean curvature in a hyperbolic space and Φ be the traceless second fundamental form of M. In this paper, it is shown that the submanifold is totally umbilical if the L² norm of |Φ| has less than quadratic growth on any geodesic ball of M and either sup_{x∈_M}|Φ|²(x) is less than some constant or Lⁿ norm of |Φ| is less than some constant. This is a generalization of the results on complete minimal submanifolds.

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Lie group analysis and exact solutions for a class of population balance equations

LIN Fubiao, ZHANG Qianhong

Journal of East China Normal University(Natural Science) 2020, 2020 (2): 15-22. DOI: 10.3969/j.issn.1000-5641.201911008

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In this paper, exact solutions for a class of population balance equations were investigated. The population balance equation was first transformed to a partial differential equation; symmetries of the partial differential equation were then obtained by use of the classical Lie group analysis method. In addition, the paper presents symmetries, optimal system of subalgebras, reduced ordinary differential integral equations, and group invariant solutions of the population balance equation. Exact solutions of the reduced ordinary differential integral equations were subsequently found using trial functions. Finally, exact solutions for a class of population balance equations are derived.

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Internal layers for a singularly perturbed differential equation with Robin boundary value condition

CHAIKOVSKII Dmitrii, Mingkang NI

Journal of East China Normal University(Natural Science) 2020, 2020 (2): 23-34. DOI: 10.3969/j.issn.1000-5641.201911043

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In this paper, we consider a second order singularly perturbed equation with a discontinuous right-hand function and Robin boundary value condition. Applying the boundary layer function method, we can construct an asymptotical approximation of the solution. We also prove the existence of the solution and obtain an estimation of the remainder based on the matching method.

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The Orlicz space equipped with the Φ-Amemiya norm contains an order asymptotically isometric copy of c₀

CUI Yun'an, AN Lili

Journal of East China Normal University(Natural Science) 2020, 2020 (2): 35-40. DOI: 10.3969/j.issn.1000-5641.201911007

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In Orlicz space, a new norm that is equivalent to the Luxemburg norm is introduced. It is called the Φ-Amemiya norm: ${\left\| x \right\|_{\Phi ,{\Phi _1}}} = \inf \left\{ {\frac{1}{k}\left( {1 + \Phi \left( {{{ I}_{{\Phi _1}}}\left( {kx} \right)} \right)} \right)} \right\}$. It is shown, furthermore, that the Orlicz function space equipped with this norm $\left\{ {{L_{\Phi ,{\Phi _{\rm{1}}}}},{{\left\| \cdot \right\|}_{\Phi ,{\Phi _1}}}} \right\}$ is a Banach space. Hence, this paper demonstrates the conditions for the Orlicz space with the Φ-Amemiya norm to contain an asymptotically isometric copy of c₀.

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Optimal conditions for the existence of positive solutions to periodic boundary value problems with second order difference equations

WANG Jingjing, LU Yanqiong

Journal of East China Normal University(Natural Science) 2020, 2020 (2): 41-49. DOI: 10.3969/j.issn.1000-5641.201811039

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By using the fixed-point index theory of cone mapping, we show the optimal conditions for the existence of positive solutions for second order discrete periodic boundary value problems
$\left\{ {\begin{array}{*{20}{l}} {\Delta^2 y(n-1)+a(n)y(n)=g(n)f(y(n)),}&{n\in[1,N]_{\mathbb{Z}},}\\ {y(0)=y(N), \;\;\;\Delta y(0)=\Delta y(N)}&{} \end{array}} \right.$
with vanishing Green’s function, where $[1,N]_{\mathbb{Z}}=\{1,2,\cdot\cdot\cdot, $$N\},\,f:[1,N]_{\mathbb{Z}}\times\mathbb{R}^+\rightarrow\mathbb{R}^+$ is continuous, $a: [1,N]_{\mathbb{Z}}\rightarrow(0,+\infty),$ and $\mathop {\max }\limits_{n \in {{[1,N]}_{\mathbb{Z}}}} a(n)\leqslant4\sin^2(\frac\pi{2N}),\,g\in C([1,N]_{\mathbb{Z}},\mathbb{R}^+), $$\mathbb{R}^+:=[0,\infty)$.

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Blow-up of solutions for nonlocal diffusion equations with a weighted gradient reaction

WANG Suzhen, MENG Haixia

Journal of East China Normal University(Natural Science) 2020, 2020 (2): 50-54. DOI: 10.3969/j.issn.1000-5641.201911006

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This paper considers the blow-up phenomena of solutions for nonlocal diffusion equations with a weighted gradient reaction, and gives the sufficient conditions for existence and blow-up. Firstly, the local existence of solutions is proven by using the Banach fixed-point theorem. Secondly, a new auxiliary function is constructed by using eigenfunctions. Finally, the results are combined with the differential inequality technique to obtain the upper bound of the blow-up time.

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Non-sequential double ionization of argon in counterrotating circularly polarized two-color laser fields

QIAN Lijie, YANG Yan, SUN Zhenrong

Journal of East China Normal University(Natural Science) 2020, 2020 (2): 55-63. DOI: 10.3969/j.issn.1000-5641.201922010

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In this paper, the non-sequential double ionization (NSDI) process of Ar in 800 nm and 400 nm counterrotating circularly polarized two-color(CRTC) laser fields was studied using the classical ensemble model. The dependence of the non-sequential double ionization mechanism and quantum yield on laser intensity, laser intensity ratio, relative phase, and pulse duration of two pulses is calculated and analyzed in detail. The energy evolution of two electrons in the time domain is obtained and two different non-sequential double ionization mechanisms are revealed. The influence of the electron collision energy for different non-sequential double ionization processes is also discussed.

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Electrostatic curved mirror of cold molecules

LI Jing, YANG Zhenghai, HOU Shunyong, WEI Bin, LIN Qinning, YANG Tao, YIN Jianping

Journal of East China Normal University(Natural Science) 2020, 2020 (2): 64-69. DOI: 10.3969/j.issn.1000-5641.201922014

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As one of the most important optical instruments, molecular (atomic) reflecting mirrors have been broadly applied in experiments for trapping, loading, and guiding of molecules (atoms); however, given that the mirrors can only change the velocity of particles in the longitudinal direction, there is no focusing capability in the lateral direction and particles can subsequently diverge. Using ND₃ as an example, we propose a compact micro electrostatic curved mirror to address this issue; we show via theoretical calculations and Monte-Carlo simulations that the proposed mirror can both direct a beam of molecules and achieve transverse bunching of molecules. This kind of reflecting mirror can be used in an extensive range of optical applications for manipulating or loading molecules, composing molecular cavities, and so forth.

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Spin density of tightly focused hybrid-order Poincaré beams

SUN Hong, DONG Guangjiong

Journal of East China Normal University(Natural Science) 2020, 2020 (2): 70-75. DOI: 10.3969/j.issn.1000-5641.201922012

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Research on spin of Poincaré beams not only has practical engineering applications, but is also important for understanding the nature of light. In this paper, we study the spin density of the tightly focused hybrid-order Poincaré beams (TFPB) and find that it has both longitudinal and transverse components. Unlike tightly focused full Poincaré beams whose longitudinal spin density is on average zero, the total longitudinal spin density of tightly focused hybrid-order Poincaré beams is not zero. The spin density of TFPB has rich controllable spatial patterns; in particular, the longitudinal spin density can be either a ring shape or a regular polygon. These features can be used to separate chiral particles or to manipulate dynamics of ultracold spinot gases.

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Optical dispersion of Bose-Einstein condensates

LIAO Yujiao, DONG Guangjiong

Journal of East China Normal University(Natural Science) 2020, 2020 (2): 76-82. DOI: 10.3969/j.issn.1000-5641.201922013

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Recent studies have shown that Bose-Einstein condensates (BEC) can act like quantum dielectric materials, which react to light fields, and thus co-manipulation of light-matter waves is possible. So far, the dispersion properties of BEC for optical fields with a large degree of detuning have not been investigated. Accordingly, in this paper, we analytically obtain formulas for the first- and second-order dispersion. Our numerical calculation shows that the refractive index and the second-order dispersion coefficient depend on the properties of red or blue detuning. In the case of red detuning, the refractive index is greater than 1 and the second-order dispersion is normal dispersion. In the case of blue detuning, the refractive index is less than 1 and the second-order dispersion is anomalous dispersion. The second-order dispersion coefficient changes dramatically with changes in detuning. When the detuning quantity is on the order of GHz, the BEC can function as a strong dispersion medium. The first-order dispersion is independent with red detuning or blue detuning; as the amount of detuning increases, the first-order dispersion decreases and the corresponding group velocity increases. Our research shows that BEC is a new dispersion medium for manipulating ultrashort pulse light.

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Lorentz symmetry violation and accelerated expansion of the universe

ZHAI Hanyu, XUE Xun

Journal of East China Normal University(Natural Science) 2020, 2020 (2): 83-89. DOI: 10.3969/j.issn.1000-5641.201922011

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The supernova observations of 1998 show that the universe is accelerating and expanding. Dark energy refers to the cosmic content of the universe's accelerated expansion. The positive cosmological constant Λ is an important factor for dark energy, but the cause of the accelerated expansion of the universe is not Λ. Lorentz invariance is the most accurate symmetry in nature, but all quantum gravitational theories predict the breakup of Lorentz symmetry. Based on the cosmological model of a large-scale Lorentz violation(LSLV), the Friedmann equation modified by effective gravitational theory is discussed and the effect of a large-scale Lorentz violation combined with a cosmological constant term can produce the observed acceleration of the universe.

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A study of nucleon-nucleon scattering in covariant chiral effective field theory at the two-loop level

SUN Jin, YANG Jifeng

Journal of East China Normal University(Natural Science) 2020, 2020 (2): 90-97. DOI: 10.3969/j.issn.1000-5641.201922008

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The amplitude of the two-loop level in N-N(nucleon-nucleon) scattering is calculated using covariant chiral effective theory. Based on the skeleton of the box diagram, the two-loop diagram results from the correction of pion self-energy. Two subtraction schemes will be employed for comparison: $\overline {{\rm{MS}}}$ and ${\rm{E}}\overline {{\rm{MS}}}$. The loop amplitude obtained with $\overline {{\rm{MS}}}$ contains terms that violate chiral power counting rules; with ${\rm{E}}\overline {{\rm{MS}}}$, the results are entirely chiral contributions with the exception of non-local “anomalous” ones that must be retained.

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Species composition and distribution pattern of weed communities in Chongqing metropolis

WU Xue, HUANG Li, JIN Cheng, QIAN Shenhua, YANG Yongchuan

Journal of East China Normal University(Natural Science) 2020, 2020 (2): 98-109. DOI: 10.3969/j.issn.1000-5641.201931002

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We arranged 86 1 km×1 km vegetation surveying plots in Chongqing metropolis using the grid method. The plots were used to investigate the species composition and distribution pattern of weed communities in the context of rapid urbanization. The findings of the study were as follows: ① 301 weed species belonging to 223 genera and 69 families were recorded. Among the recorded species, species of the Compositae and Gramineae were the most abundant; ② Annual weeds and dwarf weeds were the dominant types of weed species; ③ The weed communities in Chongqing metropolis were primarily comprised of native species. There were 31 exotic weed species and 11 invasive weed species recorded in the study; ④ The similarities in weed species composition across high-, medium- and low-urbanization areas were low. Additionally, the composition of dominant species within the weed community varied by area; ⑤ Urbanization had impacted weed biodiversity, evidenced by the lower number of weed species and the Shannon-Wiener diversity index in the high urbanization areas compared to that of the medium and low urbanization areas; ⑥ The number of weed species in the 86 sample plots showed a polycentric pattern with increasing distance between the survey plot and city center. Overall, urbanization had a significant impact on the composition and diversity of weed communities in mountainous multi-center cities, but the urbanization gradient of weed species is different from that of plain single-center cities.

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Interspecies associations and species-habitat associations in the evergreen broad-leaved forest of Tiantong National Forest Park, Zhejiang

YANG Qingsong, LIU Heming, ZHU Tongtong, ZHANG Shouhe, WANG Xihua

Journal of East China Normal University(Natural Science) 2020, 2020 (2): 110-119. DOI: 10.3969/j.issn.1000-5641.201931004

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The objective of this study was to clarify the relationship between interspecies associations and species habitat preferences in Tiantong National Forest Park. A total of 109 species of 20 hm² evergreen broad-leaved forest plots were selected and tested for interspecies associations and species-habitat associations. The results indicated that: ① the ratio of species pairs with significant associations increased with spatial scale and the ratio of negative associations was higher than positive; ② 89.9% of species were significantly correlated with at least one habitat variable, including 73.4% of species positively and 65.1% of species negatively correlated with habitats; ③ at scales larger than 20 m, the results of interspecies associations were consistent with those of species pair habitat preferences; but at smaller scales (i.e., < 5 m), most species pairs did not show significant interspecies associations, indicating there are not habitat preferences but rather other ecological processes influencing interspecies association patterns. The results provide a theoretical basis for further understanding the mechanism of species coexistence in evergreen broad-leaved forests.

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Preparation and application of crosslinked polyvinyl alcohol in electrosorption

CHEN Ling, MAO Shudi, ZHANG Yi, LI Zhe, PIAO Xianqing, SUN Zhuo, ZHAO Ran

Journal of East China Normal University(Natural Science) 2020, 2020 (2): 120-130. DOI: 10.3969/j.issn.1000-5641.201931003

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Sulfosuccinic acid (SSA) can be used as a crosslinking agent and a donor of a hydrophilic group when fabricating a cation exchange membrane. In this study, SSA was crosslinked with polyvinyl alcohol to form a cation exchange membrane for a capacitive deionization system. In this study, the impact of manufacturing parameters (i.e., crosslinker content, crosslinking temperature) on the deionization performance of a composite membrane were investigated in detail. A comparison was made between a capacitive deionization system (CDI) without an ion exchange membrane and a membrane capacitive deionization system (MCDI) coated with a PVA/SSA layer. The results show that the adsorption capacity and charge efficiency can be enhanced by 15% and 25%, respectively, with the PVA/SSA membrane layer; furthermore, the optimal mass fraction of SSA is 5%, and the optimal crosslinking temperature is 100 ℃.

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Preparation and fluorescence detection properties of ZnO nanostructure based on microdroplets

HUANG Binbing, XIE Yan, XIE Wenhui, ZHAO Zhenjie, LI Xin

Journal of East China Normal University(Natural Science) 2020, 2020 (2): 131-139. DOI: 10.3969/j.issn.1000-5641.201933001

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In this paper, we discuss ZnO nanostructures synthesized by a hydrothermal method in a droplet microreactor. The microfluidic chip used integrates a multi-function unit that includes a T-channel for droplet formation, a Y-channel for droplet fusion, and an S-channel for rapid mixing and observation of the nanoparticle formation process. By adjusting the flow rates of the aqueous phase and the oil phase, we studied the morphology and size of droplets; fluorescence detection of the ZnO nanostructure synthesized, moreover, was evaluated by an FITC-labeled goat anti-bovine IgG. This work shows that ZnO nanostructures can be prepared by fluid dynamic coupling of droplets and that the morphology and size of the nanostructures vary with droplet size. When the flow rates of the oil phase, ammonia water, and ferric solution were 600, 30, and 90 μL/h, respectively, the ZnO nanostructure synthesized at 75 ℃ showed optimal fluorescence detection performance.

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Journal of East China Normal University(Natural Science) 2020, 2020 (3): 0-0.

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A discussion on the diversion process of tide-dominated estuary bifurcation: The North Branch estuary of the Yangtze River

LU Jiayu, GE Jianzhong, DING Pingxing

Journal of East China Normal University(Natural Science) 2020, 2020 (3): 1-12. DOI: 10.3969/j.issn.1000-5641.201941015

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The North Branch estuary of the Yangtze River is a typical tide-dominated estuary with bifurcation. The hydrodynamics and diversion processes are the major factors in sediment transport and geomorphology evolution of the tide-dominated estuary. This paper is based on data from the bottom tripod system and a cross-section survey of the North Branch in April 2018, whereby the dominant flow of each channel is calculated. The results show that during the spring tide cycle, the Santiao Port and the Guyuansha south waterway are flood-dominated and the net tidal current flows landward, whereas the Guyuansha north waterway is ebb-dominated, and the net flow has a seaward direction. Moreover, a high-resolution numerical FVCOM model is used to simulate the diversion process of the North Branch estuary. The results suggest that: the cross-sectional area of Guyuansha south waterway is much bigger than that of the north waterway, and the propagation direction of the lateral tide is consistent with the orientation of the Guyuansha south waterway, which mainly has onshore movement through the Guyuansha south waterway. The spatial distribution of the flood tide flow is significantly uneven in these two waterways. Meanwhile, tidal current from the Guyuansha south waterway crosses the shallow shoal and reaches the north waterway. It produces a net flow with the seaward direction through the north waterway. The flood-tide and ebb-tide diversion ratio of the Guyuansha north waterway are 29.7% and 47.2%, respectively, during the spring tide period and 41.6% and 43.1%, respectively, during the neap tide period. The residual patterns indicate that the tidal current enters the estuary from the south waterway and exits through the north waterway. These indicators and diversion characteristics can help predict estuarine sediment transport and geomorphological evolution processes within an individual bifurcated channel.

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Numerical simulation of saltwater intrusion mitigation by building a sluice in the North Branch of the Changjiang Estuary

ZHU Jianrong, LU Peiyi, TANG Chuanmin, CHEN Qing, Lü Hanghang

Journal of East China Normal University(Natural Science) 2020, 2020 (3): 13-22. DOI: 10.3969/j.issn.1000-5641.201941017

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The most prominent feature of saltwater intrusion in the Changjiang Estuary is the saltwater spillover from the North Branch into the South Branch during the dry season; the spillover is the only source of saltwater for the Dongfengxisha, Taicang, and Chenhang Reservoirs as well as the main source of saltwater for the Qingcaosha Reservoir. A three dimensional numerical saltwater intrusion model, validated on the Changjiang Estuary, was applied to simulate and analyze salinity variation both during and after construction of the sluice at the upper reaches of the North Branch; the model considered tide, climatic river discharge, and wind in January and February. The simulated results showed that the South Branch is occupied by freshwater, the phenomenon of saltwater spillover from the North Branch vanishes and the salinity in the upper reaches of the North Branch decreases substantially after building the sluice. The salinity at the water intakes of the Dongfengxisha, Taicang, and Chenhang Reservoirs approaches 0. The salinity at the water intake of the Qingcaosha Reservoir decreases significantly and is less than 0.45 and there is freshwater at all time. The operation of the sluice in the numerical experiments is adopted in two ways. One is open during ebb current, closed during flood current in the daytime, and open during flood current in the nighttime. The other is open during ebb current and closed during flood current in the daytime and nighttime. The salinity variations in the South Branch with the two operational schemes are nearly identical. This can be attributed to the fact that the saltwater intrusion in the upper reaches of the North Branch is substantially reduced by the former sluice operational scheme, and a freshwater area with salinity approaching 0.45 appears. Even though the sluice is open during day flood current, the water entering the South Branch is freshwater and the total seaward residual current in the South Branch is enhanced. Considering the numerical simulation results and operation costs, the former sluice operational scheme is recommended. The water intake time is significantly improved, not only for the Dongfengxisha, Chenhang, and Qingcaosha Reservoirs in Shanghai, but also for the Taicang Reservoir in Jiangsu; moreover, security in water supply is ensured for both places.

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Influence of water level rise on currents and saltwater intrusion in the Changjiang Estuary

TANG Chuanmin, ZHU Jianrong

Journal of East China Normal University(Natural Science) 2020, 2020 (3): 23-31. DOI: 10.3969/j.issn.1000-5641.201941001

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A semi-implicit estuarine, coastal, and ocean model (ECOM-si) was used to simulate and analyze the influence of a rise in water level on runoff, tidal and wind-driven currents, and on current and saltwater intrusion under the combined effects of various dynamic factors. In a scenario where the water level rises 30 cm in the Changjiang Estuary, numerical simulation results show that seaward runoff decreases due to augmentation of the river transection area; tidal currents decrease slightly with increases in water depth; the wind-driven current by northerly winds in the dry season is enhanced, which flow landward in the North Channel and seaward in the South Channel forming horizontal circulation; and the wind-driven current in the North Branch is strengthened. After the water level rise, saltwater intrusion in the North Branch is enhanced; salinity changes slightly in the middle reaches of the South Branch; the most distinct areas of saltwater intrusion enhancement are in the North Channel and North Passage, where the salinity rise is greater than 1 in neap tide and is somewhat reduced in spring tide; the salinity rise in the northern outlet of the North Channel reaches the maximum value observed in the entire estuary; and salinity on the shoal at the river mouth of the South Passage reduces because the water level rises and the nonlinear effect weakens. The water level rise, moreover, results in a salinity increase at the water intake of the three reservoirs (Qingcaosha, Chenhang, and Dongfengxisha) in the water source of the South Branch, which reduces water intake time and affects the safety of the water supply.

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Impact of the South-to-North Water Diversion Project on saltwater intrusion and freshwater resources in the Changjiang Estuary

SU Aiping, Lü Hanghang, WU Yufan

Journal of East China Normal University(Natural Science) 2020, 2020 (3): 32-42. DOI: 10.3969/j.issn.1000-5641.201941031

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The South-to-North Water Diversion Project is an interbasin water diversion project, whose impact on changes in freshwater resources in the Changjiang Estuary is of widespread interest. In this paper, we used a 3D numerical model of estuarine saltwater intrusion to study the impact on saltwater intrusion and freshwater resources in the Changjiang Estuary from both short-term and long-term perspectives. The study, moreover, was focused on the eastern and middle route water transfer schemes of the Project. The results indicate that during the neap-spring tide period in mid-to-late February, the unavailable water intake time, corresponding to salinity greater than 0.45 at the water inlets of the Dongfengxisha, Chenhang, and Qingcaosha is 7.74, 3.08, and 2.72 days, respectively. In the case of a short-term water transfer scheme at river discharge of 1 000 m³/s, saltwater intrusion is intensified, especially at the river mouths of the North Channel, North and South Passages, and in the upper reaches of the North Branch, where salinity rise is most noticeable and a large area shows a salinity rise greater than 0.5; meanwhile, the supply of freshwater in the South Branch decreases. During the neap-spring tide period in mid-to-late February, the unavailable water intake time at the water inlets of the Dongfengxisha, Chenhang and Qingcaosha Reservoirs increases by 1.43, 2.14 and 2.13 days, respectively. In the case of long-term water transfer schemes at river discharge of 1 600 m³/s, the salinity rise in the entire estuary is even more noticeable; a large area of salinity rise greater than 1 shows up on the river mouths of the North Channel, North and South Passages, and a small area of salinity rise greater than 1.5. The supply of freshwater in the South Branch also decreases. During the neap-spring tide period in mid-to-late February, the unavailable water intake time at the water inlets of Dongfengxisha, Chenhang, and Qingcaosha Reservoirs increases by 1.49, 3.08, and 3.08 days, respectively.

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