Search

In this paper, a nonlocal two-component complex modified Korteweg–de Vries (mKdV) equation is investigated and its Darboux transformation is derived. By using the Darboux transformation, soliton solutions are obtained which include dark soliton solution, quasi-W-type soliton, quasi-M-type soliton and periodic solution.

The Sasa-Satsuma equation, a higher-order nonlinear Schr\"{o}dinger equation, is an important integrable equation, which displays the propagation of femtosecond pulses in optical fibers. In this paper, we investigate a generalized Sasa-Satsuma(gSS) equation. The Darboux transformation(DT) for the focusing and defocusing gSS equation is constructed. By using the DT, various of soliton solutions for the generalized Sasa-Satsuma equation are derived, including hump-type, breather-type and periodic soliton. Dynamics properties and asymptotic behavior of these soliton solutions are analyzed. Infinite number conservation laws and conserved quantities for the gSS equation are obtained.

The total first marriage rate (TFMR) of Chinese women shows a downward trend in fluctuations from 1970 to 2016, but it is affected by the tempo distortion caused by changes in the mean age at first marriage. Thus, we compare the total first marriage rate (TFMR) and tempo-adjusted period proportion ever married (PPEM*) to estimate the extent to which the TFMR is affected by tempo effects. We also decompose the women’s TFMR change into its quantum and tempo components from 1970 to 2016 to analyze how much of the changes in TFMR are due to the quantum changes and how much of it is caused by tempo effects. The results show that the tempo effects have had a persistent influence on the period TFMR of Chinese women from 1970 to 2016. The recent decline in the TFMR in Chinese women is mainly due to the first marriage delay, not signaling a retreat from universal marriage.

A partir des donnees issues du recensement general de la population de 2014, nous analysons a l’echelle des bassins de vie, le lien entre migration residentielle a destination des espaces ruraux et periurbains et segregation socio-spatiale. Nos resultats montrent que les individus sont sensibles aux caracteristiques sociodemographiques du voisinage dans leurs territoires d’origine et de destination. Alors que le capital humain est source de retention pour les territoires d’origine, les individus mobiles apparaissent sensibles au degre d’homogeneite sociale des territoires. Enfin, l’influence des caracteristiques sociodemographiques sur les migrations residentielles vers les territoires ruraux et periurbains varie selon les categories socioprofessionnelles.Classification JEL : J61, R23, R15, C01.

To understand the groundwater environmental quality and the impact of trace elements in the construction of urban agglomeration in China, this study collected 58 groundwater samples from the core area of the Chang-Zhu-Tan urban agglomeration (Changsha, Zhuzhou, Xiangtan) and quantitatively analyzed the content of 13 dissolved trace element and their spatial distribution characteristics. The health risk assessment model was further used to evaluate the human health risk caused by trace element pollution in groundwater. It was observed that Ba had the highest average concentration (0.28 mg·L−1), whereas Cd had the lowest (2.1 × 10−5 mg·L−1). Compared with China’s groundwater environmental quality standard, the exceeding rates of Se, Mn, Zn, and Ni concentrations were 37.93%, 17.24%, 1.72% and 1.72%, respectively. Ba, Cd, Co, Cr, Cu, Fe, Mo, and Pb did not exceed the corresponding standards. The 13 trace elements were distributed in a scattered pattern in space and the trace elements in both banks of the Xiang River, Zhuzhou, Weishui River and surrounding areas were relatively high. Health risk assessments showed that the carcinogenic risk values of Cd, Cr, and Pb and the health risk values of 10 non-carcinogenic elements were less than the corresponding maximum acceptable risk level. The health risks associated with non-carcinogenic substances through ingestion were higher than those associated with dermal absorption. Among the non-carcinogenic substances, Ba and Mn posed the greatest health risks. With respect to drinking water exposure, Cr had the highest carcinogenic risk, followed by Pb. Furthermore, Cd had the lowest carcinogenic risk. This study recommended that continuous monitoring of Ba, Mn, and Cr in groundwater should be practiced by assessing the risk of these elements in the Chang-Zhu-Tan urban agglomeration.

Although straw mulching and nitrogen applications are extensively practiced in the agriculture sector, large uncertainties remain about their impacts on crop yields and especially the environment. The responses of summer maize yields, fertilizer use efficiency, and greenhouse gas (GHG) emissions including carbon dioxide (CO

It is a challenge to characterize soil respiration of crop residue return systems in the North China Plain (NCP) under no-tillage (NT) and conventional tillage (CT) practices. In this study, we addressed the "hot spot" research challenge of impacts of tillage practices on soil carbon storage and soil CO

Background: Japanese quail (Coturnix japonica) are important and widely distributed poultry in China. Researchers continue to pursue genetic selection for heavier quail. The intestinal microbiota plays a substantial role in growth promotion; however, the mechanisms involved in growth promotion remain unclear.Results: We generated 107.3 Gb of cecal microbiome data from ten Japanese quail, providing a series of quail gut microbial gene catalogs (1.25 million genes). We identified a total of 606 main microbial species from 1,033,311 annotated genes distributed among the ten quail. Seventeen microbial species from the genera Anaerobiospirillum, Alistipes, Barnesiella, and Butyricimonas differed significantly in their abundances between the female and male gut microbiotas. Most of the functional gut microbial genes were involved in metabolism, primarily in carbohydrate transport and metabolism, as well as some active carbohydrate-degrading enzymes. We also identified 308 antibiotic-resistance genes (ARGs) from the phyla Bacteroidetes, Firmicutes and Euryarchaeota. Studies of the differential gene functions between sexes indicated that abundances of the gut microbes that produce carbohydrate-active enzymes varied between female and male quail. Bacteroidetes was the predominant ARG-containing phylum in female quail; Euryarchaeota was the predominant ARG-containing phylum in male quail.Conclusion: This article provides the first description of the gene catalog of the cecal bacteria in Japanese quail as well as insights into the bacterial taxa and predictive metagenomic functions between male and female quail to provide a better understanding of the microbial genes in the quail ceca.

Agricultural tillage practices have a significant impact on the generation and consumption of greenhouse gases (GHGs), the primary causes of global warming. Two tillage systems, conventional tillage (CT) and no-tillage (NT), were compared to evaluate their effects on GHG emissions in this study. Averaged from 2018 to 2020, significant decreases of CO

In this paper, we investigate a multi-component AB system that appears in geophysical fluid dynamics. We construct bright–dark soliton solutions of the system using the Hirota’s bilinear method. We obtain asymptotic behaviors of two-soliton solution for the two-component AB system and prove that the interactions between two bright and two dark solitons are elastic. Under various parameter conditions, the oblique interactions and bound states of solitons are analyzed in detail. By use of the Pfaffian technique, we present N -bright and N − dark soliton solutions of the two- and multi-component AB system. The results obtained in this paper can be helpful for the study of vector multi-dark solitons in many physical systems such as nonlinear optics and fluid dynamics.

River ecosystems are under increasing stress in the background of global change and ever-growing anthropogenic impacts in Central Asia. However, available water quality data in this region are insufficient for a reliable assessment of the current status, which come as no surprise that the limited knowledge of regulating processes for further prediction of solute variations hinders the development of sustainable management strategies. Here, we analyzed a dataset of various water quality variables from two sampling campaigns in 2019 in the catchments of two major rivers in Central Asia—the Amu Darya and Syr Darya Rivers. Our results suggested high spatial heterogeneity of salinity and major ion components along the longitudinal directions in both river catchments, pointing to an increasing influence of human activities toward downstream areas. We linked the modeling outputs from the global nutrient model (IMAGE-GNM) to riverine nutrients to elucidate the effect of different natural and anthropogenic sources in dictating the longitudinal variations of the riverine nutrient concentrations (N and P). Diffuse nutrient loadings dominated the export flux into the rivers, whereas leaching and surface runoff constituted the major fractions for N and P, respectively. Discharge of agricultural irrigation water into the rivers was the major cause of the increases in nutrients and salinity. Given that the conditions in Central Asia are highly susceptible to climate change, our findings call for more efforts to establish holistic management of water quality.

To get more insight into the relation between discrete model and continuous counterpart, a new integrable semi-discrete Kundu–Eckhaus equation is derived from the reduction in an extended Ablowitz–Ladik hierarchy. The integrability of the semi-discrete model is confirmed by showing the existence of Lax pair and infinite number of conservation laws. The dynamic characteristics of the breather and rational solutions have been analyzed in detail for our semi-discrete Kundu–Eckhaus equation to reveal some new interesting phenomena which was not found in continuous one. It is shown that the theory of the discrete system including Lax pair, Darboux transformation and explicit solutions systematically yields their continuous counterparts in the continuous limit.

Understanding the response of soil respiration to global warming in agro-ecosystem is crucial for simulating terrestrial carbon (C) cycle. We conducted an infrared warming experiment under conventional tillage (CT) and no-tillage (NT) farmland for winter wheat and summer maize rotation system in North China Plain (NCP). Treatments include CT with and without warming (CTW and CTN), NT with and without warming (NTW and NTN). The results indicated that warming had no significant effect on soil moisture in irrigated farmland of NCP (P>0.05). The elevated average soil temperature of 1.1–1.6°C in crop growing periods could increase annual soil CO2 emission by 10.3% in CT filed (P>0.05), but significantly increase it by 12.7% in NT field (P

In this paper, we investigate a general integrable nonlocal coupled nonlinear Schrodinger (NLS) system with the parity-time (PT) symmetry, which contains not only the nonlocal self-phase modulation and the nonlocal cross-phase modulation, but also the nonlocal four-wave mixing terms. This nonlocal coupled NLS system is a nonlocal version of a coupled NLS system. The general N-th Darboux transformation for the nonlocal coupled NLS equation is constructed. By using the Darboux transformation, its soliton solutions are obtained. Dynamics and interactions of different kinds of soliton solutions are discussed.

Very recently, Ablowitz and Musslimani introduced a new integrable nonlocal nonlinear Schrodinger equation. In this paper, we investigate an integrable nonlocal modified Korteweg-de Vries equation (mKdV) which can be derived from the well-known AKNS system. We construct the Darboux transformation for the nonlocal mKdV equation. Using the Darboux transformation, we obtain its different kinds of exact solutions including soliton, kink, antikink, complexiton, rogue-wave solution, and nonlocalized solution with singularities. It is shown that these solutions possess new properties which are different from the ones for mKdV equation.

In this paper, the gauge equivalence between the modified Landau–Lifshitz equation and the perturbed defocusing nonlinear Schrodinger equation is proved from the perspective of geometry of given curvature condition. By using the gauge equivalence and the soliton perturbation theory of defocusing nonlinear Schrodinger equation, the first-order approximate 1-soliton solution to the modified Landau–Lifshitz equation is given.

The generalized coupled integrable dispersionless (CID) equation describes the current-fed string in a certain external magnetic field. In this paper, we propose a multi-component complex CID equation. The integrability of the multi-component complex equation is confirmed by constructing Lax pairs. One-soliton and two-soliton solutions are investigated to exhibit rich evolution properties. Especially, similar as the multi-component short pulse equation and the first negative AKNS equation, periodic interaction, parallel solitons, elastic and inelastic interaction, energy re-distribution happen between two solitons. Multi-soliton solutions are given in terms of Pfaffian expression by virtue of Hirota’s bilinear method.

This study examined the effects of a high-dose Saccharomyces cerevisiae inoculant alone or jointly with Lactobacillus plantarum on nutrient preservation, fermentation quality, and aerobic stability of sweet corn stalk silage. Fresh stalks (231 g dry matter (DM)/kg) were chopped and subjected to the following treatments: (1) deionized water (Uninoculated, U), (2) S. cerevisiae at 1 &times, 108 cfu/g of fresh forage (S), and (3) S. cerevisiae at 1 &times, 108 cfu/g plus L. plantarum at 1 &times, 105 cfu/g (SL). Treated stalks were ensiled in 5-litre laboratory silos for 30, 60, and 90 d. The S and SL silages had a greater (p &lt, 0.001) pH and greater crude protein, ammonia nitrogen/total nitrogen, neutral detergent fibre, acid detergent fibre, and ethanol contents at all three ensiling periods than the U silage. Acetate, propionate and volatile fatty acids in the S and SL silages after 30 and 90 d of ensiling were greater (p &lt, 0.05) than those in the U silage, but they were lower (p &lt, 0.05) in the S and SL silages than in the U silage after 60 d. The lactate and V-score of the S and SL silages were lower (p &lt, 0.001) than those of the U silage at all three ensiling periods. Compared with the U group, the aerobic stability of the S silage after 90 d of ensiling decreased (p &lt, 0.05), and the aerobic stability of the SL silage was unaffected (p &gt, 0.05). Overall, the quality of sweet corn stalk silage was not improved by inoculation with 108 cfu/g of S. cerevisiae alone or in combination with 1 &times, 105 cfu/g of L. plantarum.

En s’appuyant sur les microdonnées du recensement canadien, cet article analyse les inégalités de revenus entre Canadiens de naissance et immigrants en provenance des pays en développement ainsi que la situation des immigrants sur le marché du travail. Nos résultats montrent clairement qu’il existe une disparité de revenus entre natifs, immigrants occidentaux et non occidentaux, et que cette disparité résulte des caractéristiques qui diffèrent entre ces trois groupes ainsi que de facteurs non observables tels que la discrimination. L’éducation n’a pas le même rendement pour tous les immigrants. La déqualification des immigrants est inégalement distribuée selon leur origine., Based on Canadian census microdata, this paper analyzes income inequality between native-born Canadians and immigrants from developing countries as well as discrimination against immigrants in the labor market. Our results clearly show that there is a disparity in income between the native-born and non-Western immigrants and that this disparity results from differences in characteristics between the three groups and unobservable factors, such as discrimination. Deskilling of immigrants is unequally distributed according to their origin.

Coupled dispersionless equation is an important model in quantum physics. Complex coupled dispersionless equation has valuable applications in geomerty. Recently, Ablowitz and Musslimani introduced and investigated a large class of reverse space, reverse time and reverse space-time nonlocal integrable equations. In this paper, we investigate a reverse space-time nonlocal complex coupled dispersionless equation, which was proposed in our paper [1]. By means of the Darboux transformation, we obtain its multi-soliton solutions from zero seed and nonzero seed. The asymptotic behavior of these solutions is discussed.

The hub-periphery development pattern of the Guangdong economy, to some extent, is a miniature of that of the Chinese economy. The Pearl River Delta, drawing from its first-nature comparative advantages in factor endowments and proximity to Hong Kong SAR, China, and Macau SAR, China, and the second-nature advantages as first-movers in the reforms in attracting and retaining domestic and foreign resources, has developed into a regional economic center. This paper examines the pattern of inter- and intra-provincial migration and that of the concentration of production, to explore the challenges and opportunities for the success of “double transfer.” The paper suggests a four-prong approach, to improve the business environment, support the realization of latent comparative advantages, increase the skill level of the labor force to support the upgrade of the production structure, and protect the vulnerable, to support the inclusive growth of the economy in Guangdong in a sustainable manner.

A semidiscrete Boussinesq system has been introduced by the means of recombination flows from a 4 × 4 spectral problem. We construct the Darboux transformation and explicit solutions for the semidiscrete Boussinesq system. We can find that the 1-fold Darboux-transformation solution of the system possesses more than one traveling waves. Especially, one of solutions comes into being two solitary waves after a period of time, which means that properties of solutions to semidiscrete integrable systems are richer than the ones in continuous integrable systems.

In this paper, we show that the nonlocal discrete focusing nonlinear Schr\"odinger (NLS) and nonlocal discrete defocusing NLS equation are gauge equivalent to the discrete coupled Heisenberg ferromagnet (HF) equation and the discrete modified coupled HF equation, respectively. Under the continuous limit, the discrete coupled HF equation and the modified discrete coupled HF equation lead to the corresponding coupled HF equation and modified coupled HF equation. This means that the nonlocal focusing and defocusing NLS equations are gauge equivalent to the coupled HF and coupled modified HF equations. The solution of the modified coupled HF equation is obtained by using the solution of nonlocal defocusing NLS equation.

Integrable and nonintegrable discrete nonlinear Schrödinger equations (NLS) are significant models to describe many phenomena in physics. Recently, Ablowitz and Musslimani introduced a class of reverse space, reverse time, and reverse space-time nonlocal integrable equations, including the nonlocal NLS equation, nonlocal sine-Gordon equation, nonlocal Davey-Stewartson equation, etc. Moreover, the integrable nonlocal discrete NLS has been exactly solved by inverse scattering transform. In this paper, we study a nonintegrable discrete nonlocal NLS, which is a direct discrete version of the reverse space nonlocal NLS. By applying discrete Fourier transform and modified Neumann iteration, we present its stationary solutions numerically. The linear stability of the stationary solutions is examined. Finally, we study the Cauchy problem for the nonlocal NLS equation numerically and find some different and new properties on the numerical solutions comparing with the numerical solutions of the Cauchy problem for the NLS equation.

Nonlinear Schr\"odinger equation, short pulse equation and complex short pulse equation have important application in nonlinear optics. They can be derived from the Maxwell equation. In this paper, we investigate a coupled focusing-defocusing complex short pulse equation. The bright-bright, bright-dark and dark-dark soliton solutions of the coupled focusing-defocusing complex short pulse equation are given. Then the breathers are derived from the dark soliton solution. The rogue wave solutions are also constructed. The dynamics and the asymptotic behavior of the soliton solutions are analyzed, which reveals that there exist the elastic or inelastic collision in bright-bright soliton solution. But the interactions of bright-dark and dark-dark soliton solutions are both elastic., Comment: 26 pages, 16 figures