In this paper, the Drinfeld-Sokolov-Satsuma-Hirota (DSSH) system is studied by using residual symmetry and the consistent Riccati expansion (CRE) method, respectively. The residual symmetry of the DSSH system is localized to Lie point symmetry in a properly prolonged system, based on which we get a new B & auml;cklund transformation for this system. New symmetry reduction solutions of the DSSH system are obtained by applying the classical Lie group approach on the prolonged system. Moreover, the DSSH system proves to be CRE integrable and new interesting interaction solutions between solitons and periodic waves are generated and analyzed.

A nonlocal coupled Kadomtsev–Petviashivili (ncKP) system with shifted parity ( Pˆsx ) and delayed time reversal ( Tˆd ) symmetries is generated from the local coupled Kadomtsev–Petviashivili (cKP) system. By introducing new dependent variables which have determined parities under the action of PˆsxTˆdd , the ncKP is transformed to a local system. Through this way, multiple even number of soliton solutions of the ncKPI system are generated from N-soliton solutions of the cKP system, which become breathers by choosing appropriate parameters. The standard Lie symmetry method is also applied on the ncKPII system to get its symmetry reduction solutions.

Two (3+1)-dimensional shallow water wave equations are studied by using residual symmetry and the consistent Riccati expansion (CRE) method. Through localization of residual symmetries, symmetry reduction solutions of the two equations are obtained. The CRE method is applied to the two equations to obtain new Bäcklund transformations from which a type of interesting interaction solution between solitons and periodic waves is generated.

In this paper, the Sharma-Tasso-Olver-Burgers (STOB) system is analyzed by the Lie point symmetry method. The hypergeometric wave solution of the STOB equation is derived by symmetry reductions. In the meantime, the consistent tanh expansion (CTE) method is applied to the STOB equation. An nonauto-Bäcklund (BT) theorem that includes the over-determined equations and the consistent condition is obtained by the CTE method. By using the nonauto-BT theorem, the interactions between one-soliton and the cnoidal wave, and between one-soliton and the multiple resonant soliton solutions, are constructed. The dynamics of these novel interaction solutions are shown both in analytical and graphical forms. The results are potentially useful for explaining ocean phenomena.

A nonlocal coupled KdV (NCKdV) system is constructed from the coupled KdV (CKdV) system by using the consistent correlated bang method. By converting the NCKdV system into a local system, a general form of N-soliton solutions of the NCKdV system is derived from N-soliton solutions of the CKdV system, among which $$N=2,\,3,\,4$$ cases multiple soliton solutions of the NCKdV system are analyzed with graphs. Various single soliton solutions and periodic wave solutions are generated directly from solutions of the CKdV system. In addition, the classical Lie symmetry method is applied on the NCKdV system to obtain its symmetry group and symmetry reduction solutions.

A nonlocal Boussinesq equation is deduced from the local one by using consistent correlated bang method.To study various exact solutions of the nonlocal Boussinesq equation,it is converted into two local equations which contain the local Boussinesq equation.From the N-soliton solutions of the local Boussinesq equation,the N-soliton solutions of the nonlocal Boussinesq equation are obtained,among which the(N=2,3,4)-soliton solutions are analyzed with graphs.Some periodic and traveling solutions of the nonlocal Boussinesq equation are derived directly from the known solutions of the local Boussinesq equation.Symmetry reduction solutions of the nonlocal Boussinesq equation are also obtained by using the classical Lie symmetry method.

The two‐mode Korteweg–de Vries (TMKdV) equation describes propagation of two different waves modes simultaneously. By using consistent correlated bang (CCB) method, a nonlocal form of the TMKdV equation is constructed and converted into two local equations with its dependent variables having definite parity. Multiple soliton solutions of the nonlocal TMKdV equation are obtained by using known multiple soliton solutions of the TMKdV equation, and some singular travelling wave solutions are also generated in a similar way. The classical Lie symmetry method is also carried on the nonlocal TMKdV equation to get its symmetry reduction solutions.

The consistent tanh expansion (CTE) method is successfully applied to the coupled integrable dispersionless (CID) system. A nonauto-Bäcklund transformation (BT) theorem includes two fields f and v 1 is obtained by using the CTE method. One obtains the consistent condition in the nonauto-BT theorem by means of the relation between the fields f and v 1 . The CID system possesses the CTE solvability property by some detailed analysis. Many interactions between one soliton and multiple resonant solitons, and between one soliton and cnoidal waves are generated by using the nonauto-BT theorem. The types of bright and gray two front waves are shown by some figures. In the meanwhile, the nonlocal symmetry is obtained by the truncated Painlevé method and the Möbious invariant form. The initial value problem and an auto-BT are constructed by the localization procedure.

A general third order of linear partial differential equation in [Formula: see text] dimensions is studied by using the ansätz method. The lump solutions which localize in all directions in the whole [Formula: see text]-space are derived by the ansätz method. Diversity interactions including interacted lumps with periodic waves, interaction between lumps and multi-soliton, and interaction among lumps, multi-soliton and periodic waves are obtained by selecting the arbitrary functions. The phenomena of interaction between a lump and one-kink soliton, interaction between a lump and periodic waves, and interaction among a lump, one-kink soliton and periodic waves are analyzed by the three-dimensional plots and contour plots. The results may enrich the existing lump solutions in the [Formula: see text]-dimensional partial differential equations.

A supersymmetric version of the Ito equation is proposed by extending the independent and dependent variables for the classic Ito equation.To investigate the integrability of the N = 1 supersymmetric Ito（sIto） equation, a singularity structure analysis for this system is carried out.Through a detailed analysis in two cases by using Kruskal’s simplified method, the sIto system is found to pass the Painlevé test, and thus is Painlevé integrable.

A (2 + 1)-dimensional coupled nonlinear partial equation which possesses a Hirota bilinear form is introduced. Based on the Hirota bilinear form, two solitary waves are constructed. In the meanwhile, lump waves are derived by using a positive quadratic function. By combining an exponential function with a quadratic function, interaction solutions between a lump and a one-kink soliton, and between a bi-lump and a one-soliton solution are generated. Some special concrete interaction solutions are depicted in both analytical and graphical ways.

By applying a simple symmetry reduction on a two-layer liquid model, a nonlocal counterpart of it is obtained. Then, a general form of nonlocal nonlinear Schrödinger (NNLS) equation with shifted parity, charge conjugate and delayed time reversal is obtained by using multi-scale expansion method. Some kinds of elliptic periodic wave solutions of the NNLS equation, which become soliton solutions and kink solutions when the modulus is taken as unity, are obtained by using elliptic function expansion method. Some representative figures of these solutions are given and analyzed in detail. In addition, by carrying out the classical symmetry method on the NNLS equation, not only the Lie symmetry group but also the related symmetry reduction solutions are given.

A nonlocal form of a two-layer fluid system is proposed by a simple symmetry reduction, then by applying multiple scale method to it a general nonlocal two place variable coefficient modified KdV (VCmKdV) equation with shifted space and delayed time reversal is derived. Various exact solutions of the VCmKdV equation, including elliptic periodic waves, solitary waves and interaction solutions between solitons and periodic waves are obtained and analyzed graphically. As an illustration, an approximate solution of the original nonlocal two-layer fluid system is also given.

Based on the Hirota bilinear operators and their generalized bilinear derivatives, we formulate two new (2+1)-dimensional nonlinear partial differential equations, which possess lumps. One of the new nonlinear differential equations includes the generalized Calogero-Bogoyavlenskii-Schiff equation and the generalized Bogoyavlensky-Konopelchenko equation as particular examples, and the other has the same bilinear form with different D p -operators. A class explicit lump solutions of the new nonlinear differential equation is constructed by using the Hirota bilinear approaches. A specific case of the presented lump solution is plotted to shed light on the charateristics of the lump.

From a two-vortex interaction model in atmospheric and oceanic systems, a nonlocal counterpart with shifted parity and delayed time reversal is derived by a simple AB reduction. To obtain some approximate analytic solutions of this nonlocal system, the multi-scale expansion method is applied to get an AB-Burgers system. Various exact solutions of the AB-Burgers equation, including elliptic periodic waves, kink waves and solitary waves, are obtained and shown graphically. To show the applications of these solutions in describing correlated events, a simple approximate solution for the two-vortex interaction model is given to show two correlated dipole blocking events at two different places. Furthermore, symmetry reduction solutions of the nonlocal AB-Burgers equation are also given by using the standard Lie symmetry method.

In many networked systems, synchronization is important and useful, and how to enhance synchronizability is an interesting problem. Based on the matrix perturbation theory, we analyze five methods of network synchronization enhancement, including the link removal, node removal, dividing hub node, pull control, and pinning control methods, and obtain explicit expressions for eigenvalue changes. By these comparisons, we find that, among all these methods, the pull control method is remarkable, as it can extend the synchronization (coupling strength) region from both the left and right sides, for any controlled node. Extensive simulation results are given to support the accuracy of the perturbation-based analysis.

Residual symmetry of the (3+1)-dimensional breaking soliton equation is obtained and localized to a Lie point symmetry in a properly prolonged system. The general form of Lie point symmetry group and the corresponding symmetry reduction solutions of the prolonged system are obtained by using the standard Lie symmetry method, which include various interaction solutions between solitons and nonlinear background waves of the (3+1)-dimensional breaking soliton equation. Furthermore, the (3+1)-dimensional breaking soliton equation is proved to be integrable in the sense of having consistent Riccati expansion. Based on this property, some new Bäcklund transformations of the (3+1)-dimensional breaking soliton equation are obtained, from which interaction solutions between solitions and cnoidal waves are explicitly given.

Through truncated Painlevé expansion of the (2 + 1)-dimensional Burgers system the residual symmetry is obtained and localized to a local one in an enlarged system by introducing new dependent variables. Using Lie’s first theorem, the Bäcklund transformation related to the localized residual symmetry is derived. Furthermore, the N-th-Bäcklund transformation of the (2 + 1)-dimensional Burgers system, which is expressed by determinants in a compact form, related to the symmetry of linear superposition of multiple residual symmetries is obtained through localization procedure.

The residual symmetry of the (3 + 1) -dimensional Burgers system is localized to a Lie point symmetry in a prolonged system and the corresponding finite transformation is obtained by using Lie’s first theorem. By further localize the linear superposition of multiple residual symmetries, the N -th Bäcklund transformations (BT) of the (3 + 1) -dimensional Burgers system are also got. By applying the standard Lie symmetry method to the prolonged system, not only the Lie symmetry group but also the symmetry reduction solutions are obtained, which include abundant interaction solutions between solitons and nonlinear waves. Furthermore, the (3 + 1) -dimensional Burgers system is proved to have consistent Riccati expansion (CRE) property, based on which some new BTs are given.