In dynamic light scattering (DLS) technology, a non-negative constraint on the solution can improve the inversion accuracy of the particle size distribution (PSD). Different non-negative constraint methods have different effects on the inversion results. Combined with the Tikhonov regularization inversion method, the following non-negativity constraint methods: negative to zero (N-to-Z), multi-negative to zero (Multi-N-to-Z), Lin-projected gradient (LPG), oblique projected Landweber (OPL), projected sequential subspace optimization (PSESOP), interior point Newton (IPN), gradient projection conjugate gradient (GPCG) and trust-region method based on the interior reflective Newton (TR-IRN) method are studied in DLS inversion. In different inversion ranges and noise levels, autocorrelation functions of unimodal and bimodal particle distributions were inverted using different non-negativity constraint methods. From the inversion results, the characteristics of the various methods were obtained, which can be treated as a reference for the implementation of non-negative constraints in Tikhonov regularization inversion of DLS.

For the low accuracy of single-scale inversion method in photon correlation spectroscopy technology, a cascadic multigrid (CMG)- truncated singular value decomposition (TSVD) inversion method that combines the TSVD regularization with CMG technology is proposed. This method decomposes the original problem into several subproblems in different scale grid space. According to the particle sizes inverted from the coarsest scale to the finest scale, the solution of an original inversion problem can be obtained. For the inversion of each subproblem, TSVD method is used. The simulation and experimental data were respectively inverted by TSVD and CMG-TSVD methods. The inversion results demonstrate that the CMG-TSVD method has higher accuracy, more strong noise immunity and better smoothness than the TSVD method.

Aiming at the teaching difficulties of signal and system course, adapting to the new situation of the information age and the engineering education of outcome-based education (OBE), adhering to the traditional classroom teaching and making full use of the network teaching platform and internet technology, a blended teaching mode of internet-engineering education (BTM-IEE) is proposed. In this mode, we adhered to the educational concept of OBE, formulated teaching objectives, optimized teaching content, and built matching teaching resources. In three teaching stages: before class, in class and after class, online-offline blended teaching was effectively organized and implemented by using internet technology, network teaching platform, independently developed a comprehensive experimental system, remote virtual experiment platform, QQ group, etc. In order to ensure a good cycle of teaching quality, a multi-dimensional evaluation system is constructed. A variety of application examples and questionnaire data showed that BTM-IEE can achieve a deep integration of in class-out of class and online-offline, improve students’ engineering application ability, autonomous learning ability, cooperation, communication ability, and cultivate innovative thinking. The horizontal and vertical comparison between the traditional and the improved teaching mode shows that the BTM-IEE can improve the teaching effect, the excellent rate is significantly increased, and the failure rate is significantly reduced. This mode provides a reference for the improvement of the teaching quality of professional courses and has important practical significance.

A self-calibrating variable magnification three-dimensional (3D) tracking system for single fluorescent nanoparticles is proposed. The system was based on astigmatic micro-imaging and has a simple configuration incorporating a dual-spot position detection unit ray transfer matrix. By analyzing this matrix and utilizing the beam vector measurement of a dual-spot position detection unit, it was demonstrated that the proposed tracking system had the self-calibration functions of coaxiality and magnification; thus, it could accurately track the adopted fluorescent nanoparticles through zoom microscopical measurements in 3D. The available measurements of the proposed system and accuracy were experimentally validated.