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Abstract The indirect‐to‐direct band‐gap transition in transition metal dichalcogenides (TMDCs) from bulk to monolayer, accompanying with other unique properties of two‐dimensional materials, has endowed them great potential in optoelectronic devices. The easy transferability and feasible epitaxial growth pave a promising way to further tune the optical properties by constructing van der Waals heterostructures. Here, we performed a systematic high‐throughput first‐principles study of electronic structure and optical properties of the layer‐by‐layer stacking TMDCs heterostructing superlattices, with the configuration space of [(MX2)n(M′X′2)10−n] (M/M′ = Cr, Mo, W; X/X′ = S, Se, Te; n = 0‐10). Our calculations involving long‐range dispersive interaction show that the indirect‐to‐direct band‐gap transition or even semiconductor‐to‐metal transition can be realized by changing component compositions of superlattices. Further analysis indicates that the indirect‐to‐direct band‐gap transition can be ascribed to the in‐plane strain induced by lattice mismatch. The semiconductor‐to‐metal transition may be attributed to the band offset among different components that is modified by the in‐plane strain. The superlattices with direct band‐gap show quite weak band‐gap optical transition because of the spacial separation of the electronic states involved. In general, the layers stacking‐order of superlattices results in a small up to 0.2 eV band gap fluctuation because of the built‐in potential. Our results provide useful guidance for engineering band structure and optical properties in TMDCs heterostructing superlattices.

In this paper, a new robust adaptive control method has been proposed for nonlinear systems with uncertainties. This method combines the advantages of self-tuning control and sliding mode control. A simple parameterization model is first derived based on a linear dynamic model and unmodeled dynamics. Based on a modified sliding surface, the design procedure is based on the indirect adaptive control concept. This controller consists of four parts: 1) the system parameters estimation; 2) the unmodeled dynamics estimation; 3) the weighting polynomials updating; and 4) the control law calculation. The key merits of this controller are as follows: 1) the controller is applicable to non-minimum phase and open-loop unstable systems; 2) the estimation of the unmodeled dynamics is introduced as a feedback compensation control to improve the response; and 3) the strict stability condition is eliminated and a desirable performance is ensured during a wide operation region. Moreover, the control problem of a shape memory alloy actuator system is considered. In the literature, the mechanism model-based controllers have been extensively reported to address this issue. As an alternative, we describe this plant as a gray-box model. The adaptation algorithm and the control law have been implemented through the Beckhoff controller. The experimental results have demonstrated that the proposed controller has wider applicability than some existing methods.