We investigate optical and piezoelectric properties of the orthorhombic PdS2 under symmetrical biaxial tensile strains with various magnitudes. The ab initio simulation results found that the peaks of the refractive index, extinction coefficient, absorption coefficient and reflectivity of the orthorhombic PdS2 red-shift with the tensile strains. Specifically, we discover that the absorption coefficient of the strained orthorhombic PdS2 (4.01×10 5 /cm-5.52×10 5 /cm) is much higher than traditional optoelectronics, piezoelectric and piezophototronic materials such as Si, Ge, GaInAs, ZnO and monolayer MoS2 demonstrating much wider absorption spectrum (670 nm-1033 nm). Moreover, the piezoelectric constant of the orthorhombic PdS2 is calculated from 0 to 8% tensile strains. Simulation results show the orthorhombic PdS2 with 4% tensile strain has a strong piezoelectric effect (1.33 C/m 2), which is 100-5000 times higher than other deformation magnitudes. The results indicate that the orthorhombic PdS2 will have potential application in piezophotonic and piezoelectric devices.

With the acceleration of urbanization, the scale of urban sewage drainage systems is also getting larger and larger. The pipeline sewage carries a large amount of domestic garbage and sludge after being decomposed by microorganisms, which produces a large amount of toxic, harmful, flammable and explosive gases, such as methane (CH4) and hydrogen sulfide (H2S). When these gases are concentrated in the drainage pipe, it is a serious safety hazard. If these gases are directly discharged into the atmosphere, it will pollute the environment on the one hand, and waste resources on the other. In order to solve this important problem, this paper designs a system for the absorption, storage and reuse of harmful gases in urban sewage pipelines for hydrogen sulfide and methane. The hydrogen sulfide and methane gas are absorbed by the gas adsorption device, and then the gas is pumped out of the adsorption device by a solar driven pump and stored in the gas storage device.

In this project, the detecting bolt loosening technology uses the CMOS camera for image acquisition, and the image is extracted by the FPGA combined with the single-chip computer. The author calculates the relative rotation angle of the bolt mark symbol before and after loosening by image analysis technology, through which we can quantify the loose angle of bolt and judge bolt’s loose condition. Then, the author uses the bolt screw maintenance machine to screw the loose bolt, which can achieve the purpose of repairing the loose bolt. This paper is of great significance in providing a theoretical basis for the theoretical design and practical engineering application of the rail maintenance machine.

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