Semi-quantum key distribution (SQKD) is an important research issue which allows one quantum participant equipped with advanced quantum devices to distribute a shared secret key securely with one classical user who has restricted capabilities. In this paper, we propose a SQKD protocol which allows one quantum user to distribute two different private secret keys to two classical users respectively at the same time. Alice distributes two particle sequences from Bell states to Bob and Charlie respectively. Once the particles have been processed and returned, Alice can simultaneously detect reflected particles by Bob and Charlie based on Bell-state measurement and generate two different raw keys. To enable more participants in sharing keys, this protocol can be extended to the m + 1 party communication scheme by employing m-particle GHZ state. In large-scale communication networks, this extended model significantly reduces the complexity of communication compared to the traditional SQKD scheme. Security analyses show that the presented protocol is free from several general attacks, such as the entangle-measure attack, the modification attack, the double CNOT attack, and so on.

Polyurethane has excellent impact resistance and chemical resistance, so polyurethane coatings are often selected to protect helicopter rotors. but the impact of rainwater when flying in rainy weather can still cause great damage to the polyurethane coating. In order to effectively improve the working life of the polyurethane coating in the rain erosion environment. This paper introduces the failure mechanism of rainwater erosion. The factors influencing the rain erosion performance of polyurethane coatings were discussed from internal and external factors respectively. And the equipment, test methods and standards of rain erosion were summarized. Finally, the problem that the rotation arm of the equipment cannot reach the rotation speed of the helicopter rotor and the incident angle of water droplets cannot be changed, and the future development direction is prospected.

Fluorosilicone rubber has excellent high temperature oil resistance and has been widely used in high temperature oil media. The performance of fluorosilicone rubber will degrade with the length of oil immersion time. In this paper, through oil resistance test, hardness test, tensile test, infrared analysis, differential scanning calorimetry analysis and thermal weight loss analysis, the performance, structure and composition changes of fluorosilicone rubber FS6265 at 150°C and RP3 kerosene soaking process are studied. The results show that in 150°C, RP3 kerosene, the mass and volume of fluorosilicone rubber FS 6265 first increase and then decrease. The hardness and tensile strength gradually decrease with the increase of immersion time, the elongation at break tends to increase slightly and then decrease. The performance changes are mainly caused by swelling, filler migration, side chain rupture and cross-linking damage. The swelling in the early stage of immersion plays a major role, and the filler migration, side chain and cross-linking failure play a major role in the later stage.