基于顺序注射的水质多参数在线监测系统设计

针对水质监测的预警、预报、溯源的数据量少，建设费用和运维成本高的问题，文中基于顺序注射技术，融合紫外分光光度法的水质检测原理，提出一种微试剂水质多参数在线监测系统，结合模块化布局设计，实现系统的小型化、自动化和智能化。基于故障树分析法建立水质检测过程故障诊断专家系统，实现水质在线监测系统自主故障诊断，减少因故障导致的经济损失，降低运维成本与人员需求。相比于传统的水质监测设备，微试剂水质多参数在线监测系统可同时检测总磷、总氮、高锰酸盐、氨氮等参数，监测仪体积小，长×宽×高为560 mm×420 mm×700 mm，试剂用量小于3 mL，仪器峰值耗电量为4.8 W·h/次。以总磷、氨氮、高锰酸盐为研究对象进行实验，结果表明，所设计监测系统测量精度高、线性度良好，相关系数≥0.989 8，重复性的相对标准偏差（RSD）≤2.552%。微试剂水质多参数在线监测仪符合水质在线监测设备的技术要求，具有应用价值，可为在线监测仪研究提供一种新的设计思路。     

Disappearance of Superconductivity and a Concomitant Lifshitz Transition in Heavily Overdoped Bi_2Sr_2CuO_6 Superconductor Revealed by Angle-Resolved Photoemission Spectroscopy

By partially doping Pb to effectively suppress the superstructure in single-layered cuprate Bi_2Sr_2CuO_(6+δ)(Pb-Bi2201) and annealing them in vacuum or in high pressure oxygen atmosphere, a series of high quality Pb-Bi2201 single crystals are obtained with T_c covering from 17 K to non-superconducting in the overdoped region. High resolution angle resolved photoemission spectroscopy measurements are carried out on these samples to investigate the evolution of the Fermi surface topology with doping in the normal state. Clear and complete Fermi surfaces are observed and quantitatively analyzed in all of these overdoped Pb-Bi2201 samples. A Lifshitz transition from holelike Fermi surface to electron-like Fermi surface with increasing doping is observed at a doping level of ~0.35. This transition coincides with the change that the sample undergoes superconducting-to-non-superconducting states.Our results reveal the emergence of an electron-like Fermi surface and the existence of a Lifshitz transition in heavily overdoped Bi2201 samples. This provides important information in understanding the connection between the disappearance of superconductivity and the Lifshitz transition in the overdoped region.     

Optical cavity structure design and optical path simulation for rapid nitric oxide detection

According to the chemiluminescence reaction mechanism of nitric oxide (NO) and ozone (O3), a new cylindrical total reflection S-type optical cavity design for rapid detection of NO gas is proposed. The optical cavity model is based on the total reflection S-type structure on the inner wall of the cylinder. Optical software ZEMAX was used to simulate the optical path of the model, and software FLUENT was used to simulate and verify the structure. The comparative analysis showed that the chemiluminescence collection efficiency of the S-type optical cavity collection path was 36.6%, and the gas reaction and mixing in the S-type optical cavity model was more sufficient, and the reaction mixing stability error was 0.049, which was 2 times higher than the traditional stability error. The model is simple in structure and meets the new national standards. It provides a practical idea of design for the real-time exhaust gas detection.     

Flat Band and Z2 Topology of Kagome Metal CsTi3Bi5

The simple kagome-lattice band structure possesses Dirac cones, flat band, and saddle point with van Hove singularities in the electronic density of states, facilitating the emergence of various electronic orders. Here we report a titanium-based kagome metal CsTi₃Bi₅ where titanium atoms form a kagome network, resembling its isostructural compound CsV₃Sb₅. Thermodynamic properties including the magnetization, resistance, and heat capacity reveal the co...