A Cell Condition-Sensitive Frequency Segmentation Method Based on the Sub-Band Instantaneous Energy Spectrum of Aluminum Electrolysis Cell Voltage

Cell voltage is a widely used signal that can be measured online from an industrial aluminum electrolysis cell.A variety of parameters for the analysis and control of industrial cells are calculated using the cell voltage.In this paper,the frequency segmentation of cell voltage is used as the basis for designing filters to obtain these parameters.Based on the qualitative analysis of the cell voltage,the sub-band instantaneous energy spectrum(SIEP)is first proposed,which is then used to quantitatively represent the characteristics of the designated frequency bands of the cell voltage under various cell conditions.Ultimately,a cell condition-sensitive frequency segmentation method is given.The proposed frequency segmentation method divides the effective frequency band into the[0,0.001]Hz band of lowfrequency signals and the[0.001,0.050]Hz band of low-frequency noise,and subdivides the lowfrequency noise into the[0.001,0.010]Hz band of metal pad abnormal rolling and the[0.01,0.05]Hz band of sub-low-frequency noise.Compared with the instantaneous energy spectrum based on empirical mode decomposition,the SIEP more finely represents the law of energy change with time in any designated frequency band within the effective frequency band of the cell voltage.The proposed frequency segmentation method is more sensitive to cell condition changes and can obtain more elaborate details of online cell condition information,thus providing a more reliable and accurate online basis for cell condition monitoring and control decisions.

出现声音嘶哑的18例Chiari畸形的诊治分析

目的探讨出现声音嘶哑等耳鼻咽喉症状的Chiari畸形患者的诊治情况。方法回顾性收集青岛大学附属医院1989年1月至2020年1月收治的18例出现声音嘶哑的Chiari畸形患者的临床资料,其中男5例,女13例,年龄3~71岁,中位年龄52岁。所有患者均接受颅脑MRI和喉镜检查,总结患者症状和首诊科室、确诊时间、总病程、声音嘶哑病程、诊断治疗情况和术后恢复时间。随访3~16年,中位随访6.5年。采用描述性方法进行分析。结果18例患者首次就诊科室包括神经科(9例)、耳鼻咽喉头颈外科(5例)、儿科(2例)、骨科(1例)、呼吸科(1例),除神经科7例初诊时明确诊断之外,就诊于其余科室的11例患者均未及时确诊。18例Chiari畸形患者确诊时病程2个月~5年,其中声音嘶哑症状出现20 d~5年。确诊后,9例患者接受后颅窝减压手术治疗,其中1例同时行脊髓空洞引流术,术后8例患者症状明显改善,症状改善时间为1~30 d;9例患者选择药物保守治疗,其中8例声嘶症状无改善,6例病情进展加重。结论后颅窝减压手术是治疗Chiari畸形的有效方式,患者预后较好。及时诊断和治疗可以改善患者预后。

Single-Cu-atoms anchored on 3D macro-porous carbon matrix as efficient catalyst for oxygen reduction and Pt co-catalyst for methanol oxidation

Single metal atoms immobilized on a carbon substrate are of great potential for enhancing the catalytic activities for oxygen reduction and methanol oxidation reactions(ORR/MOR)owing to the maximized atom utilization.Herein,single copper atoms(SCAs)are loaded on macro-porous nitrogen-doped carbon(Cu-NC)derived from zeolitic imidazolate framework-8(ZIF-8),which are used as catalysts for ORR and Pt-supports for MOR.For ORR,the catalyst marked as Cu-NC-3 exhibits a higher peak potential of 0.87 V(vs.Reversible hydrogen electrode)than that of commercial Pt/C(0.83 V),mainly attributing to that the 3D macro-porous structure of Cu-NC-3 provides adequate space for uniform dispersion of SCAs as the main active species,and smooth diffusion pathways for fast transport of substances(O_(2),H_(2)O),therefore reducing the overpotential and the intermediate(H_(2)O_(2))generation to enhance ORR activity.For MOR,Pt-Cu-NC-3 has a higher mass activity of 1217.4 mA/mg Pt than that of Pt/C(752.4 mA/mg Pt),and its activity maintenance(decline of 27.6%)is also better than Pt/C(decline of 44.0%)after 5000 cyclic voltammetry(CV)cycles.The interactions between SCAs and Pt nanoparticles should facilitate the generation of OH−from water molecules,which can fast eliminate the adsorbed CO to recover the Pt active sites to improve MOR performance.This synthesis strategy affords a new inspiration to prepare single metal atoms loaded on ZIFs-derived macro-structure with diverse activities for ORR/MOR.