Structure design and surface interference analysis of double crown surface configuration of multistage face gears

A novel transmission using the multistage face gears as the core component is used to realize variable speed with differential gear shifting, there are multiple face gears superimposed on the radial direction, meshing with planetary wheel at the same time, which achieves different outputs speed through braking different face gears. In order to solve the interference problems caused by asynchronous meshing motion between several face gears and the same cylinder gear, this study mainly focuses on the meshing theory study based on the double crown surfaces in tooth profile and tooth orientation. The surface structure of straight tooth and double crown are constructed according to the related surface equations, the corresponding interference conditions are obtained by comparison, every single stage face gear model is designed and assembled. This study shows that the double crown configuration surface structure can easily improve contact characteristics compared with straight tooth surface structure of face gear. In addition, the double crown configuration surface structure can improve the distribution and direction of contact path. This study is expected to establish a new tooth surface model, which can provide the best machining parameters for the face gears

DYNAMIC CONSTRUCTION CONTROL METHOD FOR A DEEP FOUNDATION PIT WITH SAND-PEBBLE GEOLOGY

Taking the water-rich sand and pebble geology deep foundation pit of Jinfu Station of Chengdu Metro Line 6 as the research object, combined with the ladder excavation method of slotting, utilizing finite difference software FLAC 3D as well as on-site monitoring result, the deformation law of the diaphragm wall during the dynamic excavation of the foundation pit is analysed, and the influence of the relative stiffness between the vertical and horizontal walls of the foundation pit on the lateral deformation of the retaining structure is discussed. The results show that while using the ladder excavation method of slotting, the maximum lateral displacement of the underground diaphragm walls decreases gradually with the excavation depth of the foundation pit, which occurs at the intersection of the middle point of the oblique excavation line and the step distance section of the transverse excavation. Additionally, the lateral displacement increases closer to the excavation section. The lateral displacement of the envelope enclosure mainly depends on the relative constraint stiffness of the vertical and horizontal underground diaphragm wall of the foundation pit. The use of the ladder layered excavation method of slotting can effectively reduce the lateral displacement of the underground diaphragm wall. The simulated result and on-site monitoring result are nearly the same. These results can provide a corresponding theory and engineering basis for the selection of excavation methods for the same type of sand and pebble stratum foundation pit

Deformation rule of bored pile & steel support for deep foundation pit in sandy pebble geology

Regarding the whole excavation process of the support system of the Southwest Jiaotong University Station of Chengdu Metro Line 6 (the deep foundation pit bored pile + steel support and support system) as the engineering background, this paper studies the deformation rule of the deep foundation pit bored pile + steel support of the sandy pebble foundation. The deformation rule of this support system, the settlement rule of the ground surface outside the pit, and the rule of the uplift of the loose at the bottom of the pit are studied. A key analysis of the positive corner of the foundation pit is conducted, and the rationality of the optimization of the support scheme is evaluated. This paper provides effective guidance for the subsequent deep foundation pit construction and provides a reference for deep foundation pit construction

Acoustic emission source location method and experimental verification for structures containing unknown empty areas

Acoustic emission (AE) localization plays an important role in the prediction and control of potential hazardous sources in complex structures. However, existing location methods have less discussion on the presence of unknown empty areas. This paper proposes an AE source location method for structures containing unknown empty areas (SUEA). Firstly, this method identifies the shape, size, and location of empty areas in the unknown region by exciting the active AE sources and using the collected AE arrivals. Then, the unknown AE source can be located considering the identified empty areas. The lead break experiments were performed to verify the effectiveness and accuracy of the proposed method. Five specimens were selected containing empty areas with different positions, shapes, and sizes. Results show the average location accuracy of the SUEA increased by 78% compared to the results of the existing method. It can provide a more accurate solution for locating AE sources in complex structures containing unknown empty areas such as tunnels, bridges, railroads, and caves in practical engineering

Higher critical closing pressure is independently associated with enlarged basal ganglia perivascular spaces

ObjectiveThis study aimed to explore the association between cerebral hemodynamic parameters focused on the critical closing pressure (CCP) and enlarged perivascular spaces (EPVS).MethodsCerebral blood velocity in the middle cerebral artery (MCAv) and non-invasive continuous blood pressure (NIBP) were measured using a transcranial Doppler (TCD) and Finometer, followed by the calculation of cerebral hemodynamic parameters including CCP, resistance area product (RAP), pulsatility index (PI), and pulse pressure (PP). EPVS were graded separately in the basal ganglia (BG) and centrum semiovale (CSO), using a visual semiquantitative ordinal scale. Patients with EPVS >10 were classified into the severe BG-EPVS group and severe CSO-EPVS group, and the remainder into the mild BG-EPVS group and the mild CSO-EPVS group. Spearman’s correlation and binary logistic regression analysis were performed to analyze the relationship between hemodynamic parameters and BG-EPVS and CSO-EPVS, respectively.ResultsOverall, 107 patients were enrolled. The severe BG-EPVS group had higher CCP, mean arterial blood pressure (MABP), systolic blood pressure (SBP), and diastolic blood pressure (DBP) than that in the mild BG-EPVS group (p < 0.05). There was no statistical difference in hemodynamic parameters between the severe CSO-EPVS group and the mild CSO-EPVS group. Spearman’s correlation analysis showed that CCP was positively associated with BG-EPVS (rho = 0.331, p < 0.001) and CSO-EPVS (rho = 0.154, p = 0.044). The binary logistic regression analysis showed that CCP was independently associated with severe BG-EPVS (p < 0.05) and not with CSO-EPVS (p > 0.05) after adjusting for confounders.ConclusionCCP representing cerebrovascular tension was independently associated with BG-EPVS