Study on Arrangement of Advance Heading for Extra-long Double-barrel Single-track Tunnel

Abstract. Fragility curves evaluating risk of railway track ballast and embankment fill scour were developed. To develop fragility curves, two well-documented single-track railway washouts during two recent floods in Japan were investigated. Type of damage to the railway was categorized into no damage, ballast scour, and embankment scour, in order of damage severity. Railway overtopping surcharge for each event was estimated via hydrologic and hydraulic analysis. Normal and log-normal fragility curves were developed based on failure probability derived from field records. A combined ballast and embankment scour model was validated by comparing the spatial distribution of railway scour with the field damage record.

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Process characterization and analysis of ceramic powder bed fusion

The International Journal of Advanced Manufacturing Technology ◽

10.1007/s00170-021-07625-y ◽

2021 ◽

Author(s):

Kevin Florio ◽

Dario Puccio ◽

Giorgio Viganò ◽

Stefan Pfeiffer ◽

Fabrizio Verga ◽

...

Keyword(s):

High Speed ◽

Ceramic Powder ◽

Integrating Sphere ◽

Alumina Powder ◽

Powder Bed Fusion ◽

Single Track ◽

Ceramic Powders ◽

Pure Alumina ◽

Powder Bed ◽

Melt Pool

AbstractPowder bed fusion (PBF) of ceramics is often limited because of the low absorptance of ceramic powders and lack of process understanding. These challenges have been addressed through a co-development of customized ceramic powders and laser process capabilities. The starting powder is made of a mix of pure alumina powder and alumina granules, to which a metal oxide dopant is added to increase absorptance. The performance of different granules and process parameters depends on a large number of influencing factors. In this study, two methods for characterizing and analyzing the PBF process are presented and used to assess which dopant is the most suitable for the process. The first method allows one to analyze the absorptance of the laser during the melting of a single track using an integrating sphere. The second one relies on in-situ video imaging using a high-speed camera and an external laser illumination. The absorption behavior of the laser power during the melting of both single tracks and full layers is proven to be a non-linear and extremely dynamic process. While for a single track, the manganese oxide doped powder delivers higher and more stable absorptance. When a full layer is analyzed, iron oxide-doped powder is leading to higher absorptance and a larger melt pool. Both dopants allow the generation of a stable melt-pool, which would be impossible with granules made of pure alumina. In addition, the present study sheds light on several phenomena related to powder and melt-pool dynamics, such as the change of melt-pool shape and dimension over time and powder denudation effects.

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Retrieving 3D Large gradient deformation Induced to Mining Subsidence Based on Fusion of Boltzmann Prediction Model and Single-track InSAR Earth Observation Technology

IEEE Access ◽

10.1109/access.2021.3089160 ◽

2021 ◽

pp. 1-1

Author(s):

Chuang Jiang ◽

Lei Wang ◽

Xuexiang Yu

Keyword(s):

Prediction Model ◽

Earth Observation ◽

Mining Subsidence ◽

Single Track ◽

Large Gradient

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Front steering design guidelines formulation for e-scooters considering the influence of sitting and standing riders on self-stability and safety performance

Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering ◽

10.1177/0954407021992176 ◽

2021 ◽

pp. 095440702199217

Author(s):

Milan Paudel ◽

Fook Fah Yap

Keyword(s):

Preventive Measures ◽

Recent Trend ◽

Dynamic Performance ◽

Design Guidelines ◽

Safety Performance ◽

Design Parameters ◽

Single Track ◽

Standing Posture ◽

Last Mile ◽

Current Design

E-scooters are a recent trend and are viewed as a sustainable solution to ease the first and last mile problem in modern transportation. However, an alarming rate of accidents, injuries, and fatalities have caused a significant setback for e-scooters. Many preventive measures and legislation have been put on the e-scooters, but the number of accidents and injuries has not reduced considerably. In this paper, the current design approach of e-scooters has been analyzed, and the most common range of design parameters have been identified. Thereafter, validated mathematical models have been used to quantify the performance of e-scooters and relate them with the safety aspects. Both standing and seated riders on e-scooters have been considered, and their influence on the dynamic performance has been analyzed and compared with the standard 26-in wheel reference safety bicycle. With more than 80% of the accidents and injuries occurring from falling or colliding with obstacles, this paper tries to correlate the dynamics of uncontrolled single-track vehicles with the safety performance of e-scooters. The self-stability, handling, and braking effect have been considered as major performance matrices. The analysis has shown that the current e-scooter designs are not as stable as the reference safety bicycle. Moreover, these e-scooters have been found unstable within the most common range of legislated riding velocity. The results corroborate with the general perception that the current designs of e-scooters are less stable, easy to lose control, twitchy, or wobbly to ride. Furthermore, the standing posture of the rider on the e-scooter has been found dangerous while braking to avoid any disturbances such as potholes or obstacles. Finally, the front steering design guidelines have been proposed to help modify the current design of e-scooters to improve the dynamic performance, hence the safety of the e-scooter riders and the surroundings.

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