Explore the vast range of titles available.

Granular soil is commonly encountered during underground constructions in and around urban areas. Due to the lack of cohesion in the granular soil, tunneling through it can easily induce excessive ground settlement and/or even collapse. This study primarily focuses on the tunnel/ground stability during the construction phase before introducing the tunnel lining. The influence of relative tunnel depth and the density of granular soil on the stability and collapse mechanisms of shallow tunnels are investigated using discrete element method (DEM). The tunneling process is numerically realized by an air bag model, which is developed to pressure/depressurize the tunnel. The pressurized air bag in the DEM is calibrated and verified against physical tests. The unloading of the tunnels is realized by reducing the pressure of the fully pressurized air bag stepwise. The soil displacement, soil volume loss as well as the evolution of soil stress are recorded and compared with predictions based on previous experimental studies. Our results show that the tunnel stability and failure mechanisms are significantly influenced by the soil density and relative tunnel depth. The tunnel stability is less dependent on the relative tunnel depth with the increment of the soil density. The soil density is shown to have a notable effect on tunnel stability, especially for relatively deep tunnels. The width of surface settlement trough does not appear to change before the tunnel collapse. However, it decreases dramatically at collapse and keeps decreasing thereafter. The tunnel stability number of different test cases in granular soil is found to be smaller than that in clayed soil but larger than that in saturated sandy soil.

Background Current screening criteria miss 30% of blunt cerebrovascular injuries (BCVIs). Motor vehicle collisions (MVCs) are the leading BCVI mechanism, and delineating MVC characteristics associated with BCVI formation may augment current screening criteria. Methods We retrospectively identified BCVI Denver injury screening criteria as able from the Crash Injury Research and Engineering Network (CIREN) database. Severe MVC markers were considered: mean change in velocity (delta-v) greater than 40 km/hour, steering wheel airbag deployment, ejection, or rollover. Results 93 BCVIs were included. Injury screening criteria were not present in 37/93 (39.8%) BCVIs. Vertebral BCVI more often had injury screening criteria than internal carotid BCVIs (73.2% vs 26.8%, P = .001). There was a significant difference in delta-v (30.78 km/hour vs 51.00 km/hour, P < .001) between BCVI with and without injury screening criteria. BCVI without injury screening criteria more often had safety device use through seatbelt position snug across the hips (94.6% vs 74.5%, P = .01) and pretensioner deployment (92.6% vs 70.2%, P = .04). Examining only drivers, BCVI without injury screening criteria more often had steering wheel airbag deployment (89.7% vs 68.9%, P = .05). Markers of severe MVC were seen in 36/37 (97.3%) BCVIs without injury screening criteria. Discussion BCVI without injury screening criteria occurred during higher deceleration MVCs with more frequent/appropriate safety device use, suggesting crash deceleration as a mechanism of BCVI formation. Expanding BCVI screening criteria to encompass severe MVCs may lessen the number of BCVI missed.

Purpose Seatbelts and airbags are the most important devices protecting drivers from cervical spine injury (CSI) following motor vehicle collisions (MVCs). However, there have been few reports on the radiographic characteristics of CSI sustained by restrained, airbag-deployed drivers. Methods A single-center, retrospective observational study was conducted using prospectively acquired data. Between January 2011 and December 2017, 564 restrained drivers, whose vehicle had been severely damaged in MVCs, underwent whole-body computed tomography for evaluation of bodily injuries. The drivers were dichotomized into airbag (+) group ( n  = 218) and airbag (−) group ( n  = 139), after excluding 207 drivers in whom airbag deployment status was unknown. Results Eight and nine drivers sustained CSIs in the airbag (+) and airbag (−) group, respectively. The frequency of CSI did not differ significantly between the two groups (3.7% vs. 6.5%, p  = 0.31). All eight CSIs in the airbag (+) group were classified as hyperextension injuries, and four of them sustained concomitant spinal cord injuries caused by dislocation. Within the airbag (+) group, the drivers with CSIs were significantly older than those without CSIs (65.2 ± 18.5 vs. 44.8 ± 18.7 years, p  = 0.002). Conclusion Although it is without doubt that the combination of seatbelt and airbag reduces the frequency and severity of CSIs following MVCs, the CSIs sustained in restrained, airbag (+) drivers may not always be mild, and elderly drivers may be at an elevated risk of CSI. In addition, the possibility of a causal role of airbags in CSI requires consideration in this population.

Minimizing the injury potential of the interactions between deploying airbags and car occupants is the major issue with the design of airbag systems. This concern was identified in 1964 by Carl Clark when he presented the results of human volunteer and dummy testing of the \"Airstop\" system that was being developed for aircraft. The following is a chronological summary of the actions taken by the car manufacturers, airbag suppliers, SAE and ISO task groups, research institutes and universities, and consumer and government groups to address this issue.

Low capacity of river banks is a problem of many world cities. Extension can be realised in many ways. One of the ways is to use a system of floating piers. Usual types of piers are filled with floating material, which supports the pier for the whole lifetime. The system of piers described in this article is innovative, because it is supported by an air bag, which can be deflated and then the whole system sinks down to the bottom of the river. This can be helpful in case of danger of floods, because there will be no need to transport the piers to a secure dock. Piers are designed for easy modular connection in various groups. The main types of groups are linear and areal. This article briefly describes the design of fibre reinforced concrete pier and other support constructions which are necessary for the right function of the system. The design of the pier was verified by hydraulic experiments on models in scale 1:10 to real pier. The article contains the description and results of the experiments that have proven the system to be feasible.

Airbag system has so many advantages including small volume, superior cushioning performance and easy to control that it has been widely used in many fields such as heavy cargo airdrop, soft landing of spacecraft and so on. In this paper, an optimal design method of the airbag is proposed. First, based on the law of thermodynamics and the deformation assumption of airbag, a mathematical model of airbag landing process is established. The results of the model calculation of the cylindrical airbag is preferably consistent with the results of finite element analysis, which shows that the airbag mathematical model is reasonable and accurate. Second, on the basis of this model, the optimal design method of the airbag without rebound is proposed to solve the problem of rebound which will result in uncontrollable attitude and secondary shock in the landing processes. In this method, the evaluation index of airbag cushioning performance is determined, then the key design parameters which have significant impact on airbag cushioning performance are studied, and the optimization model of airbag under constraint with no rebound is subsequently established and solved. Third, by this method, a cylindrical airbag without rebound is obtained. Compared with the non-optimized one, the maximum impact acceleration of the optimized cylindrical airbag is smaller. Consequently, the effectiveness of the proposed optimal design method is verified.

Due to federal regulations, automobile air bag availability was a model-specific discontinuous function of model year for used vehicles in the 1990s and early 2000s. We use the discontinuities and the gradual increase in the supply of air bags to trace out the demand curve for air bags and the implied distribution of the Value of a Statistical Life (VSL) across consumers. Although imprecise, our preferred point estimates indicate that the median VSL is between $9 million and $11 million and that a sizable portion of consumers placed negative values on air bags, probably due to distrust of the technology.

Accident emergency calling systems (AECSs) are signaled by the deployment of airbags, which causes them to automatically emit information providing the location of the accident site to a public service answering party (PSAP). In some realworld accidents, airbags have failed to deploy. This study clarifies the factors that influence the nondeployment of front airbags in vehicle-vehicle collisions, investigating nondeployment of the driver-side front airbags in sedans and light passenger cars (LPCs) from Japanese accident data. The component rates of deployment for front airbags tend to be higher than those of nondeployment at higher values of pseudo-ΔV in vehicle-vehicle frontal impacts. For both sedans and LPCs, the transition zones between nondeployment and deployment of the front airbag occur at pseudo-ΔV values of 30-50 km/h (ΔV ≈ 21-35 km/h). For mutual impact locations where sedans and LPCs impact opponent vehicles at pseudo-ΔV ≥ 40 km/h (ΔV ≈ 28 km/h) in frontal impacts, the component rate of front airbag nondeployment is higher than that of deployment in right-to-right impacts. The results indicate that factors influencing front airbag nondeployment in vehicle-vehicle collisions are ΔV, impact offset configuration, and crossing angle. Considering front airbag nondeployment in real-world accidents, AECSs should have other functions, such as a manual button, to emit information in addition to automatic emission via airbag signaling.

In this paper a new air-bag prototype suitable for protecting valuable objects mounted on the drone is presented. The paper provides a complimentary study involving both numerical simulations and experimental study. The experimental research results are presented for typical air-bag's textile material and were used as a base for the material model calibration process. This model was used for the numerical simulations of the proposed air-bag prototype, which were carried out in the LS-Dyna environment. Based on the outcome of the study, the proposed prototype seems to be a suitable device for preventing the unmanned vehicle equipment from unexpected accidents.