scholarly journals The impact of ambient pressure and tunnel inclination angle on the smoke transport in a subway tunnel

2021 ◽  
Author(s):  
Guang Chen
Keyword(s):  
Inclination Angle ◽  
Ambient Pressure ◽  
Three Dimensional ◽  
Concentration Field ◽  
Air Entrainment ◽  
Subway Tunnel ◽  
Environmental Pressures ◽  
Smoke Transport ◽  
Inclination Angles ◽  
The Impact

Abstract The subway tunnel will be built in the plateau where the pressure is relatively low, and the tunnel will tilt at a certain angle due to topographic factors. In order to investigate the smoke transport characteristics of moving subway trains caught fire under different ambient pressures and different tunnel inclination angles, three-dimensional full-scale calculation models of subway trains, two stations and one tunnel are established, and three different environmental pressures (50kPa, 75kPa, 100kPa) and three different tunnel inclination angles (− 1.5 °, 0 °, + 1.5 °) are simulated. The IDDES turbulence model based on kω-sst RANS combined with the overset grid technology is used to simulate the subway train movement and the detailed flow field. The velocity and temperature distribution characteristics and smoke concentration field are studied in detail. The soot density of smoke and temperature increases with reduced ambient pressure due to the weakening of air entrainment and the decreased air density and the influence of ambient pressure on smoke diffusion decreases with the increase of pressure. The longitudinal airflow induced by the stack effect under the negative inclination angle of the tunnel is helpful to prevent the flowing back of smoke.

scholarly journals The Effect of Vertical and Oblique Inclinations on Fracture Stability and Reoperation Risks in Femoral-Neck Fractures of Nongeriatric Patient

2021 ◽  
Vol 9 ◽  
Author(s):  
Dajun Jiang ◽  
Shi Zhan ◽  
Hai Hu ◽  
Hongyi Zhu ◽  
Changqing Zhang ◽  
...  
Keyword(s):  
Femoral Neck ◽  
Inclination Angle ◽  
Evaluation System ◽  
Preoperative Evaluation ◽  
Three Dimensional ◽  
Reoperation Rate ◽  
Femoral Neck Fractures ◽  
Youden Index ◽  
Inclination Angles ◽  
Fracture Stability

Background: For nongeriatric patients with femoral neck fractures (FNFs), preoperative evaluation of fracture three-dimensional inclination is essential to identify fracture stability, select appropriate fixation strategies, and improved clinical prognoses. However, there is lack of evaluation system which takes into account both vertical and oblique inclinations. The purpose of this study was to comprehensively investigate the effect of vertical and oblique inclinations on fracture stability and reoperation risks.Methods: We retrospectively reviewed the medical records of 755 FNFs patients with over 2 years follow-up. The 3-D inclination angle in vertical (α) and oblique plane (β) were measured based on CT images. The optimal threshold for unstable 3-D inclination were identified by seeking the highest Youden Index in predicting reoperation and validated in the biomechanical test. According to the cut-off value proposed in the diagnostic analysis, forty-two bone models were divided into seven groups, and were all fixed with traditional three parallel screws. Interfragmentary motion (IFM) was used for comparison among seven groups. The association between reoperation outcome and 3-D inclination was analysed with a multivariate model.Results and Conclusion: The overall reoperation rate was 13.2%. Unstable 3-D inclination angles with an optimally determined Youden index (0.39) included vertical (α > 70°) and oblique (50°<α < 70° and β > 20°/β < −20°) types. Biomechanical validation showed these fractures had significantly greater (p < 0.05) interfragmentary motion (1.374–2.387 mm vs. 0.330–0.681 mm). The reoperation rate in 3-D unstable group (32.7%) is significantly (p < 0.001) higher than that in 3-D stable group (7.9%). Multivariate analysis demonstrated that 3-D inclination angle was significantly (OR = 4.699, p < 0.001) associated with reoperation. FNFs with α > 70°; 50°<α < 70° and β > 20°/β < −20° are real unstable types with significantly worse interfragmentary stability and higher reoperation risks. Fracture inclination in vertical and oblique planes is closely related to reoperation outcomes and may be a useful complement to the way FNFs are currently evaluated.

scholarly journals The Symmetric Nature of the Position Distribution of the Human Body Center of Gravity during Propelling Manual Wheelchairs with Innovative Propulsion Systems

Symmetry ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 154
Author(s):  
Bartosz Wieczorek ◽  
Mateusz Kukla ◽  
Łukasz Warguła
Keyword(s):  
Inclination Angle ◽  
Center Of Gravity ◽  
Propulsion Systems ◽  
Manual Propulsion ◽  
Inclination Angles ◽  
Hybrid Transmission ◽  
Secondary Objective ◽  
Body Center ◽  
The Impact ◽  
Average Position

Objective: The main objective of the tests conducted was to analyze the position variability of the human body’s center of gravity during propelling the wheelchair, and to demonstrate the properties enabling the description of this variability by means of plane figures with a symmetry axis. A secondary objective was to show the impact of the used manual propulsion type and the wheelchair inclination angle in relation to the plane on the dimensions of the position variability areas of the center of gravity. Method and materials: Three patients participated in the research representing 50 centiles of anthropometric dimensions. Each patient carried out fifteen measurement tests on three wheelchairs for three inclination angles of the wheelchair frame in relation to the level. Each measurement test consisted of five propulsion cycles for which the positions of the center of gravity were determined with the sampling frequency of 100 Hz. The measured positions of the center of gravity were approximated with ellipses containing 95.4% of the measurements conducted, assuming their dimension scaling basis in the form of the double value of standard deviation defined based on the registered results. Results: Based on the measurements conducted, the average values of five ellipses parameters were determined for nine cases in which a variable was the type of wheelchair propulsion and its inclination angle in relation to the level. The area of the highest variability of the position of the center of gravity was measured for the wheelchair with a multispeed transmission. The average dimensions of the ellipse semi-axis amounted to 108.53 mm for the semi-axis a and 29.75 for the semi-axis b, the average position of the ellipse center amounted to x = 114.51 mm and y = −10.53 mm, and the average inclination angle of the ellipse α amounted to −6.92°. The area of the lowest variability of the position of the center of gravity was measured for the wheelchair with a hybrid transmission. In this case, the average dimensions of the ellipse semi-axis amounted to 64.07 mm for the semi-axis a and 33.85 for the semi-axis b; whereas, the average position of the ellipse center amounted to x = 245.13 mm and y = −28.24 mm, and the average inclination angle of the ellipse α amounted to −0.56°.

ANALYSES OF PEDESTRIAN’S HEAD-TO-WINDSHIELD IMPACT BIOMECHANICAL RESPONSES AND HEAD INJURIES USING A HEAD FINITE ELEMENT MODEL

2019 ◽  
Vol 20 (01) ◽  
pp. 1950063 ◽  
Author(s):  
ZHIHUA CAI ◽  
YUN XIA ◽  
XINGYUAN HUANG
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Impact Velocity ◽  
Inclination Angle ◽  
Head Injuries ◽  
Element Model ◽  
Head Model ◽  
Inclination Angles ◽  
Biomechanical Responses ◽  
The Impact

Head injuries in the vehicle crashes or pedestrian accidents can usually cause death or permanent disabilities, and head injuries resulting from the impact of car windshields remain a major problem. Anatomically, more realistic head models are required to more accurately document and evaluate the head-to-windshield impact responses and head injuries. The current study developed a head finite element model and carried out various simulations to investigate the head-to-windshield impact biomechanical responses and assess the head injuries. First, a 50th percentile three-dimensional finite element head model was developed and validated by using previously published cadaver experimental data. Then, the biomechanical responses were predicted under a head-to-windshield impact at different impact velocities (10, 12, and15[Formula: see text]m/s) and different inclination angles of the windshield (35∘, 40∘, and 45∘). Finally, head injuries were investigated through examining various injury parameters. The results indicated that the contact force, the acceleration, the intracranial pressure, the deformation of the skull, and the negative pressure rose when the impact velocity and the inclination angles increased. Thus, the vehicle impact velocity and the inclination angle of the windshield greatly affect the severity of the resulting injuries on pedestrians’ heads, with the severity increasing with the impact velocity and windshield inclination angle.

Impact Analysis of Foundation Pit Excavation on the Deformation of Nearby Subway Tunnel

2014 ◽  
Vol 935 ◽  
pp. 233-236
Author(s):  
Hui Shen ◽  
Jin Feng Bi ◽  
Tong Qi Ping
Keyword(s):  
Impact Analysis ◽  
Simulation Analysis ◽  
Three Dimensional ◽  
Subway Tunnel ◽  
Foundation Pit ◽  
Soil Subsidence ◽  
Maximum Value ◽  
Margin Of Safety ◽  
Design Proposal ◽  
The Impact

Bracing of foundation pit design proposal based on the excavation near a block of Suzhou Rail Transit Line 1 is used to build a subway tunnel-pit-envelope three-dimensional computational model, which is analyzed by FLAC3D, software for numerical simulation analysis, to evaluate the impact of the foundation pit excavation on the deformation of the subway tunnel. The calculated results show that: when the pit is excavated to the bottom, the deformation of the tunnel achieves the maximum value, 0.6mm of y direction and 6.54mm of z direction. The pipelines with shallow depth are subject to the deformation caused by the soil subsidence back of the envelope, whose maximum value has reached 7.6mm beyond the control standards. In terms of the deformation of the subway tunnel structure, the deformation can meet the control requirements, and have a certain margin of safety.

scholarly journals Analysis of Three-Dimensional Vibration Characteristics of Single-Circle Double-Track Subway Tunnel under Moving Load

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Chunquan Dai ◽  
Mengying Yang ◽  
Quanlei Wang ◽  
Tingzhi Yang ◽  
Kun Jiang
Keyword(s):  
Dynamic Response ◽  
Moving Load ◽  
Compressive Strain ◽  
Three Dimensional ◽  
Urban Rail Transit ◽  
Time Interval ◽  
Subway Tunnel ◽  
Double Line ◽  
Double Track ◽  
The Impact

With the development of urban rail transit, subway lines are becoming more and more denser, the departure time interval is short, and the probability of subway trains meeting is high. The impact of vibration caused by double-line subway meeting on the surrounding environment cannot be ignored. Taking the typical cross-section of a single-circle double-track subway tunnel as an example, a single running scenario and three typical meeting scenarios, namely, 4 s meeting, 6 s meeting, and 8 s meeting scenarios were considered, and a track-tunnel-foundation three-dimensional ABAQUS finite element model was established. The dynamic response of monitoring points at different distances between the center of the track bed and the center line of the track was analyzed. Results showed that due to the consistent load action period, the center acceleration of the track bed increases significantly during the meeting, the main frequency of vibration and the peak value of the 1/3 octave spectrum were increased by about 5 Hz, and the vibration level at the dominant frequency was increased by about 7 dB. The center displacement of the track bed and the peak compressive strain increased significantly under the 4 s meeting and 6 s meeting working scenarios; while the 8 s meeting and 4 s single running scenarios were basically the same, only the action time was doubled. The dynamic response of the 4 working scenarios decreases with the increase of distance, and the attenuation rate gradually decreases and has gradually stabilized within 15–19 m above the vault.

Numerical Simulation of Flow Characteristics in an Inclining Rotating Kiln with Continuous Feeding

2019 ◽  
Vol 17 (10) ◽  
Author(s):  
Xin Zheng ◽  
Baosheng Jin ◽  
Yong Zhang ◽  
Youwei Zhang ◽  
Chunlei Zhou
Keyword(s):  
Velocity Distribution ◽  
Influencing Factor ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Multiphase Model ◽  
Rotating Speed ◽  
Inclination Angles ◽  
Continuous Feeding ◽  
Rotary Kilns ◽  
The Impact

Abstract The granular behaviors in rotating kilns have been investigated using a three-dimensional CFD model based on Euler-Euler multiphase model and the kinetic theory of granular flow. The model is validated by comparing with published experiment data and existing theory. The continuous feeding progress and inclination angles are both taken into account in this work for thorough discussion. Typical regimes of solid motions and velocity distributions are shown in the simulation results. The results show that the impact caused by feeding process has an obvious influence on the velocity distribution of z axis, especially at the charging end of the kiln. A small inclination angle has a slight influence on the velocity distribution of z axis, and causes the thickness of the active region increasing with the increasing of axil distance. The rotating speed is the biggest influencing factor for the velocity distribution in the transverse plane. The result can help the development of three-dimensional models for rotary kilns and the improvement of kiln design and performance.

A Systematic Approach to Predicting Critical Heat Flux for Inclined Sprays

2007 ◽  
Vol 129 (4) ◽  
pp. 452-459 ◽  
Author(s):  
Milan Visaria ◽  
Issam Mudawar
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Inclination Angle ◽  
High Speed ◽  
Systematic Approach ◽  
Test Surface ◽  
Great Success ◽  
Spray Formation ◽  
Inclination Angles ◽  
The Impact

This study provides a new systematic approach to predicting the effects of spray inclination on critical heat flux (CHF). Experiments were performed with three pressure spray nozzles over a broad range of inclination angles at five flow rates and subcoolings of 15°C and 25°C. These experiments also included high-speed video analysis of spray formation, impact, and recoil for a 1.0×1.0cm2 test surface. Inclined sprays produced elliptical impact areas, distorted by lateral liquid flow that provided partial resistance to dryout along the downstream edge of the impact ellipse. These observations are used to determine the locations of CHF commencement along the test surface. A new theoretical model shows that increasing inclination angle away from normal decreases both the spray impact area and the volumetric flux. These trends explain the observed trend of decreasing CHF with increasing inclination angle. Combining the new model with a previous point-based CHF correlation shows great success in predicting the effects of spray inclination on CHF.

scholarly journals Method to evaluate the effect of inclination angle of steel open-type check dam on debris flow impact load

2018 ◽  
Vol 10 (1) ◽  
pp. 95-115 ◽  
Author(s):  
Toshiyuki Horiguchi ◽  
Yoshiharu Komatsu
Keyword(s):  
Debris Flow ◽  
Natural Disasters ◽  
Inclination Angle ◽  
Impact Load ◽  
Time History ◽  
Check Dam ◽  
Open Type ◽  
Inclination Angles ◽  
The Impact ◽  
Type Check

Although the latest statistics indicate a decrease in the number of victims of natural disasters in Japan, the number of sediment disasters has increased. A countermeasure against natural disasters is provided by the installation of a steel open-type check dam (hereafter, open Sabo dam). The open Sabo dam is expected to capture boulders (more than 1.0 m in diameter) contained in debris flow of which boulders concentrate in front part. When a debris flow impacts an open Sabo dam, the large impact load on the steel pipes are caused by the impact of boulders under debris flow. Therefore, it is important to evaluate the impact of both boulders and the following soil and small gravels including fluid force of the open Sabo dam from the design point of view. Although an open Sabo dam has various shapes especially, the every open Sabo dams is evaluated by the same design method in Japan. It is necessary to propose the load evaluation method in the experiment scale in contrast with different shape of open Sabo dam. This article presents an experimental approach to determine the effect of the front inclination angle of steel open Sabo dams on the impact load. The debris flow impacts 1/40 scale models of steel open Sabo dams which are set in a flow channel flume, and the debris flow load is measured by using three load cells placed horizontally at the back of the Sabo dam model. Different front inclination angles are set for each Sabo dam models. The time history of the impact load is examined by comparing the loads corresponding to four kinds of dams, which are different from the front inclination angles, and decrease of impact load considering the buffering effect of driftwoods in debris flow.

Analyzing the Impact of X-Ray Tomography on the Reliability of Integrated Circuits

2015 ◽  
Author(s):  
Halit Dogan ◽  
Md Mahbub Alam ◽  
Navid Asadizanjani ◽  
Sina Shahbazmohamadi ◽  
Domenic Forte ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Integrated Circuit ◽  
3D Imaging ◽  
Three Dimensional ◽  
Serial Sectioning ◽  
Promising Technique ◽  
Flash Memories ◽  
X Ray ◽  
3D Information ◽  
The Impact

Abstract X-ray tomography is a promising technique that can provide micron level, internal structure, and three dimensional (3D) information of an integrated circuit (IC) component without the need for serial sectioning or decapsulation. This is especially useful for counterfeit IC detection as demonstrated by recent work. Although the components remain physically intact during tomography, the effect of radiation on the electrical functionality is not yet fully investigated. In this paper we analyze the impact of X-ray tomography on the reliability of ICs with different fabrication technologies. We perform a 3D imaging using an advanced X-ray machine on Intel flash memories, Macronix flash memories, Xilinx Spartan 3 and Spartan 6 FPGAs. Electrical functionalities are then tested in a systematic procedure after each round of tomography to estimate the impact of X-ray on Flash erase time, read margin, and program operation, and the frequencies of ring oscillators in the FPGAs. A major finding is that erase times for flash memories of older technology are significantly degraded when exposed to tomography, eventually resulting in failure. However, the flash and Xilinx FPGAs of newer technologies seem less sensitive to tomography, as only minor degradations are observed. Further, we did not identify permanent failures for any chips in the time needed to perform tomography for counterfeit detection (approximately 2 hours).

scholarly journals Numerical simulation of the impact of an integrated renovation project on the Maowei Sea hydrodynamic environment

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Cui Wang ◽  
Ling Cai ◽  
Yaojian Wu ◽  
Yurong Ouyang
Keyword(s):  
Water Exchange ◽  
Land Reclamation ◽  
Three Dimensional ◽  
Exchange Capacity ◽  
Reclamation Project ◽  
Hydrodynamic Environment ◽  
Sea Area ◽  
Water Quality Models ◽  
The Impact ◽  
Main Factor

AbstractIntegrated renovation projects are important for marine ecological environment protection. Three-dimensional hydrodynamics and water quality models are developed for the Maowei Sea to assess the hydrodynamic environment base on the MIKE3 software with high resolution meshes. The results showed that the flow velocity changed minimally after the project, decreasing by approximately 0.12 m/s in the east of the Maowei Sea area and increasing by approximately 0.01 m/s in the northeast of the Shajing Port. The decrease in tidal prism (~ 2.66 × 106 m3) was attributed to land reclamation, and accounted for just 0.86% of the pre-project level. The water exchange half-life increased by approximately 1 day, implying a slightly reduced water exchange capacity. Siltation occurred mainly in the reclamation and dredging areas, amounting to back-silting of approximately 2 cm/year. Reclamation project is the main factor causing the decrease of tidal volume and weakening the hydrodynamics in Maowei Sea. Adaptive management is necessary for such a comprehensive regulation project. According to the result, we suggest that reclamation works should strictly prohibit and dredging schemes should optimize in the subsequent regulation works.

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