Modelling and analysis of the vehicle underbody and the occupants subjected to a shallow-buried-mine blast impulse

2016 ◽  
Vol 231 (2) ◽  
pp. 214-224 ◽  
Author(s):  
Xinlei Zhang ◽  
Yunbo Zhou ◽  
Xianhui Wang ◽  
Zongqian Wang
Keyword(s):  
Computation Time ◽  
Arbitrary Lagrangian Eulerian ◽  
Peak Acceleration ◽  
Worst Case ◽  
Hybrid Iii ◽  
Multiple Material ◽  
Jump Velocity ◽  
A Charge ◽  
Initial Impulse ◽  
Good Agreement

When a charge is ignited at the bottom of a vehicle, the underbody and the occupants are the most vulnerable. The protection of the vehicle underbody is still a significant problem in the environment of a buried-mine blast impulse. The first part of this study presents an algorithm that can be used to simulate a shallow-buried-mine blast. Models using the multiple-material arbitrary Lagrangian–Eulerian algorithm and the initial-impulse mine algorithm respectively were constructed on the basis of experiments carried out by Anderson et al. The accuracy and superiority of the initial-impulse mine algorithm were proved by comparing the results for the jump velocity and the computation time. The second part introduces a blast experiment on a full-scale armoured vehicle. The occupant was represented by a Hybrid III 50th-percentile adult-male dummy. A numerical model was established using the initial-impulse mine method; the seat position represented the worst-case situation, which was same as for the experiments. A comparison of the experimental data and the simulation results, which include the peak acceleration of the floor and the force to which the dummy’s tibia is subjected, showed good agreement.

scholarly journals A Useful Manufacturing Guide for Rotary Piercing Seamless Pipe by ALE Method

2020 ◽  
Vol 8 (10) ◽  
pp. 756
Author(s):  
Ameen Topa ◽  
Burak Can Cerik ◽  
Do Kyun Kim
Keyword(s):  
Numerical Simulations ◽  
Maximum Stress ◽  
Three Dimensional ◽  
Material Model ◽  
Manufacturing Processes ◽  
Arbitrary Lagrangian Eulerian ◽  
Analysis Method ◽  
Seamless Pipe ◽  
Ale Formulation ◽  
Good Agreement

The development of numerical simulations is potentially useful in predicting the most suitable manufacturing processes and ultimately improving product quality. Seamless pipes are manufactured by a rotary piercing process in which round billets (workpiece) are fed between two rolls and pierced by a stationary plug. During this process, the material undergoes severe deformation which renders it impractical to be modelled and analysed with conventional finite element methods. In this paper, three-dimensional numerical simulations of the piercing process are performed with an arbitrary Lagrangian–Eulerian (ALE) formulation in LS-DYNA software. Details about the material model as well as the elements’ formulations are elaborated here, and mesh sensitivity analysis was performed. The results of the numerical simulations are in good agreement with experimental data found in the literature and the validity of the analysis method is confirmed. The effects of varying workpiece velocity, process temperature, and wall thickness on the maximum stress levels of the product material/pipes are investigated by performing simulations of sixty scenarios. Three-dimensional surface plots are generated which can be utilized to predict the maximum stress value at any given combination of the three parameters.

Dynamic Collision Detection Using Space Partitioning

1990 ◽  
Author(s):  
M. A. Ganter ◽  
B. P. Isarankura
Keyword(s):  
Collision Detection ◽  
Computation Time ◽  
Local Region ◽  
Detection Time ◽  
Space Partitioning ◽  
Worst Case ◽  
Simulated Environment ◽  
Time Required ◽  
Six Degree Of Freedom ◽  
Partitioning Technique

Abstract A technique termed space partitioning is employed which dramatically reduces the computation time required to detect dynamic collision during computer simulation. The simulated environment is composed of two nonconvex polyhedra traversing two general six degree of freedom trajectories. This space partitioning technique reduces collision detection time by subdividing the space containing a given object into a set of linear partitions. Using these partitions, all testing can be confined to the local region of overlap between the two objects. Further, all entities contained in the partitions inside the region of overlap are ordered based on their respective minimums and maximums to further reduce testing. Experimental results indicate a worst-case collision detection time for two one thousand faced objects is approximately three seconds per trajectory step.

The Study on a New Approximate Method of Computing Electromagnetic Scattering from Multilayer Rough Sea Surfaces

2014 ◽  
Vol 533 ◽  
pp. 268-273
Author(s):  
Jia Sheng Tian ◽  
Wan Pan ◽  
Jian Shi
Keyword(s):  
Electromagnetic Scattering ◽  
Computation Time ◽  
Sea Surface ◽  
Analysis Method ◽  
Large Matrix ◽  
Random Rough Surfaces ◽  
Strong Winds ◽  
Rough Sea Surface ◽  
Rough Sea ◽  
Good Agreement

At high sea states strong winds make the sea surface broken, and become a multilayer-rough sea surface made of a large number of foams and droplets. Similarly, if the sea surface covered by oil and other dirts will also belong to the mutilayer rough sea surfaces of various medium properties. In this paper, applying the Kirchhoff Approximation (KA) and the electromagnetic theory of stratified media, electromagnetic scattering characteristics from a multilayer rough medium surface are calculated. Firstly, a detailed analysis of electromagnetic reflection from multilayer parallel interfaces under different incident angles is carried out. Secondly, combining the preceding two results and courses, electromagnetic scattering from the multilayer random rough surfaces is studied. The computed results are in good agreement with those by using the method of moments (MOM) and reported by some experts. Finally, the random rough sea surface covered by spilling oil or droplets and foams is calculated in detail. Compared with MOM, the new approximate analysis method in the paper can avoid a large matrix inversion, and thus greatly reduce the computation time and improve the computational efficiency.

A Method for Simultaneously Satisfying Important Constraints and Dependencies for Many Different Types of Processes in Embedded Real-Time Systems

2011 ◽  
Author(s):  
Jia Xu
Keyword(s):  
Real Time ◽  
Computation Time ◽  
Real Time Systems ◽  
Worst Case ◽  
Release Times ◽  
Different Types ◽  
High Assurance ◽  
Run Time ◽  
Soft Deadline ◽  
Time Systems

In most embedded, real-time applications, processes need to satisfy various important constraints and dependencies, such as release times, offsets, precedence relations, and exclusion relations. Embedded, real-time systems with high assurance requirements often must execute many different types of processes with such constraints and dependencies. Some of the processes may be periodic and some of them may be asynchronous. Some of the processes may have hard deadlines and some of them may have soft deadlines. For some of the processes, especially the hard real-time processes, complete knowledge about their characteristics can and must be acquired before run-time. For other processes, prior knowledge of their worst case computation time and their data requirements may not be available. It is important for many embedded real-time systems to be able to simultaneously satisfy as many important constraints and dependencies as possible for as many different types of processes as possible. In this paper, we discuss what types of important constraints and dependencies can be satisfied among what types of processes. We also present a method which guarantees that, for every process, no matter whether it is periodic or asynchronous, and no matter whether it has a hard deadline or a soft deadline, as long as the characteristics of that process are known before run-time, then that process will be guaranteed to be completed before predetermined time limits, while simultaneously satisfying many important constraints and dependencies with other processes.

Principles of Operation and Experimental Results for a Small Wastewater Treatment Plant of 300 Population Equivalents

1993 ◽  
Vol 28 (10) ◽  
pp. 387-392 ◽  
Author(s):  
M. Bongards ◽  
T. Hengstermann ◽  
M. Köhne
Keyword(s):  
Wastewater Treatment ◽  
Wastewater Treatment Plants ◽  
Treatment Plant ◽  
Water Volume ◽  
Experimental Plant ◽  
Worst Case ◽  
Theoretical Simulation ◽  
Sludge Stabilization ◽  
System Equations ◽  
A Charge

Small wastewater treatment plants play a very important role in German environmental politics. Presented here is a new system for biological wastewater treatment with simultaneous aerobic sludge stabilization. This system operates as a charge process and can be used in the range of 300 to 2000 population equivalents. Different modes of operation were tested in an experimental plant. The system is applicable for both separate sewerage systems and combined systems with large amounts of storm water. The quality of the purified water was good and even under the worst case conditions it met the demands of standard discharge consent conditions. A theoretical simulation of the operation has not yet been started, because the system equations are very complex, due to the variable water volume.

Numerical Simulation of Pulsed Laser Bending

2002 ◽  
Vol 69 (3) ◽  
pp. 254-260 ◽  
Author(s):  
X. R. Zhang ◽  
G. Chen ◽  
X. Xu
Keyword(s):  
Steel Plate ◽  
Pulsed Laser ◽  
Computation Time ◽  
Domain Size ◽  
Laser Pulses ◽  
New Method ◽  
Laser Bending ◽  
Computational Capability ◽  
Thermomechanical Effect ◽  
Good Agreement

The aim of this work is to develop an efficient method for computing pulsed laser bending. During pulsed laser bending, thousands of laser pulses are irradiated onto the target. Simulations of the thermomechanical effect and bending resulted from all the laser pulses would exceed the current computational capability. The method developed in this work requires only several laser pulses to be calculated. Therefore, the computation time is greatly reduced. Using the new method, it is also possible to increase the domain size of calculation and to choose dense meshes to obtain more accurate results. The new method is used to calculate pulsed laser bending of a thin stainless-steel plate. Results calculated for a domain with a reduced size are in good agreement with those obtained by computing all the laser pulses. In addition, experiments of pulsed laser bending are performed. It is found that experimental data and computational results are consistent.

A Charge-Diffusion-Filtration Model for Endothelial Surface Glycocalyx

Volume 4 ◽  
2004 ◽  
Author(s):  
Bin Chen ◽  
Bingmei Fu
Keyword(s):  
Experimental Data ◽  
Electrical Potential ◽  
Charged Surface ◽  
Endothelial Surface ◽  
Charged Macromolecules ◽  
Microvessel Permeability ◽  
A Charge ◽  
Microvessel Wall ◽  
Good Agreement ◽  
Filtration Model

Endothelial surface glycocalyx plays an important role in the regulation of microvessel permeability by possibly changing its charge and configuration. To investigate the mechanisms of how surface properties of the endothelial cells control the changes in microvessel permeability, we extended the electrodiffusion model developed by Fu et al. (Am. J. Physiol. 284:H1240-1250, 2003), which is for the interendothelial cleft with a negatively charged surface glycocalyx layer, to include the filtration due to hydrostatic and oncotic pressures across the microvessel wall as well as the electrical potential across the glycocalyx layer. On the basis of the hypotheses proposed by Curry (Microcirculation 1(1): 11–26, 1994), the predictions from this electrodiffusion-filtration model provide a remarkably good agreement with experimental data for permeability of negatively charged α-lactalbumin summarized in Curry (Microcirculation 1(1): 11–26, 1994) under various conditions. In addition, we applied this new model to describe the transport of negatively charged macromolecules, bovine serum albumin (BSA), across venular microvessels in frog mesentery. A very interesting prediction is that the convective component of albumin transport is greatly diminished by the presence of a negatively charged glycocalyx under both normal and increased permeability conditions.

scholarly journals Initial Model for the Impact of Social Distancing on CoVID-19 Spread

2020 ◽  
Author(s):  
Genghmun Eng
Keyword(s):  
Exponential Growth ◽  
Growth Function ◽  
Worst Case ◽  
Social Distancing ◽  
Sick People ◽  
Large Numbers ◽  
The World ◽  
The Usa ◽  
The Impact ◽  
Good Agreement

AbstractThe initial stages of the CoVID-19 coronavirus pandemic all around the world exhibit a nearly exponential rise in the number of infections with time. Planners, governments, and agencies are scrambling to figure out “How much? How bad?” and how to effectively treat the potentially large numbers of simultaneously sick people. Modeling the CoVID-19 pandemic using an exponential rise implicitly assumes a nearly unlimited population of uninfected persons (“dilute pandemic”). Once a significant fraction of the population is infected (“saturated pandemic”), an exponential growth no longer applies. A new model is developed here, which modifies the standard exponential growth function to account for factors such as Social Distancing. A Social Mitigation Parameter [SMP] αS is introduced to account for these types of society-wide changes, which can modify the standard exponential growth function, as follows: The doubling-time tdbl = (In 2)/Ko can also be used to substitute for Ko, giving a {tdbl, αS} parameter pair for comparing to actual CoVID-19 data. This model shows how the number of CoVID-19 infections can self-limit before reaching a saturated pandemic level. It also provides estimates for: (a) the timing of the pandemic peak, (b) the maximum number of new daily cases that would be expected, and (c) the expected total number of CoVID-19 cases. This model shows fairly good agreement with the presently available CoVID-19 pandemic data for several individual States, and the for the USA as a whole (6 Figures), as well as for various countries around the World (9 Figures). An augmented model with two Mitigation Parameters, αS and βS, is also developed, which can give better agreement with the daily new CoVID-19 data. Data-to-model comparisons also indicate that using αS by itself likely provides a worst-case estimate, while using both αS and βS likely provides a best-case estimate for the CoVID-19 spread.

Numerical Simulation of Twin-Parachute Inflation Process for Aircraft Ejection Escape

2020 ◽  
Author(s):  
Liwu Wang ◽  
Mingzhang Tang ◽  
Sijun Zhang
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Numerical Model ◽  
Physical Models ◽  
The Other ◽  
Arbitrary Lagrangian Eulerian ◽  
Safe Distance ◽  
Structure Interaction ◽  
Parachute Inflation ◽  
Good Agreement

Abstract In order to study the safe distance between twin-parachute during their inflation process for fighter ejection escape, the fighter was equipped with two canopies and two seats, two types of parachute were used to numerically simulate their inflation process, respectively. One of them is C-9, the other a slot-parachute (S-P). Their physical models were built, then the meshes inside and around both parachutes were generated for fluid-structure interaction (FSI) simulation. The penalty function and the arbitrary Lagrangian-Eulerian (ALE) method were employed in the FSI simulation. To validate the numerical model for FSI simulation, at first the single parachute of the twin-parachute was used for the FSI simulation, the predicted inflation times for both types of parachute were compared with the experimental data. The computed results are in good agreement with experimental data. As a result, the inflation times were predicted with twin-parachute for both kinds of parachute. On the basis of the locations of ejected seats after the separation of seat and pilot, the initial locations and orientations of twin-parachute were also obtained. The numerical simulations for both kinds of parachute were performed by the FSI method, respectively. Our results illustrate that when the interval time for two seats ejected is greater than 0.25s, two pilots attached the twin-parachute are safe, and the twin-parachute would not interfere each other. Moreover, our results also indicate that the FSI simulation for twin-parachute inflation process is feasible for engineering applications and have a great potential for wide use.

Adsorption of Amines to Thylakoid Surfaces and Estimations of ΔpH

1985 ◽  
Vol 12 (1) ◽  
pp. 9 ◽  
Author(s):  
AB Hope ◽  
DB Matthews
Keyword(s):  
Steady State ◽  
Fluorescence Quenching ◽  
Binding Constant ◽  
Protonated Form ◽  
Proton Motive Force ◽  
Amine Concentration ◽  
Apparent Binding Constant ◽  
Mgcl2 Concentration ◽  
A Charge ◽  
Good Agreement

The adsorption of the fluorescent, weak amine ΔpH indicators 9-aminoacridine and N-(1-naphthyl)ethylenediamine to thylakoids of pea chloroplasts in the dark was measured as a function of amine concentration, at several pH's between 8 and 5, and with varied MgCl2 concentration. It was concluded that it was the protonated form of the amine that was adsorbed. Maximum amounts adsorbed, saturation occurring at about 1 mM amine concentration in the presence of 5 mM KCl and 10 mM MgCl2, were up to 1 mol (mol Chl)-1. This was calculated as exceeding the number of available surface negative charges (0.26 for a charge density of 0.025 C m-2). An apparent binding constant of 400-500 μM (concentration for half saturation) was noted for both amines under the above conditions. A model was developed that enabled the estimation of the relative amounts of amine bound to the inside and outside thylakoid surfaces in the steady state, in the light. By this means corrections to the apparent ΔpH calculated from fluorescence quenching of the amines could be established. These corrections amounted to about 1 pH unit for the diamine and more for 9-aminoacridine. The predictions of the model were in good agreement with experimental relations between estimated, light-induced ΔpH values and amine concentration. The implications of a lower ΔpH for earlier estimations of proton motive force in relation to photophosphorylation are briefly considered.

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