Mechanism analysis and prediction of explosive formed projectile’s axial fracture

2021 ◽  
Author(s):  
Li Ding ◽  
Jianwei Jiang ◽  
Shuyou Wang ◽  
Liuqi Ji
Keyword(s):  
Theoretical Analysis ◽  
Critical Velocity ◽  
Velocity Gradient ◽  
Wave Theory ◽  
Axial Direction ◽  
Experimental Results ◽  
Model Parameters ◽  
Mechanism Analysis ◽  
Long Rod ◽  
Axial Fracture

To explain the axial fracture phenomenon of Explosively Formed Projectile (EFP), the fracture mechanism of long rod EFP during the forming phase is analyzed by the stress wave theory. When the velocity gradient [Formula: see text] between the head and tail parts exceeds the critical value [Formula: see text], the EFP would fracture in the axial direction. Based on the Johnson–Cook constitutive model parameters and the special conditions in the forming phase of EFP, the critical velocity gradient [Formula: see text] can be determined by theoretical calculation and then validated by experimental results for both copper and tantalum EFPs. The experimental results for EFP’s fracture agree well with the prediction of the theoretical analysis. The theoretical analysis method can be applied as an important measure to determine the critical velocity gradient and predict the fracture of long rod EFP, providing reference for the application of new kinds of high density materials in the EFP research area.

scholarly journals Ideal Current-voltage Characteristics and Rectification Performance of Molecular Rectifier under Single Level based Tunneling and Hopping Transport

2020 ◽  
Author(s):  
Xianneng Song ◽  
Xi Yu ◽  
Wenping Hu
Keyword(s):  
Experimental Results ◽  
Physical Parameters ◽  
Model Parameters ◽  
Mechanism Analysis ◽  
Hopping Transport ◽  
Molecular Diode ◽  
Current Voltage ◽  
Significant Difference ◽  
Molecular Rectification ◽  
And Performance

In this work, we systematically studied the rectifying properties of molecular junction based on asymmetric tunneling and hopping charge transport in a single electronic state model using Landauer formula and Marcus theory. We first analyzed the asymmetric I-V characteristics and revealed distinct physical origins of the rectification under the two types of transports. We found significant difference in I-V characteristics of the two and the hopping transport can afford a much higher rectification ratio than tunneling. Next, the effect of key physical parameters on rectification performance under tunneling and hopping, like asymmetric factor, energy barrier, temperature and molecule-electrode coupling et al, were extensively evaluated, which provided a theoretical baseline for molecular diode design and performance modulation. At last, we further analyzed representative experimental results using the two models. We successfully reproduced the experimental results by adjusting the model parameters and revealed the coexistence of the tunneling and hopping processes in the ferrocene based molecular diode. The model method thus can work as powerful tool in mechanism analysis for the molecular rectification study.

Study of Critical Velocity of Stick-Slip Sliding

1960 ◽  
Vol 82 (4) ◽  
pp. 393-398 ◽  
Author(s):  
B. R. Singh
Keyword(s):  
Experimental Study ◽  
Theoretical Analysis ◽  
Critical Velocity ◽  
Mechanical Model ◽  
Analog Computer ◽  
Experimental Results ◽  
Milling Machine ◽  
Friction Damping ◽  
Stick Slip ◽  
Electric Analog

The motion of a body sliding under boundary friction, at a velocity slower than a particular critical velocity of the system, proceeds in a discontinuous or stick-slip form. This paper presents a theoretical analysis and an experimental study of the critical velocity of stick-slip sliding. The influence of various parameters such as friction, damping, stiffness, and sliding mass of the system on the critical velocity was studied on a mechanical model arranged on a milling machine. The arrangement was also simulated on an electric analog computer. Good correlation was observed between the theoretical values and the experimental results on the mechanical model and on the analog computer.

scholarly journals Ideal Current-voltage Characteristics and Rectification Performance of Molecular Rectifier under Single Level based Tunneling and Hopping Transport

2020 ◽  
Author(s):  
Xianneng Song ◽  
Xi Yu ◽  
Wenping Hu
Keyword(s):  
Experimental Results ◽  
Physical Parameters ◽  
Model Parameters ◽  
Mechanism Analysis ◽  
Hopping Transport ◽  
Molecular Diode ◽  
Current Voltage ◽  
Significant Difference ◽  
Molecular Rectification ◽  
And Performance

In this work, we systematically studied the rectifying properties of molecular junction based on asymmetric tunneling and hopping charge transport in a single electronic state model using Landauer formula and Marcus theory. We first analyzed the asymmetric I-V characteristics and revealed distinct physical origins of the rectification under the two types of transports. We found significant difference in I-V characteristics of the two and the hopping transport can afford a much higher rectification ratio than tunneling. Next, the effect of key physical parameters on rectification performance under tunneling and hopping, like asymmetric factor, energy barrier, temperature and molecule-electrode coupling et al, were extensively evaluated, which provided a theoretical baseline for molecular diode design and performance modulation. At last, we further analyzed representative experimental results using the two models. We successfully reproduced the experimental results by adjusting the model parameters and revealed the coexistence of the tunneling and hopping processes in the ferrocene based molecular diode. The model method thus can work as powerful tool in mechanism analysis for the molecular rectification study.

Holdup and holdup profiles in the reciprocating plate extractor VPE

1990 ◽  
Vol 55 (11) ◽  
pp. 2648-2661 ◽  
Author(s):  
Helena Sovová ◽  
Vladislav Bízek ◽  
Jaroslav Procházka
Keyword(s):  
Steady State ◽  
Experimental Results ◽  
Model Parameters ◽  
Dispersed Phase ◽  
Pulse Form ◽  
Sieve Plates

In this work measurements of mean holdup of dispersed phase, of axial holdup profiles and of flooding points in a reciprocating plate contactor with both the VPE-type plates and the sieve plates were carried out. The experimental results were compared with a monodisperse model of steady-state column hydrodynamics and the model parameters were evaluated. Important differences in the behaviour of the two plate types could be identified. Comparison was also made between two reciprocating drives of different pulse form.

PHOTOINDUCED NONLINEAR OCTUPOLAR POLARIZATION: TRANSIENT AND PERMANENT REGIMES

1996 ◽  
Vol 05 (04) ◽  
pp. 653-670 ◽  
Author(s):  
CÉLINE FIORINI ◽  
JEAN-MICHEL NUNZI ◽  
FABRICE CHARRA ◽  
IFOR D.W. SAMUEL ◽  
JOSEPH ZYSS
Keyword(s):  
Theoretical Analysis ◽  
Second Harmonic ◽  
Experimental Results ◽  
Polar Field ◽  
Rotational Spectrum ◽  
Dual Frequency ◽  
One Dimensional ◽  
Ethyl Violet ◽  
Disperse Red 1 ◽  
Good Agreement

An original poling method using purely optical means and based on a dual-frequency interference process is presented. We show that the coherent superposition of two beams at fundamental and second-harmonic frequencies results in a polar field with an irreducible rotational spectrum containing both a vector and an octupolar component. This enables the method to be applied even to molecules without a permanent dipole such as octupolar molecules. After a theoretical analysis of the process, we describe different experiments aiming at light-induced noncentrosymmetry performed respectively on one-dimensional Disperse Red 1 and octupolar Ethyl Violet molecules. Macroscopic octupolar patterning of the induced order is demonstrated in both transient and permanent regimes. Experimental results show good agreement with theory.

scholarly journals Variation of Passive Biomechanical Properties of the Small Intestine along Its Length: Microstructure-Based Characterization

2021 ◽  
Vol 8 (3) ◽  
pp. 32
Author(s):  
Dimitrios P. Sokolis
Keyword(s):  
Small Intestine ◽  
Orientation Angle ◽  
Axial Direction ◽  
Material Model ◽  
Biomechanical Properties ◽  
Intestinal Wall ◽  
Model Parameters ◽  
Material Models ◽  
Hyper Elastic ◽  
Rat Tissue

Multiaxial testing of the small intestinal wall is critical for understanding its biomechanical properties and defining material models, but limited data and material models are available. The aim of the present study was to develop a microstructure-based material model for the small intestine and test whether there was a significant variation in the passive biomechanical properties along the length of the organ. Rat tissue was cut into eight segments that underwent inflation/extension testing, and their nonlinearly hyper-elastic and anisotropic response was characterized by a fiber-reinforced model. Extensive parametric analysis showed a non-significant contribution to the model of the isotropic matrix and circumferential-fiber family, leading also to severe over-parameterization. Such issues were not apparent with the reduced neo-Hookean and (axial and diagonal)-fiber family model, that provided equally accurate fitting results. Absence from the model of either the axial or diagonal-fiber families led to ill representations of the force- and pressure-diameter data, respectively. The primary direction of anisotropy, designated by the estimated orientation angle of diagonal-fiber families, was about 35° to the axial direction, corroborating prior microscopic observations of submucosal collagen-fiber orientation. The estimated model parameters varied across and within the duodenum, jejunum, and ileum, corroborating histologically assessed segmental differences in layer thicknesses.

scholarly journals Characterization of Moisture Diffusion in Cured Concrete Slabs at Early Ages

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Xiao Zhang ◽  
Hongduo Zhao
Keyword(s):  
Process Model ◽  
Model Simulation ◽  
Moisture Diffusion ◽  
Experimental Results ◽  
Concrete Slabs ◽  
Model Parameters ◽  
Early Age ◽  
Water Curing ◽  
Early Age Concrete

The objective of this paper is to investigate the characterization of moisture diffusion inside early-age concrete slabs subjected to curing. Time-dependent relative humidity (RH) distributions of three mixture proportions subjected to three different curing methods (i.e., air curing, water curing, and membrane-forming compounds curing) and sealed condition were measured for 28 days. A one-dimensional nonlinear moisture diffusion partial differential equation (PDE) based on Fick’s second law, which incorporates the effect of curing in the Dirichlet boundary condition using a concept of curing factor, is developed to simulate the diffusion process. Model parameters are calibrated by a genetic algorithm (GA). Experimental results show that the RH reducing rate inside concrete under air curing is greater than the rates under membrane-forming compound curing and water curing. It is shown that the effect of water-to-cement (w/c) ratio on self-desiccation is significant. Lower w/c ratio tends to result in larger RH reduction. RH reduction considering both effect of diffusion and self-desiccation in early-age concrete is not sensitive to w/c ratio, but to curing method. Comparison between model simulation and experimental results indicates that the improved model is able to reflect the effect of curing on moisture diffusion in early-age concrete slabs.

Implementation of a High-Precision Ultrasonic Rain Gauge

2013 ◽  
Vol 300-301 ◽  
pp. 382-388
Author(s):  
Zhan Wei Xu ◽  
Gui Lin Zheng
Keyword(s):  
Theoretical Analysis ◽  
High Precision ◽  
Rain Gauge ◽  
Experimental Results ◽  
Full Description ◽  
Self Calibration ◽  
Velocity Of Ultrasound

A novel rain gauge based on acoustic self-calibration principle is proposed in the paper. Acoustic self-calibration principle can eliminate the uncertainty of the velocity of ultrasound and achieve accurate measurement of rainfall. The rain gauge not only overcomes the influence on the rainfall measurement under intensive rainfall conditions, but also improves the precision of rain gauge. Plenty of experiments have been done to validate the design. Both theoretical analysis and experimental results show the effectiveness of the rain gauge. A full description of the rain gauge and implementation are presented.

scholarly journals New Topologies of Lossless Grounded Inductor Using OTRA

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Rajeshwari Pandey ◽  
Neeta Pandey ◽  
Sajal K. Paul ◽  
A. Singh ◽  
B. Sriram ◽  
...  
Keyword(s):  
Theoretical Analysis ◽  
Experimental Results ◽  
Pspice Simulation ◽  
Operational Transresistance Amplifier

Two alternate topologies of lossless grounded inductor have been proposed using operational transresistance amplifier (OTRA). Three applications using the proposed inductors are also included. PSPice simulation and experimental results have been included to demonstrate the performance and verify the theoretical analysis.

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