Narrow Results

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in 2011 caused the widespread contamination of Fukushima Prefecture by radioactive cesium. The cesium radioisotopes are considered to have remained in the soil for seven years. We investigated this situation by analyzing soil from paddy fields in the area. We investigated the structure of soil particles using scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDS) and autoradiogram (ARG). We estimated the percentage of clay in the soil based on its composition, and then obtained the radioactivity of the cesium radioisotopes for each soil particle size as a function of penetration. The cesium radioisotopes were exponentially distributed in soil containing a large proportion of clay. Hence, we confirmed that the quantity of clay in the soil is a very important factor with respect to the possibility of the resumption of agriculture in the restricted area.

The interaction of the flying plate with the Long-rod penetrator has been studied both experimentally and numerically using the LS DYNA 3D finite element code. The influence of the plate velocity and plate material on this interaction has been investigated in details. Numerical results show that there was a relatively large damage of the projectiles. The extent of this damage well agree with our experimental foundings. The numerical simulation of the damaged projectiles with some targets has been also performed

The RHT concrete strength model and failure model are employed for the numerical simulations of composite projectile penetrating concrete targets. The simulations show that RHT parameters, specially the failure parameters, greatly influence the penetration depth, exit velocity. The failure mode of concrete should be paid great attentions in numerical analysis. If the crushing failure is the primary mechanism, RHT model seems effective. For the cracking process of concrete, the model should be tensile failure description. Reasonable material parameters are important in penetration simulations. Comparison between numerical analysis and experimental date is made for discussion about the parameter effects.

Combination of different materials used both in the projectile and the sandwich panel is getting more important in designing for maximization of energy absorption during impact. In the present study, we have simulated the bulging process during projectile impact for axisymmetric impact problems. We have discussed the bulging velocity tendency depending on some important geometrical and material parameters such as the yield strength, and tensile limit of the core for several different core thickness and different elapsed time after impact by using the AUTODYN commercial software. From our simulation, we have found that material properties have more dominant effects than the geometric properties on the bulging velocity.

Aluminum alloy foam offers a unique combination of good characteristics, for example, low density, high strength and energy absorption. During penetration, the foam materials exhibit significant nonlinear deformation. The penetration of aluminum alloy foam struck transversely by cone-nosed projectiles has been theoretically investigated. The dynamic cavity-expansion model is used to study the penetration resistance of the projectiles, which can be taken as two parts. One is due to the elasto-plastic deformation of the aluminum alloy foam materials. The other is dynamic resistance force coming from the energy of the projectiles. The penetration resistance expression is derived and applied to analyze the penetration depth of cone-nosed projectiles into the aluminum alloy foam target. The effect of initial velocity, the geometry of the projectiles on the penetration depth is investigated.

Numerical studies were conducted on the ballistic performance of alumina ceramic (AD95) tiles based on depth of penetration method, when subjected to normal impact of tungsten long rod projectiles at velocities ranging from 1100 to 2000 ms^-1. The residual depth on after-effect target was derived in each case, and the ballistic efficiency factor was determined using the corresponding penetration depth on medium carbon steel. Anti-penetration experiment study of the AD95 ceramic tiles to tungsten long rod projectiles has been carried out to verify the accuracy of numerical simulation model. The result shows that numerical simulation results agree well with the corresponding experiment results and AD95 ceramic has excellent ballistic performance than medium carbon steel. The ballistic efficiency factor increases with velocity increasing when impact velocity lower than 1300 ms^-1, and when it was higher than 1300 ms^-1 the ballistic efficiency factor has almost no difference.

This paper describes the development of the needle-free injection with a pulsed micro-injector. The novel injection system consists of a micro-injector, a solenoid valve with an electron-control system and a high pressure liquid supply system. The diameters of the orifice are 200µm~ 300µm. The performance of both pulsed and continuous injections is characterized. Results show that the mass flow rate is increased linearly for the liquid pressure ranging from 50bar to 125bar. The jet velocity increases from 50.6m/s to 104m/s as the liquid pressure increases from 50bar to 125bar. Penetration test to the soft solid materials shows that the penetration depth is increased from 2mm to 7mm depending on the injection power under single pulsed injection. It is believed that the technique will be useful for the drug delivery as well as the localized tumor treatment.

To analyze the process of jet penetration in water medium quantitatively, the properties of jet penetration spaced target with water interlayer were studied through test and numerical simulation. Two theoretical models of jet penetration in water were proposed. The theoretical model 1 was established considering the impact of the shock wave, combined with the shock equation Rankine–Hugoniot and the virtual origin calculation method. The theoretical model 2 was obtained by fitting theoretical analysis and numerical simulation results. The effectiveness and universality of the two theoretical models were compared through the numerical simulation results. Both the models can reflect the relationship between the penetration velocity and the penetration distance in water well, and both the deviation and stability of theoretical model 1 are better than 2, the lower penetration velocity, and the larger deviation of the theoretical model 2. Therefore, the theoretical model 1 can reflect the properties of jet penetration in water effectively, and provide the reference of model simulation and theoretical research.

To improve the real-time performance and the target adaptability of penetration fuze detonation control systems, and to enhance the system fusion processing capability for multi-sensor information, this paper uses a modular design concept to construct a miniaturized (ø38mm×4mm) fuze detonation control system that is capable of real-time processing of data from multiple information sources. The core component of this system is the GD32E230 microcontroller, which features a high dominant frequency and low power consumption. This device is integrated with a ferroelectric memory and signal processing circuits that match the sensors. To address the issue of unclear traditional acceleration signal penetration and the difficulties associated with the identification of these signals, the approach in this paper improves feature recognition accuracy through rapid acquisition and fusion of multiple types of sensor output signal, and self-adaptive identification of multilayered targets and single-layer thick targets is achieved. During the programming of the embedded system, the hardware register is operated directly, the instruction execution sequence is optimized, and the program execution efficiency is improved by using the function characteristic that some microcontroller unit peripherals do not occupy the central processing unit when working, thus allowing the intended purpose of improving the system’s real-time performance to be achieved. A semi-physical simulation method is then used to verify the performance of the penetration fuze detonation control system. The results obtained show that the system has 100%-layer counting accuracy for multilayered targets and a relative error of less than 1% for the calculated residual velocities of single-layer thick targets, thus validating the effectiveness of the system.

For concrete target penetration and/or perforation simulation, the Holmquist–Johnson–Cook (HJC) material model is widely used as concrete material model. However, the strain rate expression of the model has failed to explain the sudden increase in concrete strength at high strain rates. The pressure-volume relationship of the HJC model is complex and requires a large number of material constants. In this study, a modified Holmquist–Johnson–Cook (HJC) model is proposed for concrete material under high velocity impact. The modification involves simplification and improvement of the strain rate expression and pressure-volume relationship. Material parameters identification procedure for the MHJC model is also elaborated. The numerical simulations using the proposed model show a good agreement with experimental observations, especially, on the residual velocities, penetration depths and failure patterns of the target plates. These validate the applicability of the MHJC model for high velocity projectile impact studies for concrete.

Determination of an injection condition which is minimally invasive to the cell membrane is of great importance in drug and gene delivery. For this purpose, a series of molecular dynamics (MD) simulations are conducted to study the penetration of a carbon nanotube (CNT) into a pure POPC cell membrane under various injection velocities, CNT tilt angles and chirality parameters. The simulations are nonequilibrium and all-atom. The force and stress exerted on the nanotube, deformation of the lipid bilayer, and strain of the CNT atoms are inspected during the simulations. We found that a lower nanotube velocity results in successfully entering the membrane with minimum disruption in the CNT and the lipid bilayer, and CNT's chirality distinctly affects the results. Moreover, it is shown that the tilt angle of the CNT influences the nanotube's buckling and may result in destroying the membrane structure during the injection process.

For at least two decades, nanoparticles have been investigated for their capability to deliver topically applied substances through the skin barrier. Based on findings that nanoparticles are highly suitable for penetrating the blood–brain barrier, their use for drug delivery through the skin has become a topic of intense research. In spite of the research efforts by academia and industry, a commercial product permitting the nanoparticle-assisted delivery of topically applied drugs has not yet been developed. However, nanoparticles of approximately 600 nm in diameter have been shown to penetrate efficiently into the hair follicles, where they can be stored for several days. The successful loading of nanoparticles with drugs and their triggered release inside the hair follicle may present an ideal method for localized drug delivery. Depending on the particle size, such a method would permit targeting specific structures in the hair follicles such as stem cells or immune cells or blood vessels found in the vicinity of the hair follicles.

In the present work, a method to direct the X-ray beam in real time to the desired locations in the cargo to increase penetration and reduce exclusion zone is presented. Cargo scanners employ high energy X-rays to produce radiographic images of the cargo. Most new scanners employ dual-energy to produce, in addition to attenuation maps, atomic number information in order to facilitate the detection of contraband. The electron beam producing the bremsstrahlung X-ray beam is usually directed approximately to the center of the container, concentrating the highest X-ray intensity to that area. Other parts of the container are exposed to lower radiation levels due to the large drop-off of the bremsstrahlung radiation intensity as a function of angle, especially for high energies (>6 MV). This results in lower penetration in these areas, requiring higher power sources that increase the dose and exclusion zone. The capability to modulate the X-ray source intensity on a pulse-by-pulse basis to deliver only as much radiation as required to the cargo has been reported previously. This method is, however, controlled by the most attenuating part of the inspected slice, resulting in excessive radiation to other areas of the cargo. A method to direct a dual-energy beam has been developed to provide a more precisely controlled level of required radiation to highly attenuating areas. The present method is based on steering the dual-energy electron beam using magnetic components on a pulse-to-pulse basis to a fixed location on the X-ray production target, but incident at different angles so as to direct the maximum intensity of the produced bremsstrahlung to the desired locations. The details of the technique and subsystem and simulation results are presented.

A computer test-bed is being established for the first-principle simulation of multi-scale structural failure under b last loads. Since t he structural failure due to explosion involves plasticity, damage, localization, thermal softening, phase transition and fragmentation, accurate constitutive models are not yet available for building materials. Also, a robust spatial discretization method is a necessity for large-scale simulation of the transition from continuous to discontinuous failure modes without invoking a fixed mesh connectivity. In this paper, the transition from continuous to discontinuous failure modes in brittle solids is identified through the bifurcation analysis of the acoustic tensor governing rate-dependent damage. A discrete constitutive model is then used to predict material failure as a decohesion or separation of continuum. To accommodate the multi-scale discontinuities involved in structural failure, the Material Point Method is developed to be a robust spatial discretization tool for the computer test-bed. As a result, the model parameters can be calibrated based on experimental data available, and routine simulation can be performed with limited computational resources. Sample problems are considered to illustrate the potential of the proposed simple procedure.

An analytical model to predict penetration of rigid projectiles into concrete targets is put forward in this paper. By assuming the resistant forces of the penetration mainly come from pressure actions behind shock waves that caused by the impact, penetration velocity can be expressed in form of material Hugoniot parameters and penetration time. The penetration will terminate when the impact pressure is less than yield strength of the target material, which gives whole duration of the penetration. Integration of the penetration velocities on the duration results in final depth of the penetration. Some experimental data are used to verify the model, and agreement between experimental data and model calculations means that the model gives a valid prediction for the penetration of thick concrete targets by rigid projectiles.

FEM models of semi-armor-piercing warhead penetrating double-layer aircraft carrier target are established, based on which the dynamic response processes of the warhead penetrating the target with two different attack angles of 0° and 10° are calculated. The results show that the posture of the warhead after penetrating the flight deck suffer an obvious change which causes notable increase in attack angle to the car deck. Ductility reaming damage mode and adiabatic plugging damage mode are exhibited in the penetration process. Durative high accelerations come forth in the penetration process leads to serious erosion in nose of the warhead and s an obvious structure distortion of the warhead. The research could provide reference for the warhead design and corresponding study on damage effect.

Aluminum alloy foam offers a unique combination of good characteristics, for example, low density, high strength and energy absorption. During penetration, the foam materials exhibit significant nonlinear deformation. The penetration of aluminum alloy foam struck transversely by cone-nosed projectiles has been theoretically investigated. The dynamic cavity-expansion model is used to study the penetration resistance of the projectiles, which can be taken as two parts. One is due to the elasto-plastic deformation of the aluminum alloy foam materials. The other is dynamic resistance force coming from the energy of the projectiles. The penetration resistance expression is derived and applied to analyze the penetration depth of cone-nosed projectiles into the aluminum alloy foam target. The effect of initial velocity, the geometry of the projectiles on the penetration depth is investigated.

The projectile into concrete targets was simulated by the nonlinear finite element software ANSYS/LS-DYNA3D. The penetration process of the projectile to target board was analyzed, Velocity and acceleration curves were analyzed based on different penetration velocity. The rules of the penetration process were obtained. Residual speed of the projectile penetrating steel fiber plate and shelter plate projectile was compared. Results of the study indicate as followings: material parameters of the projectile and target board were reasonable, shelter plate made of steel structure of steel fiber concrete can lower projectile speed obviously and quickly, and it has better anti-penetration ability.