Mode Of Penetration Research Articles

Pore-scale direct numerical simulation of Haines jumps in a porous media model

Direct numerical simulations are presented for a porous media model consisting of two immiscible fluids, an invading and defending phase, in a two-dimensional micro-geometry filled with randomly sized and randomly distributed cylinders. First, interface instability and penetration modes are studied when varying the wetting features of a single pore in the porous medium. It is found that the displacement patterns not only change with the capillary number, as previously observed, but also are a function of the contact angle, even for a viscosity ratio of unity. This is an important conclusion suggesting that capillary number and viscosity ratio alone cannot completely describe the pore-scale displacement. Second, rapid pore-scale displacement is considered, where the displacements are accompanied by sudden interface jumps from one site to another, known as Haines jumps. The characteristic time and length scales of a Haines jump are examined to better understand the transient dynamics of the jump. We then focus on analyzing the Haines jump in a simple pore configuration where cylinders of equal size are placed at the vertices of equilateral triangles. We use this geometry to provide more insight into the effect of the contact angle at which the Haines jump is predicted.

Microparticle impact-bonding modes for mismatched metals: From co-deformation to splatting and penetration

We present a comprehensive experimental campaign of high-velocity microparticle impacts with different combinations of particle and substrate materials to identify possible deformation regimes. Based on experimental observations of the impact sites, we identify three typical modes of behavior, namely, splatting, co-deformation, and penetration. We develop a theoretical framework to predict the operative regime for a given particle/substrate combination, ranging from splatting and penetration at two extremes of a spectrum, and co-deformation in the center. We propose an impact ratio based on the materials’ properties, which can successfully quantify the spectrum. Co-deformation is expected when the ratio is around unity, while much larger or smaller ratios give rise to penetration and splatting, respectively.

Drag reduction analysis of counterflow jets in a short penetration mode

The characteristics around counterflow jets are difficult to predict, because of the many variables involved. To analyze counterflow jets with different freestreams, a numerical simulation was conducted, by solving a two-dimensional axisymmetric RANS equation. The trends in drag reduction were reviewed in short penetration mode, with freestream conditions (altitude: 10 to 19 km, M∞: 2.0 to 4.0). According to the results of the numerical analysis, it was determined that the differences in overall flow structure arise from the freestream Mach number. The recirculation zone is the key feature of the flow. In the flow mechanism, the recirculation zone is affected by the velocity and pressure at the boundary, and the position and pressure of the reattachment point are the main parameters influencing the recirculation zone. Observed differences in the flow structure depending on the freestream Mach number can be explained by these parameters. As a result, different drag reduction curves can be drawn for each freestream Mach number, and a maximum value on drag reduction exists.

Effect of Counterflowing Jet on Supersonic Slender-Body Configurations: A Numerical Study

Previous studies have demonstrated that the use of counterflowing supersonic jets operating in the long penetration mode (LPM), directed from the nose of blunt bodies against a supersonic/hypersonic freestream, can greatly reduce the drag and heat loads on the vehicle. However, the benefits of LPM for slender bodies of revolution operating at low supersonic speeds, applicable to supersonic transport applications, remain largely unknown. This Paper conducts a systematic parametric study for the effects of a counterflowing jet on two slender body models (cone-cylinder and quartic body of revolution, respectively) operating at a freestream Mach number of 1.6, using time-accurate computations performed with an unstructured Navier–Stokes solver. Different ranges of jet flow rates, jet exit Mach numbers, nozzle exit diameters, and jet-to-base diameter ratios are examined systematically. The jet-to-base diameter ratio is determined to be the most important parameter to facilitate the establishment of the LPM regime. Depending on the geometry of the slender body, longer jet penetration (thus larger shock-standoff distance) associated with the LPM does not always result in larger drag reduction. Furthermore, current results indicate that inclusion of an LPM jet is likely to cause large oscillations of surface pressure and drag on these slender geometries.

Dynamic alloying of high manganese steel

The option of creating a composite material based on high manganese steel by the method of dynamic alloying in the superdeep penetration mode by flows of powder particles is considered. The dynamic effect of powdered microparticles on a matrix billet transforms the original cast steel into a composite material and leads to a change in mechanical properties.

Development of Cell Penetrating Peptides for Effective Delivery of Recombinant Factors into Target Cells.

The cell membrane is a protective layer that strictly controls the passage of molecules restricting the delivery of biomolecules such as drugs, oligonucleotides, peptides, and siRNA into the cells. This shortcoming has been overcome by the discovery of Cell-Penetrating Peptides (CPPs) that has undergone 30 years of evolution. To date, CPPs are largely modified to improve its efficacy and to suit the different delivery applications. The modes of CPPs penetration are still an unresolved mystery and requires further investigations to increase its effectiveness and to diversify its use. Despite having huge potential as a biomolecule carrier, CPPs also have some drawbacks. In this review, the natural and synthetic CPPs, the modifications that have been conducted on CPPs to improve its efficacy, its extended applications, modes of penetration and limitation as well as challenges will be discussed.

BIOEROSION IN THE PLEISTOCENE OF SOUTHERN ITALY: ICHNOGENERA <em>CAULOSTREPSIS</em> AND <em>MAEANDROPOLYDORA</em>

The ichnogenera Caulostrepsis Clarke and Maeandropolydora Voigt are re—examined and redescribed on the basis of new material from Cretaceous deposits at Ivö (Sweden) and in particular from Pleistocene deposits from southern Italy. The morphological differences between the two ichnogenera are explained as having originated by different modes of substrate penetration. Maeandropolydora's gallery is extended from the end of one limb (axial boring), whereas Caulostrepsis's gallery advances at the vertex (lateral boring). Combinations of the two processes give rise to intermediate forms: Caulostrepsis contorta, in which lateral boring prevails and Maeandropolydora decipiens, in which axial boring is predominant. Structures that are U—shaped or produced by elaboration of this basic U—plan (C. contorta) are referred to the ichnogenus Caulostrepsis; the ichnospecies are separated according to presence/absence of vane, pouches, apertural pits and apertural grooves. The different ichnospecies of Maeandropolydora are characterized by presence or absence of pouches or by galleries tending to run in pairs,

Combination of counterflow jet and cavity for heat flux and drag reduction

In the present work, a computational study is carried out to explore the potential of a combination of a forward-facing cavity and a counterflow jet for drag and heat flux mitigation for an axisymmetric body in a supersonic free stream of Mach 2. A comparison between the axisymmetric body with a forward-facing cavity and counterflow jet and the baseline geometry without the cavity and jet is made. The first part of this study focuses on capturing the transition point of the two counterflow jet modes, Long Penetration Mode (LPM) and Short Penetration Mode (SPM), by changing the pressure ratio of the nozzle. It gave an appropriate nozzle operating pressure selection based on the design requirement. The LPM is found to be suitable when only drag reduction is required, while the SPM provides both drag and heat flux reduction, but at a higher operating jet pressure. Next, a study is conducted to characterize the effect of the angle of attack on system performance. The LPM shows improvement over the baseline geometry for only a narrow range of angles of attack, while the SPM provides improved performance for a wider range of angles of attack. The effect of cavity and cavity dimensions on performance is then studied.

Hypersonic drag reduction mechanism of a novel combinational spike and multi-opposing jets aerodynamic configuration

The shock wave drag significantly affects the aerodynamic performance of hypersonic vehicles, a novel combinational configuration is proposed to reduce the drag in this paper. The basic configurations are the spike, nose cone, front and rear jets, respectively. The numerical method is used to study the drag reduction performance. The combinational configuration has weaker reattachment shock wave than the other configurations, and both the peak pressure of nose cone and drag coefficient are decreased by more than 45%, which verifies the excellent drag reduction performance of combinational configuration. The influencing factors are analyzed in this paper. Lengthening the spike and increasing the total pressures of two jets can make the reattachment shock wave away from wall, weaken its intensity and increase the drag reduction performance. Furthermore, the change rates of wall pressure distribution of the nose cone and drag coefficient gradually decrease. When the sizes of two nozzles are small, the rear jet appears as the long penetration mode. When the sizes of two nozzles are larger than corresponding critical sizes, respectively, the rear jet will convert to the short penetration mode. Increasing the sizes of two nozzles makes the reattachment shock wave away from wall and increases drag reduction performance with the rear jet being SPM as well. The size and total pressure of front jet has greater influence on the drag coefficient. The influence of above factors on the flow characteristics and mass flow rate of nozzle is also studied in this paper.

Parametric study on drag reduction with the combination of the upstream energy deposition and the opposing jet configuration in supersonic flows

The drag reduction characteristics play an important role in the supersonic vehicle design phase. According to two drag reduction schemes, the opposing jet and the upstream energy deposition have aroused the widespread interest of researchers. In the current study, the drag reduction effectiveness of a blunt body with the combination of the upstream energy deposition and the opposing jet configuration in supersonic flows is investigated numerically. The three-dimensional coupled implicit compressible Reynolds Averaged Navier-Stokes (RANS) equations coupled with the Menter's shear stress transport (SST) turbulence model are applied to numerically predict flow fields of the blunt body, the variance analysis method is introduced to a parametric study on the drag reduction. Results indicate that a larger overall drag is decreased by the combinational configuration than the single strategies of the opposing jet and the energy deposition. The proposal of the combination of the upstream energy deposition and the opposing jet configuration can be used as an effective method of drag reduction. Meanwhile, due to the existence of the upstream energy deposition, the stability and penetrability of the opposing jet substantially increase, especially for the long penetration mode. Further, some recommendations are provided for the drag reduction factor and drag reduction effectiveness.

Nanoneedle Platforms: The Many Ways to Pierce the Cell Membrane

AbstractEstablishing techniques to efficiently and nondestructively access the intracellular milieu is essential for many biomedical and scientific applications, ranging from drug delivery, to electrical recording, to biochemical detection. Cell penetration using nanoneedle arrays is currently a research focus area because it not only meets the increasing therapeutic demands of cell modifications and genome editing, but also provides an ideal platform for tracking long‐term intracellular information. Although the precise mechanism driving membrane penetration by nanoneedle arrays is still unclear, the low cytotoxicity, wide range of delivered materials, diverse cell type targets, and simple material structures of nanoneedle arrays make these splendid platforms for cell access. Here, the recent progress in this field is reviewed by examining device architectures and discussing mechanisms for nanoneedle penetration, and the major studies demonstrating the most general applicability of nanoneedle arrays, typical methodologies to access the intracellular environment using nanoneedles with spontaneous or assisted penetration modes, as well as biosafety aspects are presented. This review should be valuable for deeply understanding the materials fabrication principles, device designs, cell penetration methodologies, biosafety aspects, and application strategies of nanoneedle array‐based systems that are of crucial importance for the development of future practical biomedical platforms.

Splash sheet characteristics induced by the impingement of multiple jets in a steelmaking converter

ABSTRACT In oxygen steelmaking, one important aspect is to depict the splashing induced by the impingement of multiple jets quantitatively. In this paper, experiments were conducted to investigate the splash sheets. The results demonstrated that with the decrease of lance height, the sheet area increased, while the sheet height decreased. The sheet diameter was much less affected by the gas flow rate compared to the sheet height. The cavity width-to-depth ratio is a critical parameter affecting the sheet shape. The sheet area produced by the 5-nozzle jet was larger than that produced by the 6-nozzle jet. Taking the sheet area reduction as the critical condition where the cavity mode changes from splashing to penetrating, the critical lance height was investigated under various ejecting conditions. This was further represented by the blowing number as a normalized formula. At last, curve fitting illustrating the conditions that lead to the penetrating mode was conducted.

Threshold conditions for thermocapillary transition to deep penetration mode in selective laser melting of metal powder bed

The keyhole mode of selective laser melting (SLM) of metal powder bed in additive technology is characterized by an intensive hydrodynamic process in a thin molten layer. Such a mode is widely used also in laser and electron beam welding indicating the similarity of hydrodynamic processes in these technologies despite a significant difference of operating parameters. The threshold conditions of thermocapillary keyhole mode transition for various metals (Cu, Fe, Ti) in a wide range of beam parameters used for selective laser melting of metal powder layer and laser welding are investigated. The condition of threshold for thermocapillary transition into keyhole mode by sticking of viscous layer to the solid boundary is formulated. The fulfillment of this condition is confirmed by the convergence of estimated values of the viscous layer thickness and the molten layer depth during the transition to a keyhole mode. Analytical estimates of keyhole threshold and comparisons with experimental values of beam power and spot size corresponding to the transition in keyhole mode for SLM processes and laser welding are presented. The correlation of these values confirms the thermocapillary mechanism of cavity formation and the similarity of hydrodynamic processes in laser welding and SLM processing in keyhole mode at wide range of operating parameters.

Conversion of cast carbon steel into composite material

Experimental estimates of the strength properties of a composite material based on carbon steel 45, created by piercing matrix steel in the mode of superdeep penetration by streams of powder particles, have been performed. Pulsed dynamic action by streams of powder particles and subsequent heat treatment converts steel into a fiber composite material.

Parameter study on drag and heat reduction of a novel combinational spiked blunt body and rear opposing jet concept in hypersonic flows

A novel combinational configuration is proposed for drag and heat reduction in this paper, the CFD numerical method is adopted to study its drag and heat reduction performance. The results show that the aerodisk enhances the compression of hypersonic free stream by the spike to reduce the intensity of reattachment shock wave. The rear jet pushes the reattachment shock wave away from the blunt body and reduce the intensity of reattachment shock wave as well. In addition, the low-temperature gas from rear jet can also cool the blunt body directly. Increasing the length-diameter ratio of the spike reduces the intensity of reattachment shock wave, the rear jet gas can be ejected farther to push the reattachment shock wave father away from the blunt body. Increasing the diameter of aerodisk enhances the compression of hypersonic free stream to reduce the intensity of reattachment shock wave, while the shock wave drag of spike gradually increases. Therefore, with the increase of diameter of aerodisk, the total drag coefficient of combinational configuration first decreases and then increases. The rear jet presents the long penetration mode and short penetration mode. Increasing the total pressure ratio and the size of nozzle can push the reattachment shock wave away from the blunt body and reduce the intensity of reattachment shock wave, more low-temperature gas can also be injected into the flow field to cool the blunt body effectively. Finally, the flat disk has better drag and heat reduction performance than conical disk and hemispherical disk.

Real-Time Prediction of Welding Penetration Mode and Depth Based on Visual Characteristics of Weld Pool in GMAW Process

The penetration depth of welding seam can reflect welding quality fundamentally, during the gas metal arc welding (GMAW) process, the penetration depth of welding seam fluctuates over time. At present, it lacks of reliable sensing method to predict penetration depth fluctuation accurately in real time. To solve the above problem, in this paper, proposing a real-time prediction method for weld penetration mode and depth based on two-dimensional visual characteristics of weld pool, establishing a monocular vision sensing system, extracting the area, length and width of weld pool as key two-dimensional visual characteristics. Taking the extracted current frame characteristics of weld pool as the input, the weld penetration of welding seam corresponding to current frame as the output, based on support vector machine (SVM) and back propagation (BP) neural network respectively, the real-time prediction models for weld penetration mode and depth were established. The predicted results show that the established models can accurately predict the penetration mode and penetration depth of welding seam in real time.

Microparticle Impact-Bonding Modes for Mismatched Metals: From Co-Deformation to Splatting and Penetration

We present a comprehensive experimental campaign of high-velocity microparticle impacts with different combinations of particle and substrate materials to identify possible deformation regimes. Based on experimental observations of the impact sites, we identify three typical modes of behavior, namely, splatting, co-deformation, and penetration. We develop a theoretical framework to predict the operative regime for a given particle/substrate combination, ranging from splatting and penetration at two extremes of a spectrum, and co-deformation in the center. We propose an impact ratio based on the materials' properties, which can successfully quantify the spectrum. Co-deformation is expected when the ratio is around unity, while much larger or smaller ratios give rise to splatting and penetration respectively.

Dimensional characteristics for dynamic processing of materials by flow particles in super-deep penetration mode

Dimensional characteristics for dynamic processing of materials by flow particles in super-deep penetration mode

Revising the penetration behavior of concrete-like and metal-like materials against the rigid projectile impact

Many studies indicate that projectile deceleration exhibits a quasi-constant behavior in the tunneling penetration stage of the rigid penetration mode for both metal-like and concrete-like materials. As to the issue, in the present paper the penetration process under the rigid penetration mode was revised, where a two-phase penetration theory is proposed including the ‘Squeeze and Push’ penetration phase and the dynamic spherical cavity expansion penetration phase. When the striking velocity is below the critical striking velocity, the ‘Squeeze and Push’ effect is generated since the cavitation size is less than the projectile diameter, where the quasi-static term overshadows the dynamic term. The interaction from the surface friction between projectile and target and the penetration force due to the main quasi-static term contributes to the occurrence of the quasi-constant phenomenon. Conversely, when the striking velocity is above the critical velocity, the penetration enters into the dynamic spherical cavity expansion penetration phase, the accompanying feature is that the tunnel becomes large beyond the projectile diameter, meanwhile the friction effect between the projectile and target disappears, the deceleration shows a well-defined peak with the rise of the striking velocity. Following the features, semi-empirical formulas are obtained. Finally, the semi-empirical formulae are discussed and validated by comparing with the typical penetration experiments including concrete-like and metal-like materials.

Lessons learned from adenovirus (1970-2019).

Animal viruses are well recognized for their ability to uncover fundamental cell and molecular processes, and adenovirus certainly provides a prime example. This review illustrates the lessons learned from studying adenovirus over the past five decades. We take a look back at the key studies of adenovirus structure and biophysical properties, which revealed the mechanisms of adenovirus association with antibody, cell receptor, and immune molecules that regulate infection. In addition, we discuss the critical contribution of studies of adenovirus gene expression to elucidation of fundamental reactions in pre-mRNA processing and its regulation. Other pioneering studies furnished the first examples of protein-primed initiation of DNA synthesis and viral small RNAs. As a nonenveloped virus, adenoviruses have furnished insights into the modes of virus attachment, entry, and penetration of host cells, and we discuss the diversity of cell receptors that support these processes, as well as membrane penetration. As a result of these extensive studies, adenovirus vectors were among the first to be developed for therapeutic applications. We highlight some of the early (unsuccessful) trials and the lessons learned from them.