Scaling Laws Behind Penetrative Turbulence:History and Perspectives

An unstably stratified flow entering into a stably stratified flow is referred to as penetrative convection,which is crucial to many physical processes and has been thought of as a key factor for extreme weather conditions.Past theoretical,numerical,and experimental studies on penetrative convection are reviewed,along with field studies providing insights into turbulence modeling.The physical factors that initiate penetrative convection,including internal heat sources,nonlinear constitutive relationships,centrifugal forces and other complicated factors are summarized.Cutting-edge methods for understanding transport mechanisms and statistical properties of penetrative turbulence are also documented,e.g.,the variational approach and quasilinear approach,which derive scaling laws embedded in penetrative turbulence.Exploring these scaling laws in penetrative convection can improve our understanding of large-scale geophysical and astrophysical motions.To better the model of penetrative turbulence towards a practical situation,new directions,e.g.,penetrative convection in spheres,and radiation-forced convection,are proposed.

A penetrative addictive for water infusion in coal seams

The manufacturing process, characteristics, and application results of arod-like penetrative additive (the penetrative rod) were discussed. The components and functions ofthe penetrative rod were studied carefully. A large number of orthogonal combined tests were carriedout and over 100 sample molds were made. Ultimately the components were decided after carefulselection among these molds, mainly including hygroscopic major components and auxiliary material.The results of on-site practical application show that such an addictive can increase the waterpenetrative ability effectively and has a remarkable effect on preventing dust production duringcoal seam excavation. The penetrating radius, the infusing velocity and the dust-preventive effectwere systematically studied.

Penetrative and migratory behavior of alkali metal in different binder based TiB_2-C composite cathodes

In electrolyte melts containing K at low temperature, the penetrative and migratory path of alkali metals （K and Na） in pitch, furan, phenolic aldehyde and epoxy based TiB2-C composite cathodes during the electrolysis process were studied by EDS and self-made modified Rapoport apparatus. The electrolysis expansion rates, the diffusion coefficients of the alkali metals and the corrosion rates of the composite cathode were also calculated and discussed. The results show that no matter what kind of binder is used, alkali metals have the same penetrative path in composite cathodes：firstly in pore, then in binder and finally in carbonaceous aggregates. K and Na penetrate into both binder and carbonaceous aggregates, which leads to the expansion of composite cathodes, and K has stronger penetration ability than Na. Electrolysis expansion rate of resin based composite cathode is smaller than that of pitch based composite cathodes, and so do the diffusion coefficient and corrosion rate. Resin based composite cathode has better resistance ability to the penetration of alkali metals than pith based composite cathode, and phenolic aldehyde based composite cathode exhibits the strongest resistance ability. The penetration rate, the diffusion coefficient of alkali metals in phenolic aldehyde based TiB2-C composite cathode and the corresponding corrosion rate are 4.72 mm/h, 2.24×10^-5 cm^2/s and 2.31 mm/a, respectively.

Three dimensional simulations of penetrative convection in a porous medium with internal heat sources

The problem of penetrative convection in a fluid saturated porous medium heated internally is analysed. The linear instability theory and nonlinear energy theory are derived and then tested using three dimensions simulation.Critical Rayleigh numbers are obtained numerically for the case of a uniform heat source in a layer with two fixed surfaces. The validity of both the linear instability and global nonlinear energy stability thresholds are tested using a three dimensional simulation. Our results show that the linear threshold accurately predicts the onset of instability in the basic steady state. However, the required time to arrive at the basic steady state increases significantly as the Rayleigh number tends to the linear threshold.

Effect of Isobutyl-triethoxy-silane Penetrative Protective Agent on the Carbonation Resistance of Concrete

Effect of isobutyl-triethoxy-silane penetrative protective agent on the carbonation resistance of the concrete was studied.The concrete specimens for the 28 d accelerated carbonation process were manufactured with w/c of 0.49 and 0.64,both in the presence and absence of silane and mineral admixture.The penetration of isobutyl-triethoxy-silane and the carbonation of concrete were investigated by penetration depth,carbonation depth,XRD,SEM,and pore size distribution.The results showed that concrete compactness played an important role in the silane penetration and carbonation resistance.Penetration depth of silane-treated concrete mainly depended on the compactness of the concrete,and could not remarkably change through the accelerated carbonation process.In the accelerated carbonation process,penetrative protective agent improved the carbonation resistance of the higher compactness concretes but accelerated the carbonization process of the lower compactness concretes.As penetrative protective agent penetrated along the external connectivity pores into concrete not filling the entire surface area,the inorganic film could not fully protect the Ca（OH）_2 phase from carbonation.After 28 d accelerated carbonation,fibrous hydration products disappeared and the surface holes decreased.Due to the formation of carbonized products,the porosity of the concrete surface decreased,especially in high-strength concrete.

Topology optimization of reactive material structures for penetrative projectiles

Recently,reactive materials have been developed for penetrative projectiles to improve impact resistance and energy capacity.However,the design of a reactive material structure,involving shape and size,is challenging because of difficulties such as high non-linearity of impact resistance,manufacturing limitations of reactive materials and high expenses of penetration experiments.In this study,a design optimization methodology for the reactive material structure is developed based on the finite element analysis.A finite element model for penetration analysis is introduced to save the expenses of the experiments.Impact resistance is assessed through the analysis,and result is calibrated by comparing with experimental results.Based on the model,topology optimization is introduced to determine shape of the structure.The design variables and constraints of the optimization are proposed considering the manufacturing limitations,and the optimal shape that can be manufactured by cold spraying is determined.Based on the optimal shape,size optimization is introduced to determine the geometric dimensions of the structure.As a result,optimal design of the reactive material structure and steel case of the penetrative projectile,which maximizes the impact resistance,is determined.Using the design process proposed in this study,reactive material structures can be designed considering not only mechanical performances but also manufacturing limitations,with reasonable time and cost.

Penetrative Bénard-Marangoni Convection in a Micropolar Ferrofluid Layer via Internal Heating and Submitted to a Robin Thermal Boundary Conditions

Penetrative Bénard-Maranagoni convection in micropolar ferromagnetic fluid layer in the presence of a uniform vertical magnetic field has been investigated via internal heating model. The lower boundary is considered to be rigid at constant temperature, while the upper boundary free open to the atmosphere is flat and subject to a convective surface boundary condition. The resulting eigenvalue problem is solved numerically by Galerkin method. The stability of the system is found to be dependent on the dimensionless internal heat source strength Ns, magnetic parameter M1, the non-linearity of magnetization parameter M3, coupling parameter N1, spin diffusion parameter N3 and micropolar heat conduction parameter N5. The results show that the onset of ferroconvection is delayed with an increase in N1 and N5 but hastens the onset of ferroconvection with an increase in M1, M3, N3 and Ns. The dimension of ferroconvection cells increases when there is an increase in M3, N1, N5 and Ns and decrease in M1 and N3.

ACUPOINT TO ACUPOINT PENETRATIVE NEEDLING AND ITS CLINICAL APPLICATION

Acupoint to acupoint penetrative needling method has a long history in traditional Chinese medicine. Chinese physicians in various dynasties hold that this type of needling method can strengthen the needling sensations and raise the therapeutic effect in clinical practice. This needling method can be divided into straight penetration, oblique penetration and transverse penetration. In clinical application, it can also be divided into external medial meridian penetration, a single meridian penetration, neighboring meridians penetration, and neighboring acupoints penetration, etc. in accordance with the involved acupoints and meridians. Clinical practice demonstrates that penetrative needling possesses advantages of stronger needling sensations, better therapeutic effect and fewer acupoints selection. For this reason, it is extensively applied in clinic.

Twins-like nanodrugs synchronously transport in blood and coalesce inside tumors for sensitive ultrasound imaging and triggerable penetrative drug delivery

Nanodrugs capable of aggregating in the tumor microenvironment(TME)have demonstrated great efficiency in improving the therapeutic outcome.Among vari-ous approaches,the strategy utilizing electrostatic interaction as a driving force to achieve intratumor aggregation of nanodrugs has attracted great attention.However,the great difference between the two nanodrugs with varied physicochemical prop-erties makes their synchronous transport in blood circulation and equal-opportunity tumor uptake impossible,which significantly detracts from the beneficial effects of nanodrug aggregation inside tumors.We herein propose a new strategy to construct a pair of extremely similar nanodrugs,referred to as“twins-like nanodrugs(TLNs)”,which have identical physicochemical properties including the same morphology,size,and electroneutrality to render them the same blood circulation time and tumor entrance.The 1:1 mixture of TLNs(TLNs-Mix)intravenously injected into a mouse model efficiently accumulates in tumor sites and then transfers to oppositely charged nanodrugs for electrostatic interaction-driven coalescence via responding to matrix metalloproteinase-2(MMP-2)enriched in tumor.In addition to enhanced tumor retention,the thus-formed micron-sized aggregates show high echo intensity essen-tial for ultrasound imaging as well as ultrasound-triggered penetrative drug delivery.Owing to their distinctive features,the TLNs-Mix carrying sonosensitizer,immune adjuvant,and ultrasound contrast agent exert potent sonodynamic immunotherapy against hypovascular hepatoma,demonstrating their great potential in treating solid malignancies.

Jet formation and penetration performance of a double-layer charge liner with chemically-deposited tungsten as the inner liner

This paper proposes a type of double-layer charge liner fabricated using chemical vapor deposition(CVD)that has tungsten as its inner liner.The feasibility of this design was evaluated through penetration tests.Double-layer charge liners were fabricated by using CVD to deposit tungsten layers on the inner surfaces of pure T2 copper liners.The microstructures of the tungsten layers were analyzed using a scanning electron microscope(SEM).The feasibility analysis was carried out by pulsed X-rays,slug-retrieval test and static penetration tests.The shaped charge jet forming and penetration law of inner tungsten-coated double-layer liner were studied by numerical simulation method.The results showed that the double-layer liners could form well-shaped jets.The errors between the X-ray test results and the numerical results were within 11.07%.A slug-retrieval test was found that the retrieved slug was similar to a numerically simulated slug.Compared with the traditional pure copper shaped charge jet,the penetration depth of the double-layer shaped charge liner increased by 11.4% and>10.8% respectively.In summary,the test results are good,and the numerical simulation is in good agreement with the test,which verified the feasibility of using the CVD method to fabricate double-layer charge liners with a high-density and high-strength refractory metal as the inner liner.

Research on the influences of motion characteristics of jetting projectile charge under water

Shaped charge warhead is important for enhancing the damage performance of underwater weapons.This paper used finite element analysis software and based on JPC water penetration experiments to examine the influence of liner parameters(wall thickness,material),charge aspect ratio,and stand-off distance on the movement characteristics of JPC in water.The findings reveal that the head diameter of the JPC increases and experiences significant erosion after entering the water,the effective length of the JPC in water undergoes two distinct phases:a growth phase and a decrease phase,with the velocity of the JPC decaying exponentially.Increasing the liner thickness,stand-off distance and the charge aspect ratio can improve the erosion resistance and the velocity retention capacity of the JPC.The optimal ranges for liner thickness and stand-off distance are 0.0363D_(k) to 0.0545D_(k)(D_(k) is the charge diameter),the stand-off distance should be within 1.0D_(k).After the charge aspect ratio higher than 1.25,the charge structure exerts minimal influence the movement characteristics of the JPC in water.Material density plays a crucial role in the velocity decay pattern of the JPC during penetration.JPC with higher densities exhibit superior velocity retention capabilities in water,with the velocity decay pattern converging if the densities are similar.Consequently,copper,tantalum and tungsten liners are deemed appropriate for underwater shaped charge warhead.Finally,the results will provide an important reference for the design of underwater shaped charge warhead.

High-speed penetration of ogive-nose projectiles into thick concrete targets:Tests and a projectile nose evolution model

The majority of the projectiles used in the hypersonic penetration study are solid flat-nosed cylindrical projectiles with a diameter of less than 20 mm.This study aims to fill the gap in the experimental and analytical study of the evolution of the nose shape of larger hollow projectiles under hypersonic penetration.In the hypersonic penetration test,eight ogive-nose AerMet100 steel projectiles with a diameter of 40 mm were launched to hit concrete targets with impact velocities that ranged from 1351 to 1877 m/s.Severe erosion of the projectiles was observed during high-speed penetration of heterogeneous targets,and apparent localized mushrooming occurred in the front nose of recovered projectiles.By examining the damage to projectiles,a linear relationship was found between the relative length reduction rate and the initial kinetic energy of projectiles in different penetration tests.Furthermore,microscopic analysis revealed the forming mechanism of the localized mushrooming phenomenon for eroding penetration,i.e.,material spall erosion abrasion mechanism,material flow and redistribution abrasion mechanism and localized radial upsetting deformation mechanism.Finally,a model of highspeed penetration that included erosion was established on the basis of a model of the evolution of the projectile nose that considers radial upsetting;the model was validated by test data from the literature and the present study.Depending upon the impact velocity,v0,the projectile nose may behave as undistorted,radially distorted or hemispherical.Due to the effects of abrasion of the projectile and enhancement of radial upsetting on the duration and amplitude of the secondary rising segment in the pulse shape of projectile deceleration,the predicted DOP had an upper limit.

Ballistic performance of spherical fragments penetrating PCrNi3MoV target plates

PCrNi3MoV steel is a medium-carbon,low-alloy quenched and tempered steel that finds its applications in military gun barrels due to the high wear resistance and ablation resistance.To study the penetration and failure modes of PCrNi3MoV plates impacted by tungsten spheres,tungsten spheres of various diameters(5 mm,8 mm,and 10 mm)were used to impact PCrNi3MoV steel plates with thicknesses of 6 mm,9 mm,and 14 mm.The penetration performance of the spheres was analyzed for different velocities,and the ultimate penetration velocity of the plate was obtained.It was found that the primary failure modes of the PCrNi3MoV plate were compression pitting failure and shear failure.Using the dimensional analysis method,a relationship between the bulge height of the steel plate and the fragment velocity,an equation for the ultimate penetration velocity,and a relationship between the target penetration energy and the fragment velocity were obtained.Then,a projectile-target action index was proposed to describe the process of tungsten spheres with different velocities impacting target plates.The results suggested that under the same thickness of the target plate,a larger-diameter fragment required more kinetic energy to obtain the same ultimate penetration effect as a smaller-diameter fragment.The equations obtained through dimensional analysis predicted values that agreed well with experimental values,indicating that these equations can be applied to engineering applications.

Efficient Penetration Testing Path Planning Based on Reinforcement Learning with Episodic Memory

Intelligent penetration testing is of great significance for the improvement of the security of information systems,and the critical issue is the planning of penetration test paths.In view of the difficulty for attackers to obtain complete network information in realistic network scenarios,Reinforcement Learning(RL)is a promising solution to discover the optimal penetration path under incomplete information about the target network.Existing RL-based methods are challenged by the sizeable discrete action space,which leads to difficulties in the convergence.Moreover,most methods still rely on experts’knowledge.To address these issues,this paper proposes a penetration path planning method based on reinforcement learning with episodic memory.First,the penetration testing problem is formally described in terms of reinforcement learning.To speed up the training process without specific prior knowledge,the proposed algorithm introduces episodic memory to store experienced advantageous strategies for the first time.Furthermore,the method offers an exploration strategy based on episodic memory to guide the agents in learning.The design makes full use of historical experience to achieve the purpose of reducing blind exploration and improving planning efficiency.Ultimately,comparison experiments are carried out with the existing RL-based methods.The results reveal that the proposed method has better convergence performance.The running time is reduced by more than 20%.

Formation behaviors of rod-like reactive shaped charge penetrator and their effects on damage capability

Formation behaviors of rod-like reactive shaped charge penetrator(RRSCP)and their effects on damage capability are investigated by experiments and numerical simulations.The pulsed X-ray technology and a spaced aluminum/steel plate with the thicknesses of 5 mm/100 mm are used.Three types of sphericalsegment aluminum-polytetrafluoroethylene-copper(Al-PTFE-Cu)reactive liners with Cu contents of 0%,46.6%,and 66%are fabricated and tested.The experimental results show that the reactive liners can form excellent rod-shaped penetrators with tail skirts under the shaped charge effect,but the tail skirts disappear over time.Moreover,rupturing damage to the aluminum plate and penetration to the steel plate are caused by the RRSCP impact.From simulation analysis,the RRSCP is formed by a mechanically and chemically coupled response with the reactive liner activated by shock in its outer walls and bottom and then backward overturning,forming a leading reactive penetrator and a following chemical energy cluster.The unique formation structure determines the damage modes of the aluminum plate and the steel plate.Further analysis indicates that the formation behaviors and damage capability of Al-PTFE-Cu RRSCP strongly depend on Cu content.With increasing Cu content,the velocity,activation extent,and reaction extent of Al-PTFE-Cu RRSCP decrease,which contribute to elongation and alleviate the negative effects of chemical reactions on elongation,significantly increasing the length-diameter ratio and thus enhancing the capability of steel plate penetration.However,the lower activation extent and energetic density will weaken the RRSCP's capability of causing rupturing damage to the aluminum plate.

The penetration depth of atomic radicals in tubes with catalytic surface properties

Catalysis of molecular radicals is often performed in interesting experimental configurations.One possible configuration is tubular geometry.The radicals are introduced into the tubes on one side,and stable molecules are exhausted on the other side.The penetration depth of radicals depends on numerous parameters,so it is not always feasible to calculate it.This article presents systematic measurements of the penetration depth of oxygen atoms along tubes made from nickel,cobalt,and copper.The source of O atoms was a surfatron-type microwave plasma.The initial density of O atoms depended on the gas flow and was 0.7×10^(21)m^(-3),2.4×10^(21)m^(-3),and 4.2×10^(21)m^(-3)at the flow rates of 50,300,and 600 sccm,and pressures of 10,35,and 60 Pa,respectively.The gas temperature remained at room temperature throughout the experiments.The dissociation fraction decreased exponentially along the length of the tubes in all cases.The penetration depths for well-oxidized nickel were 1.2,1.7,and 2.4 cm,respectively.For cobalt,they were slightly lower at 1.0,1.3,and 1.6 cm,respectively,while for copper,they were 1.1,1.3,and 1.7 cm,respectively.The results were explained by gas dynamics and heterogeneous surface association.These data are useful in any attempt to estimate the loss of molecular fragments along tubes,which serve as catalysts for the association of various radicals to stable molecules.

Reply to the note by Li Piani et al.

In 2017,a ballistic phenomenological model was proposed by the authors of Ref.[1] to numerically simulate the experimental depths of small caliber projectiles impacting walls made of adobe.The opportunity for a new model in the field revealed from the observation that two older models recently used by the authors of Ref.[2] shared a linear relationship between the penetration depth P and the impacting velocity v_(O).

Numerical investigation of sinusoidal pulsating gas intake to intensify the gas-slag momentum transfer in the top-blown smelting furnace

The variation characteristics of bubble morphology and the thermal-physical properties of bubble boundary in the top-blown smelting furnace were explored by means of the computational fluid dynamics method.The essential aspects of the fluid phase(e.g.,splashing volume,dead zone of copper slag,and gas penetration depth)were explored together with the effect of sinusoidal pulsating gas intake on the momentum-transfer performance between phases.The results illustrated that two relatively larger vortices and two smaller vortices appear in the bubble waist and below the lance,respectively.The expansion of larger ones as well as the shrinking of smaller ones combine to cause the contraction of the bubble waist.Compared to the results of the case with a fixed gas injection velocity(V_(g)=58 m/s),the splashing volume and dead zone volume of the slag under the V_(g)=58+10sin(2πt)condition are reduced by 24.9%and 23.5%,respectively,where t represents the instant time.Gas penetration depth and slag motion velocity of the latter are 1.03 and 1.31 times high-er than those of the former,respectively.

Machine learning optimization strategy of shaped charge liner structure based on jet penetration efficiency

Shaped charge liner(SCL)has been extensively applied in oil recovery and defense industries.Achieving superior penetration capability through optimizing SCL structures presents a substantial challenge due to intricate rate-dependent processes involving detonation-driven liner collapse,high-speed jet stretching,and penetration.This study introduces an innovative optimization strategy for SCL structures that employs jet penetration efficiency as the primary objective function.The strategy combines experimentally validated finite element method with machine learning(FEM-ML).We propose a novel jet penetration efficiency index derived from enhanced cutoff velocity and shape characteristics of the jet via machine learning.This index effectively evaluates the jet penetration performance.Furthermore,a multi-model fusion based on a machine learning optimization method,called XGBOOST-MFO,is put forward to optimize SCL structure over a large input space.The strategy's feasibility is demonstrated through the optimization of copper SCL implemented via the FEM-ML strategy.Finally,this strategy is extended to optimize the structure of the recently emerging CrMnFeCoNi high-entropy alloy conical liners and hemispherical copper liners.Therefore,the strategy can provide helpful guidance for the engineering design of SCL.

αDecay in extreme laser fields within a deformed Gamow-like model

In this study, the effect of extreme laser fields on the α decay process of ground-state even–even nuclei was investigated.Using the deformed Gamow-like model, we found that state-of-the-art lasers can cause a slight change in the α decay penetration probability of most nuclei. In addition, we studied the correlation between the rate of change of the α decay penetration probability and angle between the directions of the laser electric field and α particle emission for different nuclei. Based on this correlation, the average effect of extreme laser fields on the half-life of many nuclei with arbitrary α particle emission angles was calculated. The calculations show that the laser suppression and promotion effects on the α decay penetration probability of the nuclei population with completely random α particle-emission directions are not completely canceled.The remainder led to a change in the average penetration probability of the nuclei. Furthermore, the possibility of achieving a higher average rate of change by altering the spatial shape of the laser is explored. We conclude that circularly polarized lasers may be helpful in future experiments to achieve a more significant average rate of change of the α decay half-life of the nuclei population.