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The time-sequenced damage behavior of the reactive projectile impacting double-layer plates is discussed. The analytical model considering the combined effect of kinetic and chemical energy is developed to reveal the damage mechanism. The influences of impact velocity and reactive projectile chemical characteristics on the damage effect are decoupled analyzed based on this model. These analyses indicate that the high energy releasing efficiency and fast reaction propagation velocity of the reactive projectile are conducive to enhancing the damage effect. The experiments with various reactive projectiles impact velocity increasing from 702 to 1385 m/s were conducted to verify this model. The experimental results presented that, the damage hole radius of the rear-plate increases with the increase of impact velocity. At the impact velocity of 1350 m/s, the radius of damage hole formed by PTFE/Al/Bi2O3, PTFE/Al/MoO3, PTFE/Al/Fe2O3projectile on the rear-plate become smaller in sequence. These results are consistent with the analytical model prediction, demonstrating that this model can predict the damage effect quantitatively. This work is of constructive significance to the application of reactive projectiles.

Chain damage is a new phenomenon that occurs when a reactive jet impacts and penetrates multi-spaced plates. The reactive jet produces mechanical perforations on the spaced plates by its kinetic energy (KE), and then results in unusual chain rupturing effects and excessive structural damage on the spaced plates by its deflagration reaction. In the present study, the chain damage behavior is initially demonstrated by experiments. The reactive liners, composed of 26 wt%Al and 74 wt% PTFE, are fabricated through a pressing and sintering process. Three reactive liner thicknesses of 0.08 CD, 0.10 CD and 0.12 CD (charge diameter) are chosen to carry out the chain damage experiments. The results show a chain rupturing phenomenon caused by reactive jet. The constant reaction delay time and the different penetration velocities of reactive jets from liners with different thicknesses result in the variation of the deflagration position, which consequently determines the number of ruptured plates behind the armor. Then, the finite-element code AUTODYN-3D has been used to simulate the kinetic energy only-induced rupturing effects on plates, based on the mechanism of behind armor debris (BAD). The significant discrepancies between simulations and experiments indicate that one enhanced damage mechanism, the behind armor blast (BAB), has acted on the ruptured plates. Finally, a theoretical model is used to consider the BAB-induced enhancement, and the analysis shows that the rupturing area on aluminum plates depends strongly upon the KE only-induced pre-perforations, the mass of reactive materials, and the thickness of plates.

Enhanced damage to the full-filled fuel tank, impacted by the cold pressed and sintered PTFE/Al/W reactive material projectile (RMP) with a density of 7.8 g/cm3, is investigated experimentally and theoretically. The fuel tank is a rectangular structure, welded by six pieces of 2024 aluminum plate with a thickness of 6 mm, and filled with RP-3 aviation kerosene. Experimental results show that the kerosene is ignited by the RMP impact at a velocity above 1062 m/s, and a novel interior ignition phenomenon which is closely related to the rupture effect of the fuel tank is observed. However, the traditional steel projectile with the same mass and dimension requires a velocity up to 1649 m/s to ignite the kerosene. Based on the experimental results, the radial pressure field is considered to be the main reason for the shear failure of weld. For mechanism considerations, the chemical energy released by the RMP enhances the hydrodynamic ram (HRAM) effect and provides additional ignition sources inside the fuel tank, thereby enhancing both rupture and ignition effects. Moreover, to further understand the enhanced ignition effect of RMP, the reactive debris temperature inside the kerosene is analyzed theoretically. The initiated reactive debris with high temperature provides effective interior ignition sources to ignite the kerosene, resulting in the enhanced ignition of the kerosene.

Hand–foot–mouth disease (HFMD) was an acute intestinal infectious disease, which mainly occurred in the children, especially under 5 years old. Enterovirus 71 (EV71) was the most common pathogen causing HFMD, especially severe HFMD. Most patients had a good prognosis, but a few patients complicated by encephalitis, pulmonary edema, and hemorrhage, myocarditis and other complications, which may cause bad prognosis and even death. In this paper, the clinical manifestations, pathogenesis, pathology, imaging changes and treatment of pulmonary inflammation, edema and hemorrhage associated EV71- induced HFMD were reviewed.

Force chains based mesoscale simulation is conducted to investigate the response behavior of aluminum-polytetrafluoroethylene (Al-PTFE) granular composites under a low-velocity impact. A two-dimensional model followed the randomly normal distribution of real Al particles size is developed. The dynamic compressive process of Al-PTFE composites with varied Al mass fraction is simulated and validated against the experiments. The results indicate that, force chains behavior governed by the number and the size of agglomerated Al particles, significantly affects the impact response of the material. The failure mode of the material evolves from shear failure of matrix to debonding failure of particles with increasing density. A high crack area of the material is critical mechanism to arouse the initiation reaction. The damage maintained by force chains during large plastic strain builds up more local stresses concentration to enhance a possible reaction performance. In addition, simulation is performed with identical mass fraction but various Al size distribution to explore the effects of size centralization and dispersion on the mechanical properties of materials. It is found that smaller sized Al particle of composites are more preferred than its bulky material in ultimate strength. Increasing dispersed degree is facilitated to create stable force chains in samples with comparable particle number. The simulation studies provide further insights into the plastic deformation, failure mechanism, and possible energy release capacity for Al-PTFE composites, which is helpful for further design and application of reactive materials.

In this research, the effect of the sintering and cooling process on geometry distortion and mechanical properties of PTFE/Al reactive material is investigated. Six particularly selected sintering temperatures, three different cooling modes (annealing cooling, normalizing cooling and rapid cooling), three different initial cooling temperatures, as well as six different final cooling temperatures were designed to compare the effects of sintering temperature, cooling rate, initial cooling temperature and final cooling temperature on the properties of reactive materials. Geometry distortion was quantitatively analyzed by a statistic on the dimensional changes of the specimens and microscopic morphology. A mechanical response properties transition from brittle to ductile was found and analyzed. By combining the thermodynamic properties of PTFE and unsteady heat conduction theory, mechanisms of cooling induced morphology change, temperature induced distortion and strength decrease were obtained. The results showed that the cooling rate has the most significant effect on the morphology transformation, while initial cooling temperature has more significant effect on the dimensional distortion than final cooling temperature. As to the mechanical properties transition from brittle to plastic, a more prominent effect of initial cooling temperature than cooling rate and final temperature was revealed.

Grinding chatter is a self-induced vibration which is unfavorable to precision machining processes. This paper proposes a forecasting method for grinding state identification based on bivarition empirical mode decomposition (BEMD) and least squares support vector machine (LSSVM), which allows the monitoring of grinding chatter over time. BEMD is a promising technique in signal processing research which involves the decomposition of two-dimensional signals into a series of bivarition intrinsic mode functions (BIMFs). BEMD and the extraction criterion of its true BIMFs are investigated by processing a complex-value simulation chatter signal. Then the feature vectors which are employed as an amplification for the chatter premonition are discussed. Furthermore, the methodology is tested and validated by experimental data collected from a CNC guideway grinder KD4020X16 in Hangzhou Hangji Machine Tool Co., Ltd. The results illustrate that the BEMD is a superior method in terms of processing non-stationary and nonlinear signals. Meanwhile, the peak to peak, real-time standard deviation and instantaneous energy are proven to be effective feature vectors which reflect the different grinding states. Finally, a LSSVM model is established for grinding status classification based on feature vectors, giving a prediction accuracy rate of 96%.

Wave shaper effect on formation behavior and penetration performance of reactive liner shaped charge (RLSC) are investigated by experiments and simulations. The reactive materials liner with a density of 2.3 g/cm3is fabricated by cold pressing at a pressure of 300 MPa and sintering at a temperature of 380 °C. Experiments of the RLSC with and without wave shaper against steel plates are carried out at standoffs of 0.5, 1.0, and 1.5 CD (charge diameter), respectively. The experimental results show that the penetration depths and structural damage effects of steel plates decrease with increasing the standoff, while the penetration depths and the damage effects of RLSC without wave shaper are much greater than that with wave shaper at the same standoff. To understand the unusual experimental results, numerical simulations based on AUTODYN-2D code are conducted to discuss the wave shaper effect, including the propagation behavior of detonation wave, the velocity and temperature distribution of reactive jet, and penetration depth of reactive jet. The simulations indicate that, compared with RLSC without wave shaper, there is a higher temperature produced inside reactive jet with wave shaper. This unusual temperature rise effects are likely to be an important mechanism to cause the initiation delay time of reactive jet to decline, which results in significantly decreasing its penetration performance.

To analysis and summarize the imaging characteristics of the complications of hand-foot-mouth disease (HFMD) in Central Nervous System (CNS).

To study the correlation between the chest X-ray classifications and different pathogens in patients with hand–foot–mouth disease.

Mechanical model and simulation model of shaper quick-return mechanism are introduced based on ADAMS. The number of rigid bodies is reduced by using composite joints constraint . It doesn’t need any other softwares and data interfaces in the simulation.The results prove the correctness of the simplified model.It improves the design efficiency and speed of simulation and provides a theoretical basis for the design and analysis of other six-bar mechanism.

Saas is an abbreviation for Software-as-a-service, it is a completely innovative software application mode provided via Internet. As a new IT service model, SaaS has two sides. This article focuses on analysis the existent security risks of SaaS and put forward a series of countermeasures and suggestions to address these issues from the technical aspects.

Late Launch, which is a kind of dynamic measurement technology proposed by both Intel and AMD, offers isolated execution environment for codes needed to be protected. However, since the specifications and documents of Late Launch have hundreds of pages, they are too long and complicated to be fully covered and analyzed. A model based on Horn clauses is presented to solve the problem that there is a lack of realistic models and of automated tools for the verification of security protocols based on Late Launch. A running example is taken to show the execution details of Late Launch. Based on the example, secrecy properties of Late Launch are verified. Whats more, the automatic theorem proving tool ProVerif is used to make the verification more fast and accurate.

In this paper, the penetration mechanism of reactive jet with non-uniform density distribution is studied. The simulations show that the density deficit occurs in the whole reactive jet, and the density increases from the jet tip to tail. The density of jet tip is approximately 1.5 g/cm3, which is lower than that of the reactive liner materials. The X-ray experiments show similar results with the simulations. The density decreasing effect of jet tip has a significant influence on the penetration behavior when the reactive jet impacts steel plate. According to the simulation results, this paper assumes that the density gradient in the jet section has linear distribution. Then, the deflagration pressure generated by each jet element at the bottom of crater is introduced into the Bernoulli equation. Based on the virtual origin model and Szendrei-Held equation, the analytical models for penetration depth and radial cratering of reactive jet with the density reduction are obtained. Moreover, to further prove the validity of analytical models, the penetration experiments of the reactive liner shaped charge against steel plate under different standoffs are carried out. There is a convergence between the analytical crater profiles and experimental results when reactive jets penetrate steel plates under different standoffs, especially at standoff of 1.5 and 2.0 charge diameters.

The dynamic formation, shock-induced inhomogeneous temperature rise and corresponding chemical reaction behaviors of PTFE/Al reactive liner shaped charge jet (RLSCJ) are investigated by the combination of mesoscale simulation, reaction kinetics and chemical energy release test. A two-dimensional granular model is developed with the randomly normal distribution of aluminum particle sizes and the particle delivery program. Then, the granular model is employed to study the shock-induced thermal behavior during the formation and extension processes of RLSCJ, as well as the temperature history curves of aluminum particles. The simulation results visualize the motion and temperature responses of the RLSCJ at the grain level, and further indicate that the aluminum particles are more likely to gather in the last two-thirds of the jet along its axis. Further analysis shows that the shock, collision, friction and deformation behaviors are all responsible for the steep temperature rise of the reactive jet. In addition, a shock-induced chemical reaction extent model of RLSCJ is built based on the combination of the Arrhenius model and the Avrami-Erofeev kinetic model, by which the chemical reaction growth behavior during the formation and extension stages is described quantitatively. The model indicates the reaction extent highly corresponds to the aluminum particle temperature history at the formation and extension stages. At last, a manometry chamber and the corresponding energy release model are used together to study the macroscopic chemical energy release characteristics of RLSCJ, by which the reaction extent model is verified.

Cloud computing is an important innovation of current computing models. At present, the research on the security of cloud computing is mainly concentrated on PCs and servers. The security of embedded system in cloud environment does not win enough attention. This paper analysis the security threats of it, and proposes a Secure Hardware Model to provide a tamper-resistant and more reliable hardware embedded platform in cloud environment. Our model adds some new components to traditional embedded system, controls the start sequence of platform’s components, verifies the integrity of crucial information for embedded platform and recovers the system if necessary. Our implementation demonstrates the feasibility of Secure Hardware Model, it enhance the secure and reliable boot of embedded system. With the constant development and application of embedded system in cloud computing field, our research will influence cloud computing greatly.

Polyvinylidene fluoride/polyurethane (PVDF/PU) blend membranes were made via immersion precipitation process, the surface morphologies and the micro-porous structures of the blend membranes were analyzed using scanning electronic microscope (SEM) and fractal theory, the water flux change with the operation pressure of the blend membranes was investigated, and the relationship between blend membrane morphology and water flux was discussed. The results showed that, the water flux of the resulting blend membranes was increased, and the contribution of different structures to water flux was in the following order: cross-section finger-shaped porous defects > cross-section through holes > blend membrane surface pores. In addition, water flux of the blend membranes was also related to the deformability of PU.

In this article, the morphologies of membranes formed by three different systems, i.e. favorable diluent/unfavorable diluent/PVDF system, water-soluble solvent/ unfavorable diluent/PVDF system, and favorable diluent/unfavorable diluent/water-soluble polymer/PVDF system, were characterized, and the relationship between porous membrane morphology and the components of favorable diluent/unfavorable diluent and water-soluble solvent/unfavorable diluent in the system was investigated. The transformation from mesopores to bicontinuous porous structures, from finger-shaped pores to bicontinuous porous structures was realized, and meanwhile PVDF microporous membranes with microfiber-shaped porous structures were manufactured.

In this article, the thermal stability of PU/PVDF blend was investigated by thermogravimetry (TG), and their rheological property was studied through testing and analyzing the rheological curves. The results showed that, with the increase in PVDF content, the thermal decomposition temperature of PU/PVDF blend increased, and by fitting relevant data to thermal decomposition dynamic equations, it was found that thermal decomposition activation energy of the blend increased gradually, i.e. the thermal stability of the blend increased gradually. Meantime, based on the curves of shear stress vs. shear rate of the blend at 180°C and 200°C, it was shown that for PU/PVDF blend, with the decrease of temperature and the increase in PVDF content, the non-Newtonian index decreased, while the viscosity of the blend increased.

To understand more about Lamb waves on composite laminates damage detection features, the Lamb wave group velocity dispersion curves are calculated and plotted by using dichotomy method in MATLAB. The signal parameters are chosen according to Group velocity dispersion curves. The dynamic response signals of the composite plate are obtained by finite element method. Damage location is calculated by the actual group velocity of Lamb wave and time of flight of the difference signal before and after damage.

Sensor data are the basis for health assessment of complex structural systems. Careful selection and logical layout of sensors is critical to enable the high reliability of system health assessment. This paper presents a methodology how to use a minimum number of sensors, and what locations of them should be placed, so that the voltage signals received from the sensor can be used to detect both presence and extent of damage. In this study, an optimization procedure is developed using Genetic Algorithm (GA) to determine the location of piezoelectric sensor for damage detection in a composite wingbox. A new damage index using all differences in voltage signals decomposed by wavelet transform is proposed. Results show that the proposed method is available at determining number and location of sensors for structural damage detection using piezoelectric patch sensors.

The paper presents an effective damage detection method of complex composite structures. It can be carried out through the experimental modal analysis of the damaged structure. The method using the improved Cross Modal Strain Energy (CMSE) technique and Niche GA has many advantages compared with other damage detection methods. The CMSE method can use any modes of the structure and the modes don’t need to be normalized or consistent in scale. The Niche GA improves the efficiency of the calculation and enhances the capacity of identifying structural damage localization. The model is the composite material airfoil case. The numerical results show that the method proposed in this paper is successful for damage detection of complex structures.

A vibration-based approach to detect crack damage in a cantilever composite wingbox is studied using the improved Hilbert-Huang Transform (HHT). The improved HHT is composed of HHT with Wavelet Packet Transform (WPT) and a simple but effective method for intrinsic mode function (IMF) selection. For different damage status, in order to obtain structural dynamic responses, which imply plentiful damage information, the composite wing boxes were excited by a contrived square wave signal. Then, the dynamic responses of intact wingbox and damaged wingbox are disposed using improved HHT. Finally, a feature index vector of structural damage, i.e. the [removed info]ariation quantity of instantaneous energy, is constructed. The obtained results show that the proposed damage feature index vector is more sensitive to small damage than those in traditional signal processing.

Dynamic characteristics have been studied for main components of machine tools by finite element method. The multi-element static and dynamic structural analysis program makes possible the analysis of main components in various computing models.

The bending problems of nonuniform beams with variable cross-section can be approximated by that of a step beam under sectionally uniform load (including both concentrated forces and couples). In this paper, the concept of Heaviside function {x−a}0 will be generalized, and a new function {x−a}n,n=0, 1, 2..., will be defined, which may be named as a generalized step function. The rules of operation will also be given to {x−a}n{x−b}0. The reciprocal of the flexural of rigidity 1/EJ and the bending momentM(x) can all be expressed in terms of {x−a}n, and substituted into the differential equation of the elastic curve of the beam respectively. Thus we may establish a set of unified method to solve various types of bending problems of straight beams. The general solution of the deflection equation will be given.

In this paper, the reaction characteristic and its application in shaped charge warhead of a novel reactive material, which introduced copper (Cu) and plumbum (Pb) into traditional polytetrafluoroethylene/aluminum (PTFE/Al), are studied. The thermal analysis and chemical reaction behavior of the PTFE/Al/Cu/Pb mixture are investigated by Differential Scanning Calorimetry (DSC),Thermo-gravimetry (TG), and X-ray Diffraction (XRD) techniques. Then, the shaped charge liners with PTFE/Al/Cu/Pb reactive materials are fabricated, and the X-ray experiments show that they could form reactive jets with excellent performance under the detonation effects of the shaped charge. Based on that, the penetration experiments of shaped charge with PTFE/Al/Cu/Pb reactive liner against steel plates are carried out, and the results demonstrate that the PTFE/Al/Cu/Pb reactive jets could produce a deeper penetration depth compared to the traditional PTFE/Al reactive jets. Meanwhile, the PTFE/Al/Cu/Pb reactive jets also show significant inner-blast effects, leading to dramatically cracking or fragmentation behavior of the penetrated steel plates. This new PTFE/Al/Cu/Pb reactive liner shaped charge presents enhanced penetration behavior for steel targets that incorporates the penetration capability of a high-density and ductility jet, and the chemical energy release of PTFE-matrix reactive materials.

Firstly, the research progress of grey model GM (1,1) is summarized, which is divided into three development stages: assimilation, alienation and melting stages. Then, the matrix analysis theory is used to study the modeling mechanism of GM (1,1), which decomposes the modeling data matrix into raw data transformation matrix, accumulated generating operation matrix and background value selection matrix. The changes of these three matrices are the essential reasons affecting the modeling and the accuracy of GM (1,1). Finally, the paper proposes a generalization grey model GGM (1,1), which is a extended form of GM (1,1) and also a unified form of model GM (1,1), model GM (1,1,α), stage grey model, hopping grey model, generalized accumulated model, strengthening operator model, weakening operator model and unequal interval model. And the theory and practical significance of the extended model is analyzed. [ABSTRACT FROM AUTHOR]