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In the field of ammunition, piezoelectric ceramics are increasingly used as part of impact fuze systems. It is an urgent problem to improve the low-temperature storage and low-temperature environment adaptability of piezoelectric ceramic power supply. In order to study the dynamic mechanical and electrical response characteristics of PZT-5H at − 40 to 25 °C, the static electrical parameters of PZT-5H at different temperatures were measured, and the Hopkinson bar experiments at different temperatures and impact velocities were carried out by using the self-established low-temperature mechanical and electrical test system. The variation of resistivity and relative permittivity of PZT-5H from − 40 to 25 °C is obtained by experiment, and the relaxation time of PZT-5H is obtained according to Debye’s theory. Combined with the observation of scanning electron microscope (SEM), the influence mechanism of porosity and crack on the electrical output characteristics of piezoelectric ceramics was obtained. The mechanism of the freezing effect of piezoelectric ceramics at low temperatures is obtained through space charge theory analysis. The variation of the dynamic piezoelectric voltage constant with temperature and time in the elastic region measured by the experiment is clarified.

To evaluate the reactive energy release of the Al/Polytetrafluoroethylene (PTFE) mixed powder (Al and PTFE with a mass percentage of 26.5%/73.5%). Based on the traditional formula, three kinds of Al/PTFE test samples with different dosages (4, 6.5, and 9 g) were mixed. By using the self-designed airtight container, and combining with the overpressure sensor, the transient optical fiber pyrometer, and the infrared thermography. The overpressure , the visible light radiation temperature in the closed container, and the infrared light radiant temperature of the container’s outer wall have been obtained by real-time measurements during the process of cooking off, and the reaction products are analyzed by X-ray energy spectrum (EDS) and X- ray diffraction (XRD). The experimental results show that most of the solid products of Al/PTFE powder in the closed container are AlF3 and a small number of intermediate carbon compositions. The released energy during the firing process of the active material Al/PTFE increases with the increase of the mixing amount; The bake-off energy of active material Al/PTFE mixture per unit mass in a closed container is about 10.2 kJ/g, and when the oxygen content in the closed container is sufficient, active material Al/PTFE per unit mass releases more energy.

In order to study the electromechanical characteristics of PZT-5H in the temperature range of -40~25℃under the impact loading, the electrostatic parameters of PZT-5H at different temperatures are measured, the liquid nitrogen cooling/Hopkinson mechanical property and piezoelectric ceramic voltage output testing system are built, Hopkinson experiments at different temperatures (-40℃, -25℃, -10℃, 0℃ and 25℃) and different impact velocities are carried out. Experimental results show that , the resistivity and relative permittivity decrease with the temperature of PZT-5H decreasing from 25℃ to -40℃, and the relative permittivity decrease about 27.92%, and the relaxation time is also deduced. By scanning electron microscope (SEM) and Energy Dispersive Spectrometer (EDS) observation, it is found that the blowhole defects and cracks of the piezoelectric ceramics have obvious effects on the electrical output characteristics of piezoelectric ceramics when the piezoelectric ceramics are struck. Based on the analysis of space charge theory, the freezing effect of piezoelectric ceramics caused by the obstruction of domain motion at low temperature is obtained. And the dynamic piezoelectric constant in the elastic region measured is about 1.66 times that of the static piezoelectric constant, which indicates that the relative dielectric constant of the piezoelectric ceramic has changed significantly under dynamic loading.

In order to study the charge characteristics of monocrystalline silicon irradiated by femtosecond pulsed laser, measurement systems of charge and infrared temperature induced by femtosecond pulse laser irradiation monocrystalline silicon are established by using oscilloscope and infrared thermal imager. The monocrystalline silicon (circle disc) irradiated by femtosecond pulse laser are carried out along the thickness direction of monocrystalline silicon. The experimental results show that the thermo-mechanical coupling effect of femtosecond pulsed laser irradiated on monocrystalline silicon will produce polarization in the target. At the initial stage of laser irradiation, the laser damage threshold of the interface between crystal surface and air is low and the charge mainly transfers along the surface of monocrystalline silicon, resulting in a high polarization. With the continuation of laser irradiation, it proves that the charge transfers in monocrystalline silicon gradually, and the polarization degree decreases with the modification of the material internal structure. After laser irradiation for a certain time, the charge transfers tend to be stable. Because the target lies in front of the laser focus, its energy density is insufficient to destroy the macrostructure of the target due to laser-pressure and temperature gradient, the polarization effect tends to be stable, resulting in a stable periodic change of charge transfer and recovery.

Ferroelectric ceramics are of interest for engineering applications because of their electromechanical coupling and the unique ability to permanently alter their atomic-level dipole structure (i.e., their polarization) and to induce large-strain actuation through applied electric fields. Although the electrical output properties of the material at different strain rates have been studied by quasi-static and dynamic loading, most prior work has ignored the important influence of temperature on the ferroelectric behavior. Here, the experiments of impacting on PZT have been performed at the same loading conditions, different environmental temperatures (−40 °C, −25 °C, 0 °C and 25 °C) and circuit connection modes. The domain switching analyses have been conducted at the different temperatures. The results show that the electromechanical coupling coefficient increases linearly, and the energy barrier across the domain switching and coercive electric field increase with the decrease of temperature, but the piezoelectric coupling behavior was weaken and the residual polarization strength was reduced. Under electrical short-circuit, the energy density of the discharge accounts for about 1‰ of the irrecoverable energy density.

Smartphone-based travel surveys have attracted much attention recently, for their potential to improve data quality and response rate. One of the first such survey systems, Future Mobility Sensing (FMS), leverages sensors on smartphones, and machine learning techniques to collect detailed personal travel data. The main purpose of this research is to compare data collected by FMS and traditional methods, and study the implications of using FMS data for travel behavior modeling. Since its initial field test in Singapore, FMS has been used in several large-scale household travel surveys, including one in Tel Aviv, Israel. We present comparative analyses that make use of the rich datasets from Singapore and Tel Aviv, focusing on three main aspects: (1) richness in activity behaviors observed, (2) completeness of travel and activity data, and (3) data accuracy. Results show that FMS has clear advantages over traditional travel surveys: it has higher resolution and better accuracy of times, locations, and paths; FMS represents out-of-work and leisure activities well; and reveals large variability in day-to-day activity pattern, which is inadequately captured in a one-day snapshot in typical traditional surveys. FMS also captures travel and activities that tend to be under-reported in traditional surveys such as multiple stops in a tour and work-based sub-tours. These richer and more complete and accurate data can improve future activity-based modeling.

CFRP/Al HC SPs (Carbon Fiber Reinforced Plastic/Aluminum Honeycomb Sandwich Panels)composite structures are widely used in the aerospace and many other fields due to their excellent performances. In order to reveal profoundly the dynamic response characteristics of CFRP/Al HC SPs composite structure under high-velocity impact loading, the experiments about aluminum honeycomb core and CFRP/Al HC SPs composite structure impacted by high-velocity projectiles have been performed by using a one-stage light gas gun loading and a high-speed camera systems, respectively. The whole physical process of collision is analyzed by using TEMA software which is provided by high-speed camera's manufacturer, and the pictures and related physical parameters of the projectile passing through the different layers at the key moments are extracted based on the set frame rate of the video. Meanwhile, the ABAQUS/Explicit module was used to conduct numerical simulation under the same conditions as the experiments, and extracting the pictures and related physical parameters during the projectile penetrating through aluminum honeycomb core and the sandwich panels at the different key moments. The results show that the durations of action for the projectile impacting the Al HC core and the CFRP/Al HC SPs at the velocity about 280 m/s were 86 μs and 240 μs in experiments, respectively, and the durations of action were 90.7 μs and 236.2 μs at the same experimental conditions in numerical simulation, which were basically consistent comparing the experimental to simulated results. Moreover, more than 70% for the kinetic energy of the projectile consumed by the sandwich panels was attributed to the front panel and the aluminum honeycomb core during the entire impact process, and all these have verified the reliability of the numerical simulation. Keywords: CFRP/Al HC SPs, ABAQUS/Explicit, Duration of action between projectile and target, Energy absorption

The infrared thermal imaging system was used in order to investigate the temperature field distributions for optical glass lenses irradiated by femtosecond pulsed laser. The experimental research of the temperature field distributions on the surface of the H-K9L optical glass lenses with anti-reflection film and film free have been accomplished by this system combining with the irradiation at different frequencies and actuation duration by the femtosecond pulsed laser. The angle between the normal direction of the mirror surface and the laser output was 45 degrees. Experimental results showed that the coating of the lens on surface increases the distortion of the heat-affected zone and the temperature field, the penetration time increases as well as the temperature gradient decreases at the same time, which was caused by the reflection reducing coating on the surface of the lenses and this kind of coating has a certain protective effect to the optical lenses. The output frequencies of the laser presented a positive correlation linearly to the maximum surface temperatures of the lens in a certain range when the output energy of single laser pulse was constant. The spectral of temperature field was dominated by low frequency signals, the higher the laser output frequency was, the larger the amplitude of the spectrum signals was. The evolutionary processes of temperature for feature points at the edge of heat-affected zone were basically the same, therefore the laser irradiation in a small angle less than 45 degrees had little influence on the distributions and the evolutionary processes of the surface temperature fields in the heat-affected zone for thin targets.

In order to reveal influence of external capacitance on the voltage input and input energy provided by the PZT-5H piezoelectric ceramic composite structure under high-speed impact loading, experiments have been performed by using one-stage light gas gun loading system combining with a power supplier circuit and power output testing system, which the aspect ratio of 1:1 column projectile impact monolithic and multi-piece piezoelectric ceramic composite structure at the near impact velocity and different storage capacity. The experimental results show that the more larger storage capacitance is, the smaller the piezoelectric ceramic output voltage is. However, the smaller of the capacitor voltage is, the smaller the value of energy storage is; with the energy storage capacitance increasing, the piezoelectric capacitance ratio and the energy conversion rate of piezoelectric ceramics decreases; In addition, the storage energy capacitor increases with the increasing of the piezoelectric ceramic layers; the relationships of storage energy capacitor and piezoelectric ceramic capacitor has a great influence on the input voltage and storage energy for storage energy capacitor.

Neutron induced fission cross sections of

Solar array is one of the core components of spacecraft exposed to space environment; it is vulnerable to the impact from space debris. Discharge of solar array induced by ultrahigh-speed collision will produce a serious threat to the power supply system of spacecraft in orbit. In order to mitigate discharge effect and simulate working state of solar array effectively during debris impacting on solar array, realizing charging through sunlight irradiance on the ground simulating experiments is very difficult. Therefore, the inverse process of solar energy generation is adopted by applied power supply to solar array. In addition, loading and measurement systems of discharge have been established in a laboratory. A two-stage light gas gun was used to launch the projectile to impact on solar array at the applied power supply voltage of 100 V, and the spacings among the cells of solar array were 0.6, 3, and 5 mm, respectively. The applied power supply system, the diagnostic system of plasma characteristic parameters, and the measuring system of discharge current and voltage were constructed to provide voltage for solar array, diagnosing characteristic parameters of plasma and measuring discharge parameters, respectively. Six sets of experiments have been performed to measure discharge current and voltage induced by plasma during 2A12 aluminum projectile impacting on the solar array with carbon fiber reinforced plastics Al honeycomb sandwich and 2A12 aluminum substrates, respectively. The experimental results showed that the discharge did happen during 2A12 aluminum projectile impacting on solar array, and the discharge current among the cells increased with the increase of the impact velocity under the given experimental conditions. Also, increasing spacings among the cells of solar array could indeed mitigate or inhibit plasma discharge effects created by hypervelocity impact on solar array at the same projectile incident angles and applied power supply.

To introduce the application background the self-powered technology for Fuze bridge fire, high overload microthermal battery activation, rocket ignition, and the aircraft escape actual condition lifesaving system ignition power supply, which intends to use the high-speed impact of piezoelectric ceramic in the process of missile launching high overload pressure or missile and target intersection in the process of high overload stress wave of piezoelectric ceramics and the transformation of power, for closer to confession technology for Fuze bridge ignition, high overload microthermal battery activation, rocket ignition, and aircraft escape system engineering problems. The stress wave propagation in the PZT-5H piezoelectric ceramic composite target and load resistance effect to the electrical output characteristics is investigated under the strong shock loading; the experiments have been performed about cylindrical steel projectiles normal impact on PZT-5H piezoelectric ceramic composite target by using polyvinylidene fluoride stress test system and electrical output test system combining with one-stage light gas gun loading system. The experimental results show that the stress duration and peak stress are about $9~\mu \text{s}$ and 232 MPa, respectively, when the cylindrical projectile impacts on piezoelectric ceramic composite target at the impact velocity of 345 m/s. The outputs of current pulse peak, voltage pulse peak, and energy peak are 20 A, 734 V, and 11 mJ under the stress interactions of 200–300 MPa. At the near-impact stress conditions, the electrical output characteristics of piezoelectric ceramics are greatly affected by the load resistance. The output voltage pulse increases with the increasing of load resistance value, and the values of the load resistance have a significant effect on output energy; output energy conversion rate is up to 82% when the load resistance is $50~\Omega $ .

In order to study the temperature distribution and thermal stress of femtosecond pulsed laser interacting with energetic materials, in this paper, a femtosecond pulse laser loading system combined with an infrared thermal imager was used to experimentally study the temperature of the material when the femtosecond pulse laser irradiated Al/PTFE reactive material. Scanning electron microscope (SEM) was used to analyze the ablation morphology of laser ablated Al/PTFE. The theoretical model of the interaction between laser and Al/PTFE reactive material was established and the numerical calculation was carried out. The thermal stress was calculated and analyzed by using the material temperature measured by the experiment according to the thermoelastic theory. The following conclusions are obtained. The material is melted and vaporized under laser irradiation and ablation marks appear. The material temperature and ablation depth in the experiment and numerical simulation have a certain consistency. The heat released by the exothermic reaction in the laser irradiation area of the material has little effect on the surrounding materials. The radial thermal stress generated during laser irradiation is compressive stress, and the circular stress along the radius of the light spot changes from compressive stress to tensile stress. The greater the laser repetition frequency and the longer the laser action time are, the greater the thermal stress is. The maximum radial compression stresses are 2.54 MPa and 4.52 MPa when the laser repetition frequencies are 500 Hz and 1000 Hz, respectively.

In order to clarify the electromechanical coupling characteristics of polymer materials and extend their applications in MEMS (Micro-electromechanical Systems), electromechanical responses of PDMS (Polydimethylsiloxane) with different electrodes and thicknesses under different loading conditions have been performed experimentally and numerically. Basic electrical parameters measurement and quasi-static tensile experiment of PDMS specimens were conducted. Furthermore, the dynamic mechanical properties and polarization voltage of PDMS with different electrodes and thicknesses under different loading conditions have been studied by Split Hopkinson Pressure Bar (SHPB) system integrating with electrical output measuring system. Beyond that, Abaqus/Explicit numerical simulation of PDMS specimen under different loading conditions was carried out based on Yeoh viscoelastic model and Prony series, then the strain gradient and the flexoelectric coefficients were obtained. The results show that the maximum stress of PDMS increases with increasing of loading speed and decreases with increasing of thickness, the maximum polarization voltage increases with increasing of strain rate, the maximum polarization voltages of PDMS with “C” electrode and “+” electrode are about 14 times of that with circular electrode, the flexoelectric coefficients of PDMS are within the range of 10−11–10−9C/m.

Although the force-electricity relationship of piezoelectric ceramics under pulse stress is found to be nonlinear, there is still lacking a reliable model describing this relationship. To bridge this research gap, the mechanical and electrical responses of PZT-5H (Pb1·0[Zr0·49Ti0·46(Nb0·25Sb0.75)0.05]1.0O3) under different strain rates were investigated through uniaxial compression tests and split-Hopkinson pressure bar (SHPB) experiments with an additional electrical output measurement system. With reference to the nonlinear viscoelastic constitutive equation and the piezoelectric equation, a PZT-5H mechano-electric model considering the strain rate effects was built based on the experimental data. The incremental form of the mechano-electric model was established based on the Piola-Kirchhoff stress tensor and Green strain tensor theory. The model was numerically simulated with a user-defined material subroutine in the explicit finite element software ABAQUS. The accuracy of the material subroutine was verified with finite element models of the uniaxial quasi-static compression and the high strain rate SHPB tests. The finite element simulation results were verified with the experimental results, and the two agreed well. The material subroutine was then adopted to predict the mechanical and electrical response of the piezoelectric ceramics inside the overload igniter during projectile launch and impact. The analysis results show that the overload igniter can be stably activated within 200 μs under the launch overload and successfully ignited within 5 μs at speed as low as 50 m/s under the impact overload.

Based on the objective reality of gradient potential existence in spacecraft surface caused by charging particles in space-plasma environment or solar wind activities, electrostatic discharge of spacecraft with surface charging or deep dielectric charging would be induced by debris or meteoroids impact. To simulate the gradient potential on the spacecraft surface in the laboratory, spacecraft surface was segmented into different parts, which different spacing reserved in two adjacent surfaces was added resistance to create different potential surfaces, and the highest potential surface as a target in the segmented surface. Circuit system realizing different gradient potential, discharge test system, as well as ultrahigh-speed camera acquired system was built by ourselves; combining with two-stage light gas gun loading system, four set experiments have been performed about hypervelocity impact on 2A12 aluminum target with gradient potential. In the experiments, spacings of 2A12 aluminum target were the same among different potential parts in every experiment, and the spacings of four set experiments were 2, 5, 10, and 15 mm, and high-potential 2A12 aluminum as the target, respectively. The experiments were performed at the impact velocity of about 3 km/s and the incidence angles of 60° (between projectile flying trajectory and target plane). Voltage probes and current probes were used to acquire discharge voltages and currents during the process of the impact. The experimental results showed that the discharge induced by impact plasma was generated between high- and low-potential targets by forming a plasma discharge channel, the gaps with 2–15 mm can evoke discharge among different targets, and the variations of the discharge current along the high- and low-potential targets did not obviously. However, the discharge duration decreased with an increasing of distance between high- and low-potential targets at the near collision velocities and the same incidence angle of the projectile. The whole physical process of discharge had experienced four stages in general, which created by hypervelocity impact 2A12 aluminum targets with gradient potential. The first stage was plasma generated by hypervelocity impact, the second stage was complex mixed plasma including plasma generated by hypervelocity impact and discharge plasma induced by split targets with gradient potential, the third stage was discharge plasma induced by hypervelocity impact, and the fourth stage was the discharge between charging particles due to the reciprocating motion of charging particles in the electromagnetic field.

One-dimensional (1-D) α-MoO3/Fe2(MoO4)3 heterostructure nanomaterials has been synthesized by a low-cost and environmentally friendly hydrothermal strategy. The structure and morphology of composites were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). The results revealed that Fe2(MoO4)3 nanoparticles were uniformly coated on the surface of α-MoO3 nanobelts. The α-MoO3/Fe2(MoO4)3 nanocomposite showed enhanced sensing response and selectivity to toluene vapor compared to bare α-MoO3 nanobelts at the optimal operating temperature of 250 °C. The improved performance can be attributed to the unique 1-D belt-like morphology of α-MoO3 support, the improved catalytic properties of Fe2(MoO4)3, and the formation of the heterojunction barrier at the interface of the two phases, which illuminates that α-MoO3/Fe2(MoO4)3 composite is a potential candidate for toluene gas sensors.

For coastal urban areas, an increase in flooding is one of the clearest climate change threats. The research presented in this paper demonstrates how a land use–transport model can be used to forecast the short- and longer-term impacts of a potential 4-ft sea level rise in greater Boston, Massachusetts, by 2030. The short-term scenario represents the immediate transport system response to inundation, which provides a measure of resiliency in the case of an extreme event, such as a storm surge. In the short run, the results reveal that transit captive users will suffer more. Transit, in general, displays less resiliency, at least in part because of the center city’s vulnerability and Boston’s radial transit system. Trip distances would modestly decrease, and average travel speeds would go down by more than 50%. Rail transit ridership would be decimated, and overall transit usage would go down by 66%. The longer-term scenario predicts how households and firms would prefer to relocate in the so-called new equilibrium when more than 10 mi2 of land disappears and the transport network inundations become permanent. Assuming no supply constraints, new residential growth centers would emerge on the peripheries of the inundated zones, primarily in the inner-core suburbs. Some regional urban centers and traditional industrial towns would boom. Firms would be hit harder, because of their heavy concentration in the inner core; firm relocation would largely follow households. Transit usage would again be decimated, but walking trips would increase. Results, however, should be viewed as cautious speculation.

Urban mobility significantly contributes to global carbon dioxide emissions. Given the rapid expansion and growth in urban areas, cities thus require innovative policies to ensure efficient and sustainable mobility. Urban typologies can serve as a vehicle for understanding dynamics of cities, which exhibit high variability in form, economic output, mobility behavior, among others. Yet, typologies relevant for sustainable urban mobility analyses are few, outdated and not large enough in scope. In this paper, we present a new typologization spanning 331 cities in 124 countries. Our sample represents 40% of the global urban population and contains the most recent data from 2008 to date. Using a factor analytic and agglomerative clustering approach, we identify 9 urban factors and 12 typologies. We discuss the implications of this new framework for researchers and planners and investigate the relationships between mobility and environmental sustainability indicators. Notably, we show an immediate application of the urban typologies to better understanding travel behavior and also describe their usage for detailed large-scale simulation in representative prototype cities for insights into sustainable future mobility policy pathways. Our data and results are publicly available for further exploration and will serve as a foundation for future analyses toward desirable urban and environmental outcomes.

In order to reveal the physical effect of Al/PTFE (mass percentage of 50%/50%) heat conduction and deflagration reaction induced by temperature gradient under the condition of flame heating, the loading and testing systems of cookoff experiment were conducted to measure the thermal response and electrical output characteristics of Al/PTFE before and after deflagration induced by temperature gradient. The thermal shock wave and thermoelectromotive force before deflagration, voltage signal induced by flame plasma expansion after deflagration were measured simultaneously. Meanwhile, the flash signal and the evolutionary process of flame region and temperature after deflagration were obtained. The results show that the thermal shock wave was generated by emergent temperature change in the stage of heat conduction, and the thermoelectromotive force was generated by the superposition of temperature gradients in different regions. The thermoelectromotive force can be equivalent to the series connection of electric source in each striped region. Under the temperature gradient of 6-10 K/mm, the maximum thermoelectromotive force can reach 0.8 V. Before deflagration, the local phase transition of molten or gaseous state induced by thermal decomposition destroyed the stable distribution of the temperature gradient of the sample, which leads to the decrease of the thermoelectric force. Based on the electric output signal of flame plasma, the reaction was divided into two stages including deflagration stage (lasting for 2–3 s) and stable combustion stage (lasting for about 10s). The average temperature of flame first increased and then decreased abruptly. The maximum temperature was 1585 K, and the propagation rate of flame was about 81.6 m/s in the initial stage of deflagration; however, the average temperature of the flame decreased slowly in the stable combustion stage, there was no obvious electrical output and the flash intensity decreased.

In order to reveal the temperature evolutionary characteristics of typical ferroelectric RAM (Random Access Memory) irradiated by femtosecond pulsed laser, a physical model of a typical ferroelectric RAM is established. The idea of using a continuous laser instead of a high-energy pulsed laser of the same energy on the laser transmission path was theoretically derived. The physical expression and thermal conduction model of the laser at different positions on the transmission path were simulated by Comsol Multiphysics simulation software. The melting and heat conduction process of the pulsed laser irradiating ferroelectric RAM are simulated, and the laser with different irradiation time is obtained. The temperature field distribution, melting and thermal conduction simulation parameters of the multi-layer target of the ferroelectric RAM are simulated by the femtosecond pulsed laser under the simulation conditions. The results show that the COMSOL Multiphysics simulation can accurately simulate the temperature field evolution of femtosecond pulsed laser irradiating ferroelectric RAM in the simulation experiment of single event effects. Heat radiation of the periphery of the ferroelectric RAM and the bottom of the heat transfer dominates. Thermal radiation transfers less energy to the pins and the periphery. After 5 s under the laser interaction, the temperature distribution of the ferroelectric RAM is stable. The heat conductivity, melting and convection characteristics of the ferroelectric RAM are basically consistent with the experimental results.

In view of the key problems of the discharge phenomenon caused by the impact of small space debris on the satellite's charged surface and the electromagnetic field induced entering the interior of the satellite after coupling through the aperture. In this paper, the characteristics of the coupling plasma, the plasma induced discharge and the propagation of the electromagnetic field induced by discharge through the aperture are studied by using the two-stage light gas gun loading system, the discharge charge monitoring system, the plasma diagnosis system and the electromagnetic testing system; Combined with the characteristic parameters of plasma inside and outside the Simulated satellite, the curves of discharge current and voltage, and the spectrum characteristics of electromagnetic radiation inside and outside the simulated satellite, the characteristics of electromagnetic field propagating into the Simulated satellite through the aperture under different potential on the surface of the simulated satellite are analyzed. The experimental results show that the characteristic parameters of the ionized plasma produced by the ionization of the target and the projectile splash increase with the increase of the surface potential of the target, and the ionized plasma determines the discharge characteristics and electromagnetic field characteristics; After the electromagnetic field generated by the impact side propagates through the aperture into the inner of the simulated satellite, the electromagnetic field in the simulated satellite appears signal attenuation in most frequency bands, but signal enhancement occurs in a few frequency bands; The main reason of electromagnetic signal attenuation is that the electromagnetic field directions at the edge of the aperture and the back of the target are opposite to that at the impact side; The enhancement of electromagnetic signals in some frequency bands is caused by the plasma entering the simulated satellite.

In order to reveal the influence of sintered and unsintered aluminum/polytetrafluoroethylene (Al/PTFE) reactive material on heat conduction, ignition and deflagration characteristics under the condition of thermal loading, the sintered and unsintered samples prepared by molding process are heated by acetylene flame as heat source. The heat conduction and deflagration behaviors of samples are measured synchronously by infrared thermal imager and high-speed camera before and after ignition. Meanwhile, combining with the three-dimensional differential equation of heat conduction in cylindrical coordinate system, the temperature gradient, heat flux and ignition moments during the process of heat conduction are solved by numerical simulation. The results show that the two kinds of samples both undergo the evolutions of temperature gradient and thermal shock wave induced by temperature gradient. The instantaneous energy accumulation caused by thermal shock wave promotes the samples to deflagrate, and the heat conduction durations before ignition, ignition temperature of sintered sample are both smaller than that of unsintered sample. The micro-morphologies before ignition indicate that the unsintered sample needs to accumulate more energy to achieve deflagration. The deflagration reaction extent of unsintered sample is more intense than that of sintered sample, however, the deflagration durations of sintered sample lasts longer. The maximum flame area of unsintered sample is 30.6% larger than that of the sintered sample, and the maximum temperatures of the flame core of sintered and unsintered sample are 1284 K and 1425 K, respectively.

In order to study the cook-off characteristics of traditionally formulated Al/PTFE (Al/PTFE mass percentage was 26.5%/73.5%) reactive materials in air environment and the effect of aluminum honeycomb skeleton (4% of the total mass of the sample, which means that mass percentage of Al/PTFE was 22.5%/73.5%) on the release energy of traditional Al/PTFE reactive materials, Al/PTFE samples with and without aluminum honeycomb skeleton were prepared on the basis of traditional preparation process. The infrared (wavelength range 1.7–5.1 μm) and visible light (wavelength range 400–700 nm) radiation temperature and the evolutionary process of ignition and deflagration of the two reactive materials during the cook-off process were measured in real time by using the self-built cook-off equipment by combining with infrared thermal imager, transient fiber pyrometer and high speed camera. The experiment results show that the ignition temperature threshold of the reactive materials with aluminum honeycomb skeleton is 27 K lower than that of the traditionally formulated reactive materials. Meanwhile reaction release energy and the radiation temperature of the sample with the aluminum honeycomb skeleton are higher, but the deflagration duration is shorter. The reaction of the materials with aluminum honeycomb skeleton is more severe than that of the traditionally formulated reactive materials, which further demonstrates that the reaction release energy of the Al/PTFE reactive materials containing the aluminum honeycomb skeleton is significantly enhanced.

The theories of impact dynamics and adiabatic temperature change were adopted to investigate the ionization degree of the plasma generated by the 2A12 aluminum target during 2A12 aluminum projectile hypervelocity impact, and the radiant temperature was also estimated during hypervelocity impact. A two-stage light gas gun combined with the plasma characteristic parameters measured by a triple Langmuir probe was applied, and then the fitting relationship between the plasma ionization degree and the theoretical impact temperature as well as the fitting relationship between the maximum electron density and impact velocity were obtained with the aid of the theoretical derivation of the plasma ionization degree and the electron temperature and electron density extracted from experiments.

To researching the damage characteristics of typical logical chip modules in spacecraft due to plasma generated by hypervelocity impacts, we have established a triple Langmuir probe diagnostic system and a logical chips measurement system, which were used to diagnose plasma characteristic parameters and the logical chip module's logical state changes due to the plasma created by a 7075 aluminum projectile hypervelocity impact on the 2A12 aluminum target. Three sets of experiments were performed with the collision speeds of 2.85 km/s, 3.1 km/s and 2.20 km/s, at the same incident angles of 30 degrees and logical chip module's positions by using a two-stage light gas gun loading system, a plasma characteristic parameters diagnostic system and a logical chip module's logical state measurement system, respectively. Electron temperature and density were measured at given position and azimuth, and damage estimation was performed for the logical chip module by using the data acquisition system. Experimental results showed that temporary damage could be induced on logical chip modules in spacecraft by plasma generated by hypervelocity impacts under the given experimental conditions and the sensors' position and azimuth.

This paper examines model and behavior uncertainty in vehicle ownership choice models. Temporal transferability tests are used to compare alternative model structures—multinomial logit (MNL), ordered logit (OL), and nested logit (NL)—and different model specifications. Preference stability is also tested. Through the use of data from the Boston, Massachusetts, metropolitan area in 1991 and 2010, it is shown that OL is more temporally transferable than MNL and NL but has a much higher local error. As the model specification becomes more complex, local error and transfer error decrease to a certain degree; the decrease in transfer error is smaller than that of local error. Overall, household vehicle ownership preferences are not stable over time but vary by specific parameter estimates. The relationships between vehicle ownership and local built environment factors and transit access are stable; the relationships related to regional location and most socioeconomic and demographic characteristics have evolved. Under an assumption that preferences have not changed over time, the use of 1991 models to forecast household vehicle ownership in 2010 underpredicts zero-vehicle households by 42.5% and overpredicts two-vehicle households by 14.8%.

In order to study the ignition performance of self-powered overload igniter based on Lead Zirconate Titanate (PZT), shock simulation tests for different electro-explosive devices (EED) were carried out by using separated Hopkinson pressure bar to simulate overload environment. The output energy of PZT, temperature rise process of bridge wire in EED, initiation temperature of the detonator, ignition energy, and initiation delay of igniter are experimentally analyzed. The experimental results show that: 1) the matching degree between the resistance of EED and PZT plays a key role in the sensitivity of the igniter; 2) Whether the igniter can detonate successfully depends not only on the maximum overload but also on the overload action time; 3) During the ignition process, the initiating explosive starts to react before the bridge wire fuses; 4) There is a delay time from the output energy to the reaction temperature of the initiating explosive to the complete reaction of the initiating explosive, which is the main reason for the delay of the igniter.

Neutron induced fission cross sections of 232Th(n,f)84Se, 232Th(n,f)84mBr, 232Th(n,f)84gBr reactions were measured based on neutrons from the D-T source. The α-particles emitted from the T(d,n)4He reaction were measured to monitor the neutron flux, while the ratio of 90Zr(n,2n)89Zr to 93Nb(n,2n)92mNb reactions was used to determine the neutron energy. The gamma-ray activity of samples was measured with a well calibrated HPGe-γ detector. In the 232Th(n,f) reaction at the neutron energies of 14.1 ± 0.3, 14.5 ± 0.3 and 14.7 ± 0.1 MeV, the cross sections are 2.74 ± 0.23, 2.75 ± 0.25, and 2.30 ± 0.21 mb for 84mBr, 3.41 ± 0.37, 3.35 ± 0.37, and 3.81 ± 0.42 mb for 84gBr, and roughly 8.79 ± 0.58, 9.36 ± 0.62, and 9.26 ± 0.62 mb for 84Se, respectively.

In the present study, soft and hard PZTs discharge experiments under extrusion/impact were carried out to analyze the electromechanical behaviors under open and short circuit conditions. The results show that when subjected to extrusion, the soft PZT is more sensitive to stress, the hard PZT has higher discharge capacity under high-impedance (regard as open-circuit) condition, and the force-electric relationship of the two PZTs satisfy the traditional piezoelectric equation. Under impact, the open-circuit elastic compliance coefficient of two PZTs increases with the increase of stress, the maximum value is about 50 times of the quasi-static value, and the piezoelectric voltage coefficient is about 20% of the quasi-static value. The short-circuit elastic compliance coefficient of soft PZT is 10 times of the quasi-static coefficient, and the dynamic piezoelectric strain coefficient is 250% of the quasi-static coefficient. However, the dynamic stress-strain of hard PZT is nonlinear and the dynamic piezoelectric strain coefficient is 500 × 10−12 m/V, which is about double of the quasi-static constant.

Aiming at the evaluation model of Aluminum/Polytetrafluoroethylene (Al/PTFE) impact reaction energy release established by Ames R G, the factors that have great influence on reaction energy release, such as vessel wall energy absorption and ejected gas energy, are ignored in the model. In fact, the sum of the initial kinetic energy and the impact reaction energy release should include the increase of target internal energy, the enthalpy of gas products, the thermal radiation energy, the kinetic energy of gas products and the energy absorbed by the vessel wall. The evolutionary rules of each part energy are quantitatively evaluated by quasi-closed vessel experiments at different impact velocities combining with various measured methods such as overpressure sensor, high speed camera, instantaneous optical pyrometer and infrared thermal imager. The Ames R G model is modified based on the results of reaction energy release at different impact velocities, and a modified model of reaction energy release considering temperature is established. The results show that with the increase of impact velocity, the enthalpy of gas products and the energy absorbed by the vessel wall increase greatly. The energy absorbed by the vessel wall accounts for most of the projectile impact energy release. The impact reaction energy release of unit mass projectile increases with the increase of impact velocities. When the impact velocities are in the range of 389–509 m/s, the increase of reaction release energy is significantly lower than that of 509–596 m/s. The modified model considering energy loss can be used to quickly evaluate and characterize the reaction energy release characteristics of active materials under impact load.

The insufficient dynamic compressive strength of the Al/PTFE energetic material with traditional ingredients has seriously restricted its application in the field of national defence. However, the improvement of strength must be at the expense of activity. In view of the contradiction, this paper pioneers aluminum honeycomb skeleton reinforcement method to achieve both strength and activity. On the basis of traditional ingredients Al/PTFE (mass percentage of 26.5%/73.5%), three types of energetic materials were prepared by cold pressing sintering process by adding different aluminum honeycomb skeletons with arm lengths of 1 mm, 1.5 mm and 2 mm, respectively. The dynamic compressive strengths of the specimen are obtained by using self-built Split Hopkinson Pressure Bar (SHPB) loading system and high-speed camera acquisition system. Meanwhile, the impact reaction release energies are also evaluated experimentally by using the one-stage light gas gun loading system combined with the transient optical fiber pyrometer measurement system, the overpressure measurement system and the infrared thermal imager measurement system. In term of dynamic compressive strength and impact reaction release energy, the performances of three types of Aluminum honeycomb reinforced energetic material were compared with those of traditional ingredients energetic material. The experimental results show that compared with the strength (25.17 MPa) of traditional ingredients Al/PTFE energetic material, the strengths of three kinds of energetic materials reinforced by aluminum honeycomb framework with arm lengths of 1 mm, 1.5 mm and 2 mm are 1.5, 3.1 and 2.2 times that of the traditional ingredients Al/PTFE, respectively; Especially, at the impact velocity of 510 m/s, the release energy of three kinds of Al/PTFE energetic materials reinforced by aluminum honeycomb framework with arm lengths of 1 mm, 1.5 mm and 2 mm were 2.52 kJ/g, 1.94 kJ/g and 2.40 kJ/g, respectively. However, the release energy of traditional ingredients Al/PTFE energetic material was only 1.85 kJ/g. Compared with the traditional ingredients Al/PTFE, the compressive strengths and release energies of three kinds of energetic materials reinforced by different arm lengths of Aluminum honeycomb were significantly improved under the same impact conditions.

With the rapid development of material science, the original aluminum alloy shield structure of spacecraft has been gradually replaced by sandwiched structure of carbon fiber reinforced resin matrix composite structure with aluminum honeycomb. In order to reveal the damage characteristics induced by debris impacting on shield structure of spacecraft and aiming at the engineering requirements that spacecraft undergo alternately high and low temperature environment during on-orbit operation, CFRPs/aluminum honeycomb core sandwich shield structure is used as the impact object. The damage characteristics of 2A12 aluminum projectile impacting on CFRPs/aluminum honeycomb sandwich structure with different aluminum honeycomb arm lengths at different impact velocities are studied by using the high and low temperature system for the target and the loading system of two-stage light gas gun. The experimental results show that the arm lengths of aluminum honeycomb have little effect on the perforation area of front and rear surfaces of CFRPs/aluminum honeycomb sandwich structure at high temperature, but the impact speed has a great effect on the perforation areas of front and rear surfaces of rear panels. The lower the impact speed is, the smaller the perforation diameter is. The deformation and ablation areas of the front and rear surfaces of the aluminum honeycomb increase with the increasing of the arm length of the aluminum honeycomb. At the same time, the physical quantities mentioned above have similar changes in low temperature environment. The fitting formulas, such as the relationships among perforations of the front and rear surfaces of CFRP and the arm lengths of aluminum honeycomb, and ablation area of aluminum honeycomb and the arm lengths of aluminum honeycomb are given at the given experimental conditions. The micro-morphology and damage characteristics of the panels and aluminum honeycomb are analyzed at the different locations near the impact point at high temperature.

BACKGROUND Ulcerative colitis (UC) is a kind of complex immune disease, the pathogenesis of which remains elusive. Destruction of the intestinal barrier, extreme inflammation, oxidative stress, and apoptosis might play key roles in the development of UC. In previous studies, we observed that Qingchang Wenzhong granule (QCWZG) had the exact effect on the remission of UC in the clinic; however, the underlying mechanism has not been identified. This study aimed to reveal the effects of QCWZG on the intestinal physical barrier and the interactive network of inflammation, oxidative stress, and apoptosis in rats with dextran sulfate sodium (DSS)-induced colitis. METHODS Sixty rats were randomly divided into six groups: blank group, model group, high/mild/low-dose QCWZG groups, and mesalazine group. The rats in the experimental group drank 4% DSS for 7 days and 1% DSS for the subsequent 7 days. Different medications or distilled water was supplied by intragastric administration for 7 days. The levels of colitis and indices related to inflammation, oxidative stress, and apoptosis were assessed. RESULTS Compared with the model group, the QCWZG group (P

Neutron induced reaction cross sections of Cerium isotopes (136Ce, 138Ce, 140Ce, 142Ce) were investigated for the (n, 2n), (n, α), (n, p) and (n, γ) reactions in the neutron energy around 14 MeV. Experimental cross sections have been obtained for 136Ce(n, 2n)135m+gCe, 138Ce(n, 2n)137mCe, 140Ce(n, 2n)139m+gCe, 142Ce(n, 2n)141gCe, 140Ce(n, p)140gLa, 142Ce(n, p)142gLa, 140Ce(n, α)137mBa, 142Ce(n, α)139Ba and 142Ce(n, γ)143Ce reactions. The measured values were compared with the literature data as well as the evaluated nuclear data from ENDF/B-VII.1, CENDL-3.1, JENDL-4.0 and the calculated results by Talys-1.8 code.

In order to obtain the elemental compositions of the projectile and target materials during 2A12 aluminum projectile shot on a natural dolomite plate, three kinds of experiments have been conducted using a spectral acquirement system established on a two-stage light gas gun for impact velocities ranging from 2.20 km/s to 4.20 km/s, at the same projectile incidence angle of 30°. Experimental results show that the elemental compositions of the projectile and target materials in the strong shock experiments have a good agreement with the original elemental compositions of the projectile and target. In addition, the relations between spectral radiant intensity and elemental compositions of the projectile and target materials have been obtained for different impact velocities, in which the spectral radiant intensity of the main elements in the material increases with increasing impact velocity, and more elements appear with increasing impact velocity since more energy would result from a higher velocity impact.

Future Mobility Sensing (FMS) is an innovative smartphone-based travel survey that was field-tested in 2012 and 2013, together with the Household Interview Travel Survey (HITS), in Singapore. This paper presents the findings of an exploratory analysis of the data collected in this test. The clustering of the day patterns from the FMS data revealed a large day-to-day variability of user behavior that could not be captured by a snapshot with a 1-day survey. Even the high cross-sectional variability from the larger sample size of a traditional survey would not have achieved the comprehensive set of heterogeneous patterns provided by FMS. Some common problems in traditional surveys—such as the underreporting of trips, the overestimation of travel times, and the inaccuracy of locations and times—can apparently be reduced by FMS. The FMS data have higher resolution and better accuracy compared with the HITS data. In addition, FMS is well suited to the collection of multiday data because additional costs are marginal and the user burden decreases over time. FMS offers a promising technology for the next generation of travel data collection.

Damages by a laser to materials are mainly caused by thermal and dynamic effects; such effects are referable for evaluating damage by a laser to the optical lens and the design of a laser system. We have designed several independent laser–material interaction measurement systems and carried out experimental research based on them. The results show that the laser plasma oscillation frequency is 500 Hz and accompanied by discharge phenomena. The average pressure stress on the material is 1.1 GPa; then it attenuates to the Lamb wave; and the surface coating of the lens reduces the radius of the heat-affected zone to one third of that without film.

Plasma-induced discharge is an important effect on the solar array of orbiting space vehicles subjected to hypervelocity impact, which will pose a serious threat to the power supply system of spacecraft. The paper investigates experimentally the process that the projectile in various impact velocities and incidence angles impact on solar array with sandwich structure comprising of a coverglass, a silica gel and a 2A12 aluminum liner at the different positions. The electron temperature and density of the plasma were diagnosed by applying in independent-constructed Triple Langmuir Probe diagnostic system, meanwhile, the charging and discharge test system were also constructed by ourselves. Three sets of experiments have been performed by two-stage light gas gun loading system and related measurement system. Especially, residual velocity was measured when projectile pierced through the solar array with composite structure. Experimental results revealed the discharge causes based on stress wave theory, and the discharge current characteristics of a primary and a secondary discharge of solar array induced by hypervelocity impact were given through hypervelocity impact experiments. Finally, it will provide a valuable benchmark for the construction of solar array against space debris.Plasma-induced discharge is an important effect on the solar array of orbiting space vehicles subjected to hypervelocity impact, which will pose a serious threat to the power supply system of spacecraft. The paper investigates experimentally the process that the projectile in various impact velocities and incidence angles impact on solar array with sandwich structure comprising of a coverglass, a silica gel and a 2A12 aluminum liner at the different positions. The electron temperature and density of the plasma were diagnosed by applying in independent-constructed Triple Langmuir Probe diagnostic system, meanwhile, the charging and discharge test system were also constructed by ourselves. Three sets of experiments have been performed by two-stage light gas gun loading system and related measurement system. Especially, residual velocity was measured when projectile pierced through the solar array with composite structure. Experimental results revealed the discharge causes based on stress wave theory, and th...

Due to the actual situation of spacecraft surface’ charging, such as convex corners, weld line, whalebone and a multiple-interfaces with different materials, all these are main factors leading to uneven charging of spacecraft surface, even creating gradient potential. If the charging spacecraft surface is impacted by debris or micrometeor, discharge effect induced by impacting will pose a serious threat to spacecraft in orbit. So realizing spacecraft charging surface with different potential differences and grasping discharge characteristics are a decisive importance at the different experimental conditions in laboratory. To simulate the spacecraft surface with a gradient potential in laboratory, spacecraft surface is split into different parts, which different gaps reserved in 2 adjacent surface is added resistance to create different potential surfaces, and the high potential surface as a impact target in the split targets. Charging circuit system realizing different gradient potential and discharge test system are built by ourselves, combining with two-stage light gas gun loading system, six sets of experiments have been performed about hypervelocity impact on 2A12 aluminum split targets with gradient potentials. In the experiments, gaps of 2A12 aluminum target are the same among different parts in every experiments, the gaps of the split targets are 2mm, 3mm, 5mm, 7mm and 10mm in the experiments, respectively. And the applied voltage is 300V in all the experiments and high-potential 2A12 aluminum plate as the impact target. The experiments have been performed at the impact velocity of about 3km/s and the incidence angles of 60o and 90o (between projectile flying trajectory and target plane), respectively. Voltage probe and current probes are used for acquiring discharge voltages and currents during the process of the impact. The experimental results showed that the discharge induced by impact plasma were generated among high and low-potential target by forming a plasma discharge channel. With the increasing of the gaps among the high and low-potential targets, the peak values of the discharge current decreased first then increased. When the gaps of split targets reached a certain value, the peak values of the discharge current decreased again. Meanwhile, the gaps among high and low-potential targets was 5mm, the peak value of the discharge current was the smallest. With the increasing of the gaps among the split targets, a primary discharge duration also increased. However, when the gaps among the split targets were greater than 5mm, increasing trend of discharge duration would slow down. When the gaps among the split targets were greater than 7mm, there was a secondary discharge phenomenon, and the physical explanations were given about the influence of different gaps among the split targets on the discharge effects created by hypervelocity impact.

Objective: The objective of this study is to study the effect of temperature, lipoxygenase activity, substrate and fruit type on formation of volatiles in the LOX pathway. Methods: Volatiles in the headspace of tomato, bell pepper, tomatillo, strawberry, apple and pear were measured during and after fruit tissue disruption in real time using selected ion flow tube mass spectrometry (SIFT-MS) at 4, 25, 37 and 45°C for 60 min, and were compared to lipoxygenase (LOX) activity and fatty acid concentration. Results: In tomatoes, bell peppers and tomatillos, (Z)a-3-hexenal, (E)-2-hexenal and hexanal increased rapidly after blending, peaked and declined, while in strawberry, apple and pear they sometimes peaked and sometimes remained constant over the 60 min. In tomato and bell pepper, the peak levels of (Z)-3-hexenal, (E)-2-hexenal and hexanal in the LOX pathway had good correlations to LOX activity, which was greatest at 25°C. In contrast, tomatillo, strawberry, apple and pear had lower LOX activity, their 6C aldehydes did not show strong correlation with LOX activity, and the volatiles increased with increasing temperature to 45°C. The concentrations of hexen-1-ol and 1- hexanol did not correlate to LOX activity for any of the fruits. In tomato, bell pepper and tomatillo, there was no significant correlation between the ratio of linoleic acid:linolenic and the ratio of hexanal:hexenal. In strawberry, apple and pear, there were good correlations between linolenic acid content and concentrations of (E)-2-hexenal, hexenal and hexen-1-ol. Conclusion: Thus the effect of enzyme activity and substrate composition on formation of volatiles in the lipoxygenase pathway remains complicated and difficult to predict.

A directionally solidified Ni3Al based alloy designated IC6A with the chemical composition Ni - (7.5 - 8.5)Al - (13.0 - 15.0)Mo - (0.02 - 0.1)B - (0.001 - 0.20)Y (wt-%) has been recently developed as a high-temperature structural material for advanced jet-engine vanes operating in the temperature range 1050 - 1100 ° C. Microstructural analysis results show that the regions consisted of Ni3Y, Mo1.24Ni0.76 and γ phases and surrounded by large size γ ′ phases precipitate in the interdendritic areas of alloy IC6A when the content of yttrium is near to the upper limit. Ni3Y and Mo1.24Ni0.76 have no obvious change during high temperature aging. A needle like or rod like phase named Y - NiMo precipitates after aging at 950 ° C for about 200 h. The high temperature cyclic oxidation resistance of alloy IC6A is fairly good owing to the presence of yttrium. The tensile properties, high temperature stress rupture properties and creep properties, high cycle fatigue properties and impact toughness of alloy IC6...

A plasma region in nanometer scale may be created by a highly charged ion impact on solid surface. The charge imbalance leads to enormous electric fields and may further induce Coulomb explosion due to electrostatic repulsion in the region. Thus, the highly charged ion is thus expected to be a powerful tool to induce surface modification in the nanometer scale. The Coulomb explosion model is applied in order to interpret the interaction mechanism and to understand the impact and energy deposition of highly charged ions on a solid surface, and to obtain the energy deposited by the ion. The energy deposition ratio is dependent on the material and charge. A high temperature and high pressure environment will be formed by the deposited energy, causing the atoms to swell up and a hillock nano-defect to be formed on surface. The height of hillock is estimated from the Coulomb explosion.