In order to improve the X-ray image quality of the explosive, we performed experiments in which a series of X-ray phase contrast images of the defects in polymer bonded explosive (PBX) under different pressures were obtained using the X-ray in-line phase contrast imaging technology.In the images obtained, we clearly observed the quasi-static evolution of the defects.The results show that this method can provide technical support for better understanding the hot-spot formation mechanism of the explosives and help to overcome the difficulty involved in obtaining a satisfactory image of the explosive with traditional X-ray radiography due to its weak absorption, and consequently diagnosing the tiny defects in explosives.

We developed a device for measuring high-pressure viscosity of liquids.The device consists of a diamond anvil cell, a microscope and a CCD detector, by which pressures can be determined using the ruby fluorescence technique.It is simple and convenient to measure the viscosities of liquids under different pressures with the falling-ball method.Using this device, we successfully obtained the viscosities of glycerin under high pressure, which are in good agreement with the published data, suggesting that our measuring device and method are both reliable.

The effects of pressure on the density, particles morphology and abrasion resistance of polycrystalline cubic boron nitride (PCBN) composite were investigated in detail using the melt infiltration method with cemented carbide under high pressure and high temperature conditions.The measured results show that the density and the abrasion resistance of the PCBN composite are enhanced along with the increase of the synthesis pressure.Furthermore, the interface between WC and cBN was characterized using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS).The results indicate that the elements of WC and cBN interpenetrate each other and generate a transition layer which enables the polycrystalline cBN to bond firmly to the WC substrate.

Raman spectra of Td-WTe₂ bulk single crystal sample with the incident laser (532 nm) beam direction parallel to the c axis were obtained under pressures up to 17 GPa.Based on the first-principles calculations, we analyzed the Raman spectrum of Td-WTe₂ bulk single crystal obtained at ambient temperature.The results indicated that the effect of pressure on the out-of-plane vibrational modes is much stronger than the in-plane vibrational modes, except for the 79.0 cm^-1 vibrational mode which is assigned to the out-of-plane vibrational mode.The vibrational mode located at 79.0 cm^-1 is less sensitive to pressure than the other vibrational modes.Moreover, we gave a detailed analysis and explanation for the effect of pressure on the vibration modes of Td-WTe₂ bulk single crystal.

The vibrational and structural properties of tetramethylsilane were investigated using the Raman scattering measurements under pressures ranging from 68.9 to 142.2 GPa and at room temperature.The results revealed that 3 vibrational modes of tetramethylsilane under 68.9 GPa remain locked in a certain position and are quite stable upon compression to 142.2 GPa.Moreover, new vibrational modes appear with the pressure going up to 72.2 GPa and all exhibit softening with further compression, suggesting that tetramethylsilane will become semi-metallic under such high pressures.

Using the in-house large-eddy simulation code MVFT, we investigated the three-dimensional multi-mode Richtmyer-Meshkov (RM) instability under multiple impingements and its dependence on initial conditions.After the initial shock, the width of the turbulent mixing zone (TMZ) grows with time in power-law.After the reshock and the impingement of the first reflected rarefaction wave, the TMZ width grows with time in the exponential law but with different growth factors.After the impingement of the first reflected compression wave, it grows with time in an approximately linear fashion, and the statistical quantities in TMZ decay with time in a similar way.The evolution of multi-mode RM instability is greatly dependent on the initial conditions between the initial shock and the impingement of the first reflected rarefaction wave.After the impingement of the first reflected rarefaction wave, the evolution of the turbulent mixing zone has lost the memory of the effect exerted by the initial conditions.

One-dimensional plane impact experiments with power gun were conducted on JOB-9003 explosives.The Hugoniot relation of unreacted JOB-9003 explosive was obtained by measuring the particle velocities at different depths with magnetic gauges.Moreover, the trinomial equation of state was calibrated with the experimental Hugoniot curve, and the JWL equation of state parameters of JOB-9003 explosive were determined.

In this work, the chemical vapor deposition method was adopted to deposit a single-layer graphene on a copper foil, which was then transferred to a fused silica substrate using the wet chemical method.Then, using the phase-contrast microscopy and the scanning electron microscopy, we studied the damage threshold, the damage probability, the damage morphology and the microstructure of the as-prepared graphene layer irradiated by a nanosecond ultraviolet laser pulse.The experimental results show that the absorptivity of the single-layer graphene produced is 2.38% at 550nm, close to the theoretical value of 2.3%, and the measured laser-induced damage threshold is 78mJ/cm² after irradiation with a wavelength of 355nm and a pulse width of 5.8ns.Moreover, we observed spherical carbon balls and carbon flowers in the laser-irradiated zone under relatively low fluence conditions, ablation framework of porous carbon at damage threshold fluence, and laser-induced nano-scale voids and folds of graphene under high-fluence laser irradiation.

In this paper, to explore the mechanism of advanced active earth-penetrating weapons, we propose a split kinetic energy projectile.The target penetrating processes of the split projectile were analyzed using the finite element method, and the calculation model was verified by comparing the results obtained from simulation and experiment.Moreover, the crushing characteristics of the concrete target were evaluated adopting the fractal geometry method.The results show that the split kinetic energy projectile can significantly improve the lateral damage capability when applied to rock or soil targets.Besides, the cumulative mass distribution of the plain concrete fragments is fairly consistent with the statistical fractal rules, indicating that the fractal dimension is a good parameter to describe the projectile's crushing characteristics.

In order to verify the probability of hand-thrown needles penetrating a glass plate, the damage features and the ballistic limit velocity were studied using both one-stage gas gun experiments and AUTODYN simulations on the glass plate impacted by common steel needles at velocities of tens of meters per second.Our results show that the damage of the glass plate concentrates in a small region around the impact point, and a cone-shaped hole is formed on the back side of the glass plate.The ballistic limit velocities are determined by the mass and the nose shape of the needles, the thickness of the glass plate, and the impact angle.Furthermore, when the velocity of the needle reaches 30 m/s and the impact angle is less than 10°, the steel needle with a mass of 0.35 g may penetrate a 1.6 mm thick glass plate.Compared with ogive-nosed steel needles, flat-nosed needles penetrate the glass plate more easily, and the damage of the glass primarily results from shear and tensile stresses.The ballistic limit velocity increases with the increases of the glass thickness and the impact angle and decreases with the increase of the needle mass.

A semi-closed pressure-loading vessel was designed to test the dynamic pressure bearing capacity of a laser ignition window.The mathematical model that describes the relationship between the propellant combustion and the pressure in the vessel was built and its validity was verified.The calculated results were fairly consistent with those achieved from tests.Then the vessel was used to test the bearing capacity of a sapphire window sample, the curves showing the pressure variation of the vessel were obtained and compared with those of the gun chamber.The results indicate that the sapphire window sample could satisfy the requirement of the gun's laser ignition.This vessel could simulate the actual dynamic pressure variation of the interior ballistic of the gun, which may provide a valid method for testing the dynamic pressure bearing capacity of the laser ignition window.

In order to investigate the main factors influencing the pulling force of a self-propelled straight-swirling integrated jet bit, we studied the effects of the inlet flow rate, wellbore diameter, and spray distance on the pulling force by combining experimental measurements and numerical simulations.The results show that the pulling force of the jet bit is influenced by the inlet flow rate, the well diameter, the flow rate ratio of forward and backward flows and the return flow in the wellbore.As the inlet flow rate increases, the pressure-reducing effects of the forward and backward jet rise, which is beneficial to the increase of the pulling force; when the wellbore diameter increases, the jet-sealing effects and the backflow interference will be weakened, leading to the pulling force increasing at first and then decreasing.At a designated inlet flow rate, an optimal wellbore diameter range can be obtained with the maximum pulling force.This work provides a significant reference for optimizing the design of jet bit parameters in radial horizontal wells.

As a sharp phase transition phenomenon, the boiling liquid expanding vapor explosion (BLEVE) is widely applicable to facilities related with launching and propulsion.In this work, the VOF (Volume of Fraction) model was employed in the simulation of the two-phase flow field, and the source item in the Navier-Stokes equation was optimized based on the fluid conditions.Moreover, the motion of the bullet was traced using an unstructured dynamic mesh method.Three kinds of superheated vapor with different filling ratios were chosen to simulate the BLEVE process and analyze the field pressure, the expanding rate, the phase transition and the bullet's acceleration.The results indicate that BLEVE is a simple and quick way of energy conversion, and the expanded two-phase flow propels the bullet out of the barrel within tens of milliseconds.

In order to study the shelf life and quality of vinasse shrimps after sterilization, we conducted thermal and high hydrostatic pressure (HHP) treatments in the sterilization process.The curves that describe the relationship between the total plate count and the sterilizing time are obtained, showing that the optimal experiment conditions of thermal and HHP treatments are 550 MPa, 10 min and 85 ℃, 20 min, respectively.The quality of shrimp samples was evaluated by the physicochemical indexes and sensory evaluation.The results show that there are little changes in pH and moisture content of samples during storage.After 30 d storage, the comprehensive scores of HHP and thermal groups are lower than those of the control group and the sensory scores of samples in the HHP group are higher than those in the thermal group.After 90 d storage, the total plate count of samples in HHP group increases to 2.5×10⁴ cfu/g, which is close to the industrial standard limit (3.0×10⁴ cfu/g) and significantly higher than the thermal group.Accordingly, the TVB-N value is also higher.