Search

In this study, a new method based on regularised orthogonal matching pursuit (ROMP) decomposition is proposed to extract the feature of the ballistic target's rotating micro-motion. Based on the establishment of the ballistic target rotation model, the general model of target's narrowband radar echo is obtained. An over-complete dictionary of atoms is established by combining the intrinsic characteristics of the signal model, and the selection of the matched atoms is carried out according to the regularisation principle. The extraction of the target's rotating micro-motion feature and the reconstruction of the original signal are realised. Simulation results show that the method can extract the micro-motion feature efficiently and accurately. [ABSTRACT FROM AUTHOR]

The micro‐motion feature extraction of precession target is an effective way for discriminating warhead from decoy in missile ballistic defence. Generally, traditional methods based on high‐resolution range profile (HRRP) sequences put forward high requirements on modulation bandwidth for the system, increasing the complexity of the system significantly. Utilising single‐frequency ladar without modulation, the authors proposed a precession parameter extraction algorithm of precession target based on high‐resolution Doppler profile (HRDP) sequences. Firstly, they model the Doppler bandwidth of the cone‐shaped precession target with the observation angle. Under the assuming that the measurement error obeys zero‐mean Gaussian distribution, the probability density function of Doppler bandwidth is established. Then, the precession parameters are estimated with measured Doppler profile sequences through maximum likelihood estimation method. Compared with the methods based on HRRPs, the proposed method based on the Doppler profile has lower requirements on the system and easier to implement. Laboratorial data has been used to validate the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

Micro‐Doppler (mD) characteristics of the ballistic targets have attracted great attention due to the potential in target discrimination. However, current investigations mainly focus on blunt‐nosed cone and cone‐cylinder‐shaped targets. In practical applications, ballistic targets are always designed as the streamlined shape due to smaller aerodynamic resistance and lower detectability. In this Letter, the mD characteristics of streamlined ballistic targets are analysed. Owing to the unique mD signatures, the sliding scattering centre induced by the reflection from the streamlined curved surface is particularly focused. Finally, simulation results via the electromagnetic computation verify the correctness of the analysis. [ABSTRACT FROM AUTHOR]

A numerical simulation of heat conduction in a grain aggregate is carried out to determine the packing fraction (the spatial fraction occupied by grains or 1-porosity) dependence of the thermal conductivity of the aggregate. Arrangements of grains are given by random ballistic deposition. It is found that the packing fraction dependence is well approximated by an exponential function. The number of contacts between grains is the crucial quantity in the conduction, and its packing fraction dependence is exponential. Heat conduction is found to be anisotropic, where the conduction along the deposition direction is more efficient than that perpendicular to the deposition direction. [ABSTRACT FROM AUTHOR]

Contrary to the moderate ballistic advantage of Al2 O3 ceramics over MgAl2 O4 polycrystals, the present study shows a reverse ratio of the ballistic strength of alumina and spinel single crystals: Spinel single crystals outperform sapphire and exhibit a similarly high stability as submicrometer Al2 O3 ceramics. The results correlate with different cleavage of single crystalline spinel and sapphire, changing the fragmentation on ballistic impact. [ABSTRACT FROM AUTHOR]

In Norway, Sweden, and Finland most beavers (Castor spp.) harvested are shot with center-fire rifles. Shooting entails problems not encountered in trapping including pelt damage from bullet holes (body shots are common) and escape of wounded animals. It was predicted that beavers shot in the body with splinter projectiles designed to fragment after impact would experience fewer exit holes (i.e., less pelt damage) and less wounding, but more meat loss, than those shot with conventional controlled expansion projectiles. Twenty-two hunters shot 163 beavers during normal hunting. As predicted, exit frequency was lower for splinter (22%) than controlled expansion projectiles (95%) but neither wounding frequency nor meat damage varied significantly. The combined wounding frequency for both projectile types was 4.3%. Ninety-eight percent of the body-shot animals retrieved (n = 111) appeared to die instantly. Beaver hunting with center-fire rifles was considered humane. [ABSTRACT FROM AUTHOR]

The ballistic performance of state-of-the-art silicon carbide armor material can exhibit a fairly wide variability in certain test configurations, which, it is proposed, may be due to the presence of large (>0.1 mm), rare defects, termed, herein, "anomalous" defects. SiC rubble resulting from ballistic tests was examined, as were quasi-static test samples. Ballistic fragment fracture surfaces revealed large carbonaceous defects that seemed to affect fracture path and mode. Low-strength biaxial flexure samples demonstrated similar defects (>0.1 mm) as failure origins. Carbonaceous defects similar in appearance but smaller in size were also found at the fracture origins of SiC bend bars. Frequently, alumina inclusions were found within the carbonaceous discontinuities. These alumina inclusions may cause the graphitic regions to form during sintering. The random distribution of such large, rare carbonaceous discontinuities from sample-to-sample, as well as batch-to-batch variability, may explain high ballistic variability for SiC armor ceramics. [ABSTRACT FROM AUTHOR]

Several hot-pressed and sintered SiC variants were impacted with tungsten-carbide (WC) spheres at velocities up to 1700 m/s. Ballistic response curves of areal density penetrated as a function of impact velocity were generated to compare ceramics for ballistic applications. Observed response curve features are shown to be similar to those observed for metal impacts. Ballistics penetration models that captured these features for metal targets were utilized to analyze the ceramic data. Visual examination of damage type and extent suggested that cavity expansion expressions for target resistance might help to quantify the strength of fully confined, damaged, comminuted ceramics. The experimental results, visual observations, and preliminary analysis using a ballistics penetration model are presented. [ABSTRACT FROM AUTHOR]

Projectiles of sintered tungsten alloy were fired directly at two kinds of steel target plates. The microstructures near the perforation of a medium, 0.45% carbon steel target plate can be identified along the radial direction as: melted and rapidly solidified layer, recrystallized fine-grained layer, deformed fine-grained layer, deformed layer and normal matrix. The adiabatic shear bands cannot be found in this intermediate strength steel. The microstructures along the radial direction of perforation of 30CrMnMo steel target plate are different from that of the medium carbon steel. There was a melted and rapidly solidified layer on the surface of the perforation, underneath there was a diffusing layer, and then fine-grained layer appeared as streamlines. Several kinds of adiabatic shear bands were found in this higher strength steel; they had different directions and widths, which were relative to the shock waves, as well as the complex deformation process of penetration. The deformation of the projectiles was rather different when they impacted on target plates of medium carbon steel and 30CrMnMo steel. The projectile that impacted on the medium carbon steel target plate was tamped and its energy dissipated slowly, while that which impacted on the 30CrMnMo steel target plate was sheared and the energy dissipated quickly. [ABSTRACT FROM AUTHOR]

To investigate micro‐Doppler signatures of precession for a warhead with empennages, the model of precession is built and mathematical formulas of a micro‐Doppler induced by different scattering centres are derived. The relationship between the micro‐Doppler appearing frequency of empennages and micro‐motion frequencies is first acquired, then two important precession features, namely coning frequency and spinning frequency, are extracted based on the micro‐Doppler. Simulation results are provided to demonstrate the validity of the proposed method. [ABSTRACT FROM AUTHOR]

Mirco‐motion analysis of ballistic targets is a useful tool for discriminating different targets in the aerospace. A micro‐motion model combining inertial parameters with a target radar coss‐section is presented. The relation between target micro‐motion states and inertial parameters is deduced. By using the time‐frequency transform method, the micro Doppler spectrogram is obtained. Simulation results show that the proposed method can be used for evaluation of ballistic targets recognition and discrimination. [ABSTRACT FROM AUTHOR]