br Influence of target hypersonic movement on radar measurements Since

Influence of target hypersonic movement on radar measurements
Since the LFM signal is one of the most famous radar signals, which is of large time-bandwidth product, and can significantly improve S/N ratio when the matching filter is performed. The PC (pulse compression) radar which emits LFM signal) is selected to discuss the problem of hypersonic target tracking in near space.
We assume that the PC radar emits the LFM signalwhere , , is the emitting pulse width, is the central carrier frequency, is the FM rate, B is the FM band width.
When the target moves at a radial speed of v, the received signal at time k can be expressed as followswhere , R0 is the target distance at time t0, c is the light speed, .
At this time, if the matched filtering technique is used to the received signal , the output of the matching filters can be expressed aswhere is the target Doppler shift. Then according to the maximum signal-to-noise ratio criterion, the signal has a maximum value at time . That is to say, the radar measurements are inevitably affected by the following dynamic biases
In order to evaluate the influence of target hypersonic movement on the tracking of near space target, the relative analysis is as follows.while the measurement errors of the conventional radar are around. That is to say, the high dynamic biases, which seriously affect the tracking of near space target, can not be neglected.

Tracking models of hypersonic sliding target in near space

Simulation
Computer simulation is used to study the performance of the proposed tracking algorithm, and four methods in Section 4.1 are compared with the proposed method in this paper.

Conclusions

Introduction
High energetic materials (HEMs) are rich sources of ARQ 621 stored in the form of chemical bonds [1]. They are thermodynamically unstable, but the kinetics of energy release can be controlled. They have found extensive use in explosives, rocket propellants and gas generators for automobile air bags [1,2]. Focus of research on HEMs has recently been to synthesize novel molecules with high energy density combined with insensitivity to hazardous stimuli [1,2]. Unfortunately, the research and development of new HECs has been very slow. RDX and HMX, which were developed many decades ago, are still being used as the main explosives due to their technological-economical characteristics such as their ready availability in large scale [2]. Powerful explosives such as CL-20 and octanitrocubane have much higher energetic performance than RDX and HMX [2,3]. But, their sensitivity to accidental stimuli is a matter of concern. Sensitivity of explosives is related to their chemical as well as physical characteristics [4]. The physical properties such as crystal size, shape, morphology, purity, inclusions and crystal defects can be altered to improve the performance of existing explosives [5,6]. Previous studies reported that the novel behaviour in deflagration to detonation transition was observed with submicron particles [7]. A few studies have indicated that the particle size of explosives influences the impact sensitivity and maximum energy output from a detonation [8]. Thus, the preparation of micrometer or sub-micrometer sized solid particles is of great interest in explosives.
However, the limited production strategies are only available for making organic nanoparticles in general compared to the large array of methods that are available for the preparation of inorganic nanoparticles. Some of the methods for the preparation of sub-micron sized HEMs includes rapid crystallisation from solvent by the addition of antisolvent [9,10], sol–gel method [11,12], rapid expansion of supercritical solution (RESS) [13,14], mechanical milling [15–17] and aero-sol method [18]. An excellent review on the various methods for the preparation of nanoenergetic materials was published recently [19]. Unfortunately, many of these techniques proved to be less attractive in large scale production of organic nano-sized materials. Among various techniques for the reduction of particle size, the antisolvent precipitation process is a simple and effective technique to produce the nanosized particles by introducing the organic solution containing an active substance to the antisolvent (e.g. water) that is solvent-miscible under rapid mixing, which generates high supersaturation leading to fast nucleation rates [20–25]. Instantaneous precipitation occurs by a rapid desolvation of the hydrophobic active ingredient in the antisolvent medium [26–29]. The antisolvent may contain hydrophilic stabilizers such as polymers or surfactants. The hydrophilic stabilizer in the antisolvent gets adsorbed on the particle surface to inhibit particle growth [20–25]. We have recently prepared nano-HECs by a simple evaporation assisted solvent-antisolvent interaction (EASAI) method using acetone as solvent at 70 °C [26,27]. The same method was also used to prepare nanodrugs [28,29]. It has been shown that the particle size can be controlled by varying a number of experimental parameters such as the concentration, ratio of solvent to antisolvent, temperature of the antisolvent during injection, stirring speed etc. Infact, a lot more experimental parameters such as ultrasonication, nozzle geometry, mixing rate, nature of solvent and nature of antisolvent also are known to affect the particle properties [30]. Although there has been some studies on the effect of many of these experimental parameters, only very few reports are there in the literature about the effects of different solvents on particle size and morphology of HECs. Here we demonstrate that particle size and even morphology of nano-HECs can be tuned by changing the solvent using the SAI method.