Crystals of γ‐HNIW were transformed into crystals of ε‐HNIW by application of a drowning‐out process in the presence of different additives, namely ethylene glycol, triacetin, and aminoacetic acid. They show different effects on the crystal morphology of ε‐HNIW and cause less angular and more regular structures. Investigation of the sensitivities of the different ε‐HNIW crystals shows that their angles and regularity have an influence on the impact sensitivity. Aminoacetic acid selectively inhibits the growth of individual ε‐HNIW crystal faces to modify the morphology into spherical shape, these ε‐HNIW crystals are of much lower sensitivity, even compared with general RDX and HMX explosives.
An X-ray diffraction method was applied for the quantitative determination of the e-Hexanitrohexaazaisowurtzitane (HNIW) in polymorphs of HNIW. The XRD patterns of four polymorphs illustrate the unique nonoverlapping peak at 19.98 which belongs to e-HNIW. The intensity ratio of the peak at 19.98 of e-HNIW to the peak at 79.68 of a-Al 2 O 3 is proportional to the weight ratio of standard e-HNIW to the internal standard of a-Al 2 O 3 , which enables the internal standard method. When the particle size of the sample is less than 10 mm, the content of e-HNIW ranging from 70 to 100 wt.-% can be determined with an absolute error below 2.0%.
A novel approach about iterative homotopy harmonic balancing is presented to determine the periodic solution for a strongly nonlinear oscillator. This approach does not depend upon the small/large parameter assumption and incorporates the salient features of both methods of the parameter-expansion and the harmonic balance. Importantly, in obtaining the higher-order analytical approximation, all the residual errors are considered in the process of every order approximation to improve the accuracy. With this procedure, the higher-order approximate frequency and corresponding periodic solution can be obtained easily. Comparison of the obtained results with those of the exact solutions shows the high accuracy, simplicity, and efficiency of the approach. The approach can be extended to other nonlinear oscillators in engineering and physics.
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