The present work aims to stabilize the room temperature allotropic transition of ammonium nitrate(AN)particles utilizing a microencapsulation technique,which involves solvent/non-solvent in which nitrocellulose(NC)has been employed as a coating agent.The SEM micrographs revealed distinct features of both pure AN and NC,contrasting with the irregular granular surface topography of the coated AN particles,demonstrating the adherence of NC on the AN surface.Structural analysis via infrared spectroscopy(IR)demonstrated a successful association of AN and NC,with slight shifts observed in IR bands indicating interfacial interactions.Powder X-ray Diffraction(PXRD)analysis further elucidated the structural changes induced by the coating process,revealing that the NC coating altered the crystallization pattern of its pure form.Thermal analysis demonstrates distinct profiles for pure and coated AN,for which the coated sample exhibits a temperature increase and an enthalpy decrease of the room temperature allotropic transition by 6℃,and 36%,respectively.Furthermore,the presence of NC coating alters the intermolecular forces within the composite system,leading to a reduction in melting enthalpy of coated AN by~39%compared to pure AN.The thermal decomposition analysis shows a two-step thermolysis process for coated AN,with a significant increase in the released heat by about 78%accompanied by an increase in the activation barrier of NC and AN thermolysis,demonstrating a stabilized reactivity of the AN-NC particles.These findings highlight the synergistic effect of NC coating on AN particles,which contributed to a structural and reactive stabilization of both AN and NC,proving the potential application of NC-coated AN as a strategically advantageous oxidizer in composite solid propellant formulations.
Amir AbdelazizDjalal TracheAhmed Fouzi TarchounHani BoukeciatYash PalSourbh ThakurWeiqiang PangThomas M.Klapötke
In this paper, we proposed an output voltage stabilization of a DC-DC Zeta converter using hybrid control. We modeled the Zeta converter under continuous conduction mode operation. We derived a switching control law that brings the output voltage to the desired level. Due to infinite switching occurring at the desired level, we enhanced the switching control law by allowing a sizeable output voltage ripple. We derived mathematical models that allow one to choose the desired switching frequency. In practice, the existence of the non-ideal properties of the Zeta converter results in steady-state output voltage error. By analyzing the power loss in the zeta converter, we proposed an improved switching control law that eliminates the steady-state output voltage error. The effectiveness of the proposed method is illustrated with simulation results.
Hafez SarkawiNoridah Mohd RidzuanMuhammad Idzdihar IdrisMohd Syafiq Mispan
针对离散时间非线性系统,提出一种基于多李雅普诺夫(Lyapunov)函数的控制器设计方法.该方法不仅能够保证闭环系统稳定性,还能够扩大闭环吸引域(Domain of attraction,DOA).首先,给出基于多Lyapunov函数下系统渐近稳定的充分条件.结果表明,由多个Lyapunov函数的负定不变集构成的并集是一个稳定的控制集合,其从控制空间到状态空间的投影是闭环DOA的估计.随后,使用区间分析算法求解集合的内近似估计,基于此算法可以求解多Lyapunov函数的负定不变集的近似值和闭环DOA的估计值,并给出相应控制器的设计方法.最后,通过仿真算例验证了本文方法的有效性.
