高频冲击作用下高阻尼气液缓冲装置动态仿真

为解决高射速武器系统后坐力控制问题,对基于最佳后坐力控制理论的缓冲装置进行了研究。通过采用湍流模型的计算方法对具有气液组合式的缓冲装置特性进行了仿真分析,并探讨了温度对该缓冲装置的影响。最后将仿真结果与试验情况进行了对比,其分析结果为缓冲装置的进一步优化提供参考。     

Tuning specific loss power of CoFe2O4 nanoparticles by changing surfactant concentration in a combined co-precipitation and thermal decomposition method

New synthetic approaches of nanoparticles (NPs) can be used for magnetic hyperthermia, destroying malignant cells without damaging healthy tissues. Here, a combination of co-precipitation and thermal decomposition techniques was employed to synthesize monodisperse CoFe₂O₄ NPs. A mixture of oleylamine and oleic acid with different concentrations was utilized as a surfactant, significantly changing magnetic, morphological and structural properties of the NPs. Increasing the surfactant concentration from 1 to 7.5 mmol resulted in maximum and minimum coercivity and saturation magnetization of 420.0 Oe 73.6 emu/g, and 67.2 Oe and 48.3 emu/g, respectively, arising from the prevention of agglomeration and reduction in crystallite size. The first-order reversal curve analysis was employed to clarify the role of the surfactant in magnetic distributions and detailed characteristics. The specific loss power of the NPs was found to be tuned for the different surfactant concentrations, achieving a maximum of 268.5 W/g at 7.5 mmol for CoFe₂O₄ NPs with enhanced superparamagnetic contribution in Néel and Brownian mechanisms. MTT assay of the NPs was also carried out, indicating their low cytotoxicity.     

Morphology- and magnetism-controlled electrodeposition of Ni nanostructures on TiO2 nanotubes for hybrid Ni/TiO2 functional applications

We investigate magnetic properties of nickel nanoparticles electrodeposited on TiO₂ nanotubes by different techniques including direct current (DC) and cyclic voltammetry (CV) deposition. TiO₂ nanotubes were fabricated by anodic oxidation from an organic electrolyte under constant voltage on Ti substrates. Using scanning and transmission electron microscopies, we observe that each technique provides different morphologies: DC electrodeposition makes large coalesced Ni nanoparticles mostly accumulated on top surface and mouths of the nanotubes, whereas CV deposition produces a homogenous dispersion of Ni nanoparticles across the nanotubes. The variation of coercivity and saturation magnetization values recorded is consistent with our scenario, though owing to large number of nanoparticles with size and shape varieties. The first order reversal curve (FORC) diagrams help to reveal the magnetic behavior of nanoparticle ensembles in relation to their morphology and crystal structure.     

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 一阶回转曲线（first order reversal curve 简称FORC）图谱法被视为研究滞后效应领域中的“指纹鉴定”，受到了地质学界和物理学界的科学家极大的关注。在磁滞后系统中，FORC图谱可以相当敏感地表征磁性颗粒间的交换作用和矫顽力的分布情况，并且能够对磁化过程中的动态问题如不同的磁场变化速率等情况做出精确的分析。FORC图谱法也可应用到其它有滞后效应的领域如铁电滞后、热滞后、弹性滞后等。文章将从磁性领域入手，通过比较Preisach模型引入FORC图谱法，利用Takacs模型验证FORC图谱的计算过程，并列举出FORC图谱在纳米双相磁性材料的应用。     

Implementation procedure for the generalized moving Preisach model based on a first order reversal curve diagram

Ftrst order reversal curves (FORC) of nanoeomposite Nd2Fe14B/Fe3B magnetic materials were measured to attain a FORC diagram, which characterizes reversible magnetization, irreversible magnetization, and magnetic interactions in a hysteresis system. Then, generalized mov-ing Preisach model (GMPM) was implemented based on the FORC diagram. Reversible and irreversible magnetizations shown in FORCs and a FORC diagram were used as an input of GMPM. Coupling interaction between reversible and irreversible magnetizations was added when calculating reversible magnetization. Meanwhile, irreversible magnetic moments' interaction was approximately represented by mean field interaction. The result shows that the simulated main curves mostly coincide with the experimental curves.     

高射速自动机后坐力控制

如何对高射速自动机后坐力及射击稳定性进行有效控制,对于自动机的适装性及系统的射击精度至关重要,是现代高射速自动机的一个重要研究方向。提出了采用最佳后坐力控制(FORC)理论对高射速自动机后坐力进行控制的思路,并以某高射速小口径自动机为应用对象,建立了其动态仿真模型,对自动机后坐运动特性进行动态仿真,并开展了高射速自动机后坐力控制试验,试验结果表明,该装置能够实现自动机在高射速下稳定浮动,后坐力较原缓冲器降低50%,本文研究结果对现代高射速自动机缓冲装置设计具有重要参考意义。     

某型FORC理论及应用研究

介绍了应用于某特种产品上的内源式FORC反后坐装置，并对该型FORC装置动力学特性进行了理论推导，给出相应微分方程组。并以此为理论背景编制针对该产品的计算软件，与试验结果进行了对比，对工程实践具有一定的指导意义。