一种新型的轴向载荷作用下的混合吸能机制

本研究结合两种常见的机制以提高系统吸收移动车辆或设备动能的能力. 该模型由两个独立的机制组成, 即圆管的膨胀和内胎的破碎, 通过内胎的摩擦、塑性变形和失效来耗散能量. 本研究调查24个在恒质量和恒体积两种不同设计控制下的案例以进行比较. 利用有限元模拟方法研究了模型的变形, 提取了耐撞性参数, 以反映机制的效率, 并对三种不同的内胎外形进行了参数化研究. 研究表明, 内环型和六角形管型模型由于经历了折叠、剪切和延性损伤三种不同的能量耗散系统, 吸收了更多的能量.     

Influence of Sintering Temperature on Intrinsic Trapping in Zinc Oxide-Based Varistors

The ac electrical data of the ZnO-Bi₂O₃ varistor system, in the frequency range 5 Hz to 13 MHz, when analyzed in the complex capacitance ( C *) plane, yields a distinct depressed semicircular relaxation having an average time constant on the order of 10⁻⁶ s. This trapping is attributed to the possible formation of ionized intrinsic/native defects. The decrease in the depression angle and average relaxation time, monitored as a function of the increasing sintering temperature (≥1100°C), indicated an improvement in the degree of uniformity in the loss-conductance and rapidity of response of the intrinsic trapping. The dependence of the ac parameters related to this trapping response obtained from the C * plane on the sintering temperature has been presented.     

Electrical conduction in anodic tungsten oxide thin films

Thin films of tungsten oxide were prepared by anodic oxidation of 99.999% pure tungsten foils using an aqueous solution containing 0.4 M KNO₃ and 0.04 M HNO₃ as the electrolyte. Different films show different colours. The current-voltage characteristics are of the log I- V^1/2 type. These characteristics can be interpreted in terms of the Poole—Frenkel type of conduction mechanism. The colours may be duo to the incorporation of H⁺ ions and the formation of HxWO₃ during the anodizing process.     

Electrochemical,surface analytical and quantum chemical studies on Schiff bases of 4-amino-4H-1, 2, 4-triazole-3,5-dimethanol (ATD) in corrosion protection of aluminium in 1N HNO<Subscript>3</Subscript>

The present study describes the inhibition of aluminium in 1N HNO₃ with different concentrations of 1,2,4-triazole precursors ATD, BATD and DBATD using gravimetric method, potentiodynamic polarization studies (Tafel), electrochemical impedance spectroscopy (EIS), adsorption studies, surface morphological studies and quantum chemical calculations at 298 K. Polarization studies clearly showed that ATD, BATD and DBATD act as mixed type inhibitors. As the electron density around the inhibitor molecule increases due to substitution, the inhibition efficiency also increases correspondingly. Quantum chemical approach was used to calculate some electronic properties of the molecule to ascertain the correlation between inhibitive effect and molecular structure of the inhibitor. The corrosion inhibition efficiencies of these molecules and the global chemical reactivity relate to some parameters, such as E _HOMO , E _LUMO , gap energy (ΔE), electronegativity (χ), global hardness (η) and the fraction of electrons transferred from the inhibitor molecule to the metallic atom (DNDelta emph{N}). In addition, the local reactivity has been analysed through the Fukui function and condensed softness indices. Both the experimental and theoretical studies agree well in this regard and confirm that DBATD is a better inhibitor than BATD and ATD. The adsorption behaviours of molecules on the copper surface have been studied using molecular dynamics method and density functional theory. The order of inhibitory action is DBATD > BATD > ATD.     

Allowable coefficient perturbations with preserved stability of a Hurwitz polynomial†

Given a polynomial P(s) = a_nsⁿ + a_n?11S^n?1 + … -+ a₁s + a₀ which satisfies the Routh-Hurwitz criterion, a procedure is given for finding non-conservative upper bounds on the allowable variations of the coefficients such that the perturbed polynomial maintains the stability property.     

Sunflower Protein Concentrates and Isolates' Low in Polyphenols and Phytate

Protein concentrates and isolates from sunflower (Helianthus annuus L.), essentially free of polyphenols and/or low in phytate, were prepared from dehulled seeds by a sequential extraction procedure using organic solvents, such as hexane for defatting and acidic butanol for removing polyphenols. Phytate was removed by aqueous extraction and separation at acidic and/or alkaline conditions, depending on the relative solubility of the protein and phytate. Reduced-phytate concentrates and isolates developed off-colors unless the polyphenol concentration was less than 0.05%. The protein solubility profile of the reduced-phytate products was much better than that of the defatted meal, especially below the isoelectric point.