Dynamical analysis and anti-oscillation-based adaptive control of the FO arch MEMS with optimality

Nonlinear Dynamics - This paper mainly investigates dynamical analysis and anti-oscillation-based adaptive control issues of the fractional-order (FO) arch microelectromechanical system (MEMS) with...     

可控交联聚醚醚酮的合成与热性能研究

聚醚醚酮因其优异的综合性能 (耐热性、耐水解、耐辐射等 )在许多领域得到应用 [1～ 4 ] .但聚醚醚酮的玻璃化转变温度 ( Tg)较低 ( 4 2 6K) ,导致其使用温度较低 (在 5 1 3K以下 ) .为进一步提高聚芳醚酮类材料的使用温度 ,人们在聚醚醚酮主链中引入刚性结构 ,通过提高聚芳醚酮的刚性度来提高聚芳醚酮的熔点 ( Tm)及 Tg,从而提高材料的使用温度 [5,6 ] .文献 [7]中聚芳醚酮的 Tm 已经高达 741 K,但此材料很难加工成型 .通常热塑性材料具有优异的加工性能 ,但使用温度较低 .热固性材料的使用温度较高 ,但在加工固定尺寸形状铸件时存在困…     

First synthesis of (±)-bis-homosarkomycin ethyl ester

A five step synthesis of (±)-bis-homosarkomycin ethyl ester 6 has been achieved starting from commercially available ethyl phosphonoacetate and ethyl 5-bromovalerate. The successful synthetic approach to 6 uses α-methylene pimelate 3 as a key intermediate.     

Synthesis and X-ray crystal structure of a new μ-hydroxo dinuclear cobalt complex containing one cis-β folded and one planar salen moiety

The reduction of [Co(III)(tmsalen)(py)₂]⁺ with NaBH₄/PdCl₂ and the successive oxidative addition of CH₂ClI, carried out in neutral methanolic solution and followed by the addition of NaOH, afford a new dinuclear complex. The molecular structure reveals that it is formed by an octahedral [Co(tmsalen)(py)(OH)] unit connected to a β-folded [Co(tmsalenCH₂)]⁺ fragment, in such a way that the latter metal completes the coordination sphere with the hydroxo group and a tmsalen oxygen from the former unit.     

On using the dynamic snap-through motion of MEMS initially curved microbeams for filtering applications

Numerical and experimental investigations of the dynamics of micromachined shallow arches (initially curved microbeams) and the possibility of using their dynamic snap-through motion for filtering purposes are presented. The considered MEMS arches are actuated by a DC electrostatic load along with an AC harmonic load. Their dynamics is examined numerically using a Galerkin-based reduced-order model when excited near both their first and third natural frequencies. Several simulation results are presented demonstrating interesting jumps and dynamic snap-through behavior of the MEMS arches and their attractive features for uses as band-pass filters, such as their sharp roll-off from pass-bands to stop-bands and their flat response. Experimental work is conducted to test arches realized of curved polysilicon microbeams when excited by DC and AC loads. Experimental data of the micromachined curved beams are shown for the softening and hardening behavior near the first and third natural frequencies, respectively, as well as dynamic snap-through motion.     

Comparison of homogeneous and heterogeneous Ga(III) catalysis in the cycloisomerization of 1,6-enynes

We describe a study of the gallium(III)-catalyzed 1,6-enynes cycloisomerization reaction in both homogeneous and heterogeneous conditions. With GaBr₃ in homogeneous conditions, some particularities were observed in terms of selectivity compared to reported GaCl₃-catalyzed reactions. The transfer of the reaction in heterogeneous conditions was realized by supporting Ga(III) salts onto montmorillonite. Both systems were compared based on reaction times, conversion, and selectivity and showed complementary activities.