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921.
A new macrocyclic decanuclear manganese(III) 30-metallacrowns-10, [Mn10(ipbmshz)8(dmpmshz)2(DMF)10]. 4DMF (1) has been prepared by supramolecular self-assembly and characterized by X-ray crystal diffraction, where ipbmshz3− is N-(4-isopropylbenzoyl)-3-methylsalicylhydrazide, dmpmshz3− is N-(2,2-dimethylpropanoyl)-3-methylsalicylhydrazide. The single-crystal structure shows that a novel ring formed by the succession of ten structural moieties of the type [Mn(III)–N–N] through hydrazide N–N groups bridging the ring Mn ions. The ligand enforces the Mn3+ ions to form the stereochemistry of a propeller configuration with alternate…ΔΛΔΛ…-type chiral forms depending on the steric repulsions between the tail groups. The decanuclear systems measure ∼2.3 nm in diameter and ∼1.2 nm in thickness. The temperature-dependent magnetic properties have been studied and showed the presence of weakly antiferromagnetic couplings between Mn (III) ions. 相似文献
922.
In our previous research (Liu et al., J Anal Appl Pyrol 63:303–325, 2002), the pseudo bi-component separated-stage model (PBSM)
was suggested for the kinetic analysis on the decomposition of lignocellulosic materials in air at relatively lower heating
rates. As a continuing work, this paper is intended to investigate the applicability of PBSM at different heating rates by
experimental analyses. Decomposition of oil tea wood has been studied by means of non-isothermal thermogravimetric analysis
in air atmosphere at 10–25 K min−1 heating rates. A two-step parallel reaction kinetic model is used to optimize the kinetic parameters of these materials in
air. Meanwhile, an improved PBSM is developed to describe the thermal degradation process of oil tea wood. Furthermore, a
comparison between the kinetic results of parallel model and PBSM reveals realistic applicability of PBSM. It is concluded
that the PBSM has relatively high accuracy for the first decomposition step in the lower temperature range, while fails to
predict the thermal decomposition behavior in the char oxidative process which occurs in the higher temperature range. 相似文献
923.
A series of novel furan-2-yl(phenyl)methanone derivatives were synthesized, and their structures were established on the basis of 1H-NMR, 13C-NMR and mass spectral data. All the prepared compounds were screened for their in vitro protein tyrosine kinase inhibitory activity and several new derivatives exhibited promising activity, which, in some cases, was identical to, or even better than that of genistein, a positive reference compound. The preliminary structure-activity relationships of these compounds were investigated and are discussed. 相似文献
924.
925.
Let D(G)=(di,j)n×n denote the distance matrix of a connected graph G with order n, where dij is equal to the distance between vi and vj in G. The largest eigenvalue of D(G) is called the distance spectral radius of graph G, denoted by ?(G). In this paper, we give some graft transformations that decrease and increase ?(G) and prove that the graph (obtained from the star Sn on n (n is not equal to 4, 5) vertices by adding an edge connecting two pendent vertices) has minimal distance spectral radius among unicyclic graphs on n vertices; while (obtained from a triangle K3 by attaching pendent path Pn−3 to one of its vertices) has maximal distance spectral radius among unicyclic graphs on n vertices. 相似文献
926.
The LiVPO4F as cathode material for lithium-ion batteries was synthesized through two steps of solid-state reactions and investigated by ex situ Fourier transform infrared (FTIR) spectroscopy for the initial charge and discharge cycle. The characterization of the effect on the structure of the LiVPO4F in the process of lithium-ion insertion/extraction at a molecular level by ex situ FTIR spectroscopy is helpful for the mechanism research for lithium-ion insertion/extraction and the improvement of the performance of lithium-ion batteries. In the process of the initial cycle, new bands of VPO4F appear in the charge and the featured bands of LiVPO4F reappear in the discharge. In this paper, ex situ FTIR spectra indicates that the structure of the LiVPO4F in the process of lithium-ion insertion/extraction is almost not affected, which clearly states that the LiVPO4F possesses stable structure as cathode material. Consequently, the LiVPO4F might be expected as a potential cathode replacement for commercial lithium-ion batteries. 相似文献
927.
928.
为方便描述聚龙一号装置与Z箍缩负载的电磁耦合过程,基于大量电参数实验数据和全电路模拟分析,建立了一个简化的集总电路模型,获得了等效电压波形和等效电阻、电感等集总参量。采用水介质三板输出线出口位置的开路电压作为等效电压,进一步拟合为正弦平方函数,峰值为3.3 MV(当前驱动器充压为65 kV),零到峰值的时间长度为102.5ns。采用简化的流阻抗模型描述磁绝缘传输线内部空间电子流的电流损失效应。将电路程序与零维负载动力学程序耦合模拟,得到了与实验结果符合的负载电流波形,尤其电流波形的前沿和峰值符合较好,分析了电磁能转化为负载动能的过程。 相似文献
929.
双面声阵列波束形成能够区分识别位于不同扫描平面的相干声源,然而该算法在低信噪比条件下识别精度较低。针对此问题提出一种迭代正则化改进算法,通过迭代方法更新正则化矩阵与波束形成输出,在不断提升正则化稳定性、抑制干扰旁瓣的基础上使声学云图主瓣向实际相干声源点处聚焦。数值仿真与实验算例结果显示,改进算法在中高频代表频率下能够正确区分相干声源前后方位,并具有相对原算法更高的识别精度。从而表明:从反问题正则化角度对原算法进行优化改进是理论可行的;正则化矩阵的具体形式与广义逆波束形成输出的空间分辨率紧密相关,且可通过迭代方法将二者整合以提高声源识别精度。 相似文献
930.