李萨如图形在检测系统中的应用

李萨如图形可以检测两个相同频率信号的相位差．主要论述具有惯性质量、弹簧和阻尼器的二阶加速度测量系统,其动态响应特性的分析方法,如何利用李萨如图形来检测力平衡式加速度传感器的动态特性,即幅频特性和相频特性,从而确定传感器的固有频率ω_n和阻尼比ξ,以此来评定传感器的综合特性．     

Asymmetric Synthesis Using Sulfinimines (N-Sulfinyl Imines)

Abstract

Sulfinimine-derived polyfunctionalized chiral building blocks, often prepared in one pot, provide efficient access, with a minimum of chemical manipulation, to enantiopure, multifunctional amine derivatives including piperidines and pyrrolidines.     

明代长江流域人口大量死亡事件时空特征及原因分析

通过检索古籍文献,整理了明代（公元1368—1644年）长江流域人口大量死亡事件（mass death events,MDE）10 a尺度的频次与县次序列,利用自然断点分级法、空间分析法等分析了MDE的时空特征及发生原因。结果表明：276 a间,长江流域有158 a发生MDE,明代后期发生频次和影响规模最大;季节上,表现为夏季多发（44.3%）,春、秋季次之;空间上,集中分布于长江中下游、尤其是长江三角洲地区,且呈从各省交界处向各省中心扩散的趋势。“未记录原因的饥荒”和“旱灾+其他灾害-饥荒”是造成明代长江流域MDE的主要原因。气候冷干期发生频次多,影响范围广,暖湿期相反,与温度和湿度呈显著负相关;人口规模和社会脆弱程度是主要的社会影响因素。在人口规模大和社会脆弱的明代后期,MDE发生频次高,波及范围广,是气候变化与社会因素共同作用的结果。     

Asymmetric synthesis of the quinolizidine alkaloid (-)-epimyrtine with intramolecular Mannich cyclization and N-sulfinyl delta-amino beta-ketoesters

A concise, six-step, enantioselective synthesis of (-)-epimyrtine employing the N-sulfinyl delta-amino beta-ketoester chiral building block is described.     

新型硫脲分子-Gd(Ⅲ)配合物对氟离子的选择性识别研究

设计合成了受体分子[[4-[(硫代碳酰氨基)氨甲基]苄基]氨基]硫脲-Gd(Ⅲ)配合物(LH-GdⅢ),研究了其UV-Vis吸收光谱对阴离子的响应.发现受体的DMSO溶液中加入F-后,吸收光谱强度发生极大变化,并于426nm处产生新的吸收峰,且观察到清晰的等吸收点.研究表明氟离子以1:1结合模式影响体系的吸收,该受体分...     

Mössbauer study of amorphous Fe40Ni40PxB20−x

The hyperfine field distributions of amorphous Fe₄₀Ni₄₀P_xB_20?x (x=10, 12, 14, 17) samples before and after different heat treatments have been determined by means of Mössbauer spectroscopy. All of these P(H) curves are characterized by a main high field maximum and an additional low field maximum, respectively. The asymmetry of distributions of high field component in P(H) of Fe₄₀Ni₄₀P_xB_20?x increases progressively from Fe₄₀Ni₄₀P₁₀B₁₀ to Fe₄₀Ni₄₀P₁₇B₃. The distributions of low field component in P(H) are affected differently by the annealing temperature. The results indicate that the phospoorus element plays an important role in the hyperfine interactions of amorphous Fe₄₀Ni₄₀P_xB_20?x The influence of annealing atmosphere has been discussed.     

Acoustic attenuation in ferroelectric Sn<Subscript>2</Subscript>P<Subscript>2</Subscript>S<Subscript>6</Subscript> crystals

The temperature and frequency dependencies of sound attenuation for the proper uniaxial ferroelectric Sn₂P₂S₆, which has a strong nonlinear interaction of the polar soft optic and fully symmetrical optic modes that is related to the triple well potential, were studied by Brillouin spectroscopy. It was found that the sound velocity anomaly is described in the Landau-Khalatnikov approximation with one relaxation time. For explanation of the observed temperature and frequency dependencies of the sound attenuation in the ferroelectrric phase, the accounting of several relaxation times is needed and, for quantitative calculations, the mode Gruneisen coefficients are more appropriate as interacting parameters than are the electrostrictive coefficients. Relaxational sound attenuation by domain walls also appears in the ferroelectric phase of Sn₂P₂S₆ crystals.     

Thermal expansion of Sn2P2S6 crystals

We present the results for thermal expansion coefficients of Sn₂P₂S₆ crystals determined both in the crystallographic system and the system based on eigenvectors of thermal expansion tensor. Peculiarities of temperature evolution of the indicative surface of thermal expansion tensor for Sn₂P₂S₆ are discussed, including the region of their ferroelectric phase transition.