Quantitative decomposition of resonance-assisted hydrogen bond energy in β-diketones into resonance and hydrogen bonding (π- and σ-) components using molecular tailoring and function-based approaches

Using the molecular tailoring and function-based approaches allows one to divide the energy of the O─H⋯O═C resonance-assisted hydrogen bond in a series of the β-diketones into resonance and hydrogen bonding components. The magnitude of the resonance component is assessed as about 6 kcal mol⁻¹. This value increases by ca. 1 kcal mol⁻¹ on going from the weak to strong resonance-assisted hydrogen bonding. The magnitude of the hydrogen bonding component varies in the wide range from 2 to 20 kcal mol⁻¹ depending on the structure of the β-diketone in question.     

Comparison of the active components of Aster tataricus from different regions and related processed products by ultra‐high performance liquid chromatography with tandem mass spectrometry

We investigated crude Aster tataricus, vinegar‐processed Aster tataricus, honey‐processed Aster tataricus, and steamed Aster tataricus as a case study and developed a comprehensive strategy integrating quantitative analysis and chemical pattern recognition methods for the evaluation and differentiation of Aster tataricus from different regions, as well as related processed products. In the study, 15 batches of raw Aster tataricus collected from seven provinces were analyzed. A sensitive and rapid ultra‐high performance liquid chromatography with tandem mass spectrometry method for simultaneous determination of 15 compounds was established to evaluate the quality of raw and processed Aster tataricus. Furthermore, multivariate statistical techniques were applied to compare the differences among Aster tataricus samples. As a result, the herbs collected from seven provinces were divided into two categories, and chlorogenic acid was the most important component distinguishing between the regions. Moreover, all of the raw and processed samples were classified by partial least squares discriminant analysis based on the 15 analyzed compounds. Results showed that raw Aster tataricus, vinegar‐processed Aster tataricus, honey‐processed Aster tataricus, and steamed Aster tataricus were clustered in four different areas. Shionone, chlorogenic acid and kaempferol were the significant constituents differentiating the raw and differently processed Aster tataricus samples.     

模拟对讲以太网传输系统的设计

介绍了目前在监控系统中普遍使用的一种模拟对讲机,通过以太网传输升级成网络数字系统的设计方案。该系统主要是由硬件ADPCM编/解码卡和嵌入式ARM7以太网传输卡构成。前者用于语音的编/解码和信令提取,信令不单独占用带宽;后者负责码流的IP封装和解封装。还对嵌入式以太网传输中几个关键问题进行了讨论。     

最新的ITU-T嵌入式变速率语音编码关键技术

介绍了ITU-T的新一代语音编码标准G.729.1的编码器、译码器原理,讨论了此标准实现码流嵌入式所采用的关键技术:嵌入式的码激励线性预测编码技术、时域频带扩展技术以及时域混叠抵消的预测变换编码技术,并通过客观评测验证了G.729.1语音编码标准的高性能。     

一种基于双C/S架构的视频监控系统

提出了一种集散武的视频监控系统,该系统采用双C/S架构,并由嵌入式视频采集终端、视频服务器和客户端3部分组成.目前,该系统已被用于网络实验室对实际实验设备的监控.     

单一失效机理引起的元器件贮存寿命评价方法研究

电子元器件长期贮存过程发生的失效是由多种失效机理共同作用的结果．以器件贮存寿命整体为基础的寿命评价难度很大。选择对器件贮存寿命影响最大的单一失效机理．以失效物理为基础．通过高加速应力试验进行寿命评价研究,获得的寿命可以较准确地反映器件真实的贮存寿命。单一失效机理贮存寿命的研究是元器件贮存可靠性工作的重要内容。     

实时嵌入式软件测试研究与应用

实时嵌入式软件的应用与开发是当今计算机软件发展领域的一个热点,要保证实时嵌入式软件的质量是非常重要的.分析了实时嵌入式软件的特点和实时嵌入式软件测试的总体结构和宿主机及目标机的体系结构,探讨了脚本语言及其解释器.     

单层圆片带引线元件的片式化实现

介绍了在单层陶瓷圆片的基础上实现单层陶瓷圆片带引线元件的片式化。即将陶瓷芯片夹于上下连体扁平引线中间并焊接,模塑环氧树脂封装,再分割切开引线,使切开后的扁平引线贴在外壳表面,得到了用单层圆片制成的片式结构元件。已开发出CCH单层塑封型片式高压瓷介电容器、CCF单层塑封型片式交流瓷介电容器、ZVD单层塑封型片式氧化锌压敏电阻器产品,其结构坚固牢靠、防潮性能好、散热性能好、可靠性高,适应用于SMT生产。     

苯并噁嗪/钛酸钡复合材料介电性能的研究

通过共混法制备了苯并噁嗪/钛酸钡复合材料,探讨了钛酸钡粒径和填充量对复合材料介电性的影响。当?(BaTiO3)=50%时,复合材料介电常数εr达54、介质损耗tanδ为0.027、体积电阻率ρv大于1011?·m、击穿电压Vb大于8×103V/mm的高εr低tanδ绝缘材料。并将其应用于制备内嵌式电容器用玻璃布复合层压板。     

基于QDCT和贝叶斯谱熵的盲彩色图像质量评价

图像质量评价算法在评价彩色图像质量时,往往会因损失色彩信息或者破坏彩色图像结构的整体性,而使得评价结果与人眼观测结果不一致.由于图像越模糊其频谱的高频分量分布越不均匀,基于四元数离散余弦变换(QDCT)和贝叶斯谱熵,提出了一种无参考模糊彩色图像质量评价算法.首先,利用四元数矩阵对彩色图像进行表示并分解成不重叠的8×8 ...