排序方式: 共有39条查询结果,搜索用时 15 毫秒
1.
2.
Jin-Qiang Liu Xin-Zhi Chen Baoming Ji Bang-Tun Zhao 《Research on Chemical Intermediates》2013,39(3):1143-1152
(S)-Indoline-2-carboxylic acid was synthesized by use of a nitro amination approach with l-phenylalanine as chiral pool. The first step of the synthesis was nitration of l-phenylalanine, with urea nitrate (UN)/H2SO4 as nitrating reagent, to give 2,4-dinitro-l-phenylalanine in 75.7 % yield in one-pot synthesis and 69.1 % yield by step-wise nitration. Intramolecular nitro amination of 2,4-dinitro-l-phenylalanine gave (S)-6-nitro-indoline-2-carboxylic acid in 65.7 % yield and more than 99.5 % enantiomeric excess (ee). The title compound, (S)-indoline-2-carboxylic acid, was obtained in 85.9 % yield and high ee by one-pot transformation of (S)-6-nitroindoline-2-carboxylic acid. The total synthesis consisted of three operations and gave the title compound in 42 % yield and more than 99.5 % ee. 相似文献
3.
4.
Yong-Gang Wang Xiao-Meng Li Dan Li Xin-Zhi Wang 《Archive of Applied Mechanics (Ingenieur Archiv)》2011,81(12):1925-1933
An integrated mathematic model and an efficient algorithm on the dynamical behavior of homogeneous viscoelastic corrugated
circular plates with shallow sinusoidal corrugations are suggested. Based on the nonlinear bending theory of thin shallow
shells, a set of integro-partial differential equations governing the motion of the plates is established from extended Hamilton’s
principle. The material behavior is given in terms of the Boltzmann superposition principle. The variational method is applied
following an assumed spatial mode to simplify the governing equations to a nonlinear integro-differential variation of the
Duffing equation in the temporal domain, which is further reduced to an autonomic system with four coupled first-order ordinary
differential equation by introducing an auxiliary variable. These measurements make the numerical simulation performs easily.
The classical tools of nonlinear dynamics, such as Poincaré map, phase portrait, Lyapunov exponent, and bifurcation diagrams,
are illustrated. The influences of geometric and physical parameters of the plate on its dynamic characteristics are examined.
The present mathematic model can easily be used to the similar problems related to other dynamical system for viscoelastic
thin plates and shallow shells. 相似文献
5.
High repetition rate pulsed laser of twin wavelengths from KTiOPO4 optical parametric oscillation 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this paper, some key techniques of KTiOPO_4 optical parametric oscillation (OPO) laser with repetitive frequencies and twin wavelengths output have been analysed theoretically and studied experimentally in detail. An intracavity optical parametric oscillator (IOPO) has been applied. Operating under 20Hz, laser output energy of more than 38mJ with twin wavelengths 1.57μm and 1.06μm has been achieved. Results of the experiments agree well with the theoretical discussion. 相似文献
6.
提出了基于现场可编程门阵列 (FPGA) 技术的混沌直接序列扩频信号盲解调的硬件电路实现方法. 设计了混沌直接序列扩频信号发射机与接收机. 发射机可产生10种不同的混沌直接序列扩频信号. 为方便接收机的硬件电路实现, 对无先导卡尔曼滤波混沌拟合盲解调算法进行了简化, 在简化模型的基础上设计了接收机硬件结构. 提出了一种动态调整偏移因子的新方法, 使接收机能实时适应混沌映射的变化. 通过高斯白噪声信道及多径信道条件下的盲解调实验, 验证了盲解调算法硬件实现的抗噪声与抗多径性能, 以及对10种不同的混沌直接序列扩频信号的自适应破译效果.
关键词:
FPGA
混沌直接序列扩频通信
盲解调 相似文献
7.
对基于半导体光放大器(SOA)中非线性偏振旋转效应(NPR)效应的单一光缓存环多数据包的全光时隙交换(TSI)处理能力进行了理论和实验研究,在使用归纳法导出单一缓存环实现多数据包全光时隙(TSI)必要条件的基础上,针对各种全光TSI操作要求得出了相应光数据包的调度方案,在实验上,以基于SOA中NPR效应的单一光缓存环实验系统,开展了多数据包全光TSI操作的实验研究,根据上述光数据包理论调度方案进行相应系统参数设定,进行了速率为10 Gb/s的3个和4个数据包的全光TSI实验,实验结果与理论预期相符合,研究成果为减少昂贵SOA元件的用量、简化基于光缓存环全光TSI系统的结构提供了可靠依据,对推进全光TSI技术的发展具有重要意义。 相似文献
9.
以Fe粉为原料, 以金属Mo, Al和Ni可溶性盐作为添加剂, 通过浸渍法制备单金属添加和双金属添加的改性铁氧化物储氢材料Fe-Mo, Fe-Al, Fe-Mo-Ni和Fe-Mo-Al, 并研究了它们的储氢性能. 结果表明样品Fe-Mo改性效果最好: 如放氢温度由改性前的500 ℃降至改性后的290 ℃左右; 300 ℃时放氢速率最高, 由改性前的低于50 μmol•min-1• Fe-g-1到改性后的325 μmol•min-1•Fe-g-1 (10次平均); 4.53 wt%的平均实验储氢量与理论值4.8 wt%较接近; 储-放氢循环稳定性随着循环次数的增加呈逐渐增加的趋势. SEM微观结构和BET比表面积分析表明添加剂的种类对样品的改性作用更重要. 相似文献
10.
Hydrogen-bonding-induced planar, rigid, and zigzag oligoanthranilamides. Synthesis, characterization, and self-assembly of a metallocyclophane 总被引:1,自引:0,他引:1
Zhu J Wang XZ Chen YQ Jiang XK Chen XZ Li ZT 《The Journal of organic chemistry》2004,69(19):6221-6227
Four oligoanthranilamides 1-4, which are incorporated with three, five, seven, or nine benzene units, respectively, have been synthesized and characterized. X-ray analysis, 1D and 2D (1)H NMR, and IR experiments reveal that all the new oligoamides adopt rigid, planar and zigzagged conformations in both solution and solid state, which are stabilized by intramolecular three-center hydrogen bonding. A 5-mer oligomer 22, which is incorporated with two acetylene groups at the ends, has also been synthesized and utilized for the self-assembly of a rigid hydrogen-bonded metallocyclophane. The new rigid oligoanthranilamides represent useful building blocks for the construction of supramolecular architectures. 相似文献