Ab initio study of the structure of 2,2-difluoroethanal in the ground and lowest excited triplet electronic states

The molecular structure of 2,2-difluoroethanal (DFE) in the ground (S₀) and lowest excited triplet (T_i) electronic states was investigated byab initio quantum-chemical methods. In the S₀ state, the DFE molecule exists as the only stablecis conformer. The T_i↓S₀ electronic excitation is accompanied by the rotation of the top and the deviation of the carbonyl fragment from planarity. For the DFE molecule in the T_i state, six minima corresponding to three pairs of enantiomers were found on the potential energy surface. Based on this potential energy surface, the problems on torsion and inversion nuclear motions were solved in the one- and two-dimensional approximations, and the interaction between these motions was revealed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 989–995, June, 2000.     

基于加速度响应控制时MTMD的地震特性

研究了由多个刚度和阻尼保持为常量且频率呈线性分布的TMD形成的MTMD的地震特性。基于虚拟激励法和Kanai Tajimi及Clough Penzien地震谱 ,建立了结构 MTMD系统的加速度传递函数 ,进而导出了设置MTMD时结构的加速度动力放大系数 (ADMF)明确表达式。于是MTMD的优化准则选择为 :结构最大加速度动力放大系数的最小值的最小化 [Min .Min .Max .ADMF]。通过最优搜寻得MTMD的最优频率间隔、平均阻尼比、调谐频率比和相应的控制有效性指标。选择结构受控频率与地震卓越频率比的不同取值 ,研究地震卓越频率对MTMD最优参数及有效性的影响     

摩擦振动信号谐波小波包特征提取

在销-盘摩擦磨损试验机上进行了船用柴油机缸套-活塞环摩擦配副摩擦磨损试验,应用谐波小波包变换分析了不同磨损状态下的摩擦振动信号.结果表明:谐波小波包变换可提取微弱的摩擦振动特征.当磨损机制为轻微的黏着磨损时,摩擦振动信号的频谱以边频为主,没有明显的固有频率,平均幅值小;当磨损机制以磨粒磨损为主时,摩擦振动信号的频谱出现较大峰值的固有频率,但仍存在大量的边频,平均幅值变大;当磨损机制以疲劳磨损为主时,摩擦振动信号频谱的固有频率更加明显,边频显著减弱,平均幅值最大.因此,谐波小波包变换可实现微弱摩擦振动信号的特征提取.     

Synthesis and photophysical studies of heteroaryl substituted-BODIPy derivatives for biological applications

Mono and di-heteroaryl-4,4′-difluoro-8-(aryl)-4-bora-3a,4a-diaza-s-indacene (BODIPy) (1–5) were synthesized using Suzuki–Miyaura couplings. Hetero aryl substitution on 3- or 3,5-positions caused large bathochromic shifts (up to ∼150 nm) in absorption (569–652 nm) and fluorescence maxima (586–679 nm) in comparison to classical BODIPy. Quantum yields were found to be as high as 0.65. Singlet oxygen production activities of these compounds were studied by monitoring the absorbance quenching of 1,3-diphenylisobenzofuran, on exposure to light (>600 nm). Cellular uptake of compound 4 was demonstrated using cervical cancer cells and fibroblast cell line and was confirmed by the images obtained using confocal microscope.     

Bionomic exploitation of a ratio-dependent predator–prey system

The present article deals with the problem of combined harvesting of a Michaelis–Menten-type ratio-dependent predator–prey system. The problem of determining the optimal harvest policy is solved by invoking Pontryagin's Maximum Principle. Dynamic optimization of the harvest policy is studied by taking the combined harvest effort as a dynamic variable. Computer simulations are carried out to illustrate our analytical findings. Biological and bioeconomical interpretations of the results are explained critically.     

(Vapour + liquid) equilibrium data for the {1,1-difluoroethane (R152a) + 1,1,1,3,3-pentafluoropropane (R245fa)} system at temperatures from (323.150 to 353.150) K

In this paper, (vapour + liquid) equilibrium (VLE) for the {1,1-difluoroethane (R152a) + 1,1,1,3,3-pentafluoropropane (R245fa)} system was determined by a static-analytical method at T = (323.150 to 353.150) K. Values of the VLE were correlated by the Peng–Robison equation of state (PR EoS) using two different models, the van der Waals (vdWs) mixing rule and the Huron–Vidal (HV) mixing rule involving the non-random two-liquid (NRTL) activity coefficient model. The correlated results show good agreement with the experimental values. For the two models, the maximum average absolute deviations of the vapour phase mole fraction are 0.0034 and 0.0035, respectively.     

集中载荷作用下不同边界条件的弯曲厚矩形板的受迫振动

运用边界积分法研究了四边简支、两对边固定另两对边简支、四边固定三种复杂边界条件下厚矩形板的受迫振动问题,求解过程清晰,从而给出了受迫振动控制方程和挠曲面方程。通过在Matlab平台上进行数值计算,得出了图表形式的计算结果,并与有限元模拟值进行对照。研究表明,边界积分法用于求解厚矩形板的受迫振动问题的准确性,本文推导的控制方程和挠曲面方程的正确性,进而对工程实际中的各种相关问题具有一定的现实意义,也为求解此类问题提供了一种新途径,可以直接运用到工程实际中。