One- and two-photon absorption properties of two metalloporphyrin complexes

The linear and nonlinear optical properties of two metalloporphyrin complexes formed by the complementary coordination of central zinc or magnesium ions to the ligand 5, 10, 15-tri-(p-tolyl)-20-phenylethynylporphyrin are theoretically investigated by using the analytic response theory at the density functional theory level. The results indicate that the studied complexes present more symmetric geometry structures than the ligand. The charge-transfer states of the two complexes in the lower energy region are all almost degenerate but those of the ligand are well separated. The ratio of the two-photon absorption cross sections of the ligand, zinc-porphyrin and magnesium-porphyrin complexes is 1.0:1.5:1.8, demonstrating that the two-photon absorption capability can be greatly increased when the ligand is coordinated with a metal ion. Moreover, several physical micro-mechanisms including electron transitions and intramolecular charge-transfer processes are discussed to explore the differences in optical property between the ligand and two complexes.     

LABVIEW下冲击试验测试信号分析模块的设计

根据GJB冲击环境试验测试要求,介绍LABVIEW平台下两类典型冲击信号分析模块的设计方法,主要讲述利用多图层叠加编程技术实现GJB150.18-1986标准规定的半正弦波与后峰锯齿波动态套容差曲线分析模块的设计以及利用递归算法实现冲击响应谱分析模块的设计。其次,采用资源DLL封装技术对LABVIEW编程实现的冲击信号分析模块进行封装,在其他编程语言中调用DLL实现冲击信号分析模块在其他编程语言中的功能链接。实践表明,LABVIEW图形化编程技术可快速实现两类冲击信号分析模块的设计,将高速数据采集模块与冲击信号分析模块集成,可有效完成冲击试验测试与信号分析处理任务。     

Separate spatial soliton pairs in a biased series centrosymmetric photorefractive crystal circuit

It is shown theoretically that three types of separate soliton pairs: bright-bright, bright-dark, and dark-dark, can be established in a biased series circuit consisting of two centrosymmetric photorefractive crystals and the two solitons in a separate soliton pair can affect each other by the light-induced current. The effects of the intensities of soliton beams and background lights on the normalized profiles of solitons are discussed.     

Film thickness dependence of electro-optic effect in epitaxial BaTiO3 thin films

Based on the phenomenological Landau-Devonshire theory, we investigate the film thickness dependence of ferroelectric and electro-optic properties of epitaxial BaTiO₃ thin films grown on SrTiO₃ and MgO substrates. By using the effective substrate lattice parameter concept, the film thickness dependence of misfit strain is incorporated into the theory. Therefore, the film thickness dependence of ferroelectric and electro-optic properties in epitaxial BaTiO₃ thin films can be explained. Moreover, a large quadratic electro-optic effect was obtained in the BaTiO₃ thin films, which is in good agreement with the experimental result of BaTiO₃ thin films on the MgO substrate.     

Effect of Al3+ substitution on structural,cation distribution,electrical and magnetic properties of CoFe2O4

We present the structural, cation distribution, electrical and magnetic studies of CoAl_xFe_2−xO₄ (x = 0.0, 0.2, 0.4, 0.6, 0.8) ferrites. The Rietveld-fitted X-ray diffraction (XRD) patterns confirm the formation of single-phase cubic spinel structures with $Fd\overline{3}m$ space group for all the samples. A comprehensive analysis of XRD-based cation distribution has been performed to see the effect of Al³⁺ ions substitution on various structural parameters such as site ionic radii, edge length, bond length and interionic distances. The dielectric constant and direct current (DC) conductivity decreases with increasing Al³⁺ substitution up to x = 0.4. However, with further increase in Al³⁺ substitution, both the dielectric constant and the DC conductivity increase. The presentation of dielectric data in the complex electric modulus form reveals the presence of a non-Debye-type relaxation behaviour in the considered ferrites. The power law behaviour of alternating current (AC) conductivity indicates a strong correlation among electrons in these systems. The isothermal magnetisation versus applied field curves with high-field slope and significant coercivity suggest that the studied materials are highly anisotropic with canted spin structures. The samples exhibit ferrimagnetic behaviour at 300 K and the magnetisation decreases with increasing Al³⁺ concentration. The as-prepared samples are promising candidates for various industrial applications.     

Study and optimization of the ultrasound-enhanced cleaning of an ultrafiltration ceramic membrane through a combined experimental–statistical approach

Membrane fouling is one of the main drawbacks of ultrafiltration technology during the treatment of dye-containing effluents. Therefore, the optimization of the membrane cleaning procedure is essential to improve the overall efficiency. In this work, a study of the factors affecting the ultrasound-assisted cleaning of an ultrafiltration ceramic membrane fouled by dye particles was carried out. The effect of transmembrane pressure (0.5, 1.5, 2.5 bar), cross-flow velocity (1, 2, 3 m s⁻¹), ultrasound power level (40%, 70%, 100%) and ultrasound frequency mode (37, 80 kHz and mixed wave) on the cleaning efficiency was evaluated. The lowest frequency showed better results, although the best cleaning performance was obtained using the mixed wave mode.A Box–Behnken Design was used to find the optimal conditions for the cleaning procedure through a response surface study. The optimal operating conditions leading to the maximum cleaning efficiency predicted (32.19%) were found to be 1.1 bar, 3 m s⁻¹ and 100% of power level.Finally, the optimized response was compared to the efficiency of a chemical cleaning with NaOH solution, with and without the use of ultrasound. By using NaOH, cleaning efficiency nearly triples, and it improves up to 25% by adding ultrasound.     

Annihilation and creation of rotating waves by a local light pulse in a protoplasmic droplet of the Physarum plasmodium

Pattern dynamics plays a fundamental role in biological functions from cell to organ in living systems, and the appearance of rotating waves can lead to pathological situations. Basic dynamics of rotating waves of contraction-relaxation activity under local perturbation is studied in a newly developed protoplasmic droplet of the Physarum plasmodium. A light pulse is applied by irradiating circularly a quarter of the droplet showing a single rotating wave. The oscillation pattern changes abruptly only when the irradiation is applied at a part of the droplet near the maximal contraction. The abrupt changes are as follows: the rotating wave disappears or is displaced when the irradiation area is very close to the center of the rotating wave, while new rotating waves are created when the irradiation area is far from the center of the rotating wave. These results support the hypothesis that the phase response curve has a discontinuous change (type 0 resetting) from delay to advance around the maximal contraction. The significance of the results is discussed in relation to “vulnerability” in excitable media and biological systems in general.     

Time-domain sweeplets for acoustic measurements

This paper proposes new types of time-domain generated sine sweeps for impulse response measurements. A general time-domain analytical formulation method, combined with numeric phase alignment and frequency-domain inverse filtering is presented. It is applied to derive three new families of controllable spectrum sine sweeps called sweeplets, capable of matching 1/f^β background noises, producing finite band defocusing and single frequency focusing shapes. Mathematical properties concentrating on practical control of the signal shapes are examined. Effects of various perturbations, such as stationary and transient background noise, harmonic distortion and finite length are presented. Applicability of the proposed method is experimentally verified by a room acoustic measurement example.     

高感度辐射变色薄膜电子剂量计

 以聚乙烯醇缩聚物为基质,以类丁二炔化合物为有机染色材料,研制了一种高灵敏度新型辐射变色膜。采用JJ-2型范格拉夫静电加速器对变色薄膜进行剂量范围为15～90 Gy的电子束辐照,结果显示:变色薄膜颜色由粉红渐变为蓝色,并随着辐照剂量的增加而逐渐加深;分光光度计测试其吸收光谱,发现主吸收峰值出现在675 nm附近,且吸收峰处的响应吸光度与电子注量具有较好的线性关系;对变色层厚度为20～80 μm的变色膜,吸收峰处的响应吸光度与其变色层厚度也成线性关系;添加不同比例的协同剂,能提高变色薄膜的响应灵敏度;变色膜辐照后续效应微弱,辐照后可以立即测量,且对测量环境变化不敏感。     

Coupling resonance of floating slab and supporting concrete box structure

This paper mainly investigates the effect of coupling resonance of floating slab and supporting short concrete box. The similarities and differences in vibration behaviors between long (30 m) and short (1.5 m) lengths of concrete box structures with the same cross-section were analyzed with finite element model (FEM). The results suggest that the major local modes for vibration and structure-borne sound radiation for long and short box structures are the same. A short concrete hollow box was constructed to verify the theoretical vibration results, and six combinations of floating slabs were installed on the box to identify the vibration and structure-borne sound control by experimental method. The resonance modes due to either concrete box or floating slab should degrade the vibration isolation performance of the floating system. There may be strong coupling between roll mode (rigid body rotation mode in the y-z plane) of the floating slab and local distortion mode of the short box structure and this can change the vibration resonance frequencies and amplify the vibration.