Effects of the deformation of reflection volume Bragg gratings on the M-factor of super-Gaussian laser beams

When high-power laser beams pass through a volume Bragg grating (VBG), the surface of VBG occurs distortion because of thermal effects, and it results in the decline of the grating’s performance. Considering distortion of the surface induces differences of the index and period, the scalar wave equations for super-Gaussian (SG) laser beams propagating in the reflection VBG have been solved by using finite-different and sparse matrix methods. The changes of the total power reflection coefficient, the beam width, the far-field beam angle and the M²-factor for the laser beams through the reflection VBG with deformation have been analyzed quantitatively. It can be shown that the deformation of the VBG affects evidently on the intensity and phase distributions, the total power reflection coefficient, the beam width, the far-field divergence angle and the M²-factor. The beam width, the far-field divergence angle, and the M²-factor of the output beams increase significantly with the distortions of the grating. The influence of the distortions of the VBG on the power reflection coefficient, the far-field divergence angle and the M²-factor of the output beams are smaller for higher beam orders.     

超声辐射下水介质中三组分一锅合成吡喃并[2,3-d]嘧啶衍生物

报道了在超声波辐射下, 水相中无催化剂下通过芳香醛与丙二腈、巴比妥酸的一锅反应, 合成了一系列吡喃并[2,3-d]嘧啶衍生物. 在超声波辐射下, 不仅饱和芳香醛与丙二腈、巴比妥酸的一锅反应在室温下能高收率地进行, 而对于α,β-不饱和醛以及二元醛与丙二腈、巴比妥酸的一锅反应也能在室温下顺利进行, 获得较高的收率. 产物的结构通过IR, 1H NMR和元素分析表征. 该方法具有操作简单和环境友好等优点.     

Silicon nano crystal filled ellipse core based quasi photonic crystal fiber with birefringence and very high nonlinearity

In this paper, we have proposed a new type of quasi photonic crystal fiber (PCF) with a silicon nano crystal core. This structure can be used to sense aqueous analysis over a wavelength range of 1.00?µm to 3.00?µm. The properties of this structure are simulated using the vector-finite element method (VFEM) employing a boundary condition. The proposed model provides a significant effect of birefringence and a very high nonlinear coefficient for two different fundamental modes, which are obtained by adjusting the size of the silicon nano crystal filled ellipse core. This provides a high nonlinearity of 4.2?×?10⁵ W^?1Km^?1 and a birefringence of ? 3.2?×?10^?1 at the wavelengths 1.00?µm and 3.00?µm, respectively. Some others properties, such as the effective area, scattering loss, confinement loss, numerical aperture (NA)and power fraction are also analyzed to measure the performance of this structure. The proposed model is useful for sensing and biomedical imaging applications. The proposed structure may also find extensive applications in optical communication and sensor systems.     

Standing wave brass-PZT square tubular ultrasonic motor

This paper reports a standing wave brass-PZT tubular ultrasonic motor. The motor is composed of a brass square tube with two teeth on each tube end. Four PZT plates are attached to the outside walls of the brass tube. The motor requires only one driving signal to excite vibration in a single bending mode to generate reciprocating diagonal trajectories of teeth on the brass tube ends, which drive the motor to rotate. Bi-directional rotation is achieved by exciting different pairs of PZT plates to switch the bending vibration direction. Through using the brass-PZT tube structure, the motor can take high magnitude vibration to achieve a high output power in comparison to PZT tube based ultrasonic motors. Prototypes are fabricated and tested. The dimension of the brass-PZT tube is 3.975 mm × 3.975 mm × 16 mm. Measured performance is a no-load speed of >1000 RPM, a stall torque of 370 μNm and a maximum output power of 16 mW when a sinusoidal driving voltage of 50 V is applied. The working frequencies of the motor are 46,050 Hz (clockwise) and 46,200 Hz (counter-clockwise).     

Changes in mechanical properties of impregnated Nomex papers 410 and 910 during accelerated aging

New materials are currently being developed for applications in transformer design. With the useful life of transformers now determined by solid insulation conditions, a better understanding of aging kinetics is important in order to improve electrical system management and planning from the technical and economic points of view. This paper summarizes an investigation of the effects of impregnating aramid and cellulose/aramid papers (Nomex 410 and 910) with insulation fluids (Nynas Polaris and Luminol Tri) at thermally accelerated conditions (170 °C) on their mechanical properties.It was found that Nomex 410 (100% aramid) showed only a small change in tensile strength (~5% decrease) after accelerated aging (around 7500 h). However, its elongation capacity was significantly reduced (~45–70% decrease for dry and wet Nomex 410, respectively) by the end of the aging process, probably due to hydrolysis. In addition, the interaction between water and aramid hydrogen bonds at high temperatures produced the rupture and then, the randomly rebuilt of these bonds in meta-aramid fibres, thereby reducing its plastic deformation capacity.In the case of Nomex 910 (aramid enhanced cellulose), its mechanical properties were maintained for a longer time than those of thermally upgraded Kraft paper (TUK), as measured by the retained percentage of tensile index. However, when the tensile index was used instead of the retained percentage, TUK showed a higher tensile index value than Nomex 910 during the initial stage, while the values for both papers became similar during the second stage. It is only at the end of the aging process that Nomex 910 presented an advantage over TUK paper due to the addition of the aramid fibres.It was also found that the inception fractures in Nomex 910, as a fibrous layered composite paper, start in the weakest part of the composite, probably in the central cellulose layer. The fracture line follows the weakest path, avoiding the aramid fibres.The results presented in this paper can be used as a benchmark for improving our understanding of aging and changes in the mechanical properties of these relatively new materials used in the solid insulation of power transformers. A better understanding of the aging characteristics (thermal degradation) of aramid-based papers should help better assess the condition of the new generation of power transformer fleets.     

基于LabVIEW的便携式锚杆长度检测系统开发

基于LabVIEW软件平台开发了便携式锚杆长度检测系统。该系统包括一个带有信号激励接收功能的便携式工控机、探头和上层控制软件。首先通过软件设置硬件参数,TB-1000信号激励接收卡在探头上激励出超声导波信号并采集反射回波,经模拟滤波器处理后进入NIPCI-5102数据采集卡,将模拟信号转换为数字信号输入PC计算机。本系统软件可对激励接收卡设置激励信号参数,并具有对采集到的信号进行频域变换、希尔伯特变换、小波降噪、快速傅利叶变换(STFT)、扫频成像等处理功能。通过实验,证明了该软件系统具有较高的实时性和可操作性,较好地实现了锚杆长度的快速检测,扩大了超声导波在此领域的应用。     

Computerized ultrasonic tomography for testing solid propellant rocket motors

Certain types of defects, such as inhomogeneities in, for example, a plastic-like propellant, are not easily detected by pulse-echo techniques, so a through transmission technique is required. However, the shape of the test object may not permit transmission through the object in any required direction as is normally necessary for computerized ultrasonic tomography.A solid propellant rocket motor is such an object and in the course of this work a scanning technique is employed together with a suitable reconstruction algorithm to obtain a reconstructed image of the cross-section under investigation, overcoming the problem of not being able to transmit pulses through the object along every line normally required. Both a computer simulation and a real system were realized for the test object and images were produced from both. The time of flight of an ultrasonic beam through the specimen is the parameter used in the reconstruction (sound velocity measurement).     

GC-MS法快速测定铅笔涂层中18种光引发剂

建立了快速测定铅笔涂层中18种光引发剂的气相色谱-质谱联用法(GC/MS).样品以二氯甲烷为提取溶剂,在30℃温度下,超声提取30 min后,萃取液用100 mg N-丙基乙二胺(PSA)分散固相萃取净化,以气相色谱-质谱法(GC-MS)测定,外标法定量.18种光引发剂在0.2～4.0 mg/L(或0.1～4.0 mg...     

The deviation factor and divergences in quantum electrodynamics,concrete examples

We consider the divergences in quantum electrodynamics. Our approach is based on ideas from the theory of generalized wave operators. In particular, we use the concept of the deviation factor. The deviation factor characterizes the deviations of the initial and final waves from the free waves. The approach is demonstrated on important examples.     

Green and rapid synthesis of dihydropyrimido [4,5‐b]quinolinetrione derivatives using CoFe2O4@PPA as high efficient solid acidic catalyst under ultrasonic irradiation

A new high efficient and green protocol for the preparation of dihydropyrimido[4,5‐b]quinolinetrione derivatives using magnetically solid acid catalyst was presented. High performance solid acid catalyst was prepared through a three‐step reaction. Firstly, CoFe₂O₄ nano particles were synthesized using co‐precipitation method. In second step, CoFe₂O₄ nano particles were coated with SiO₂ shell through treatment with tetraethyl orthosilicate (CoFe₂O₄@SiO₂). Finaly, CoFe₂O₄@SiO₂ was modified with polyphosphoric acid (CoFe₂O₄@SiO₂/PPA) in a simple manner. Green reusable catalyst was characterized in details using FTIR, VSM, TEM, FESEM, EDX and used as catalyst for the synthesis of dihydropyrimido[4,5‐b]quinolinetrione derivatives. Reaction was performed under ultrasonic irradiation as green, effective and mild conditions and products were achieved in high to excellent yields. Green and eco‐friendly conditions, short reaction times with high yield of products in addition to easy workup are some merits of presented method.