Vibration behaviors of a box-type structure built up by plates and energy transmission through the structure

The vibration behaviors of a box-type built-up structure and energy transmission through the structure are investigated analytically. The modeling of the structure is developed by employing the improved Fourier series method and treating the structure as four elastically coupled rectangular plates. The general coupling and boundary conditions are accounted for using the artificial spring technique and can easily be obtained by assigning the springs with corresponding values. The exact double Fourier series solutions considering both the flexural and in-plane vibrations are obtained by using the Rayleigh–Ritz approach, which are validated by comparison with the Finite Element Method (FEM) results. Since the modification of any parameter in this analytical model from one case to another is as simple as modifying the material properties, and does not involve any change to the solution procedures, thus this will make a parametric study and further mechanism analysis easier compared to most existing procedures. Subsequently, special attention is focused on the energy transmission and mechanism of the box-type structure by structural intensity analysis. Numerical analyses cover several important parameters including symmetrical and non-symmetrical coupling conditions and the excitations, and three types of models, namely the rigidly, elastically and weakly coupled models are involved. The results of the power flow and structural intensity are presented to obtain a clear physical understanding of the physical mechanisms of energy transmission. It is shown that the energy transmission behaviors can be significantly influenced by the coupling conditions and location of the excitation as well as the excitation frequency. Some unexpected interesting phenomena on the energy transmission were revealed, especially for the non-symmetrical model, and the corresponding mechanisms were interpreted. This study provides new and interesting insights into the vibration behaviors and energy transmission of the class of built-up box-type structure.     

Optimization of ultrasound-assisted extraction (UAE) of flavonoids compounds (FC) from hawthorn seed (HS)

Hawthorn seed (HS), an important by-product of the Hawthorn industry, is rich in potentially health-promoting flavonoids compounds. In this paper, the ultrasound-assisted extraction (UAE) of FC from HS was investigated. Important variables and their levels were obtained using Plackett-Burman (PB) design and Box-Behnken (BB) design. A mathematical model was developed to show the effects of each variable and their combinatorial interactions on extraction yield of FC. A high coefficient of determination (R² = 91.26%) indicated good agreement between the experimental and predicted values of FC yield. The optimum levels of these significant parameters were determined using response surface methodology (RSM), which revealed these as follows: ultrasound temperature 65 °C, ultrasonic time 37 min, extraction temperature 91 °C, extraction time 1.5 h, solid-liquid ratio of 1:18, and 72% ethanol. Under the optimum condition, the UAE rate of FC was up to 91.7%, and the yield of FC was 16.45 ± 0.02 mg/g (P < 0.05) that was 1.32-fold the yield of conventional reflux extraction (CRE).     

Theoretical analysis of feedback high birefringence fiber loop mirror for application in single-frequency fiber lasers

A feedback high birefringence fiber loop mirror with a piece of erbium-doped fiber and a polarization controller is newly proposed. When the erbium-doped fiber is properly pumped to offset the loss of the feedback ring in the loop mirror, narrowband transmission peaks with large effective free spectral range can be achieved by the intrinsic vernier effect between orthogonally polarized lights respectively traveling along the two primary axes of the high birefringence fiber. In addition, the side transmission suppression ratio can reach about 6 dB. These special properties are independent of the polarization state of the input signal, which makes it feasible for the proposed feedback high birefringence fiber loop mirror to be employed as a narrowband filter in single-frequency fiber lasers.     

基于PXI总线高速图像采集显示系统设计

为解决高速Camera Link数据视频图像信号的采集与显示问题,提出了以PXI系统为平台,利用FPGA强大的并行处理能力及内部丰富的块RAM资源,模块化设计PXI接口模块,Camera Link数据接收模块,SDRAM缓存模块及VGA显示控制模块,同时利用FPGA构造出相应的VGA时序信号,控制视频转换芯片ADV7123实现两路图像数据的图形显示的系统设计。试验结果表明,该系统可实现输入100MB/s图像数据的实时显示,达到了预期的效果,具有一定的实用性和推广价值。     

Montmorillonite K10 Clay: An Effective Solid Catalyst for One‐Pot Synthesis of Polyhydroquinoline Derivatives

An efficient one‐pot four‐component coupling process for the synthesis of polyhydroquinoline derivatives catalyzed by montmorillonite K10 clay is described. This procedure has such advantages as short reaction time, high yields, and simple workup. The catalyst could be reused several times and keeps its initial activity in the recycle reactions.     

Rh(III)-catalyzed oxidative olefination of N-(1-naphthyl)sulfonamides using activated and unactivated alkenes

Rhodium(III)-catalyzed oxidative olefination of N-(1-naphthyl)sulfonamides has been achieved at the peri position. Three categories of olefins have been successfully applied. Activated olefins reacted to afford five-membered azacycles as a result of oxidative olefination-hydroamination. Unactivated olefins reacted to give the olefination product. 2-fold oxidative C-C and C-N coupling was achieved for allylbenzenes.     

三维编织复合材料几何建模及数值分析

论文根据三维编织复合材料的结构特点,把整体结构分为内部单胞、表面单胞和角单胞三种类型的子单胞,考虑空间纤维束的相互扭结和挤压所造成的纤维束的弯曲和截面变形,针对每种类型的子单胞,建立了相应的几何分析模型.引入周期性位移边界条件,建立了材料的弹性性能预报模型,得到了三维编织复合材料的工程弹性常数.通过数值比较可以看出,论文所给出的数值计算结果与实验结果吻合较好,从而验证了本文模型的有效性.     

In vivo comparison of the optical clearing efficacy of optical clearing agents in human skin by quantifying permeability using optical coherence tomography

The objective of this work is to quantify and compare the optical clearing efficacy of glucose, propylene glycol, glycerol solutions through the human skin tissue in vivo by calculating permeability coefficient of three solutions. Currently, the permeability coefficient of agent in tissues was extracted from optical coherence tomography (OCT) amplitude data mainly through the OCT signal slope and the OCT amplitude methods. In this study, we report the OCT attenuation coefficient method which is a relatively novel and rarely reported methodology to measure the permeability coefficient during the optical skin clearing procedure. The permeability coefficients for 40% propylene glycol, glucose and glycerol were (2.74 ± 0.05) × 10(-6) cm s(-1), (1.78 ± 0.04) × 10(-6) cm s(-1) and (1.67 ± 0.04) × 10(-6) cm s(-1), respectively. It could be clearly seen that the permeability coefficient of the 40% propylene glycol solution is higher than that of 40% glucose solution, and the permeability coefficient of the 40% glucose solution is higher than that of the 40% glycerol solution. These indicate 40% propylene glycol solution is more effective than others in the human skin in vivo. We then compare and prove consistency of optical clearing efficacy figured out by three different methods.     

Time domain finite volume method for the transient response and natural characteristics of structural-acoustic coupling in an enclosed cavity

A time domain finite volume method（TDFVM）based on wave theory is developed to analyze the transient response and natural characteristics of structural-acoustic coupling problems in an enclosed cavity.In the present method,the elastic dynamic equations and acoustic equation in heterogeneous medium are solved in solid domains and fluid domains respectively.The structural-acoustic coupling is implemented according to the continuity condition of the particle velocity along the normal direction and the normal traction equilibrium condition on the interface.Several numerical examples are presented to validate the effectiveness and accuracy of the present TDFVM.Then the effects of water depth on the acoustic and vibration characteristics and the natural characteristics of a structural-acoustic coupling system are analyzed.The numerical results show that the increase of water depth leads to a stronger coupling between the water and structure and the decrease of natural frequencies of coupling system,The computational cost and memory of this method are small and it can be applicable to structural-acoustic coupling problems in the heterogeneous fluid.