一种新型的自基准哈特曼波前传感器

根据波前径向斜率测量原理,提出一种利用五棱镜扫描方法实现了新型自基准哈特曼波前传感器,其突出优点和特点是毋需任何外部信标或标准大平面反射镜提供工作基准。理论分析和实验结果表明,该传感器波前传感灵敏度与干涉仪相当,而对工作环境和光源并无苛刻要求,可用于天基主动光学系统、地基天文望远镜和大口径平行光管等的装校检验。     

Applying gray-scaled detour phase hologram on liquid crystal on silicon spatial light modulator (LCoS-SLM)

In order to solve the representation problem of computer-generated holograms, multiple algorithms have been devised. One of which is the well-known detour phase method. This method has recently been modified to be optimized to display the generated hologram on twisted nematic spatial light modulators. In this paper, we apply the modified gray-scaled detour phase holograms on another type of spatial light modulators, which is of utmost importance in the field, namely the reflective liquid crystal on silicon spatial light modulator.     

Frequency analysis of a wavefront curvature sensor: selection of propagation distance

The linear condition, spatial resolution and filter model of a curvature sensor are obtained by a brief and intelligible frequency analysis approach. The bounded interval of propagation distance is given by considering the linear condition and the noise in intensity measurement. The effects of nonlinearity and measurement noise on different frequency aberrations are discussed. We provide a guide to choose the propagation distance of a curvature sensor. The propagation distance should be large for low-frequency aberrations, which are greatly affected by the measurement noise, and small for high-frequency aberrations, which are greatly limited by the nonlinear effect. For a wavefront composed of various frequencies, it is important to select a proper propagation distance for less nonlinear effects and better noise suppression.     

Calibration and performance of a pyramid wavefront sensor for the eye

We describe the calibration and performance of a pyramid wavefront sensor designed for use in a retinal imaging camera. The effect of the image modulation and the sensor binning on the measurements are explained in detail and various tests to validate the performance are described. The wavefront sensor was incorporated into an adaptive optics system that used a magnetically actuated deformable mirror, and results on static test optics are shown.     

液晶空间光调制器相位调制特性研究

研究了美国BNS公司生产的Modal P256反射型电寻址液晶空间光调制器的相位调制特性和时间响应特性.采用He-Ne激光作光源,建立迈克尔孙干涉光路观察波前相位变化,给出器件的相位调制特性曲线.分析测量了器件的相位响应不一致性和像素间的相位交连.通过测量液晶器件对方波和正弦控制信号的相位响应延迟,分析了液晶空间光调制器(LC-SLM)的时间响应特性.理论分析与实验结果说明:在特定的入射偏振条件下,LC-SLM实现纯相位调制,可用作高分辨力波前校正器件,然而极慢的响应速度和极低的时间带宽限制了它在动态变化波前相差校正中的应用.     

哈特曼波前传感器的自动孔径搜索与匹配方法

为了使夏克-哈特曼波前传感器(SHWFS)能保证精度的同时又能获得更大的动态范围,介绍了一种用于SHWFS的自动子孔径搜索与匹配算法。该方法在实施时,先根据待测量图像计算背景阈值,然后以减阈值后的图像中心位置的一个光斑为参考光斑的参考中心,按图像的横、纵方向依次搜索其它光斑点,接着将搜索的结果拼接起来得到所有孔径的分布,最后根据两幅图像得到的各自的子孔径分布按横、纵方向平移进行配准,以达到最优的匹配结果。文中利用实验对本论文提出的方法进行了验证。结果表明,本文提出的方法能够实现SHWFS的子孔径搜索与匹配,提高哈特曼的动态范围。     

纱线张力传感器弹性体有限元分析及优化设计

弹性体的结构设计是纱线张力传感器设计的关键。通过建立纱线张力传感器弹性体的有限元模型,用有限元模态分析法对弹性体结构进行分析,得到弹性体结构的固有频率与振型。在计算机仿真环境下对弹性体结构进行优化设计,提高了弹性体结构的固有频率,从而使纱线张力传感器的稳定性得到提高。     

自适应降噪麦克风壳体声学有限元分析与设计

基于DSP技术的自适应主动降噪麦克风是近年来适应超高噪声下通讯应用而发展起来的麦克风技术。该技术依靠两个独立的无指向型传声元件实现降噪。这两个传声元件通常背靠背地封装在一起。根据自适应滤波理论,系统的降噪性能与这两个元件间对应背景噪声的空间相干函数及对应近场语音的传递函数有关。这两个函数又与麦克风封装壳体的几何设计直接相关。为优化降噪性能,建立了一个以有限元声学仿真为基础的,考虑声场特性及麦克风壳体几何形状的主动降噪性能的模型。依据此模型,提出了新型附加反射板的壳体设计方案。仿真和实验结果显示,相对传统壳体设计,有限元优化后的新方案可以提高麦克风降噪性能大于15dB,提高输出信噪比大于10dB。     

Subwavelength filter and sensor design based on end-coupled composited ring-groove resonator

A plasmonic filter and sensor is designed based on an end-coupled ring-groove composited resonator (RGCR). According to the magnetic field distributions of the resonance modes, a horizontal or vertical groove is added to the perfect ring resonator, and the transmission peaks for the 1st and the 2nd modes can be linearly changed by the length of the groove. In this case, the proposed structure can act as an on-chip optical filter with flexible wavelength manipulation. When the groove is rotated with an angle of π/4, Fano resonance arises due to the mode interference. Dual asymmetric sharp transmission peaks are achieved around the wavelength of the former 2nd resonance mode. High figure of merit and high sensitivity are obtained for the structure, and it is believed that the device can find widely applications in the biochemistry sensing area. The corresponding spectra and the propagation characteristics are numerically investigated by using the finite-difference time-domain method.     

Containers monitoring through the Physical Internet: a spatial 3D model based on wireless sensor networks

The Physical Internet concept was developed to address the current unsustainability problem of logistic systems. The key elements are the encapsulation and the handling of world-standard smart green modular containers (π-containers) throughout an open global logistic infrastructure. Logistic processes such as partial loading/unloading or splitting/merging of π-containers play an important role for a successful Physical Internet. However, the large variety of transformation processes can introduce desynchronisation between the physical and informational flows, i.e. the real composition of a composite π-container (a set of stacked π-containers) can differ of the information stored in the supply chain management system. To overcome this problem, this paper proposes a system to generate and maintain automatically a virtual three-dimensional layout reflecting the spatial distribution of π-containers. The proposed approach uses smart π-containers equipped with wireless sensor nodes. The relative position of π-containers can be determined by the neighbourhood relationships between the sensor nodes. From this information, a constraint set is formulated in a Constraint Satisfaction Problem where each solution is a potential loading pattern. The methodology is developed and computational experiments are proposed, as a proof-of-concept. The results show that our proposed method yields quick and satisfactory results.     

Propagation model and error analysis of an E-field sensor based on pockels effect and waveguide

Electric field measurement sensors based on the crystal Pockels effect are widely used. Currently, the development aims for electric field sensors are mainly focused on miniaturizing and integrating the sensor structure and improving measurement sensitivity and precision. The goal of this study was to analyse the sources of error in Pockels effect electric field measurement sensors, consider the mutual influence and accumulation effect of the various error factors, and establish a basic mathematical model of the measurement system with error components. Calculation and analysis were used to classify the function and change trend of several main errors, providing reference data for the structure design and error compensation of the sensor. The results show that the polarizing angle and the analyser angle have the same influence on assembly error. The inherent error is positively related to the electric field intensity. The periodic accumulation characteristic error under large electric field is also discussed. In order to avoid this error under an intense electric field, a suitable test electric field range was determined.     

基于均匀设计及非线性偏最小二乘法的非闭合电极ECT传感器参数优化设计

提出了一种非闭合电极电容层析成像(ECT)传感器结构参数的优化方法.采用均匀设计结合非线性偏最小二乘(NPLS)回归,提取传感器结构参数(电极极板的宽度 L、绝缘外壳的壁厚δ1.、屏蔽罩与绝缘外壳间距δ2及绝缘外壳材料的相对介电常数ε)与待优化指标(敏感场的均匀度及灵敏度指标p1、最大与最小电容的比值 K)间的函数关系,建立相应的优化目标泛函,通过对优化目标泛函的求解,最终获得传感器结构参数的最优值.并以 10 电极非闭合电极 ECT 传感器为研究对象,进行了结构参数的优化设计,根据优化结果设计制作了非闭合电极 ECT 传感器,对其成像进行了仿真与实测.结果表明,参数优化后的传感器图像重建质量优于未优化的传感器.     

SectionBuilder: An innovative finite element tool for analysis and design of composite rotor blade cross-sections

SectionBuilder is a finite element based tool for analysis and design of composite rotor blade cross-sections. The tool can create the cross-sections with parametric shapes and arbitrary configurations. It has the ability to generate single- and multi-cell cross-sections with arbitrary lay-ups where the material properties for each layer can be defined on the basis of the design requirements. It can create the variation of thickness of skin and D-spars for rotor blades by considering ply drops. Cross-sections are often reinforced by core material for constructing realistic rotor blade cross-sections. The tool has the ability to integrate core materials into the cross-sections. After meshing the cross-section, the tool determines the sectional properties using finite element analysis. This tool computes sectional properties including stiffness matrix, compliance matrix, mass matrix, and principal axes. A visualization environment is integrated with the tool for visualizing the stress and strain distributions over the cross-section. The detail about the development steps and application of SectionBuilder is presented in this paper.     

基于非线性本构关系的复合材料风机叶片有限元极限分析与设计

为了研究具有三维复杂构形的复合材料风机叶片的逐次破坏过程和极限承载能力, 将复合材料细观力学非线性本构理论桥联模型与有限元软件ABAQUS通过用户子程序UGENS结合起来对风力发电机叶片结构进行极限强度分析。只需提供纤维和基体的材料性能参数、 纤维体积含量以及蒙皮和增强筋的铺层数据包括铺设角、 层厚和铺层数, 就可预报出复合材料复杂叶片结构的整体承载能力以及叶片破坏所处的位置, 为正确评估和合理设计风机叶片结构提供了一种简便有效的分析方法。以一种20kW风机叶片为例, 用此方法实现了新型复合材料叶片结构的极限分析和合理设计, 提高了叶片的强度和刚度, 有效降低了叶片的重量。本文中的方法同样适用于其它复合材料复杂结构的极限分析与强度设计。      

采用国际标准的冷冻集装箱性能测试室的改进设计及分析

主要依据国际标准ISO1496-2及ATP协议(国际易腐食品运输及其运输专用装备的协议)改进设计并建造了一个用于冷冻集装箱热工性能测试的试验系统.通过与原试验系统的比较分析,完成了环境室空气处理方案设计、测试用制冷系统的更新配置及温湿度控制方法的调整,并顺利地进行了漏热试验与冷机试验的项目考核.     

A new discrete Kirchhoff-Mindlin element based on Mindlin-Reissner plate theory and assumed shear strain fields—part I: An extended DKT element for thick-plate bending analysis

This is the first of a two-part paper on plate bending elements with shear effects included. This paper presents a new three-node, nine-d.o.f. triangular plate bending element valid for the analysis of thick to thin plates. The element, called DKMT, has a proper rank (contains no spurious zero-energy modes), passes the patch test for thin and thick plates in an arbitrary mesh and is free of shear locking. Very good results have been obtained for thin and thick plates' by the element. An extended DKQ element for thick-plate bending analysis is evaluated in Part II.²⁴     

A new discrete Kirchhoff-Mindlin element based on Mindlin–Reissner plate theory and assumed shear strain fields—part II: An extended DKQ element for thick-plate bending analysis

This is the second part of a two-part paper on plate bending elements with shear effects included. This paper presents a new four-node, 12-d.o.f. quadrilateral plate bending element valid for the analysis of thick to thin plates. The element called DKMQ, has a proper rank (contains no spurious zero-energy modes), passes the patch test for thin and thick plates in an arbitrary mesh and is free of shear locking. Very good results have been obtained for thin and thick plates by the element. An extended DKT element for thick-plate bending analysis is evaluated in Part I.¹⁹     

An improved discrete Kirchhoff quadrilateral element based on third‐order zigzag theory for static analysis of composite and sandwich plates

A new improved discrete Kirchhoff quadrilateral element based on the third‐order zigzag theory is developed for the static analysis of composite and sandwich plates. The element has seven degrees of freedom per node, namely, the three displacements, two rotations and two transverse shear strain components at the mid‐surface. The usual requirement of C¹ continuity of interpolation functions of the deflection in the third‐order zigzag theory is circumvented by employing the improved discrete Kirchhoff constraint technique. The element is free from the shear locking. The finite element formulation and the computer program are validated by comparing the results for simply supported plate with the analytical Navier solution of the zigzag theory. Comparison of the present results with those using other available elements based on zigzag theories for composite and sandwich plates establishes the superiority of the present element in respect of simplicity, accuracy and computational efficiency. The accuracy of the zigzag theory is assessed by comparing the finite element results of the square all‐round clamped composite plates with the converged three‐dimensional finite element solution obtained using ABAQUS. The comparisons also establish the superiority of the zigzag theory over the smeared third‐order theory having the same number of degrees of freedom. Copyright © 2006 John Wiley & Sons, Ltd.     

Optimization of acyclovir oral tablets based on gastroretention technology: Factorial design analysis and physicochemical characterization studies

The purpose of this research was to prepare a floating drug delivery system of acyclovir. Floating matrix tablets of acyclovir were developed to prolong gastric residence time and increase its bioavailability. The tablets were prepared by direct compression technique, using polymers such as hydroxypropylmethylcellulose 4000, Compritol 888. Sodium bicarbonate was used as a gas-generating agent. A 3² factorial design using the Design Expert Software (version 7.1.6) was applied to optimize the drug release profile systematically. The amounts of hydroxypropylmethylcellulose 4000 (X₁) and Compritol 888 (X₂) were selected as independent variables and the percentage drug released in 1 (Q₁), 6 (Q₆), and 12 (Q₁₂) h as dependent variables. The results of factorial design indicated that a high level of both hydroxypropylmethylcellulose 4000 (X₁) and Compritol 888 (X₂) favors the preparation of floating controlled-release of acyclovir tablets. Also, a good correlation was observed between predicted and actual values of the dependent variables chosen for the study. By fitting the data into zero-order, first-order, and Higuchi models, we concluded that the release followed Higuchi diffusion kinetics. Storage of the prepared formulations at 40°C/75% relative humidity for 3 months showed no significant change in drug release profiles and buoyancy of the floating tablets. We can conclude that a combination of hydroxypropylmethylcellulose 4000, Compritol 888, and sodium bicarbonate can be used to increase the gastric residence time of the dosage form up to 12?h. These floating tablets seem to be a promising gastroretentive drug delivery system.