高效耗能黏弹性阻尼框架结构减震性能研究

提出了高效耗能黏弹性阻尼器,研究了该阻尼器对框架结构的减震机理。首先给出了高效耗能黏弹性阻尼器的结构构造,推导了小震、大震与巨震作用下的阻尼放大系数计算公式,由此分析了该放大系数的变化规律。此外,还推导了设置高效耗能黏弹性阻尼框架结构的等效阻尼比。分析表明,框架结构设置高效耗能黏弹性阻尼器在阻尼等效前后顶部位移反应时程曲线相差不超过10%。     

弓张式超磁致伸缩材料换能器的设计与分析

为了提高超磁致伸缩换能器的作动行程,以获得足够大的发音强度,并使之满足发音装置体积小、装配零件少的要求,结合超磁致伸缩材料（GMM）的优良特性,提出一种基于三角放大原理的弓张式GMM换能器。该换能器以GMM棒作为驱动元件,通过固定弓张结构的一端,将双向输出转变为单向输出,同时利用柔性铰链结构,进一步增大换能器的位移输出。通过分析换能器的工作原理,计算得到其理论放大倍数为2.73,与所建立的有限元仿真模型计算得到的放大倍数2.8相近。制作了试验样机并搭建了相应的试验系统,得到在1 kHz范围内换能器最大输出位移为15.5 m,与仿真结果14.058 m相近。提出的弓张结构实现了换能器的位移放大,相应的分析方法也较好地反映了换能器的输出特性。     

Development of variable‐magnification X‐ray Bragg optics

A novel X‐ray Bragg optics is proposed for variable‐magnification of an X‐ray beam. This X‐ray Bragg optics is composed of two magnifiers in a crossed arrangement, and the magnification factor, M, is controlled through the azimuth angle of each magnifier. The basic properties of the X‐ray optics such as the magnification factor, image transformation matrix and intrinsic acceptance angle are described based on the dynamical theory of X‐ray diffraction. The feasibility of the variable‐magnification X‐ray Bragg optics was verified at the vertical‐wiggler beamline BL‐14B of the Photon Factory. For X‐ray Bragg magnifiers, Si(220) crystals with an asymmetric angle of 14° were used. The magnification factor was calculated to be tunable between 0.1 and 10.0 at a wavelength of 0.112 nm. At various magnification factors (M≥ 1.0), X‐ray images of a nylon mesh were observed with an air‐cooled X‐ray CCD camera. Image deformation caused by the optics could be corrected by using a 2 × 2 transformation matrix and bilinear interpolation method. Not only absorption‐contrast but also edge‐contrast due to Fresnel diffraction was observed in the magnified images.     

放大反应-氯化钠增敏光度法测定食品中的微量碘

样品中的有机碘高温灰化后,在酸性条件下,经饱和溴水将I^-氧化为IO3^-.在0．06％的磷酸酸度条件下,以KI还原KIO3,使样品中的碘放大六倍。系统优化选择了定波长、磷酸酸度、氯化钠质量浓度、淀粉用量、碘化钾用量等。在选定的最佳实验条件下,碘质量浓度在0～3．2μg／mL范围旱良好线性关系,相关系数为0．9995;方法榆出限为0．028μg／mL,回收率为96．27％～106．43％。     

Micro-Expression Recognition Using Uncertainty-Aware Magnification-Robust Networks

A micro-expression (ME) is a kind of involuntary facial expressions, which commonly occurs with subtle intensity. The accurately recognition ME, a. k. a. micro-expression recognition (MER), has a number of potential applications, e.g., interrogation and clinical diagnosis. Therefore, the subject has received a high level of attention among researchers in affective computing and pattern recognition communities. In this paper, we proposed a straightforward and effective deep learning method called uncertainty-aware magnification-robust networks (UAMRN) for MER, which attempts to address two key issues in MER including the low intensity of ME and imbalance of ME samples. Specifically, to better distinguish subtle ME movements, we reconstructed a new sequence by magnifying the ME intensity. Furthermore, a sparse self-attention (SSA) block was implemented which rectifies the standard self-attention with locality sensitive hashing (LSH), resulting in the suppression of artefacts generated during magnification. On the other hand, for the class imbalance problem, we guided the network optimization based on the confidence about the estimation, through which the samples from rare classes were allotted greater uncertainty and thus trained more carefully. We conducted the experiments on three public ME databases, i.e., CASME II, SAMM and SMIC-HS, the results of which demonstrate improvement compared to recent state-of-the-art MER methods.     

光杠杆显示微小形变放大倍数的探讨

通过构建物理模型,利用几何知识和光的反射定律分析、探讨了光杠杆显示微小形变放大倍数计算的几种情况。     

地震作用下MSCSS控制优化参数研究

通过利用复模态分析法定义巨子型结构体系MSCSS(Mega-sub Controlled Structure System)的动力放大系数DMF(Dynamic Magnification Factor)表达式,取激励接近结构基频频段内的动力放大系数为指标,反映了结构各部分参数设置(质量比、刚度比、附加阻尼比及附加柱刚度比)对结构调频减震机理的影响。并采用最大最小化准则选取结构的最优参数范围,该分析法适用于分析不同巨层MSCSS的参数设置。     

潜在视功能检测仪光学参数特性的研究与优化

针对潜在视功能检测仪临床使用中量程有限和对高度屈光不正患者检测结果有一定误差的现象，研究了其光学系统成像特性，建立了系统对视力板成像的视觉放大率公式，分析了准直透镜、成像透镜焦距变化对视觉放大率的影响。系统中视力板移动检测时，准直透镜焦距影响视觉放大率变化快慢，决定视觉放大率曲线的平缓程度；成像透镜焦距对视觉放大率产生整体影响，使视觉放大率曲线产生整体平移。找出了系统的理想参数，能使视觉放大率在整个视力板移动范围内保持不变，消除了检测过程中视力板放大率不同带来的检测误差。通过对各参数的数值分析，得到最优参数，系统检测量程从原来的－7D～＋12D扩大为－11D～＋15D。     

Experimental Modal Damping Identification of a Mechanical Structure Using Video Magnification Technique

Vibration can be introduced in all mechanical fields in our life. Engineers try to avoid its negative effect leading in some cases to deformation in the machines. Many researches are dedicated to study the identification of damping especially in multi degree of freedom systems with particular attention to the source of energy dissipation. They focus on developing new tools or methods which may be used in real problems to obtain accurate results about the amount (or value) and the location of energy dissipation in the structure. The aim of this paper is to present an original procedure aims to experimentally determine the modal damping ratio of a mechanical structure. The proposed procedure consists of extracting the Frequency Response Function of the vibrating system using the video magnification method and then calculate the modal damping ratio using the 3-dB method. These experimental measurements are carried out by giving an external force on a cantilever beam, then the modal damping ratios are extracted using motion magnification. The obtained results show a relative error less than 4.2% between the experimental measurements and the analytical calculation for the Frequency Response Function (FRF) curves. The novelty of the paper is to combine the video magnification technique and the 3dB method in a procedure that aims to experimentally measure the modal damping of a mechanical structure. The proposed procedure in this paper represents the damping identification as a simple and easy engineering application.     

WELD ROOT MAGNIFICATION FACTORS FOR SEMI-ELLIPTICAL CRACKS IN T-BUTT JOINTS

Many researchers have focused their efforts on fatigue failures occurring on weld toes. In recent years, more and more fatigue failures occur on weld roots. Therefore, it is important to explore the behaviour of weld root fatigues. This paper investigates numerically the Magnification factors (Mk) for types of semi-elliptical cracks on the weld root of a T-butt joint. The geometry of the joint is determined by four important parameters: crack depth ratio, crack shape ratio, weld leg ratio and weld angle. A singular element approach is used to generate the corresponding finite element meshes. For each set of given four parameters of the semi-elliptical root crack, the corresponding T-butt joint is numerically simulated and its Mk at the deepest point of the weld root crack is obtained for the respective tension and shear loads. The variation range of the four parameters covers 750 cases for each load, totaling 1500 simulations are completed. The numerical results obtained are then represented by the curve to explore the effects of four parameters on the Mk. To obtain an approximate equation representing Mk as a function of the four parameters for each load, a multiple regression method is adopted and the related regression analysis is performed. The error distributions of the two approximate equations are compared with the finite element data. It is confirmed that the obtained approximate functions fit very well to the database from which they are derived. Therefore, these two equations present a valuable reference for engineering applications in T-butt joint designs.