利用热释电红外传感器探测人体运动特征

热释电红外(PIR)传感器探测人体发出的红外辐射,在有效探测范围内可实现运动人体的检测.由于它的低成本低功耗,在入侵检测及自动照明控制等方面有广泛的应用.本文对用这种传感器提取人体行走时的运动特征进行了研究.人作为动态的分布式的红外源由体貌特征及步态特征所决定,利用探头表面安装有菲涅耳透镜的PIR传感器得到时域电压信号,对信号的频谱特性进行分析来解析人体的运动特征.采用主成分分析方法对不同个体不同速度的数据进行分类,探讨了这种方式应用于人体运动特征信息的提取及分类识别的可行性.实验结果表明,不同的人以不同的速度步行的频谱数据足以用来分类识别,为安全级别较低场所的人体身份识别提供了一种低成本的方案.     

利用电子鼻技术鉴别棉织物的异味

利用PEN3电子鼻分别对带有鱼腥味、煤油味、霉味、香水味、芳香烃味以及正常的纯棉织物进行了检测,并利用样品雷达图对各种样品进行了鉴别。采用主成分分析法(PCA)和线性判别分析法(LDA)进行数据分析,结果表明电子鼻可以有效区分棉织物中的各种异味。     

利用ANSYS软件分析悬臂起重机金属结构的应力

由于定柱旋臂起重机的几何结构和载荷比较复杂,在传统的设计和选型过程中,只根据经验来确定其参数,缺乏精确的强度计算,从而安全系数取得过大。本文利用有限元分析软件ANSYS ,以BZD2 - 4×5A4型旋臂起重机为例,对其金属结构进行数值模拟分析,得出其构件较精确的应力值,并进一步确定出应力危险区,为改进起重机金属结构的受力情况和结构设计、减小起重机的重量及减少设计余量提供了理论依据。1　有限元模型的建立如图1所示,BZD2 - 4×5A4型旋臂起重机由立柱、旋臂驱动装置、横梁和电动葫芦等组成。该机的金属结构选取低碳结构钢Q2 35BF…     

复合材料低速冲击损伤超声红外热波检测能力评估

为评估超声红外热成像对复合材料低速冲击损伤的检测能力,提出了评估流程和评估标准。设计并制作了复合材料层合板,分别采用超声红外热成像和超声C扫描两种方法对不同冲击能量下的冲击损伤进行了检测研究,以超声C扫描结果作为参照,对比分析了超声红外热成像的检测结果并对损伤大小进行了定量识别。结果表明:超声红外热成像不仅能够对冲击损伤进行准确的定位,还能有效地检测出冲击引起的纤维断裂、基体开裂和分层等具体的损伤形式,检测速度快,非常适合用于在线检测;与超声C扫描相比,超声热成像方法对冲击损伤大小的识别误差小于6%,检测精度较高,满足检测要求。     

Irradiance-based emissivity correction in infrared thermography for electronic applications

This work analyzes, discusses, and proposes a solution to the problem of the emissivity correction present in infrared thermography when coatings with known emissivity cannot be deposited on the inspected surface. It is shown that the conventional technique based on two reference thermal images and the linearization of the blackbody radiation dependence on temperature is not a reliable and accurate solution when compared with the coating procedure. In this scenario, a new approach based on the direct processing of the output signal of the infrared camera (which is proportional to the detected irradiance) is proposed to obtain an accurate emissivity and surrounding reflections map, perfectly compensating the thermal maps. The results obtained have been validated using a module as a test vehicle containing two thermal test chips which incorporate embedded temperature sensors.     

Intermittent contact AFM using the higher modes of weak cantilever

Employing the higher vibration modes of weak cantilevers enables operating frequencies up to megahertz to be reached, at the same time keeping the force on the sample reasonably low. This allows the interaction time between the tip and the surface to be reduced and should cause the response of surface to be dominated by surface stiffness. The simple distributed mass cantilever model is presented which shows that higher eigenmodes exhibit better sensitivity to surface properties. The images of laser-treated polymer on glass show the ability of the method to distinguish between the material phases with different properties.     

A study on the fracture characteristics of tapered double cantilever beams made of heterogeneous composites with adhesive interfaces

Journal of Mechanical Science and Technology - In this study, CFRP and aluminum properties were investigated by carrying the static experiment on the shape-dependent bonding structure, and designed...     

Direct measurement of cantilever spring constants and correction for cantilever irregularities using an instrumented indenter

A method is presented that allows direct measurement of a wide range of spring constants of cantilevers using an indentation instrument with an integrated optical microscope. An uncertainty of less than 10% can be achieved for spring constants from 0.1 to 10(2) Nm. The technique makes it possible to measure the spring constant at any desired location on a cantilever of any shape, particularly at the tip location of an atomic force microscopy cantilever. The article also demonstrates a technique to detect and correct apparent length anomalies of cantilevers by analyzing spring constants at multiple positions.     

Calibration of a gamma-ray telescope using tagged positron annihilation photons

Measurements of detection efficiency, angular resolution, and energy resolution properties of a gamma-ray telescope used to study celestial gamma rays from balloon flight altitudes are described. Nearly monochromatic photons produced at the National Bureau of Standards tagged photon facility were used for the calibration. Details of the photon beam configuration and properties and results of the measurements made at photon energies of 15.1 and 31.1 MeV are presented. Finally, the data are compared with a Monte Carlo analysis of the instrument properties.     

Identification of weak interfaces in composites using transmission electron microscopy

A new experimental technique was developed to identify crack paths with a resolution of nanometres in fibre-reinforced composites. Cracks were introduced through Vickers indentations on one side of the sample prior to starting the thinning process. Indentations were placed close to the fibres in order to get enough cracks at the fibre/matrix interface in the electron-transparent region of the thinned sample. The technique was used in a Nicalon-fibre Al₂O₃ matrix composite prior to and after a heat treatment at 1200 °C for 1 h. The analysis of the crack paths allowed the identification of the weakest interface in each condition.     

High-throughput analysis of thin-film stresses using arrays of micromachined cantilever beams

We report on a technique for making high-throughput residual stress measurements on thin films by means of micromachined cantilever beams and an array of parallel laser beams. In this technique, the film of interest is deposited onto a silicon substrate with micromachined cantilever beams. The residual stress in the film causes the beams to bend. The curvature of the beams, which is proportional to the residual stress in the film, is measured by scanning an array of parallel laser beams generated with a diffraction grating along the length of the beams. The reflections of the laser beams are captured using a digital camera. A heating stage enables measurement of the residual stress as a function of temperature. As the curvature of each beam is determined by the local stress in the film, the film stress can be mapped across the substrate. This feature makes the technique a useful tool for the combinatorial analysis of phase transformations in thin films, especially when combined with the use of films with lateral composition gradients. As an illustration, we apply the technique to evaluate the thermomechanical behavior of Fe-Pd binary alloys as a function of composition.     

Profile measurement of a wide-area resist surface using a multi-ball cantilever system

In the semiconductor industry, a device that can measure the surface profile of thin film like photoresist with high accuracy and high speed is needed. Since the surface of photoresist is very smooth and deformable, a device is required that will measure vertically with nanometer resolution and not damage the film during the measurement. We developed an apparatus using a multi-ball cantilever and white light interferometer to measure the surface profile of thin film. However, this system, as assessed with a scanning method, suffers from the presence of a moving stage and systematic sensor errors. Therefore, this paper describes an approach using a multi-ball cantilever as coupled distance sensors together with an autocollimator as an additional angle measuring device, which has the potential for self-calibration of a multi-ball cantilever. Using this method, we constructed an experimental apparatus and made measurements on resist film. The results demonstrated the feasibility of the constructed multi-ball cantilever system with the autocollimator for measuring thin film with high accuracy.     

Structural damage identification of a cantilever beam using excitation force level control

Most studies in damage identification so far have concentrated on comparing modal parameters of a structure with an open crack with those of an intact structure. In this study, a new damage identification method for beam-like structures with a fatigue crack is proposed, which does not require comparative measurement on an intact structure but several measurements at different level of excitation forces on the cracked structure. The idea comes from the fact that dynamic behavior of a structure with a fatigue crack changes with the level of the excitation force. In other words, a beam with a real fatigue crack would behave as an intact beam at low excitation forces due to the crack closure. The 2nd spatial derivatives of frequency response functions along the longitudinal direction of a beam are used as the sensitive indicator of crack existence. Then, weighting function is employed in the averaging process in frequency domain to account for the modal participation of the differences between the dynamic behavior of beam with a fatigue crack at the low excitation and one at the high excitation. Subsequently, a damage index is defined such that the location and level of the crack may be identified. Finally, it is shown that damage identification method using the proposed damage index is very successful through experiment and finite element analysis.     

HREM structure characterization of interfaces in semiconducting multi-layers using molecular-dynamics-supported image interpretation

Multi-layer structures in binary systems, for example InAs/AlSb and AlSb/GaSb, as well as ternary InGaAs/AlGaAs quantum wells grown by molecular beam epitaxy (MBE) are investigated by high-resolution electron miscroscopy (HREM). Interpretation of the micrographs requires methods of image analysis and the computer simulation of the HREM contrast. The relaxed atomic structure of the interfaces is modelled by molecular dynamics (MD) and energy minimization. The importance of strain relaxations to the image interpretation will be demonstrated and compared with the image spread and shift caused by the microscope aberrations. The possibility of revealing the compositional variations and the elastic deformations at the interfaces by HREM imaging under special defocus and sample thickness conditions will be discussed.     

联合载荷作用下悬臂梁大变形分析的打靶法

利用微积分基本知识，这里导出了集中力和任意横向分布载荷作用下悬臂梁的挠曲线微分方程。基于两点边值问题的打靶法，分别计算了两种联合载荷作用下悬臂粱的大变形。所得微分方程不仅具有普遍性，而且本文的计算方法对类似问题的解决具有一定的借鉴意义。     

电子显微镜在金属-半导体纳米线界面原位合金化中的应用

利用原位电子显微方法研究了金属-ZnSe半导体纳米线界面合金化过程,结果表明:在脉冲电流的作用下,ZnSe纳米线可以产生明显的焦耳热效应,导致金属-ZnSe纳米线界面发生合金化反应.通过调整纳米线与金属电极的接触面积,可将焦耳热效应准确控制在界面内,进而实现纳米尺度的合金化反应.     

Identification of pseudo-natural frequencies of an axially moving cantilever beam using a subspace-based algorithm

This study focuses on extraction of frequency information of a linear time-varying system using free response data. Frequency information is obtained from the pseudo-modal parameters that were defined in a previous study. A subspace-based identification algorithm is introduced. An improved version is proposed to make the algorithm less sensitive to measurement noise. An axially moving cantilever beam is used as the experimental system. A dynamic model is presented to show that lateral vibration of the axially moving cantilever beam is governed by a linear time-varying model. A computer simulation is conducted to compare the true pseudo-modal parameters and approximate ones that can be identified using the improved algorithm. The experimental study focuses on the capabilities of the algorithm and the factors that affect the identification results. A method of grouping identified structural pseudo-natural frequencies is proposed. Limitations of the algorithm are discussed.     

Verification of the performance of rotatable jig for a single cantilever beam method using the finite element analysis

The performance of new jig for single cantilever beam test method was verified by finite element analysis. Two types of jig were designed for a small specimen that had relatively short length compared to the width of cantilever; one was simple fixed jig and the other was specially designed rotatable jig. The rotatable jig has a rotatable seesaw which adjusts the experimental misalignments between the specimen and test machine. Among the three translational and three rotational misalignments, following three important factors were considered; rotation about x-axis, rotation about z-axis, and translation in y-axis. Adhesive layer was modeled by cohesive zone element, and crack propagation behavior and the deviation of energy release rate were investigated. The fixed jig showed undesired asymmetric crack propagation and large deviation of energy release rate when it had rotational misalignment about x-axis. However, the proposed new rotatable jig showed almost symmetrical crack propagation and small deviation of energy release rate regardless of misalignments. Rotational motion of the seesaw automatically compensated the rotational misalignment of the specimen. The rotatable jig also showed relatively small deviation of energy release rate compared with the fixed jig by the rotational misalignment about the z-axis. In contrast, the rotatable jig showed deviation of energy release rate by translational misalignments in the y-axis. However, the magnitude of the deviation was very small within the controllable range of experimental misalignment. In conclusion, it was found out that the proposed jig was appropriate for the measurement of adhesion of a small specimen by single cantilever beam method.

     

采用视觉特征整合的红外弱小目标检测

针对红外光学系统在复杂背景下的弱小目标检测问题,建立了基于特征整合的信息处理模型,提出了采用视觉特征整合的弱小目标检测方法。该方法首先利用视网膜神经节细胞感受野的数学模型DOG(Different-of-Gaussian)对红外图像进行初级信息处理,初步检测出弱小目标。而后,分为空域和频域两个通道进行特征提取。在空域通道,利用图像信息构造二阶微分Hessian矩阵,通过计算其直迹与行列式进行局部极值的判定,提取出含有弱小目标的结构分量特征;在频域通道,利用小波对图像频域进行二级分解,提取出含有弱小目标的高频分量特征。最后,将空域通道与频域通道的分量特征整合,提取出复杂背景下的弱小目标。实验结果表明:当虚警率为10-3时,该方法对弱小目标的平均检测概率为95.17%。基本满足红外弱小目标检测方法的稳定可靠、精度高等要求。     

Note: vibration reduction control of an atomic force microscope using an additional cantilever

Since an atomic force microscope is used to measure sub-nanometer level precision, it is sensitive to external vibration. If the vibration can be measured by using an additional sensor, we can obtain the vibration-free signal by subtracting the vibration signal from the signal containing the vibration. To achieve a highly effective vibration rejection ratio, it is important to decide where to locate the additional sensor. This is because the vibration measured at the sensing position should have the same phase as that of the vibration in the signal. Vibration reduction control using this electrical sensing method is verified through time domain analysis and topology images of a standard grid sample.