Extended hartmann test based on the pseudoguiding property of a hartmann mask completed by a phase chessboard

We propose to add a specific phase chessboard to the classical Hartmann mask used for wave-front sensing. By doing this we obtain a pseudoguiding of the energy issuing from this mask, allowing for an increase in the sensitivity of the Hartmann test. This property is illustrated by experiment, and a comparison between classical and new Hartmanngrams is presented.     

Evaluation of a proposed test method to measure surface and volume resistance of static dissipative packaging materials

This investigation examined a proposed method to provide a reliable and reproducible test to measure and evaluate the virtual surface and virtual volume resistance of packaging materials used to protect products from electrostatic discharge. The method also tests the ability of materials to dissipate electric charge as a result of conductivity between two points on the same side of a surface or on opposite sides of that material. The measurements provide a means to compare different materials and their ability to protect products from electrostatic discharge. The study found that the LDPE extruded foam cushion showed the highest virtual surface resistance, followed by the nylon/PE laminate, HDPE and LDPE air-cell bubblewrap material tested.     

Pixel-based absolute topography test for three flats

We demonstrate a method of performing the absolute three-flat test by using reflection symmetries of the surfaces and an algorithm for generating the rotation of arrays of pixel data. Most of the operations involve left/right and top/bottom flips of data arrays, operations that are very fast on most frame grabbers and are available on most commercial phase-measuring interferometers. We demonstrate the method with simulated data as well as with actual data from 150-mm-diameter surfaces that are flat to less than 25 nm peak to valley.     

一种应用于杆试验的数据采集系统的设计研究

杆试验在无线电引信的测试中占有十分重要的地位,本文从提高测试精度、实时性和方便性等出发,使用超声定距作为数据采集系统的启动信号,考虑到电磁兼容性问题,设计一种基于DSP的数据采集系统,本系统应用于弹内实时数据采集,采集数据后取出到地面使用计算机进行仿真.     

Tissue reactions to polyethylene implants with different surface topography

This study investigates the importance of implant surface topography on soft tissue response. The tissue response in the rat abdominal wall to discs of low density polyethylene with smooth to coarse surfaces was evaluated after one, six or 12 weeks. Capsule thickness and immunohistochemical quantification of monocytes–macrophages were used as measures. The macrophage specific antibody ED1 was used for identification of newly recruited macrophages and the ED2 antibody for the mature tissue macrophages. The smoother surfaces gave a thicker capsule than the rougher surfaces, and at one week also larger total numbers of cells and ED1 positive macrophages at interface. The capsule thickness increased over time for the smooth and intermediate surface topographies. In contrast, the cell numbers generally decreased over time. In conclusion, a coarse surface elicited lesser tissue reaction compared with a smooth surface. © 1999 Kluwer Academic Publishers     

Fluid surface compensation in digital holographic microscopy for topography measurement

A novel technique is presented for surface compensation and topography measurement of a specimen in fluid medium by digital holographic microscopy (DHM). In the measurement, the specimen is preserved in a culture dish full of liquid culture medium and an environmental vibration induces a series of ripples to create a non-uniform background on the reconstructed phase image. A background surface compensation algorithm is proposed to account for this problem. First, we distinguish the cell image from the non-uniform background and a morphological image operation is used to reduce the noise effect on the background surface areas. Then, an adaptive sampling from the background surface is employed, taking dense samples from the high-variation area while leaving the smooth region mostly untouched. A surface fitting algorithm based on the optimal bi-cubic functional approximation is used to establish a whole background surface for the phase image. Once the background surface is found, the background compensated phase can be obtained by subtracting the estimated background from the original phase image. From the experimental results, the proposed algorithm performs effectively in removing the non-uniform background of the phase image and has the ability to obtain the specimen topography inside fluid medium under environmental vibrations.     

Development of the surface topography on silica glass due to ion-bombardment

Mechanically polished fused silica surfaces have been bombarded by energetic Ar⁺ ions and the development of surface topography examined by scanning electron microscopy and by transmission electron microscopy of direct carbon replicas in order to study the parameters affecting the surface finish such as charging, angle of ion incidence and rotation of the specimen, A theory based on a simple model of initial surface unevenness on a microscopic scale is proposed to explain the observed surface features due to ion-bombardment.     

三轴加速度传感器阵列振动测试新方案

针对加速度传感器阵列测试较高频率下多维线振动与角振动同时存在的复杂振动六自由度参数的过程中,多个单轴传感器的使用会引入多个安装误差,使系统对于空间大小的要求过于严格,同时增加了计算量等问题,提出一种利用三轴加速度传感器替代单轴加速度传感器的新阵列方案,在对以上限制因素有效改进的同时,简化了阵列结构.通过原理推导与实例仿真验证了新方案是可行的.     

A compliance-based approach to measure fracture resistance curve for surface cracked steel plates

This paper proposes a compliance-based approach to determine the fracture resistance $J$ – $R$ curve for surface cracks in high-strength steel (S690) plate specimens in a four-point-bend set up. This study extends the $\eta $ -approach used in the fracture test for the typical specimens with a through-thickness crack, to the surface cracks in plate specimens in calculating the energy release rate from the area below the measured moment versus the crack-plane rotation. The energy release rate, computed from the detailed finite element models using the domain integral approach, confirms a constant $\eta $ value for surface cracked steel plates. Coupled with the post-test sectioning, the unloading compliance method quantifies the extended crack-front profiles ahead of the fatigue pre-cracked surface notch, using the crack-size versus the compliance relationship derived from linear-elastic finite element analyses. The fracture resistance curves thus obtained remain similar at different locations along the crack front and comparable with the fracture resistance measured using a standard side-grooved compact tension specimen at a finite crack extension.     

An integrated machine-process-controller model to predict milling surface topography considering vibration suppression

Surface topography is an important factor in evaluating the surface integrity and service performance of milling parts. The dynamic characteristics of the manufacturing system and machining process parameters significantly influence the machining precision and surface quality of the parts, and the vibration control method is applied in high-precision milling to improve the machine quality. In this study, a novel surface topography model based on the dynamic characteristics of the process system, properties of the cutting process, and active vibration control system is theoretically developed and experimentally verified. The dynamic characteristics of the process system consist of the vibration of the machine tool and piezoelectric ceramic clamping system. The dynamic path trajectory influenced by the processing parameters and workpiece-tool parameters belongs to the property of the cutting process, while different algorithms of active vibration control are considered as controller factors. The milling surface topography can be predicted by considering all these factors. A series of experiments were conducted to verify the effectiveness and accuracy of the prediction model, and the results showed a good correlation between the theoretical analysis and the actual milled surfaces.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00386-7     

Implementation of sine condition test to measure optical system misalignments

Rather than measuring aberrations across the field to quantify the alignment of an optical system, we show how a single, on-axis measurement of the pupil mapping can be used to measure the off-axis performance of the system and determine the state of alignment. In this paper we show how the Abbe sine condition can be used to relate the mapping between the entrance and exit pupils to image aberrations that have linear field dependence. This mapping error then can be used to measure the linear astigmatism caused by the misalignment. Additionally, we present experimental results from the sine condition test on a simple system.     

A buckled plate test to measure interfacial toughness in composites

A new, buckled plate (BP) test has been used to measure transverse toughness as the parameter characterizing interfacial adhesion in unidirectional, continuous-fibre composites. The test is simple, with advantages over other interfacial methods. The theory and experimental details are presented. The results of BP tests are discussed for polycarbonate/carbon fibre composites. Evaluations have been made with regard to specimen dimensions, testing speed, crack length, modulus, fibre volume fraction, and processing conditions. Transverse toughness is a sensitive measure of the interfacial adhesion, giving results similar to transverse tensile strength. The test has also been used to measure longitudinal toughness. This test should be widely applicable to many composite systems.     

A new method to measure the acoustic surface impedance outdoors

In the European countries noise pollution is considered to be one of the most important environmental problems. With respect to traffic noise, different researchers are working on the reduction of noise at the source, on the modelling of the acoustic absorption of the road structure and on the effects of the pavement on the propagation. The aim of this paper is to propose a new method to measure the acoustic impedance of surfaces located outdoors, which allows us to further noise propagation models, in order to evaluate exactly the noise exposure.     

Development of a modified concrete rheometer to measure the rheological behavior of conventional and self-consolidating concretes

The modified concrete rheometer (MCR) apparatus developed in this study is based on existing concrete rheometers, the main differences being the gap size and measurement method, and thus the interpretation of the results. The gap between the inner cylinder wall and the tip of the vane was set to 6.4 times the diameter of the largest coarse aggregate in order to reduce interaction between the aggregate and the wall and the friction force from the wall. The MCR apparatus was used to measure yield torque directly at different low rotational speeds (above 0.003 rev/s). A study of the yield torque and viscosity of 37 fresh concrete mixtures was also made, with a particular focus on self-compacting concrete or self-consolidating concrete (SCC), and the results were compared with those obtained using other workability tests. The test results showed that the MCR can differentiate between conventional concrete (CC), powder-type SCC and SCC with viscosity-modifying agents (VMA). The rheological behavior of powder-type SCC was found to be influenced by the composition of Class F fly ash and ground granulated blast-furnace slag (GGBFS), and this type of concrete exhibited a wider range of viscosity and yield torque values. Despite the lower powder content and larger water to binder ratio (w/b), the viscosity of VMA-type SCC was shown to be slightly lower than that of powder-type SCC, and the values were clustered together within a certain range; thus, the workability of SCC containing VMA is more easily controlled. In addition, the MCR apparatus can also be applied to CC of differing viscosity and yield torque, thus making this apparatus suitable for determination of the workability of all kinds of fresh concrete.     

X-ray topography contrast of edge dislocations perpendicular to the 6H-SiC crystal surface

Features of the X-ray topography (XRT) images of edge dislocations perpendicular to the (0001) surface of a 6H-SiC single crystal are described. The contrast of topographs obtained in the regime of anomalous X-ray transmission is compared to the contrast of images obtained using section X-ray topography in the transmission geometry.     

Lattice design for subaperture stitching test of a concave paraboloid surface

Lattice design is subtle and complicated for the subaperture stitching test of aspheric surfaces. Methods are described in this paper for the collection and arrangement of subapertures, and calculation of the best-fit sphere for each subaperture. The best-fit sphere is determined by minimizing the mean-square aspheric deviations in the form of a surface integral. Finally, a numerical example is given to illustrate the procedure, and also to verify the validity of our proposed methods.     

Principles underlying a guideline for applying HAZOP to programmable electronic systems

This paper reports on the experience of the authors, both in applying Hazard and Operability Studies (HAZOP) to programmable electronic systems (PES) and in researching the subject. A survey during the preparation of a guideline on the application of HAZOP to PES revealed common difficulties in this application. HAZOP is introduced, the difficulties are explained, and means of overcoming them are described.