The problem of freeform surface reconstruction starting from a cloud of points measured by a laser scanning system is examined. The objective is to fully integrate reverse enginccring and laser scanning for rapid product development. The measuring principle and the configruation of the system are investigated. Based on non-uniform rational B-spline (NURBS) curve and surface, the freeform curve, the surface reconstruction method, the step and parameterization algorithms are introduced. The interfaces between initial graphic exchange specification (IGES) and sterco lithograpgy interface specification (STL) with CAD and rapid prototyping manufacturing (RPM) system are discussed. The system is developed bascd on an open graphics library (OPEN GL) software environment. A practical case is presented to illustrate the cffcctivenessof the approach.

It is a hard nut to crack how to ensure the sensors keep survives to measure the jet flow pressure with several hundred microseconds to about 20 milliseconds under the severe radiation condition with dose rate at 131013 rad (Si)/s and strong explosion shock. A novel method we have proposed with the plastic deformation principle of metal material and pressure threshold can solve the problem effectively, especially in the large scale chemical explosion test.

Aimed at the problems of inferior precision and bad maneuverability for three-dimensional (3D) measurement by projected fringe pattern, a flexible new 3D technique for performing system calibration and measuring was proposed. First, we analyzed the principle of conventional 3D measurement with projected fringe pattern, and pointed out the shortcoming of measurement system. Then, the CCD camera calibration technique is analyzed and we set up the perspective projection model which transforms the computer image coordinate to 3D world coordinate, and we get the coordinate of the CCD camera image lens. Third, the position of projection lens optical center can be obtained using the above model. At last, some experiment results presented show that this technique is more simple and robust in engineering than conventional measurement method.

A three-dimensional profile measurement sstem based on a projection coded grating technoque is presented. The system uses a designing and decoding technique for grey coded gratings. The coded grating has black, white and grey stripes. The period triples a conventional grating. lt greatly increcses the height measuring range without any decrease in stripe separation. The shape of object and be obtainde from only one grating image. The systm is suitable for instantaneous measurement of moving objects including human face. The technique proposed pedmites rapid 3D measurement and no moving parts are involvde in the system. The hardware is relatively simple. Special data processing software is develped. Results of a practical example confirm the effcetiveness of the proposed method.

Potentiodynamic polarization and impedance measurements are used to examine the effects of temperature on the passivation behavior and corrosion resistance of 13 Cr martensitic stainless steel in CO2 and Cl environment. Different specimens are tested during exposure to 90, 120 and 150℃. Reaction mechanisms are decided from polarization curves. The characteristics of the surface film are determined from impedance transfer function model, which involve the reactions occurring at the metal/passive film as well as diffusion processes. Information concerning system electrochemical parameters is used to interpret the effects of temperature on the passive film and corrosion resistance. These results are consistent with the SEM and XPS analysis.

Based on silicon on insulator (SOI) technology, a novel high temperature pressure sensor with high frequency response is designed and fabricated, in which a buried silicon dioxide laycu in the silicon material is developed by the separation by implantation of oxygen (SIMOX) techonology. This layer can isolate leak currents between the top silicon layer for the detecting circuit and body silicon at a tcnpcratuec of about 200℃. In addition, the tcchnology of silicon and glass bonding is used to create a package of the sensor without internal strain. A structural model and test data from the sensor are presented. The experimental rcsults showed that this kind of sensor posscsscs good static performance in a high temperature environment and high frequency dynamic characteristics, which may satisfy the pressure measurement demands of the oil industry, aviation and space, and so on.

A miniature glucose biosensor has been developed based on electropolymerization of polypyrrole-glucose oxidase on a multilayered gold interdigitated ultramicroelectrode array with containing trenches. The basal band ultramicroelectrode with a functional width of 362 nm is fabricated using multilayered materials and conventional photolithographic techniques. The electrode surface is inside the containing trenches, the depth of which is larger than 1.5m. High quality electrodes with uniform geometries are characterized by microscopy and electrochemical techniques. The corrosion resistance is investigated on exposure to the normal saline, which indicates that the electrodes are adequate for acute experiments lasting a few hours. Fabricated by electropolymerization, the glucose oxidase/polypyrrole (GOx/PPy) biosensors can be used for detecting glucose concentration in the linear range of 0-10 mmol/L, with a sensitivity of 13.4 nA/(mmol L) and a correlation coefficient of 0.998, respectively.

The principle of silicon-on-insulator (SOI) and low pressure chemical vapour deposited (LPCVD) to make the piezoresisitive pressure gauge is developed. A novel structure of the sensors for harsh environment is designed. In particular, the high temperature pressure sensors were used in: automotive industry, aviation engineering, as well as in oil fields, industrial measurement and control systems. The sensor could be used in 200℃ environment, and could endure the impact of instances high temperature (about 1000, and less than 0.5s) because of it's mechanical structure of cantilever bonded with SOI strain gauge. The test data of the sensor is obtained, and the result is satisfied.

In reverse engineering, it is very challenging to acquire the 3D profile information of an object rapidly with high accuracy. This becomes even harder to measure the profile of a large object, such as an automobile body press part as it has a wide scope and is not easy to realize. A new non-contact measuring method using multi structure linear lighting (or multi light-knife) based on laser scanning measurement technology is presented in this paper. The principle of the multi light-knife is first presented. To improve the accuracy of the measuring device developed in this work, a virtual net mapping and the least square theory is applied to calibrate the measuring device of the multi light-knife in the whole measuring field. When the device is used to measure automobile body press parts, a route planning method is used to ease the contradiction between measuring accuracy and the range of measurement. System calibration is achieved by compensating the platform error. Experiments on a rear view mirror case show that the multi light-knife is a very effective device and can become a very promising way to acquire the 3D profile information of large objects. r 2003 Elsevier Ltd. All rights reserved.

Many machined surfaces such as those processed by turning, drilling, electrical discharging achining, grinding and rubbing, which have the property of self similarity or self-affinity, can be characterised with fractal geometry. Up to now the emphasis of most researchers has been on isotropic surfaces with a profile of several fractal parameters. In this paper, we first review the characterisation of a profile with fractal geometry and the relation between fractal parameters of the profile and that of a three-dimensional machined surface. Afterward, we propose a concise method based on two-dimensional Fourier transform to compute the surface fractal dimension and to analyse the anisotropy along three-dimensional machined surfaces. The precise three-dimensional topography of a machined surface is taken with atomic force microscopy. After spatial power spectrum obtained by two-dimensional fast Fourier transform, surface fractal parameters are acquired by averaging power spectrum along every direction with nominal same amplitude and anisotropy is analysed according to spectrum amplitude within a certain direction. The results show that this has some advantages over other three-dimensional fractal characterisation methods. It is also obvious this method can be used for either an isotropic surface or an anisotropic one. 2001 Elsevier Science Ltd. All rights reserved.