Abstract: The pulse description word (PDW) measurement method of digital channelized reconnaissance receiver was investigated. The parameter measurement flow of digital channelized reconnaissance receiver was introduced. The measurement methods of the instantaneous amplitude, the instantaneous frequency, the pulse width of wideband frequency modulated signal and the direction of arrival (DOA) were discussed in detail, which have been applied to reconnaissance receiver in ESM system successfully.
Abstract: Product tolerance is one of the key factors which can determine the good or bad performance of mechanical products. Its size not only affects the manufacturing and assembly process, but also affects product features . Thus tolerance optimization design gets more and more attention. In this paper, an improved physical programming method is used to make mathematical modeling for tolerance allocation problem of assembly dimensional chain, and PSO algorithm is also used to improve solving ability. And the effective solution for tolerance optimization is designed.
Abstract: The measurement uncertainty of vortex flowmeter was examined when the gas flow measured was injected with liquid. This test was performed in a multiphase flow calibration facility. A vortex flowmeter of 50 mm in diameter was installed in a 100 mm test section. The gas volume flow rate was held in 141m3/h and the liquid was injected into the gas flow. The liquid volume fractions used at the gas volume flow rate were 0.0106%, 0.0213%,0.0355%,0.0496%,0.0638%,0.0780% and 0.0922%. The small amount of liquid in the gas as discrete droplet is called discrete liquid phase. Analysis on the vortex shedding frequency obtained from a frequency spectra showed that the strouhal values changed from 0.305 to 0.385 with the discrete liquid phase increasing and the total uncertainty of vortex flowmeter was from 0.869% to 2.196%. The experimental result can supply experimental basis for the measurement error correction of vortex flowmeter worked in gas flow with discrete liquid phase.
Abstract: Screw thread, as the most basic and widely used mechanic element, has many traditional methods to verify its dimension consistency. Machine vision technology is gradually applied to inspect screw thread in fastener industry because of its fast, precise and repeatable features. Based on analysis of the features and problems of previous vision measurement methods, this paper provides calculation, analysis and simulation of screw thread’s 3D mathematic model, and finally provides corresponding algorithm to correct calculation error resulting from shading effect of backlight projecting.
Abstract: Traditional pelvimetry for a pregnant women is mainly relied on a ruler or estimation based on the vaginal touch, which results a very high measuring error. A new pelvimetry based on electromagnetic tracker is proposed in this paper , and a measure system has been developed . It’s a non-invasive method to measure key parameters of a pelvis because of the character of high accuracy, without line-of-sight restrictions and non-radiation of electromagnetic tracking technology. Its precise measuring data can well fulfill clinical pelvimetry needs, and be helpful for a physician to make decisions to go on a vaginal delivery or not during a labor.
Abstract: This paper presents an algorithm for detecting the small infrared target under complex background. An method, Local Mutation Weighted Information Entropy (LMWIE), is proposed to suppress background. Then, enhance targets’ gray value by calculating the local energy. For the problem that the gray value of noises is enhanced with the gray value improvement of targets, image segmentation bases on the adaptive threshold. Experiment results indicate that it is a robust and effective small target detection algorithm.
Abstract: Recently most of modern absolute measurement rotation the flats or spheres in the interferometer. We review traditional absolute testing of flats methods and emphasize the method of reconstruction of rotational shear. The rotation of the lens can lead to some errors such as angle rotation error, center excursion error and other coordinate system motion error. 36 Zernike polynomials are used to generate 3 flats and Matlab are used to simulate the arithmetic. There have some phase problems on FFT arithmetic in Matlab which can cause some errors. Results are shown about how these errors influence the accuracy. The analysis results can also be used in other interferometer systems which have the motion of the coordinate system.
Abstract: To reduce noise and make the structure of the car more rational, we established modal test system of car's body-in-white in this paper. Car body-in-white was mounted on rigid platform with four coil springs. The car was excited by an electromagnetic exciter. The method of single-point excitation and multi-point collecting vibration was used in this test. Excitation point was chosen in the bearing beam. Signals picked up by the acceleration sensors were processed in the software of Mescope. With this system, different modal frequencies and modal characteristics of the car are acquired. The results show that modal parameters are effective and reliable and those parameters can be basis for the designer to improve the structure of the car.
Abstract: In this paper, we analysed the level of radiation noise and distribution of noise sources of car’s engine and front panels by using sound intensity method. To get the nephogram of sound intensity and sound power spectrum, we used the sound intensity probe and Multi-channel Data Acquisition Regulation System B&K 3560-D and Pulse Data Processing Analysis Software. By analysing experimental results, we can conclude the location of noise sources of these parts. The measurement results will serve as a reference for the car noise reduction.
Abstract: Ultrasonic attenuation coefficient is firstly calculated utilizing the finite difference time domain method based on a novel 2-D RVM for carbon fiber reinforced plastic (CFRP) composite materials. The results show that the void morphology has detrimental effect on ultrasonic attenuation. Even at the fixed porosity, ultrasonic attenuation coefficient fluctuates due to the randomness of void morphology in CFRP composite materials. This work significantly helps to understand ultrasonic scattering mechanism of voids and formulation of CFRP composite material properties.