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Finite differences of various orders are used in linear estimation when the measurements contain not only fluctuation noise
but also piecewise-continuous interference of degree type.
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Translated from Izmeritel’naya Tekhnika, No. 4, pp. 16–21, April, 2006. 相似文献
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Translated from Izmeritel'naya Tekhnika, No. 9, pp. 29–30, September, 1989. 相似文献
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The present era is witnessing advancement in digital electronics and microprocessor which enables manufacturing sector capable
to produce complex components within small tolerance zone in the tune of nanometre and at one machining center. All motion
control systems have some form of position feed back system fitted with the machine. Such systems are not generally accurate
due to the errors in the positioning performance of the machine tool which will change over time to time due to wear, damage
and environmental effects. The complex structure of multi-axis CNC machine tools produce an inaccuracy at the tool tip caused
by kinematic parameter deviations resulting in manufacturing errors, assembly errors or quasi-static errors. Analysis of these
errors using a laser measurement system provides the manufacturers a way to achieve better accuracy and hence higher quality
output from these processes. In this communication, techniques to measure the linear positional errors of axes of CNC machine
tools by a laser interferometer calibration system and accuracy enhancement using the data obtained from the calibration cycle
by feeding into the machine’s controller with the help of linear error compensation package are discussed. 相似文献
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A study of improving overlay accuracy by applying a new outlier handling method in FPD manufacturing
As the pixel size of display devices has been reduced, overlay accuracy between layers needs to be more improved in flat panel display (FPD) manufacturing. However, because of large substrate size and non-uniform processes in FPD manufacturing, an improvement of overlay accuracy has been a challenging work. As an effort to improve overlay accuracy, overlay error correction, which is a kind of feedback control similar to one in semiconductor manufacturing, has also been applied in the photo lithography processes for FPD. However, its characteristics and problems were not technically well investigated as much as in semiconductor manufacturing. This paper investigates one of the problems encountered in the practice of the overlay error correction: outliers in the measurement of overlay errors. Such outliers can cause undesirable effects on overlay accuracy, if used for the overlay error correction. In order to systematically cope with such outliers, a new framework is proposed for detecting and handling outliers as well as for verifying the result. In the consideration of the proposed framework, a new outlier detecting and handling method is also proposed. This method is based on a robust regression technique and is compared with others through simulation to confirm its better performance. 相似文献
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Gran F Jensen JA 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2008,55(1):12-23
This paper describes a method for spatial encoding in synthetic transmit aperture ultrasound imaging. This allows several ultrasonic sources to be active simultaneously. The method is based on transmitting pseudorandom sequences to spatially encode the transmitters. The data can be decoded after only one transmission using the knowledge of the transmitted code sequences as opposed to other spatial encoding techniques, such as Hadamard or Golay encoding. This makes the method less sensitive to motion, and data can be acquired using fewer transmissions. The aim of this paper is to analyze the underlying theory and to test the feasibility in a physical system. The method has been evaluated in simulations using Field II in which the point-spread functions were simulated for different depths for a 7 MHz linear array transducer. A signal-to-noise ratio (SNR) simulation also was included in the study in which an improvement in SNR of approximately 1.5 dB was attained compared to the standard synthetic transmit aperture (STA) firing scheme. Considering the amount of energy transmitted, this value is low. A plausible explanation is given that is verified in simulation. The method also was tested in an experimental ultrasound scanner and compared to a synthetic transmit aperture ultrasound imaging scheme using a sinusoidal excitation. The performance of the proposed method was comparable to the reference with respect to axial and lateral resolution, but it displayed poorer contrast with sidelobe levels at approximately - 40 dB compared to the mainlobe. 相似文献
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A new 3D equilibrated residual method improving accuracy and efficiency of flux-free error estimates
Núria Parés Pedro Díez 《International journal for numerical methods in engineering》2019,120(4):391-432
The paper presents a novel strategy providing fully computable upper bounds for the energy norm of the error in the context of three-dimensional linear finite element approximations of the reaction-diffusion equation. The upper bounds are guaranteed regardless the size of the finite element mesh and the given data, and all the constants involved are fully computable. The upper bound property holds if the shape of the domain is polyhedral and the Dirichlet boundary conditions are piecewise-linear. The new approach is an extension of the flux-free methodology introduced by Parés and Díez in the paper “A new equilibrated residual method improving accuracy and efficiency of flux-free error estimates”, which introduces a guaranteed, low-cost, and efficient flux-free method substantially reducing the computational cost of obtaining guaranteed bounds using flux-free methods while retaining the good quality of the bounds. Besides extending the 2D methodology, specific new modifications are introduced to further reduce the computational cost in the three-dimensional setting. The presented methodology also provides a new strategy to obtain equilibrated boundary tractions, which improves the quality of standard techniques while having a similar computational cost. 相似文献
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为了解决少量测点条件下利用近场声全息技术重建结构表面法向振速精度和分辨率不高甚至失效的问题,提出了一种基于声压声辐射模态的全息面插值算法,可有效提高结构法向振速重建精度和分辨率。计算全息面声压声辐射模态向量;根据声压声辐射模态收敛性,求取截断声压声辐射模态展开系数的最小二乘解或Tikhonov正则化解,由此计算出插值点处的声压值;利用插值后的全息面数据重建结构表面法向振速。简支平板激励仿真和音箱实验均表明,少量测点条件下利用该方法能够有效提高结构法向振速重建精度和分辨率,验证了方法的有效性。同时音箱实验验证了方法的可行性。 相似文献
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M.N. Nasrabadi F. BakhshiM. Jalali A. Mohammadi 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2011,659(1):378-382
Nuclear-based explosive detection methods can detect explosives by identifying their elemental components, especially nitrogen. Thermal neutron capture reactions have been used for detecting prompt gamma 10.8 MeV following radioactive neutron capture by 14N nuclei. We aimed to study the feasibility of using field-portable prompt gamma neutron activation analysis (PGNAA) along with improved nuclear equipment to detect and identify explosives, illicit substances or landmines. A 252Cf radio-isotopic source was embedded in a cylinder made of high-density polyethylene (HDPE) and the cylinder was then placed in another cylindrical container filled with water. Measurements were performed on high nitrogen content compounds such as melamine (C3H6N6). Melamine powder in a HDPE bottle was placed underneath the vessel containing water and the neutron source. Gamma rays were detected using two NaI(Tl) crystals. The results were simulated with MCNP4c code calculations. The theoretical calculations and experimental measurements were in good agreement indicating that this method can be used for detection of explosives and illicit drugs. 相似文献
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Quality and resolution of integrated microsystems using Hall sensors dedicated to an angular encoder are strongly dependent on the accuracy of the relative position of Hall sensors and on the offset of electronic front end circuitry. In this paper, we describe a CMOS microsystem built on two integrated circuits. This contactless encoder microsystem gives three sine and square signals with a phase shift of 120/spl deg/ and provides an angular error of less than 4/spl deg/ without external trimming or feedback. The Hall sensor assembly with the engine consists of fixing a small permanent magnet on the rear axis of the motor. Then, the sensor is positioned in front of this magnet. 相似文献
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Digital periodic signal analysis often requires synchronized sampling with the signal being analyzed. In certain practical situations, however, this condition is difficult to satisfy. As a result, a number of undesirable effect such as the spectral leakage associated with the discrete Fourier transform (DFT), and the truncation errors in digital wattmeters arise and degrade system performance. This paper presents a new approach which attempts to remedy the underlying problem. The basic idea of the proposed method is to modify the actual sampled sequence such that it becomes an ideal sample sequence which is synchronized with the signal subjected to sampling. A simple algorithm for modifying the sampled sequence on-line is derived based on interpolation. The proposed approach requires quite modest additional computational burden which makes it suitable for real-time signal professing. To illustrate the practical applicability of the proposed algorithm, the paper considers two distinct but common cases. First, it shows how the proposed method can be used in the case of DFT analysis of harmonic signals, and secondly, it considers the digital wattmeter application area in electrical power-system measurement. Results show that the proposed algorithm is capable of reducing both the leakage effect in DFT analysis and truncation errors in digital wattmeters 相似文献
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Mariotti Christian Le Piver Françoise Aubry Ludovic 《International journal for numerical methods in engineering》2015,101(10):731-743
This paper presents a coupling method between a discrete element code CeaMka3D and a finite element code Sem. The coupling is based on a least‐squares method, which adds terms of forces to finite element code and imposes the velocity at coupling particles. For each coupling face, a small linear system with a constant matrix is solved. This method remains conservative in energy and shows good results in applications. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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I. A. Teshev 《Measurement Techniques》1992,35(10):1201-1204
Translated from Izmeritel'naya Tekhnika, No. 10, pp. 49–51, October, 1992. 相似文献