Non-ideal Measurement Conditions Research Articles

Adaptive Time-Varying Parameter Estimation via Weak Measurement

Extending quantum sensing to time-varying parameter estimation is a potential and challenging task in practical application. To achieve this goal, we propose an adaptive method to estimate an unknown time-varying parameter through light-intensity split detection and the insertion of reference phases in the weak measurement. Theoretical analysis and numerical simulation are applied to illustrate the feasibility and practical applications of our method. The results demonstrate that the method has adjustable sensitivity and linear dynamic range, and is robust to nonideal measurement conditions. Moreover, we analyze the precision of our method and show that its precision limit can surpass the standard quantum limit and approach the Heisenberg scaling when using a squeezed light of optimal Gaussian state.

Positioning variation synthesis for an automated drilling system in wing assembly

• Built the positioning variation model of an eye-in-hand automated drilling system. • Proposed positioning variation synthesis strategy with engineering constraints. • Determined allowable values of positioning variation sources for automated drilling. Tight position tolerance is required for fastener holes in wing manufacturing. Automated drilling system with high positioning accuracy is the key to achieve the requirement. The paper seeks to determine allowable values of variation sources and guarantee the hole position tolerance. The process of reference hole positioning and the compensation of drilling positions are firstly explored and formalized for an automated drilling system integrated with an industrial camera. Based on this, a positioning variation model for automated drilling considering positioning error measurement and compensation is built. After that, positioning variation synthesis being imposed engineering constraints on is mathematically modeled based on the theory of mathematical statistics. In the positioning variation synthesis, imperfect camera installation, nonideal measurement conditions, equipment positioning error, etc. are included. The positioning variation model and involving synthesis strategy have been used to develop an automated drilling system for wing assembly. Experiments conducted on the developed drilling system show that the fastener holes’ desired position tolerance 0.3 mm will not be exceeded, which is a necessary condition of the satisfactory drilling quality of the aircraft wing.

Imaging ellipsometry measurement noises associated with non-uniform retardation of the compensator

Owing to high accuracy in the whole measurement range, the compensator-rotating method is a powerful technique for transmission/reflection ellipsometric measurements. The compensator-rotating imaging ellipsometer, which is a system combing the optical microscope and single measurement point ellipsometer, faces non-ideal measurement conditions involving nonuniformity of the retardation across the compensator. In this paper, we study the effect of non-ideal measurement conditions on the measurement noises and introduce the systematic solution.

Eddy covariance based surface‐atmosphere exchange and crop coefficient determination in a mountainous peatland

AbstractIn the soil–plant–atmosphere continuum, fluxes of water, energy, and carbon determine the water and carbon balance of peat bogs. We used eddy covariance (EC) measurements to study surface atmosphere exchange and its drivers above an ombrotrophic peat bog (Odersprungmoor) in the Harz Mountains, Germany, with nonideal measurement conditions during the growing season in 2013. For montane peatlands, only very few EC flux measurements exist due to site constraints, for example, surface slope, limited fetch, and frequent dew formation on open path sensors. The measured data were carefully filtered resulting in valid and representative fluxes for the bog. The evapotranspiration (ET) was further characterized by determining the adjusted crop coefficient (Kc*) for July and August and comparing it with Kc* values from 7 years of the FLUXNET site Mer Bleue bog, Ontario, Canada. While soil moisture was taken into consideration, the adjustment was nevertheless necessary as plant health and nutrient supply were not evaluated as required by FAO guidelines. Actual ET at OM was well described by the Kc* model (Kc* = 0.85, R2 = 0.85). The primary control on ET was available energy and atmospheric conditions and, marginally, the soil moisture conditions. This Kc* value is comparable to the calculated Kc* values for MB, which ranged between 0.82 and 0.86 (R2 between 0.84 and 0.97). Since these Kc* ranges are narrow for the different sites and years, we hypothesize that these values are good estimates for the true crop coefficients of Sphagnum‐dominated peat bogs.

Finite element and analytical solutions for van der Pauw and four-point probe correction factors when multiple non-ideal measurement conditions coexist

This paper presents an extensive collection of calculated correction factors that account for the combined effects of a wide range of non-ideal conditions often encountered in realistic four-point probe and van der Pauw experiments. In this context, "non-ideal conditions" refer to conditions that deviate from the assumptions on sample and probe characteristics made in the development of these two techniques. We examine the combined effects of contact size and sample thickness on van der Pauw measurements. In the four-point probe configuration, we examine the combined effects of varying the sample's lateral dimensions, probe placement, and sample thickness. We derive an analytical expression to calculate correction factors that account, simultaneously, for finite sample size and asymmetric probe placement in four-point probe experiments. We provide experimental validation of the analytical solution via four-point probe measurements on a thin film rectangular sample with arbitrary probe placement. The finite sample size effect is very significant in four-point probe measurements (especially for a narrow sample) and asymmetric probe placement only worsens such effects. The contribution of conduction in multilayer samples is also studied and found to be substantial; hence, we provide a map of the necessary correction factors. This library of correction factors will enable the design of resistivity measurements with improved accuracy and reproducibility over a wide range of experimental conditions.

The European project on high temperature measurement solutions in industry (HiTeMS) – A summary of achievements

High temperature measurement in industry is subject to large uncertainties due to the non-ideal measurement conditions; for example unknown emissivity and window transmission for radiation thermometry, sensor contamination and ageing causing unpredictable drift in contact thermometry. This paper gives an overview of a European Metrology Research Programme (EMRP) project “High Temperature Metrology for Industrial Applications” (HiTeMS) whose objective was to address, on a broad front, a number of unsolved measurement challenges in the domain of high temperatures (above 1000°C) both in non-contact and contact thermometry. It brought together a total of 15 partner organisations; National Metrology Institutes (NMIs) (10), industrial companies (4) and a Fraunhofer Institute. The project started in September 2011 and was completed August 2014. Significant progress has been made in all the temperature measurement challenges tackled.

相位差异法检测不理想环境下的非共光路像差

A no-common path calibration system was desighned for the Adaptive Optical (AO) system in a 1.23 m ground telescope. To solve some practical problems of no-common path static aberration calibration, the evaluation function for the multi-channel Phase Diversity (PD) processing method was presented for a condition of the defocusinng amount difficult to be measured. Then, a method to use the detected aberration and the modulated deformable mirror to iterate each other for convergence was proposed to make up the effect of nonideal measurement conditions on aberration detection. As compared with two-channel PD processing, the multi-channel PD processing method has stronger tolerance to the forms of target sources and higher accuracy of wavefront solution in theory. The processing method was used to measure the no-common path aberration of the AO system in the 1.23 m telescope. Experimental results demonstrate that the proposed method achieves the higher accuracy of wavefront solution and the aberration has been compensated by using the initial bias of a deformable mirror. Moreover, the whole imaging quality of the optical system is improved effectively.

Measurement error analysis and accuracy enhancement of 2D vision system for robotic drilling

Robotic drilling for aircraft structures demands higher accuracy on industrial robots than their traditional applications. Positioning error measurement and compensation based on 2D vision system is a cost-effective way to improve the positioning accuracy in robotic drilling. In this paper, we first discuss the principle of error measurement and compensation with a 2D vision system for robotic drilling and the determination of tool center point of the vision system so that the Abbe errors are eliminated in the measurement process. Measurement errors due to nonideal measurement conditions, i.e. nonperpendicularity of the camera optical axis to the workpiece surface and incorrect object distance, are mathematically modeled and experimentally verified. A method utilizing four laser displacement sensors is proposed to ensure perpendicularity of the camera optical axis to the workpiece surface and correct object distance in the measurement process, and hence to achieve high accuracy in 2D vision-based measurement. Experiments performed on a robotic drilling system show that the 2D vision system can achieve an accuracy of approximately 0.1mm with the proposed method.

Describing Uncertainties Encountered during Laboratory Turbocharger Compressor Tests

To improve the existing turbocharger compressor technologies (surge margin increase, improving compression abilities, etc.), compressor tests require accurate determination of efficiency, pressure, and exact surge line emplacement. Moreover, due to nonideal measurement conditions typically encountered during turbocharger compressor performance testing, it is imperative to define measurement uncertainties to the experiments. This article deals with how reliable the results of the turbocharger compressor tests for a given test facility are. This article begins with a general introduction to measurement uncertainties, and a description of the turbocharger test facility together with sources of error of the different transducers is then presented. Uncertainty equations are derived from compressor performance relations; transducer errors were introduced to uncertainty equations so that the efficiency, pressure, and mass flow uncertainties of compressor at different functioning points can be predicted before compressor testing. Uncertainty analysis of nine different compressor functioning points was carried out. Finally, parameters that mostly affect the compressor performance results were identified.

Contrast-enhanced near-infrared laser mammography with a prototype breast scanner: feasibility study with tissue phantoms and preliminary results of imaging experimental tumors.

Near-infrared (NIR) optical mammography without contrast has a low specificity. The application of optical contrast medium may improve the performance. The concentration-dependent detectability of a new NIR contrast medium was determined with a prototype optical breast scanner. In vivo imaging of experimental tumors was performed. The NIR contrast agent NIR96010 is a newly synthesized, hydrophilic contrast agent for NIR mammography. A concentration-dependent contrast resolution was determined for tissue phantoms consisting of whole milk powder and gelatin. A central part of the phantoms measuring 2 x 2 cm2 without contrast was replaced with phantom material containing 1 micromol/L to 25 nmol/L NIR96010. The composite phantoms were measured with a prototype NIR breast scanner with lasers of lambda1 = 785 nm and lambda2 = 850 nm wavelength. Intensity profiles and standard deviations of the transmission signal in areas with and without contrast were determined by linear fit procedures. Signal-to-noise ratios and spatial resolution as a function of contrast concentration were determined. Near-infrared imaging of five tumor-bearing SCID mice (MX1 breast adenocarcinoma, tumor diameter 5-10 mm) was performed before and after intravenous application of 2 micromol/kg NIR96010. Spectrometry showed an absorption maximum of the contrast agent at 755 nm. No spectral shifts occurred in protein-containing solution. Signal-to-noise ratio in the transmission intensity profiles ranged from 1.1 at 25 nmol/L contrast to 28 at 1 micromol/L. At concentrations <40 nmol/L, no differentiation from the background was possible. The transitional area between the contrast-free edge of the phantom and the central contrast-containing part appeared in the profiles as a steep increase with a width of 4.2 +/- 1.8 mm. The experimental tumors were detectable in nonenhanced images as well as contrast-enhanced images, with better delineation after contrast administration. In postcontrast absorption profiles, a 44.1% +/- 11.3% greater absorption increase was seen in tumor tissue compared with normal tissue. The laser wavelength lambda1 of the prototype laser mammography device was not situated at maximum absorption of the contrast agent NIR96010 but on the descending shoulder of the absorption spectrum. This implies a 20% signal loss for contrast detection. Despite the nonideal measurement conditions, concentrations as low as 40 nmol/L were detectable in vitro. In vivo, all tumors were detectable in color-coded nonenhanced scans as well as in contrast-enhanced scans, with better delineation after contrast administration.

In Situ Multi-Wavelength Ellipsometric Control of Thickness and Composition For Bragg Reflector Structures

AbstractWe have demonstrated real-time feedback control of thickness and composition for Bragg reflector structures using in situ multi-wavelength ellipsometry. This demonstration was performed under conditions which were not ideal for ellipsometric measurements: the angle of incidence for the ellipsometric measurement beam was far away from the Brewster angle, substrate rotation was enabled (which caused an angular wobble in the measurement beam), and strain effects were present in the ellipsometer windows. Furthermore, to simulate drift in the MBE system (and test the effectiveness of the ellipsometer control), the Ga effusion cell was ramped to change the Ga flux by 50% during two of the growth runs. Results of the growth control precision and accuracy are presented; the influence of the non-ideal measurement conditions on the ellipsometer growth control capability is also discussed.

Experimental study of repeatability errors in 3D sound intensity measurements in narrow frequency bands

When investigating the 2D or 3D intensity of complex ‘real life’ noise sources, rather than the intensity normal to a surface, to obtain more detailed information about the radiated sound field great care has to be taken both in measuring and in interpreting the results. In this study it is shown that in measurements of 3D intensity for fixed points and in narrow frequency bands, large errors can be expected for a well-defined simple source if the positioning is imprecise and for a complex source even if the positioning device and the probe are of highest quality. Comparisons have been made between a two-microphone and a six-microphone probe, hand-held and robot-controlled. The comparisons show that, except for the case of an ideal measurement with a simple source and a high-precision robot, significant errors can be expected for all the tested measurement cases. The measurements also show that the positioning of the microphone is of major importance for the repeatability accuracy. The accuracy obtained with a 3D-probe is notably better than with a 1D-probe. The errors when measuring the complex source with a robot-controlled 3D-probe, however, are still so high, especially for the non-dominant directions, that interpretations have to be made with great care. Under non-ideal measurement conditions, the errors are found to be exponentially dependent upon the sound field pressure/intensity relationship (the pI-index).

The Precision of Reverberant Sound-Power Measurements

Determination of sound power in a reverberation room is subject to a random error whose size can be estimated and controlled by the knowledgeable laboratory manager. Under ideal measurement conditions the random error can be expressed as a product of three factors: a frequency-averaging factor governed by spectrum shape and room reverberation time, a spatial-averaging factor determined by the number and separation of fixed microphones or the path shape and size for a traversing microphone, and a rotating-diffuser factor depending on the size and shape of the rotating diffuser in relation to room size and reverberation time. Continuing progress in this field is teaching us to incorporate nonideal measurement conditions into our error estimates. In particular, we report progress in understanding the effects on random error due to (1) finite averaging time, (2) presence of a direct field component, and (3) insufficient modal overlap at low frequency.