Model-based Measurement Research Articles

Electron and proton conductivity of Fe-N-C cathodes for PEM fuel cells: A model-based electrochemical impedance spectroscopy measurement

Impedance spectra of a PEM fuel cell with three Fe-N-C cathodes have been measured under the H2/N2 testing regime. The spectra have been fitted using a recently developed physics-based impedance model, which takes into account finite proton (σp) and electron (σe) conductivity of the oxygen-free cathode catalyst layer. Fitting allowed to extract numerical data for σp, σe, the double layer capacitance, and the inductance of cables used for measuring impedance spectra. The values of σp and σe are close to what previously found for standard Pt/C electrodes, which is found for the first time using PGM-free catalysts. The method enables simultaneous measurement of reference proton and electron conductivity of PEMFC cathode.

Gear Shape Parameter Measurement Using a Model-Based Scanning Multi-Distance Measurement Approach.

To reduce wind turbine failures by defective drive trains, deviations in the geometry of large gears (diameter ≳ 1 m) must be extensively determined with single-digit micrometer uncertainties. Fixed measuring volumes limit standard measuring methods like coordinate and gear measuring instruments for large gear measurements. Therefore, a model-based scanning multi-distance measurement approach for gear shape parameters is presented. The measurement approach has a scalable design and consists of a confocal-chromatic sensor, rotary table as a scanning unit and model-based signal processing. A preliminary study on a midsize spur gear demonstrates the general feasibility of the model-based scanning multi-distance measurement approach. As a result, the mean base circle radius as the fundamental gear shape parameter is determined with an uncertainty of <5 μm. The calibration and adjustment of the sensor arrangement were performed with a known calibration gear. Scalability is not experimentally validated in this article. However, simulations verify the scalability of the measurement approach in a first step. For gears with 1 m in diameter and varying tooth flank geometries, the estimated achievable uncertainty of the mean base circle radius is still <5 μm. Therefore, the model-based scanning multi-distance measurement approach is a promising alternative for gear inspection.

Detection and Independent Validation of Model-Based Quantitative Transcriptional Regulation Relationships Altered in Lung Cancers.

Differential expressions of genes are widely evaluated for the diagnosis and prognosis correlations with diseases. But limited studies investigate how transcriptional regulations are quantitatively altered in diseases. This study proposes a novel model-based quantitative measurement of transcriptional regulatory relationships between mRNA genes and Transcription Factor (TF) genes (mqTrans features). This study didn't consider the regulatory relationships between TF genes, so the mRNA genes were the protein-coding genes excluding the TF genes. The models are trained in the control samples in a lung cancer dataset and evaluated in two independent datasets and the hold-out testing samples from the third dataset. Twenty-nine mRNA genes are detected with transcriptional regulations quantitatively altered in lung cancers. The transcriptional modification technologies like RNA interference (RNAi) may be utilized to restore the altered transcriptional regulations in lung cancers.

Clinically applicable model-based method, for physiologically accurate flow waveform and stroke volume estimation

Background and ObjectivesCardiovascular dysfunction can be more effectively monitored and treated, with accurate, continuous, stroke volume (SV) and/or cardiac output (CO) measurements. Since direct measurements of SV/CO are highly invasive, clinical measures are often discrete, or if continuous, can require recalibration with a discrete SV measurement after hemodynamic instability. This study presents a clinically applicable, non-additionally invasive, physiological model-based, SV and CO measurement method, which does not require recalibration during or after hemodynamic instability. Methods and ResultsThe model’s ability to predict flow profiles and SV is assessed in an animal trial, using endotoxin to induce sepsis in 5 pigs. Mean percentage error between beat-to-beat SV measured from an aortic flow probe and estimated by the model was −2%, while 90% of estimations fell within −24.2% and +27.9% error. Error between estimated and measured changes in mean SV following interventions was less than 30% for 4 out of the 5 pigs. Correlations between model estimated and probe measured flow, for each pig and hemodynamic interventions, was r2 = 0.58 − 0.96, with 21 of the 25 pig intervention stages having r2 > 0.80. ConclusionThe results demonstrate the model accurately estimates and tracks changes in flow profiles and resulting SV, without requiring model recalibration.

Conventional vs. model-based measurement of patterned line widths from scanning electron microscopy profiles

Scanning electron microscopy (SEM) is a practical tool to determine the dimensions of nanometer-scale features. Conventional width measurements use arbitrary criteria, e.g., a 50 % threshold crossing, to assign feature boundaries in the measured SEM intensity profile. To estimate the errors associated with such a procedure, we have simulated secondary electron signals from a suite of line shapes consisting of 30 nm tall silicon lines with varying width, sidewall angle, and corner rounding. Four different inelastic scattering models were employed in Monte Carlo simulations of electron transport to compute secondary electron image intensity profiles for each of the shapes. The 4 models were combinations of dielectric function theory with either the single-pole approximation (SPA) or the full Penn algorithm (FPA), and either with or without Auger electron emission. Feature widths were determined either by the conventional threshold method or by the model-based library (MBL) method, which is a fit of the simulated profiles to the reference model (FPA + Auger). On the basis of these comparisons we estimate the error in the measured width of such features by the conventional procedure to be as much as several nanometers. A 1 nm difference in the size of, e.g., a nominally 10 nm transistor gate would substantially alter its electronic properties. Thus, the conventional measurements do not meet the contemporary requirements of the semiconductor industry. In contrast, MBL measurements employing models with varying accuracy differed one from another by less than 1 nm. Thus, a MBL measurement is preferable in the nanoscale domain.

Model-based measurement of internal geometry of solid parts with sub-PSF accuracy using laser-ultrasonic imaging

The problem of workpiece tolerance verification is of high interest in the field of nondestructive testing and evaluation. In this paper, reflection mode immersion 2D laser-ultrasound tomography is proposed for control of dimensions of solid objects with piecewise linear surface profiles. Pulsed laser radiation is used for generation of short ultrasonic probe pulse providing high spatial resolution. Wideband array of piezofilm sensors is used for detection of the waves reflected by the external and internal surfaces of the object. The image reconstruction algorithm accounts for refraction of acoustic waves at the liquid-solid interface. The contrast-enhanced reconstructed image is processed using the virtual model of the inspected part and the least-squares method to measure its actual dimensions. The accuracy obtained in the experiments with PMMA and duralumin samples is better than 100 μm in axial direction and is better than the size of the point-spread function in the material of the inspected part.

Model-based estimation of the stress-strain curve of metal strips

ABSTRACT The identification of the stress-strain curve of metal strips is a common task in the metals industry. As an alternative to commonly used tensile test machines, an inexpensive, model-based optical measurement method is presented. Particular importance was placed on the cost and usability of the method. The indirect approach computes the stress-strain curve based on a measured strip bending line. For the measurement, a metal strip is bent over a solid roll. A defined weight can be mounted at the end of the strip to control the local bending moment in the strip. The bending line of the strip is optically measured by a camera. The identification is carried out based on an optimization problem, where the quadratic error between the measured and the modelled strip bending line is minimized. Experimental results and measurements from a tensile test machine show a good agreement and thus verify the proposed identification method.

Fault diagnosis based on measurement reconstruction of HPT exit pressure for turbofan engine

Aero-engine gas path health monitoring plays a critical role in Engine Health Management (EHM). To achieve unbiased estimation, traditional filtering methods have strict requirements on measurement parameters which sometimes cannot be measured in engineering. The most typical one is the High-Pressure Turbine (HPT) exit pressure, which is vital to distinguishing failure modes between different turbines. For the case of an abrupt failure occurring in a single turbine component, a model-based sensor measurement reconstruction method is proposed in this paper. First, to estimate the missing measurements, the forward algorithm and the backward algorithm are developed based on corresponding component models according to the failure hypotheses. Then, a new fault diagnosis logic is designed and the traditional nonlinear filter is improved by adding the measurement estimation module and the health parameter correction module, which uses the reconstructed measurement to complete the health parameters estimation. Simulation results show that the proposed method can well restore the desired measurement and the estimated measurement can be used in the turbofan engine gas path diagnosis. Compared with the diagnosis under the condition of missing sensors, this method can distinguish between different failure modes, quantify the variations of health parameters, and achieve good performance at multiple operating points in the flight envelope.

Model-based measurement error detection of a coagulant dosage control system

Online instruments are widely used in wastewater treatment plants and drinking water treatment plants for process monitor and control. Although maintenances of online sensors are important routine works, potential measurement errors of online sensors are challenging not only monitoring of coagulation process but also the coagulant dosage control system, what this paper is focusing on. In order to estimate and detect the potential measurement errors, this paper proposes a concept of model-based measurement error detection. Relying on the model of the outlet software senor, the differences between simulations and measurements of outlet turbidity can be used as indicator of inlet measurement errors. Based on the concept, this paper enables to quantify the measurement errors and build up a novel detection method. In addition, the paper compares the proposed detection method with a traditional method—the normal variation range. The results show that the proposed method has a better efficiency to detect the measurement error.

A Model-Based Hybrid Ultrasonic Gas Flowmeter

Combining the transmission “Z” mode and the reflection “V” mode, a new hybrid dual-path ultrasonic sensor is designed to make full use of the advantages of the two modes. With the hybrid sensor and a new model-based time-of-flight (TOF) measurement method, a new model-based hybrid ultrasonic gas flowmeter is developed. The model-based TOF measurement method, which includes a signal filtering part and a model fitting part, is proposed to implement accurate TOF measurement. The signal filtering is implemented by a Butterworth bandpass filter and the model fitting is implemented by a hybrid Gauss–Newton structured BFGS method. A new hybrid ultrasonic flowmeter prototype with the inner diameter of 100 mm was developed and dynamic experiments were carried out. Experimental results show that the development of the hybrid ultrasonic flowmeter is successful. With the flowmeter prototype, the maximum relative error and the repeatability error of gas flowrate measurement are 1.80% and 0.45%, respectively, for a common flowrate ranges from 30 to 500 m3/h.

Low-frequency acoustoelastic-based stress state characterization: Theory and experimental validation

Abstract The acoustoelastic theory has been widely utilized for nondestructive stress measurements in structural components. Most of the currently available techniques operate at the high-frequency, weakly-dispersive portions of the dispersion curves and rely on time-of-flight measurements to quantify the effects of stress state on wave speed. High-frequency elastic waves are known to be less sensitive to the state-of-stress of the structure. As a result of such low sensitivity, calibration at a known stress state is required to compensate for material uncertainties, texture effects, and geometry variations of the structure under test. In this work, a new model-based stress measurement technique is developed. The technique integrates the acoustoelastic theory with numerical optimization and allows the utilization of the highly-stress-sensitive, strongly-dispersive, low-frequency flexural waves for reference-free stress measurements. The technique is experimentally validated on a long, rectangular aluminum beam, where accurate stress measurements have been achieved at low excitation frequencies. For instance, with a 500 Hz excitation signal, the error in the measured state-of-stress is found to be in the order of 1 MPa for the different loading scenarios considered in this study. Experimental results show that the developed technique is capable of measuring the state-of-stress without the need for calibration at a known stress state, which makes it ideal for in-service structures.

Nonlinear observer with observability-based parameter adaptation for vehicle motion estimation

In the framework of self-driving cars and driver-assistance systems the demand for reliable information about the vehicle ego-motion is increasing. This paper describes an estimation scheme, based on a nonlinear observer design, that provides velocity and attitude angle estimates. The approach relies on a state-affine representation of a kinematic model bolstered by a dynamic model-based measurement equation. By means of a thorough observability analysis, global exponential convergence is theoretically guaranteed. Additionally, in order to minimize the errors introduced by the dynamic model limitations, an observer tuning rule is proposed. The adaptation of the tuning parameters is built upon an online observability assessment of the system without the support of the dynamic model. Experimental results show that the presented approach reliably estimates the motion states.

A Model-Based Transit-Time Ultrasonic Gas Flowrate Measurement Method

Based on the transit-time ultrasonic gas flowrate measurement principle, a new model-based time-of-flight (TOF) measurement method is proposed. The proposed TOF measurement method includes two parts, the signal preprocessing and the model-fitting. Zero-phase filtering and independent component analysis with reference (ICA-R) are used to realize the signal preprocessing. The least-squares algorithm is used to implement the model-fitting and hence to obtain the TOF. A new single-acoustic-path ultrasonic gas flowmeter prototype with the inner diameter of 100 mm is developed and experiments are carried out to test the performance of the prototype. Experimental results show that the proposed signal preprocessing can effectively correct the distorted/noise-polluted measurement signal. In addition, the proposed model-based TOF measurement method is effective and can implement TOF measurement with higher repeatability and low standard deviation. For the gas flowrate ranges from 5 to 50 $\text{m}^{3}$ /h, the repeatability error of gas flowrate measurement is less than 1.99% and the maximum relative error of flowrate measurement is less than 3.27%. For the gas flowrate ranges from 50 to 500 $\text{m}^{3}$ /h, the repeatability error of gas flowrate measurement is less than 0.51% and the maximum relative error of flowrate measurement is less than 1.43%.

Combining model-based measurement results of critical dimensions from multiple tools

Model-based measurement techniques use experimental data and simulations of the underlying physics to extract quantitative estimates of the measurands of a specimen based upon a parametric model of that specimen. The uncertainties of these estimates are based upon not only the uncertainties in the experimental data, but also the sensitivity of that data to the model parameters, and parametric correlations among those parameters. The combination of two or more model-based techniques as well as the Bayesian approach are shown to be optimal for obtaining the lowest possible uncertainties. As an example, using this form of hybrid metrology, state-of-the-art sub-14 nm wide lines from semiconductor manufacturing are measured using a combined regression from critical-dimension small-angle x-ray scattering and scanning electron microscopy that leads to lower uncertainties.

A model-based measurement method for intelligent circuit breaker with data communication

In this paper, an object-oriented information model of an intelligent vacuum circuit breaker based on its physical structure and function (service) was established to integrate the measuring information flow of field parameters, the monitoring information flow of status data, and the operating and controlling information flow. The status parameters of the intelligent vacuum breaker were detected by analysing the principles and methods based on IEC61850 and IEC62271 standards. The IEC 61850 standard repository can be extended according to the characteristics of the intelligent vacuum breaker status parameters, and the IED server model was constructed to be suitable for the vacuum breaker. A key feature of the new method is the use of a multimode fibre that is incorporated into the IED server model to transmit the status parameters from the target to the sensor. The main characteristic of the measurement method is that it exhibits real-time transmission of data collection. The model includes temperature testing of the switch contact, vacuum arc testing, detection of vacuum switch motion and primary circuit parameters testing. Furthermore, we show how the IEC61850 standard can be used to give a better insight on data communication of the data collector and intelligent circuit breaker. Experimental results showed that the feasibility of intelligent vacuum breaker status monitoring through the switching-on test. It purposes to achieve information integration and a frame communication platform for the intelligent vacuum breaker.

Model-based Measurement of Actual Volatility in High-frequency Data

In this paper we aim to measure actual volatility within a model-based framework using high-frequency data. In the empirical finance literature it is known that tick-by-tick prices are subject to market micro-structure such as bid-ask bounces and trade information. Such market micro-structure effects become more and more apparent as prices or returns are sampled at smaller and smaller time intervals. High-frequency returns are used for the computation of realised volatility. Recent theoretical results have shown that realised volatility is a consistent estimator of actual volatility but when it is subject to micro-structure noise, the estimator diverges. Parametric and nonparametric methods can be adopted to account for the micro-structure bias. Here we measure actual volatility using a model that takes account of micro-structure noise together with intra-daily volatility patterns and stochastic volatility. The coefficients of this model are estimated by maximum likelihood methods that are based on importance sampling techniques. It is shown that such Monte Carlo techniques can be employed successfully for our purposes in a feasible way. As far as we know, this is a first serious attempt to model the basic components of the mean and variance of high-frequency prices simultaneously. An illustration is given for three months of tick-by-tick transaction prices of the IBM stock traded at the New York Stock Exchange.

Multi-scale biomedical systems: measurement challenges

Multi-scale biomedical systems are those that represent interactions in materials, sensors, and systems from a holistic perspective. It is possible to view such multi-scale activity using measurement of spatial scale or time scale, though in this paper only the former is considered. The biomedical application paradigm comprises interactions that range from quantum biological phenomena at scales of 10-12 for one individual to epidemiological studies of disease spread in populations that in a pandemic lead to measurement at a scale of 10+7. It is clear that there are measurement challenges at either end of this spatial scale, but those challenges that relate to the use of new technologies that deal with big data and health service delivery at the point of care are also considered. The measurement challenges lead to the use, in many cases, of model-based measurement and the adoption of virtual engineering. It is these measurement challenges that will be uncovered in this paper.

P-195L:Late-News Poster: Head Position Model-based Latency Measurement System for Virtual Reality Head Mounted Display

This paper presents a novel quantifiable latency measurement system specialized for HMD devices. After analyzing the head position, we implement the rotary platform and the pixel luminance change detector. Then, we accurately measure the latency between the HMD physical movement and an output image change.

Model-Based Quantification of Glucagon-Like Peptide-1–Induced Potentiation of Insulin Secretion in Response to a Mixed Meal Challenge

Glucagon-like peptide-1 (GLP-1) is a powerful insulin secretagogue that is secreted in response to meal ingestion. The ability to quantify the effect of GLP-1 on insulin secretion could provide insights into the pathogenesis and treatment of diabetes. We used a modification of a model of GLP-1 action on insulin secretion using data from a hyperglycemic clamp with concomitant GLP-1 infusion. We tested this model using data from a mixed meal test (MMT), thereby measuring GLP-1-induced potentiation of insulin secretion in response to a meal. The GLP-1 model is based on the oral C-peptide minimal model and assumes that over-basal insulin secretion depends linearly on GLP-1 concentration through the parameter Π, representing the β-cell sensitivity to GLP-1. The model was tested on 62 subjects across the spectrum of glucose tolerance (age, 53 ± 1 years; body mass index, 29.7 ± 0.6 kg/m(2)) studied with an MMT and provided a precise estimate of both β-cell responsivity and Π indices. By combining Π with a measure of L-cell responsivity to glucose, one obtains a potentiation index (PI) (i.e., a measure of the L-cell's function in relation to prevailing β-cell sensitivity to GLP-1). Model-based measurement of GLP-1-induced insulin secretion demonstrates that the PI is significantly reduced in people with impaired glucose tolerance, compared with those with normal glucose tolerance. We describe a model that can quantitate the GLP-1-based contribution to insulin secretion in response to meal ingestion. This methodology will allow a better understanding of β-cell function at various stages of glucose tolerance.

High-Efficiency PCB- and Package-Level Wireless Power Transfer Interconnection Scheme Using Magnetic Field Resonance Coupling

As technology develops, the number of chips increases while the thickness of mobile products continuously decreases, which leads to the need for high-density packaging techniques with high numbers of power and signal lines. By applying wireless power transfer technology at the printed circuit board (PCB) and package levels, the number of power pins can be greatly reduced to produce more space for signal pins and other components in the system. For the first time, in this paper, we propose and demonstrate a high-efficiency PCB- and package-level wireless power transfer interconnection scheme. We enhance the efficiency by applying magnetic field resonance coupling using a matching capacitor. The proposed scheme can replace a high number of power interconnections with rectangular spiral coils to wirelessly transfer power from the source to the receiver at the PCB and package levels. The equivalent circuit model is suggested with analytic equations, which is then analyzed to optimize the test vehicle design. For the experimental verification of the suggested model, the $Z$ -parameter results obtained from the model-based equation and measurement of the designed and fabricated test vehicles are compared at up to 1 GHz. The power transfer efficiency from the source coil to the receiver coil in this scheme is able to reach 85.6%. Finally, we designed and fabricated a CMOS full-bridge rectifier and mounted it on the receiver board to convert the transferred voltage from ac voltage to dc voltage. A measured dc voltage of 2.0 V is sufficient to operate the circuit, which generally consists of 1.5 V devices.