Varying-coefficient functional linear regression

Functional linear regression analysis aims to model regression relations which include a functional predictor. The analog of the regression parameter vector or matrix in conventional multivariate or multiple-response linear regression models is a regression parameter function in one or two arguments. If, in addition, one has scalar predictors, as is often the case in applications to longitudinal studies, the question arises how to incorporate these into a functional regression model. We study a varying-coefficient approach where the scalar covariates are modeled as additional arguments of the regression parameter function. This extension of the functional linear regression model is analogous to the extension of conventional linear regression models to varying-coefficient models and shares its advantages, such as increased flexibility; however, the details of this extension are more challenging in the functional case. Our methodology combines smoothing methods with regularization by truncation at a finite number of functional principal components. A practical version is developed and is shown to perform better than functional linear regression for longitudinal data. We investigate the asymptotic properties of varying-coefficient functional linear regression and establish consistency properties.Comment: Published in at http://dx.doi.org/10.3150/09-BEJ231 the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm

Ultrasonic metal sheet thickness measurement without prior wave speed calibration

Conventional ultrasonic mensuration of sample thickness from one side only requires the bulk wave reverberation time and a calibration speed. This speed changes with temperature, stress, and microstructure, limiting thickness measurement accuracy. Often, only one side of a sample is accessible, making in situ calibration impossible. Non-contact ultrasound can generate multiple shear horizontal guided wave modes on one side of a metal plate. Measuring propagation times of each mode at different transducer separations, allows sheet thickness to be calculated to better than 1% accuracy for sheets of at least 1.5 mm thickness, without any calibration

Shear wave generation using a spiral electromagnetic acoustic transducer

A spiral electromagnetic acoustic transducer (EMAT) is efficient in eddy current generation and has been used for surface defect inspection using Rayleigh waves or thickness gauging based on plane waves in echo mode. Measured and calculated particle velocities and directivities are presented. It is found that the shear wave is not predominantly a plane wave. It has zero amplitude on the axis of the generation EMAT and has maximum amplitude at the critical angle. The shear wave could be used in the steel industry for both internal and surface defect inspections together with Rayleigh wave

Focused Rayleigh wave EMAT for characterisation of surface-breaking defects

Developments towards higher resolution and the ability to detect small defects are bringing a step-change in non-destructive testing. This paper presents a new method for increasing resolution, using a focused electromagnetic acoustic transducer (EMAT) optimised to generate Rayleigh waves at 2 MHz. This high frequency allows detection of mm-depth defects, and the focusing allows sizing of much shorter defects than is possible when using standard EMATs. The focusing behaviour and the aperture angle effect are analysed using laser vibrometry and finite element modeling, showing that a reduced aperture shifts the focal point from the designed value and increases the focal depth. The dual-EMAT has excellent signal to noise ratio (up to 30 dB) and has been used in single shot mode to image a variety of surface-breaking defects, including detecting and positioning a pair of real defects in an aluminium billet sample, and a machined defect of 2 mm length, 0.2 mm width, and 1.5 mm depth, giving an upper limit on the defect length of 2.1 +- 0.5 mm. The results can be used to design an EMAT with optimised focal behaviour for defect detection

Dynamic expression of CEACAM7 in precursor lesions of gastric carcinoma and its prognostic value in combination with CEA

<p>Abstract</p> <p>Background</p> <p>The significance of carcinoembryonic antigen-related cell adhesion molecule 7 (CEACAM7) expression in gastric carcinoma and precancerous lesions and its correlation with CEA expression has rarely been previously investigated.</p> <p>Methods</p> <p>CEACAM7 and CEA expression was detected by immunohistochemistry in consecutive sections of 345 subjects with gastric carcinoma and precancerous lesions. Laser confocal analysis was performed to determine CEACAM7 and CEA localization. Correlation between CEACAM7 and CEA expression with clinicopathological parameters was statistically analyzed.</p> <p>Results</p> <p>CEACAM7 expression correlated with pathologic grading (P = 0.006), Lauren's classification (P = 0.023), and CEA expression (Spearman R = 0.605, P < 0.001) in gastric carcinoma. CEACAM7 co-localized with CEA predominantly in the cytoplasmic membrane of cancerous cells. CEA expression was correlated with lymph node metastasis (P = 0.031). CEACAM7 and CEA expression increased progressively from precursor lesions to gastric carcinomas. A combination of CEACAM7 and CEA expression was determined to be an independent predictor for patients with gastric carcinoma by multivariate analysis (P = 0.001).</p> <p>Conclusions</p> <p>CEACAM7 expression correlates with tumor differentiation and CEA expression in gastric carcinoma. CEACAM7 and CEA expression may synergistically promote gastric carcinogenesis. Combined CEACAM7 and CEA expression analysis can be a useful postoperative predictor for patients with gastric carcinoma.</p

Optimal Transport for Treatment Effect Estimation

Estimating conditional average treatment effect from observational data is highly challenging due to the existence of treatment selection bias. Prevalent methods mitigate this issue by aligning distributions of different treatment groups in the latent space. However, there are two critical problems that these methods fail to address: (1) mini-batch sampling effects (MSE), which causes misalignment in non-ideal mini-batches with outcome imbalance and outliers; (2) unobserved confounder effects (UCE), which results in inaccurate discrepancy calculation due to the neglect of unobserved confounders. To tackle these problems, we propose a principled approach named Entire Space CounterFactual Regression (ESCFR), which is a new take on optimal transport in the context of causality. Specifically, based on the framework of stochastic optimal transport, we propose a relaxed mass-preserving regularizer to address the MSE issue and design a proximal factual outcome regularizer to handle the UCE issue. Extensive experiments demonstrate that our proposed ESCFR can successfully tackle the treatment selection bias and achieve significantly better performance than state-of-the-art methods.Comment: Accepted as NeurIPS 2023 Poste

Magnetic phase transitions in Gd64Sc36 studied using non-contact ultrasonics

The speed and attenuation of ultrasound propagation can be used to determine material properties and identify phase transitions. Standard ultrasonic contact techniques are not always convenient due to the necessity of using couplant; however, recently reliable non-contact ultrasonic techniques involving electromagnetic generation and detection of ultrasound with electromagnetic acoustic transducers (EMATs) have been developed for use on electrically conducting and/or magnetic materials. We present a detailed study of magnetic phase transitions in a single crystal sample of Gd64Sc36 magnetic alloy using contact and non-contact ultrasonic techniques for two orientations of external magnetic field. Phase diagrams are constructed based on measurements of elastic constant C33, the attenuation and the efficiency of generation when using an EMAT. The EMATs are shown to provide additional information related to the magnetic phase transitions in the studied sample, and results identify a conical helix phase in Gd64Sc36 in the magnetic field orientation