Distortion Measure Research Articles

Secure halftone image steganography based on density preserving and distortion fusion

Most state-of-the-art halftone image steganographic methods measure the flipping distortion according to the statistics of the image database but neglect the characteristic of a single image. In this paper, a halftone image steganography based on density preserving and distortion fusion is proposed for minimizing the flipping distortion. Different from ordinary binary images, halftone images express the texture information by the intensity of local regions that are represented by the pixel density. Based on the density distribution of a halftone image, the embedding costs defined by a single existing distortion function are modified adaptively to maintain the original texture structure as much as possible. Furthermore, to select more appropriate flipped pixels, a distortion fusion strategy is developed from the perspective of anti-steganographic analysis, which can be applied to a batch of distortion functions. Finally, the syndrome-trellis code (STC) is applied to minimize the embedding distortion for playing the advantage of the distortion measurement. Experimental results show that the proposed steganographic scheme achieves great visual quality and strong statistical security without degrading the embedding capacity.

Distortion Control for Dissimilar Welding of SS321 to Hastelloy C-276 with CO2 Laser Beam Butt Joints Using Taguchi Methods

The laser beam welding process is a promising technology because of its reliability and ability to automate the process easily. This study aims to analyze distortion for dissimilar laser weld joints. Hastelloy C276 and SS321 plates are joined by using the CO2 Laser beam welding. Welding current, welding speed and shielding gas flow are chosen as process parameters for preparing butt joints. Each of the factors has two levels to control the parameters of the output. Experimentation was conducted with four trails by using an L4 orthogonal array. The quality of the welds and bead geometry are verified through macrostructure examination. The Vernier height gauge was used for the measurement of distortion in the weldments. Lower the better-quality characteristic is chosen for the response. ANOVA studies identified laser power at 81%, the weld speed at 16% parameters is a contribution with a statistical of about 95%. Full penetration was observed for all the experimental trails.

Modeling and detection of heat haze in computer vision based displacement measurement

Computer vision has become widely applied for structural displacement monitoring. However, heat haze is one of the major challenges. Image distortions caused by heat haze in hot weather can result in displacement errors. Therefore, a comprehensive study of properties of heat haze-induced distortions and displacement errors is conducted. Firstly, an image distortion estimation method is proposed for estimating heat haze-induced image distortions. Secondly, displacement errors due to heat haze are analyzed. A heat haze error model is formulated to describe the properties of heat haze errors, and the explicit effect of the environmental factor of temperature on the heat haze error model. Thirdly, a heat haze detection method is proposed to enable detection of heat haze’s influence on vision-based displacement sensors by extracting features from distortion measurements and applying a classification algorithm. Field tests in hot weather and experiments with dark heaters for introducing heat haze are conducted for validations.

Solid-state nuclear magnetic resonance of spin-9/2 nuclei 115 In and 209 Bi in functional inorganic complex oxides.

Indium and bismuth are technologically important elements, in particular as oxides for optoelectronic applications. 115 In and 209 Bi are both I = 9/2 nuclei with high natural abundances and moderately high frequencies but large nuclear electric quadrupole moments. Leveraging the quadrupolar interaction as a measure of local symmetry and polyhedral distortions for these nuclei could provide powerful insights on a range of applied materials. However, the absence of reported nuclear magnetic resonance (NMR) parameters on these nuclei, particularly in oxides, hinders their use by the broader materials community. In this contribution, solid-state 115 In and 209 Bi NMR of three recently discovered quaternary bismuth or indium oxides are reported, supported by density functional theory calculations, numerical simulations, diffraction and additional multinuclear (27 Al, 69,71 Ga, and 121 Sb) solid-state NMR measurements. The compounds LiIn2 SbO6 , BiAlTeO6 , and BiGaTeO6 are measured without special equipment at 9.4 T, demonstrating that wideline techniques such as the QCPMG pulse sequence and frequency-stepped acquisition can enable straightforward extraction of quadrupolar tensor information in I = 9/2 115 In and 209 Bi even in sites with large quadrupolar coupling constants. Relationships are described between the NMR observables and local site symmetry. These are amongst the first reports of the NMR parameters of 115 In, 121 Sb, and 209 Bi in oxides.

Interferometric 4D-STEM for Lattice Distortion and Interlayer Spacing Measurements of Bilayer and Trilayer 2D Materials.

Van der Waals materials composed of stacks of individual atomic layershave attracted considerable attention due to their exotic electronic properties that can be altered by, e.g., manipulating the twist angle of bilayer materials or the stacking sequence of trilayer materials. To fully understand and control the unique properties of these few-layer materials, a technique that can provide information about their local in-plane structural deformations, twist direction, and out-of-plane structure is needed. In principle, interference in overlap regions of Bragg disks originating from separate layers of a material encodes 3D information about the relative positions of atoms in the corresponding layers. Here, an interferometric 4D scanning transmission electron microscopy technique is described that utilizes this phenomenon to extract precise structural information from few-layer materials with nm-scale resolution. It is demonstrated how this technique enables measurement of local pm-scale in-plane lattice distortions as well as twist direction and average interlayer spacings in bilayer and trilayer graphene, and therefore provides a means to better understand the interplay between electronic properties and precise structural arrangements of few-layer 2D materials.

Impact of Dust on Spectral Distortion Measurements of the Cosmic Microwave Background

Abstract Spectral distortions of the cosmic microwave background (CMB) are sensitive to energy injection by exotic physics in the early universe. The proposed Primordial Inflation Explorer (PIXIE) mission has the raw sensitivity to provide meaningful limits on new physics, but only if foreground emission can be adequately modeled. We quantify the impact of interstellar dust on Compton y and μ measurements by considering a range of grain size distributions and compositions constrained by theoretical and observational priors. We find that PIXIE can marginalize over a modest number of dust parameters and still recover y and μ estimates, though with increased uncertainty. As more foreground components are included (synchrotron, free–free), estimates of y degrade, and measurement of μ in the range sometimes considered for the standard ΛCDM of 2 × 10−8 becomes infeasible without ancillary low-frequency foreground information. An additional concern is dust absorption of the CMB monopole, a subtle effect that must be included. We quantify one form of model discrepancy error, finding that the error introduced by fitting our interstellar medium dust model with a modified blackbody is too large for CMB spectral distortions to be detectable. The greatest challenge may be the cosmic infrared background (CIB). We find that μ and y are extremely sensitive to modeling choices for the CIB, and quantify biases expected for a range of assumptions.

The CEO Problem With rth Power of Difference and Logarithmic Distortions

The CEO problem has received much attention since first introduced by Berger et al., but there are limited results on non-Gaussian models with non-quadratic distortion measures. In this work, we extend the quadratic Gaussian CEO problem to two non-Gaussian settings with general rth power of difference distortion. Assuming an identical observation channel across agents, we study the asymptotics of distortion decay as the number of agents and sum-rate, R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sum</sub> , grow without bound, while individual rates vanish. The first setting is a regular source-observation model with rth power of difference distortion, which subsumes the quadratic Gaussian CEO problem, and we establish that the distortion decays at <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</i> (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sum</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-r/2</sup> ) when r ≥ 2. We use sample median estimation after the Berger-Tung scheme for achievability. The other setting is a non-regular source-observation model, including uniform additive noise models, with rth power of difference distortion for which estimation-theoretic regularity conditions do not hold. The distortion decay <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</i> (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sum</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-r</sup> ) when r ≥ 1 is obtained for the non-regular model by midrange estimator following the Berger-Tung scheme. We also provide converses based on the Shannon lower bound for the regular model and the Chazan-Zakai-Ziv bound for the non-regular model, respectively. Lastly, we provide a sufficient condition for the regular model, under which quadratic and logarithmic distortions are asymptotically equivalent by an entropy power relationship as the number of agents grows. This proof relies on the Bernstein-von Mises theorem.

Empirical validation of gradient field models for an accurate ADC measured on clinical 3T MR systems in body oncologic applications.

To empirically corroborate vendor-provided gradient nonlinearity (GNL) characteristics and demonstrate efficient GNL bias correction for human brain apparent diffusion coefficient (ADC) across 3T MR systems and spatial locations. Spatial distortion vector fields (DVF) were mapped in 3D using a surface fiducial array phantom for individual gradient channels on three 3T MR platforms from different vendors. Measured DVF were converted into empirical 3D GNL tensors and compared with their theoretical counterparts derived from vendor-provided spherical harmonic (SPH) coefficients. To illustrate spatial impact of GNL on ADC, diffusion weighted imaging using three orthogonal gradient directions was performed on a volunteer brain positioned at isocenter (as a reference) and offset superiorly by 10-17cm (>10% predicted GNL bias). The SPH tensor-based GNL correction was applied to individual DWI gradient directions, and derived ADC was compared with low-bias reference for human brain white matter (WM) ROIs. Empiric and predicted GNL errors were comparable for all three studied 3T MR systems, with <1.0% differences in the median and width of spatial histograms for individual GNL tensor elements. Median (±width) of ADC (10-3mm2/s) histograms measured at isocenter in WM reference ROIs from three MR systems were: 0.73±0.11, 0.71±0.14, 0.74±0.17, and at off-isocenters (before versus after GNL correction) were respectively 0.63±0.14 versus 0.72±0.11, 0.53±0.16 versus 0.74±0.18, and 0.65±0.16 versus 0.76±0.18. The phantom-based spatial distortion measurements validated vendor-provided gradient fields, and accurate WM ADC was recovered regardless of spatial locations and clinical MR platforms using system-specific tensor-based GNL correction for routine DWI.

Characterization of dynamic distortion in LED light output for optical wireless communications

Light-emitting diodes (LEDs) are widely used for data transmission in emerging optical wireless communications (OWC) systems. This paper analyzes the physical processes that limit the bandwidth and cause nonlinearities in the light output of modern, high-efficiency LEDs. The processes of carrier transport, as well as carrier storage, recombination, and leakage in the active region appear to affect the communications performance, but such purely physics-based models are not yet commonly considered in the algorithms to optimize OWC systems. Using a dynamic modeling of these phenomena, we compile a (invertable) signal processing model that describes the signal distortion and a parameter estimation procedure that is feasible in an operational communications link. We combine multiple approaches for steady-state and dynamic characterization to estimate such LED parameters. We verify that, for a high-efficiency blue GaN LED, the models become sufficiently accurate to allow digital compensation. We compare the simulation results using the model against optical measurements of harmonic distortion and against measurements of the LED response to a deep rectangular current modulation. We show how the topology of the model can be simplified, address the self-calibration techniques, and discuss the limits of the presented approach. The model is suitable for the creation of improved nonlinear equalizers to enhance the achievable bit rate in LED-based OWC systems and we believe it is significantly more realistic than LED models commonly used in communications systems.

Measuring Self-Serving Cognitive Distortions with Special Reference to Juvenile Delinquency: A Validation of the "How I Think" Questionnaire in a Sample of Portuguese Adolescents.

The present study aims to test the psychometric properties of the Portuguese version of the "How I Think" (HIT) questionnaire. The HIT questionnaire is a self-report measure of self-serving cognitive distortions. Our sample was comprised of 442 Portuguese-speaking adolescents and young adults (254 males and 188 females), aged between 12 and 20 years. Of the total 442 participants, 351 were recruited from a Portuguese school and 91 from four Portuguese detention centers for juvenile delinquents. Data analysis provided evidence supporting the original six-factor model solution, composed of a four-category typology of self-serving cognitive distortions (i.e., Selfcentered, Blaming Others, Minimizing/Mislabeling, and Assuming the Worst), an Anomalous responding, and one Positive filler factor. Further, results showed satisfactory internal consistency, convergent validity, and discriminant validity. In conclusion, this article provides Portuguese researchers and practitioners with a valid measure of self-serving cognitive distortions.

Transformation-Aware Similarity Measurement for Image Retargeting Quality Assessment via Bidirectional Rewarping

Image retargeting is an effective way to adapt images for target displays with different aspect ratios and sizes. Meanwhile, effective image retargeting quality assessment (IRQA) is important for optimizing the image retargeting operations. In this paper, we propose a transform-aware similarity (TRASIM) measurement metric for IRQA, including bidirectional geometric distortion measurement, bidirectional information loss measurement, and global salient structure distortion measurement. The main innovation of the TRASIM is to build a universal framework to establish the similarity transformation via bidirectional rewarping to simulate different types of retargeting operators. Based on the similarity transformation, geometric distortion and content loss are measured to determine the retargeting quality. Experimental results on two widely used databases (CUHK and RetargetMe) indicate that the proposed TRASIM has higher consistency with subjective ranks, compared with the state-of-the-art IRQA metrics.

Effect of welding sequence and welding current on distortion, mechanical properties and metallurgical observations of orbital pipe welding on SS 316L

Orbital pipe welding was often used to manufacture piping systems. In orbital pipe welding, a major challenge is the welding torch’s position during the welding process, so that additional methods are needed to overcome these challenges. This paper discusses the influence of welding sequence and welding current on distortion, mechanical properties and metallurgical observations in orbital pipe welding with SS 316L pipe square butt joints. The variation of the orbital pipe welding parameters used is welding current and welding sequence. The welding current used is 100 A, 110 A, and 120 A, while the welding sequence used is one sequence, two sequences, three sequences, and four sequences. The welding results will be analyzed from distortion measurement, mechanical properties test and metallurgical observations. Distortion measurements are made on the pipe before welding and after welding. Testing of mechanical properties includes tensile tests and microhardness tests, while metallurgical observations include macrostructure and microstructural observations. The results show that maximum axial distortion, transverse distortion, ovality, and taper occurred at a welding current of 120 A with four sequences of 445 µm, 300 µm, 195 µm, and 275 µm, respectively. The decrease in ultimate tensile strength is 51 % compared to the base metal’s ultimate tensile strength. Horizontal and vertical microhardness tests show that welding with one sequence produces the greatest microhardness value, but there is a decrease in the microhardness value using welding with two to four sequences. Orbital pipe welding results in different depths of penetration at each pipe position. The largest and smallest depth of penetration was 4.11 mm and 1.60 mm, respectively

Measurement of expansion factor and distortion for expansion microscopy using isolated renal glomeruli as landmarks.

Expansion microscopy has enabled super resolution imaging of biological samples. The accurate measurement of expansion factor and distortion typically requires locating and imaging the same region of interest in the sample before and after expansion, which is often time-consuming to achieve. Here we introduce a convenient method for relocation by utilizing isolated porcine glomeruli as landmarks during expansion. Following heat denaturation and proteinase K digestion protocols, the glomeruli exhibit expansion factor of 3.5 to 4 (only 7%-16% less expanded than the hydrogel), and 1% to 2% of relative distortion. Due to its appropriate size of 100 to 300 μm, the location of the glomerulus in the sample are visible to eyes, while its detailed shape only requires bright field microscopy. For expansion factors ranging from 3 to 10, the region in the vicinity of the glomerulus can be easily re-identified, and sometimes allows quantification of expansion factor and distortion under bright field without fluorescent labels.

Hybrid chaotic substitution and block-DCT-based ECG steganography with boosted embedding capacity

A novel idea of exploiting the chaotic sequences for substitution in the DCT coefficients of ECG signal according to the secret data is proposed in this work. The chaotic values are selected as per the decimal number generated from a bundle of secret bits. The selected chaotic values sensibly manipulates only the low- energy DCT coefficients, thus preservinge the diagnostic features of the ECG signal. The approach engenders unprecedented rise in the eEmbedding cCapacity (EC) as every substitution involves secret bits equal to the bundle size. The remarkable feature of the approach is that unlike existing steganography techniques, the perceptual quality of the stego-ECG is minimally affected with increase in the EC. The performance of the proposed technique is evaluated in terms of non-diagnostic distortion measures and clinically diagnostic error measures, while EC and bit error rate (BER) assess the steganography efficiency. The security analysis done in terms of key space verifies the robustness of the algorithm. The experimentation is done on the standard databases (both normal and abnormal) as well as on the self-recorded database. An average PRD, PSNR, WWPRD, WEDD and EC measured on all 48 records of MIT-BIH arrhythmia database of 5 min come out to be 2.51 × 10−3, 55.82, 0.088, 4.45 × 10−3 and 4.16, respectively marking the competency of the proposed technique in ECG steganography applications.

Exponential calibration for correlation coefficient with additive distortion measurement errors

AbstractThis paper studies the estimation of correlation coefficient between unobserved variables of interest. These unobservable variables are distorted in an additive fashion by an observed confounding variable. We propose a new identifiability condition by using the exponential calibration to obtain calibrated variables and propose a direct‐plug‐in estimator for the correlation coefficient. We show that the direct‐plug‐in estimator is asymptotically efficient. Next, we suggest an asymptotic normal approximation and an empirical likelihood‐based statistic to construct the confidence intervals. Last, we propose several test statistics for testing whether the true correlation coefficient is zero or not. The asymptotic properties of the proposed test statistics are examined. We conduct Monte Carlo simulation experiments to examine the performance of the proposed estimators and test statistics. These methods are applied to analyze a temperature forecast data set for an illustration.

Меры «VaR в степени t» и «ES в степени t» как новые подклассы мер катастрофических финансовых рисков во множестве мер риска искажения (Measures “VaR to the Extent of T” and “ES to the Extent of t” As New Subclasses of Measures of Catastrophic Financial Risks in a Variety of Measures of Risk Distortion)

Russian Abstract: Меры риска искажения в последние годы широко используются в финансовых и страховых приложениях благодаря своим привлекательным свойствам. Целью работы является исследование вопроса принадлежности мер риска «VaR в степени t», введенных в научный оборот автором к классу мер риска искажения, а также описание соответствующих функций искажения. В данной работе вводится новый класс мер риск «ES в степени t» и также исследуется вопрос о принадлежности этих мер риска, к классу мер риска искажения, а также описания соответствующих функций искажения. В работе описывается композитный метод, как метод построения новых функций искажения и соответствующих мер риска искажения. Этот метод используется для доказательства принадлежности мер риска «VaR в степени t» и «ES в степени t» к классу мер риска искажения. Представлены также различные примеры для иллюстрации соответствующих понятий и результатов, проявляющих важность мер риска «VaR в степени t» и «ES в степени t», как подмножеств мер риска искажения, позволяющих выявлять финансовые риски различной степени катастрофичности. Автор делает вывод, что меры риска «VaR в степени t» и «ES в степени t» может быть полезно в практике риск-менеджмента компаний при оценке маловероятных рисков высокой катастрофичности. English Abstract: Distortion risk measures have been widely used in financial and insurance applications in recent years due to their attractive properties. The aim of the work is to study the issue of belonging to the VaR to degree t risk measures introduced into scientific circulation by the author to the class of distortion risk measures, as well as to describe the corresponding distortion functions. This work introduces a new class of risk measures ES to degree t and also examines the issue of belonging to these risk measures, to the class of distortion risk measures, as well as descriptions of the corresponding distortion functions. The paper describes the composite method as a method for constructing new distortion functions and corresponding distortion risk measures. This method is used to prove that the risk measures VaR to degree t and ES to degree t belong to the class of distortion risk measures. Various examples are also presented to illustrate relevant concepts and outcomes that demonstrate the importance of VaR to degree t and ES to degree t risk measures as subsets of distortion risk measures that identify financial risks of varying degrees of catastrophicity. The author concludes that the risk measures VaR to the extent of t and ES to the extent of t can be useful in the practice of risk management of companies in assessing unlikely risks of high catastrophe.

A standard system phantom for magnetic resonance imaging.

PurposeA standard MRI system phantom has been designed and fabricated to assess scanner performance, stability, comparability and assess the accuracy of quantitative relaxation time imaging. The phantom is unique in having traceability to the International System of Units, a high level of precision, and monitoring by a national metrology institute. Here, we describe the phantom design, construction, imaging protocols, and measurement of geometric distortion, resolution, slice profile, signal‐to‐noise ratio (SNR), proton‐spin relaxation times, image uniformity and proton density.MethodsThe system phantom, designed by the International Society of Magnetic Resonance in Medicine ad hoc committee on Standards for Quantitative MR, is a 200 mm spherical structure that contains a 57‐element fiducial array; two relaxation time arrays; a proton density/SNR array; resolution and slice‐profile insets. Standard imaging protocols are presented, which provide rapid assessment of geometric distortion, image uniformity, T 1 and T 2 mapping, image resolution, slice profile, and SNR.ResultsFiducial array analysis gives assessment of intrinsic geometric distortions, which can vary considerably between scanners and correction techniques. This analysis also measures scanner/coil image uniformity, spatial calibration accuracy, and local volume distortion. An advanced resolution analysis gives both scanner and protocol contributions. SNR analysis gives both temporal and spatial contributions.ConclusionsA standard system phantom is useful for characterization of scanner performance, monitoring a scanner over time, and to compare different scanners. This type of calibration structure is useful for quality assurance, benchmarking quantitative MRI protocols, and to transition MRI from a qualitative imaging technique to a precise metrology with documented accuracy and uncertainty.

Logarithmic calibration for nonparametric multiplicative distortion measurement errors models

A logarithmic calibration estimation procedure is proposed for nonparametric regression models under the multiplicative distortion measurement errors setting. The unobservable response variable and covariates are both distorted in a multiplicative fashion by an observed confounding variable. By using the logarithmic calibration estimation procedure for unobserved variables, we consider to study the estimates of nonparametric mean function and its first derivative, the variance function, the Sharpe ratio function and correlation curve. We obtain asymptotic normality results for the proposed nonparametric estimators. Monte Carlo simulation experiments are conducted to examine the performance of the proposed estimators. The proposed estimators are applied to analyse a real dataset for an illustration.

A comparative study of sound sources separation by independent component analysis and binaural model

Humans’ auditory system can separate mixed sounds based on their sources easily. However, mimicking this ability by computer algorithm is not an easy task. Some approaches have been developed, particularly based on the statistical approach and binaural modeling. From statistical methods, independent component analysis (ICA) grows fast to mimics sound separation and localization by human auditory processing. On the other side, mathematical modeling to model binaural hearing has been built block by block. This paper is a comparative study of both approaches, a statistical method represented by FastICA and binaural modeling represented by the frequency domain binaural model. The task is to mimic how to binaural processing works to separate sound sources. The result of the comparison was given by the perceptual evaluation of speech quality (PESQ) and Itakura-Saito (IS) distortion measurement. PESQ scores ICA method obtains better performance than the binaural model while, in contrast, IS scores the binaural model better than ICA.

The Rate-Distortion Risk in Estimation From Compressed Data

Consider the problem of estimating a latent signal from a lossy compressed version of the data when the compressor is agnostic to the relation between the signal and the data. This situation arises in a host of modern applications when data is transmitted or stored prior to determining the downstream inference task. Given a bitrate constraint and a distortion measure between the data and its compressed version, let us consider the joint distribution achieving Shannon's rate-distortion (RD) function. Given an estimator and a loss function associated with the downstream inference task, define the RD risk as the expected loss under the RD-achieving distribution. We provide general conditions under which the operational risk in estimating from the compressed data is asymptotically equivalent to the RD risk. The main theoretical tools to prove this equivalence are transportation-cost inequalities in conjunction with properties of compression codes achieving Shannon's RD function. Whenever such equivalence holds, a recipe for designing estimators from datasets undergoing lossy compression without specifying the actual compression technique emerges: design the estimator to minimize the RD risk. Our conditions are simplified in the special cases of discrete memoryless or multivariate normal data. For these scenarios, we derive explicit expressions for the RD risk of several estimators and compare them to the optimal source coding performance associated with full knowledge of the relation between the latent signal and the data.