scholarly journals Defect Detection using Power Spectrum of Torsional Waves in Guided-Wave Inspection of Pipelines

2019 ◽  
Vol 9 (7) ◽  
pp. 1449 ◽  
Author(s):  
Houman Nakhli Mahal ◽  
Kai Yang ◽  
Asoke Nandi
Keyword(s):  
Power Spectrum ◽  
Single Point ◽  
Excitation Frequency ◽  
Guided Wave ◽  
Torsional Wave ◽  
Material Loss ◽  
Optimum Frequency ◽  
Cross Sectional ◽  
Torsional Waves ◽  
Excitation Sequence

Ultrasonic Guided-wave (UGW) testing of pipelines allows long-range assessment of pipe integrity from a single point of inspection. This technology uses a number of arrays of transducers separated by a distance from each other to generate a single axisymmetric (torsional) wave mode. The location of anomalies in the pipe is determined by inspectors using the received signal. Guided-waves are multimodal and dispersive. In practical tests, nonaxisymmetric waves are also received due to the nonideal testing conditions, such as presence of variable transfer function of transducers. These waves are considered as the main source of noise in the guided-wave inspection of pipelines. In this paper, we propose a method to exploit the differences in the power spectrum of the torsional wave and flexural waves, in order to detect the torsional wave, leading to the defect location. The method is based on a sliding moving window, where in each iteration the signals are normalised and their power spectra are calculated. Each power spectrum is compared with the previously known spectrum of excitation sequence. Five binary conditions are defined; all of these need to be met in order for a window to be marked as defect signal. This method is validated using a synthesised test case generated by a Finite Element Model (FEM) as well as real test data gathered from laboratory trials. In laboratory trials, three different pipes with defects sizes of 4%, 3% and 2% cross-sectional area (CSA) material loss were evaluated. In order to find the optimum frequency, the varying excitation frequency of 30 to 50 kHz (in steps of 2 kHz) were used. The results demonstrate the capability of this algorithm in detecting torsional waves with low signal-to-noise ratio (SNR) without requiring any change in the excitation sequence. This can help inspectors by validating the frequency response of the received sequence and give more confidence in the detection of defects in guided-wave testing of pipelines.

scholarly journals Improved Defect Detection Using Adaptive Leaky NLMS Filter in Guided-Wave Testing of Pipelines

2019 ◽  
Vol 9 (2) ◽  
pp. 294 ◽  
Author(s):  
Houman Nakhli Mahal ◽  
Kai Yang ◽  
Asoke Nandi
Keyword(s):  
Signal To Noise Ratio ◽  
Single Point ◽  
Element Model ◽  
Wave Mode ◽  
Guided Wave ◽  
Least Mean Square ◽  
Material Loss ◽  
Optimum Frequency ◽  
Cross Sectional ◽  
Axisymmetric Wave

Ultrasonic guided wave (UGW) testing of pipelines allows long range assessments of pipe integrity from a single point of inspection. This technology uses a number of arrays of transducers, linearly placed apart from each other to generate a single axisymmetric wave mode. The general propagation routine of the device results in a single time domain signal, which is then used by the inspectors to detect the axisymmetric wave for any defect location. Nonetheless, due to inherited characteristics of the UGW and non-ideal testing conditions, non-axisymmetric (flexural) waves will be transmitted and received in the tests. This adds to the complexity of results’ interpretation. In this paper, we implement an adaptive leaky normalized least mean square (NLMS) filter for reducing the effect of non-axisymmetric waves and enhancement of axisymmetric waves. In this approach, no modification in the device hardware is required. This method is validated using the synthesized signal generated by a finite element model (FEM) and real test data gathered from laboratory trials. In laboratory trials, six different sizes of defects with cross-sectional area (CSA) material loss of 8% to 3% (steps of 1%) were tested. To find the optimum frequency, several excitation frequencies in the region of 30–50 kHz (steps of 2 kHz) were used. Furthermore, two sets of parameters were used for the adaptive filter wherein the first set of tests the optimum parameters were set to the FEM test case and, in the second set of tests, the data from the pipe with 4% CSA defect was used. The results demonstrated the capability of this algorithm for enhancing a defect’s signal-to-noise ratio (SNR).

scholarly journals Stereo-DIC Measurements of a Vibrating Bladed Disk: In-Depth Analysis of Full-Field Deformed Shapes

2021 ◽  
Vol 11 (12) ◽  
pp. 5430
Author(s):  
Paolo Neri ◽  
Alessandro Paoli ◽  
Ciro Santus
Keyword(s):  
Single Point ◽  
Excitation Frequency ◽  
Phase Variation ◽  
Operating Conditions ◽  
Image Correlation ◽  
Response Analysis ◽  
Full Field ◽  
Low Speed ◽  
Bladed Disk ◽  
Depth Analysis

Vibration measurements of turbomachinery components are of utmost importance to characterize the dynamic behavior of rotating machines, thus preventing undesired operating conditions. Local techniques such as strain gauges or laser Doppler vibrometers are usually adopted to collect vibration data. However, these approaches provide single-point and generally 1D measurements. The present work proposes an optical technique, which uses two low-speed cameras, a multimedia projector, and three-dimensional digital image correlation (3D-DIC) to provide full-field measurements of a bladed disk undergoing harmonic response analysis (i.e., pure sinusoidal excitation) in the kHz range. The proposed approach exploits a downsampling strategy to overcome the limitations introduced by low-speed cameras. The developed experimental setup was used to measure the response of a bladed disk subjected to an excitation frequency above 6 kHz, providing a deep insight in the deformed shapes, in terms of amplitude and phase distributions, which could not be feasible with single-point sensors. Results demonstrated the system’s effectiveness in measuring amplitudes of few microns, also evidencing blade mistuning effects. A deeper insight into the deformed shape analysis was provided by considering the phase maps on the entire blisk geometry, and phase variation lines were observed on the blades for high excitation frequency.

scholarly journals Suicidal ideation, psychopathology and associated factors among HIV-infected adults in Indonesia

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Youdiil Ophinni ◽  
Adrian ◽  
Kristiana Siste ◽  
Martina Wiwie ◽  
Gina Anindyajati ◽  
...  
Keyword(s):  
Suicidal Ideation ◽  
Single Point ◽  
Cross Sectional Study ◽  
Anxiety Symptoms ◽  
Cd4 Count ◽  
Depression Symptoms ◽  
Early Screening ◽  
Cross Sectional ◽  
Aids Epidemic ◽  
Hiv Aids

Abstract Background Suicidal behavior is a prevalent psychiatric emergency in HIV-infected adults. Detection of suicidal ideation is important in planning early psychiatric intervention and optimizing HIV/AIDS management. Characterization of suicidal ideation among HIV-infected adults is crucial; however, practically there is no data in Indonesia, the country with the second largest burden of HIV/AIDS epidemic in Asia. This study aims to identify suicidal ideation and analyze the associated psychopathology and determining factors among HIV-infected adults in Indonesia. Methods An observational cross-sectional study was conducted among HIV-infected adults aged 18–65 years old receiving antiretroviral therapy (ART). Measurement using Symptom Checklist-90 (SCL-90) was performed to assess the existing psychopathology. Firth’s penalized logistic regression analysis was performed to identify factors associated with suicidal ideation. Results A total of 86 subjects were recruited. Most subjects were male (65.1%), median age was 35 years, and median latest CD4 count was 463 cells/μl. Lifetime suicidal ideation was identified in 20 subjects (23.3%). Mean SCL-90 T-score for depressive and anxiety symptoms were both significantly higher among subjects with suicidal ideation (M = 60.75, SD = 12.0, p = 0.000 and M = 57.9, SD = 2.8, p = 0.001, respectively) compared to those without. Bivariate analyses showed that lifetime suicidal ideation was associated with depressive and anxiety symptoms, non-marital status, CD4 count < 500 cells/μl, and efavirenz use. Multivariate analysis identified that a single-point increase in SCL-90 depression symptoms score (AOR 1.16, 95% CI 4.5–123.6, p = 0.000) and efavirenz use (AOR 5.00, 95% CI 1.02–24.6, p = 0.048) were significant independent factors related to suicidal ideation. Conclusion Suicidal ideation is commonly found among Indonesian HIV-infected adults on ART. Depressive symptoms and efavirenz use are independent factors related to the presence of suicidal ideation. Thus, early screening of psychopathology as well as substitution of efavirenz with other ART regiment are recommended to prevent suicide and improve HIV/AIDS management outcome.

scholarly journals Electromigration-induced directional steps towards the formation of single atomic Ag contacts

2020 ◽  
Vol 11 ◽  
pp. 680-687
Author(s):  
Atasi Chatterjee ◽  
Christoph Tegenkamp ◽  
Herbert Pfnür
Keyword(s):  
Fourier Transforms ◽  
Single Point ◽  
Point Contact ◽  
Single Atom ◽  
Point Contacts ◽  
Cross Sectional ◽  
Shell Effects ◽  
Theoretical Approaches ◽  
Average Grain Size ◽  
Thinning Process

Even though there have been many experimental attempts and theoretical approaches to understand the process of electromigration (EM), it has not been quantitatively understood for ultrathin structures and at grain boundaries. Nevertheless, we showed recently that it can be used reliably for the formation of single atomic point contacts after careful pre-structuring of the initial Ag nanostructures. The process of formation of nanocontacts by EM down to a single-atom point contact was investigated for ultrathin (5 nm) Ag structures at 100 K by measuring the conductance as a function of the time during EM. In this paper, we compare the process of thinning by EM of structures with constrictions below the average grain size of Ag layers (15 nm) with that of structures with much larger initial constrictions of around 150 nm having multiple grains at the centre constriction prior to the formation of a point contact. Even though clear morphological differences exist between both types of structures, quantized conductance plateaus showing the formation of single point contacts have been observed for both. Here we put emphasis on the thinning process by EM, just before a point contact is formed. To understand this thinning process, the semi-classical regime before the contact reaches the quantum regime was analyzed in detail. For this purpose, we used experimental conductance histograms in the range between 2G 0 and 15G 0 and their corresponding Fourier transforms (FTs). The FT analysis of the conductance histograms exhibits a clear preference for thinning along the [100] direction. Using well-established models, both atom-by-atom steps and ranges of stability, presumably caused by electronic shell effects, can be discriminated. Although the directional motion of atoms during EM leads to specific properties such as the instabilities mentioned, similarities to mechanically opened contacts with respect to cross-sectional stability were found.

scholarly journals Phenotyping of CYP 4501A2 Activity by Total Overnight Salivary Caffeine Assessment (TOSCA) in Patients on Warfarin Treatment: A Cross-Sectional Study

2017 ◽  
Vol 24 (6) ◽  
pp. 928-935 ◽  
Author(s):  
Giovanni Tarantino ◽  
Domenico Capone ◽  
Paola Contaldi ◽  
Adriana Gianno ◽  
Mosca Teresa ◽  
...  
Keyword(s):  
Adverse Events ◽  
Drug Concentration ◽  
Ethical Issues ◽  
Single Point ◽  
Warfarin Dose ◽  
Individual Variability ◽  
Bleeding Complications ◽  
Close Monitoring ◽  
Cross Sectional ◽  
Warfarin Sodium

Warfarin is an oral anticoagulant, commonly used for primary and secondary prevention of venous and arterial thromboembolic events. The drug is characterized by narrow therapeutic index, widespread individual variability in clinical response, and high rates of adverse events, particularly bleeding complications. For these reasons, a close monitoring of the dosage, using the frequent assessment of coagulation status by means of International Normalized Ratio value, is mandatory. Warfarin is metabolized by hepatic cytochrome P-450. High CYP 450 activity may lead to low drug concentration and requires high warfarin doses to reach efficacy; conversely, low CYP 450 activity is responsible for high drug concentration and needs for low doses to avoid potential toxicity risks. The major isoforms of CYP involved in the metabolism of warfarin sodium are CYP1A2 (for the R-warfarin) and CYP2C9 (for the S-warfarin). The probes for testing CYP1A2 are phenacetin and caffeine while for CYP2C9 tolbutamide. Although S-warfarin has major activity, it was decided to exclude its phenotyping for ethical issues, being mandatory to use a drug (tolbutamide). Instead, it was chosen to test the 1A2 isoform, as the activity of the latter isoform could be investigated by using caffeine contained in the caffeinated beverages. Specifically, a single-point concentration of salivary caffeine (total overnight salivary caffeine assessment [TOSCA]) after an overnight period of the caffeinated beverages abstinence was utilized. In the present study, 75 nonsmoker patients regularly receiving warfarin sodium were enrolled. The results have showed a significant association of the warfarin dose with TOSCA values (coefficient = –0.15, standard error = 0.04, 95% confidence interval = –0.24 to –0.06, t = –3.23, P = .002). In conclusion, the phenotyping of CYP1A2 by TOSCA could be useful, if further proven, to help manage patients on warfarin in order to lessen severe adverse events.

scholarly journals Estimating Deterioration in the Concrete Tie-Ballast Interface Based on Vertical Tie Deflection Profile: A Numerical Study

2016 ◽  
Author(s):  
Hailing Yu
Keyword(s):  
Direct Detection ◽  
Numerical Study ◽  
Interface Condition ◽  
Vertical Deflection ◽  
Cohesive Elements ◽  
Material Loss ◽  
Element Analysis ◽  
Cross Sectional ◽  
Technical Requirements ◽  
Support Conditions

In ballasted concrete tie track, the tie-ballast interface can deteriorate resulting in concrete tie bottom abrasion, ballast pulverization and/or voids in tie-ballast interfaces. Tie-ballast voids toward tie ends can lead to unfavorable center binding support conditions that can result in premature concrete tie failure and possible train derailment. Direct detection of these conditions is difficult. There is a strong interest in assessing the concrete tie-ballast interface conditions indirectly using measured vertical deflections. This paper seeks to establish a link between the vertical deflection profile of a concrete tie top surface and the tie-ballast interface condition using the finite element analysis (FEA) method. The concrete tie is modeled as a concrete matrix embedded with prestressing steel strands or wires. The configurations of two commonly used concrete ties, one with 8 prestressing strands and the other with 20 prestressing wires, are employed in this study. All models are three-dimensional and symmetric about the tie center. A damaged plasticity model that can predict onset and propagation of tensile cracks is applied to the concrete material. The steel-concrete interface is homogenized and represented with a thin layer of cohesive elements sandwiched between steel and concrete elements. Strand- or wire-specific elasto-plastic bond models developed at the Volpe Center are applied to the cohesive elements to account for the interface bonding mechanisms. FE models are developed for both original and worn concrete ties, with the latter assuming hypothetical patterns of reduced cross sections resulting from abrasive interactions with the ballast. Static analyses of pretension release in these concrete ties are conducted, and vertical deflection gradients along tie lengths are calculated and shown to correspond well with the worn cross sectional patterns for a given reinforcement type. The ballast is further modeled with Extended Drucker-Prager plasticity, and hypothetical voids are applied toward the tie ends along the concrete tie-ballast interface to simulate center binding support conditions. The distance range over which the concrete tie is supported in the center is variable and yields different center binding severity. Static simulations are completed with vertical rail seat loads applied on the concrete tie-ballast assembly. The influences of various factors on the vertical deflection profile, including tie type, vertical load magnitude, center binding severity, cross sectional material loss and prestress loss, are examined based on the FEA results. The work presented in this paper demonstrates the potential of using the vertical deflection profile of concrete tie top surfaces to assess deteriorations in the tie-ballast interface. The simulation results further help to clarify minimum technical requirements on inspection technologies that measure concrete tie vertical deflection profiles.

The effects of corporate brand symbolism on consumer satisfaction and loyalty

2016 ◽  
Vol 28 (3) ◽  
pp. 481-498 ◽  
Author(s):  
Tatiana Anisimova
Keyword(s):  
Social Life ◽  
Consumer Satisfaction ◽  
Single Point ◽  
Social Aspects ◽  
Consumer Loyalty ◽  
Cross Sectional ◽  
Corporate Brand ◽  
Content Type ◽  
Strategic Role ◽  
The Impact

Purpose – The purpose of this paper is to test the effects of corporate brand symbolism on consumer satisfaction and loyalty on a sample of Australian automobile consumers. Design/methodology/approach – Survey research was employed to test the study hypotheses. The regression analysis was used to evaluate the relationships between an independent variable (corporate brand symbolism) and dependent variables (consumer satisfaction and loyalty). Findings – Support was found for all hypotheses formulated in this study. Regression results reveal consistent favourable and significant effects of corporate brand symbolism on both consumer satisfaction and loyalty. Research limitations/implications – Although this paper makes contributions in international marketing, the cross-sectional nature of the data collection method limits the information gained to the single point in time. This research studied the impact of corporate brand symbolism on consumers of one original equipment manufacturers (OEM). Having a larger number of participating car manufacturers/OEMs would have provided a wider insight. However, time and resources limitation did not allow to study a larger sample. In the future, practitioners are recommended to further understand the relationship between self and social aspects of brand symbolism in order to formulate more targeted communication strategies. Practical implications – The findings of this study point to the strategic role of the brand in generating both satisfaction and loyalty. In the light of increasing advertising costs and decreasing consumer loyalty, strengthening corporate brand symbolism makes a lot of economic sense. The findings suggest that managers need to take into account consumer need for identity expression and consider this in their branding strategies. Social implications – Humans are social beings by nature. However, international brand research has paid relatively little attention to how products are used by consumers in everyday life, including their social life. Consumer behaviours increasingly depend on social meanings they imbue brands with beyond products’ functional utility. It is argued the focus of symbolic consumption needs to be broadened and integrated more with social science concepts. Originality/value – This study captures a construct of corporate brand symbolism by including self and social aspects of symbolism. The current study also comprehensively measures consumer loyalty, including cognitive, affective and behavioural types of loyalty.

Contribution of Lamb wave modes in the formation of higher order modes cluster (HOMC) guided waves

2021 ◽  
pp. 095440622110424
Author(s):  
Z Abbasi ◽  
F Honarvar
Keyword(s):  
Finite Element ◽  
Wave Packet ◽  
Lamb Wave ◽  
Guided Waves ◽  
Element Model ◽  
Higher Order ◽  
Guided Wave ◽  
Cross Sectional ◽  
Higher Order Modes ◽  
Wave Modes

In recent years, Higher Order Modes Cluster (HOMC) guided waves have been considered for ultrasonic testing of plates and pipes. HOMC guided waves consist of higher order Lamb wave modes that travel together as a single nondispersive wave packet. The objective of this paper is to investigate the effect of frequency-thickness value on the contribution of Lamb wave modes in an HOMC guided wave. This is an important issue that has not been thoroughly investigated before. The contribution of each Lamb wave mode in an HOMC guided wave is studied by using a two-dimensional finite element model. The level of contribution of various Lamb wave modes to the wave cluster is verified by using a 2D FFT analysis. The results show that by increasing the frequency-thickness value, the order of contributing modes in the HOMC wave packet increases. The number of modes that comprise a cluster also increases up to a specific frequency-thickness value and then it starts to decrease. Plotting of the cross-sectional displacement patterns along the HOMC guided wave paths confirms the shifting of dominant modes from lower to higher order modes with increase of frequency-thickness value. Experimental measurements conducted on a mild steel plate are used to verify the finite element simulations. The experimental results are found to be in good agreement with simulations and confirm the changes observed in the level of contribution of Lamb wave modes in a wave cluster by changing the frequency-thickness value.

scholarly journals Identification of Potential Biomarkers of Chronic Kidney Disease in Individuals with Diabetes: Protocol for a Cross-sectional Observational Study (Preprint)

2019 ◽  
Author(s):  
Ashani R Lecamwasam ◽  
Mohammadreza Mohebbi ◽  
Elif I Ekinci ◽  
Karen M Dwyer ◽  
Richard Saffery
Keyword(s):  
Chronic Kidney Disease ◽  
Kidney Disease ◽  
Data Collection ◽  
Gut Microbiome ◽  
Single Point ◽  
Therapeutic Interventions ◽  
Kidney Dysfunction ◽  
Early Diabetes ◽  
Cross Sectional ◽  
Potential Biomarkers

BACKGROUND The importance of identifying people with diabetes and progressive kidney dysfunction relates to the excess morbidity and mortality of this group. Rates of cardiovascular disease are much higher in people with both diabetes and kidney dysfunction than in those with only one of these conditions. By the time these people are identified in current clinical practice, proteinuria and renal dysfunction are already established, limiting the effectiveness of therapeutic interventions. The identification of an epigenetic or blood metabolite signature or gut microbiome profile may identify those with diabetes at risk of progressive chronic kidney disease, in turn providing targeted intervention to improve patient outcomes. OBJECTIVE This study aims to identify potential biomarkers in people with diabetes and chronic kidney disease (CKD) associated with progressive renal injury and to distinguish between stages of chronic kidney disease. Three sources of biomarkers will be explored, including DNA methylation profiles in blood lymphocytes, the metabolomic profile of blood-derived plasma and urine, and the gut microbiome. METHODS The cross-sectional study recruited 121 people with diabetes and varying stages (stages 1-5) of chronic kidney disease. Single-point data collection included blood, urine, and fecal samples in addition to clinical data such as anthropometric measurements and biochemical parameters. Additional information obtained from medical records included patient demographics, medical comorbidities, and medications. RESULTS Data collection commenced in January 2018 and was completed in June 2018. At the time of submission, 121 patients had been recruited, and 119 samples remained after quality control. There were 83 participants in the early diabetes-associated CKD group with a mean estimated glomerular filtration rate (eGFR) of 61.2 mL/min/1.73 m2 (early CKD group consisting of stage 1, 2, and 3a CKD), and 36 participants in the late diabetic CKD group with a mean eGFR of 23.9 mL/min/1.73 m2 (late CKD group, consisting of stage 3b, 4, and 5), <i>P</i><.001. We have successfully obtained DNA for methylation and microbiome analyses using the biospecimens collected via this protocol and are currently analyzing these results together with the metabolome of this cohort of individuals with diabetic CKD. CONCLUSIONS Recent advances have improved our understanding of the epigenome, metabolomics, and the influence of the gut microbiome on the incidence of diseases such as cancers, particularly those related to environmental exposures. However, there is a paucity of literature surrounding these influencers in renal disease. This study will provide insight into the fundamental understanding of the pathophysiology of CKD in individuals with diabetes, especially in novel areas such as epigenetics, metabolomics, and the kidney-gut axis. INTERNATIONAL REGISTERED REPORT DERR1-10.2196/16277

scholarly journals Willingness to Stop Smoking: A Cross-Sectional Study of a Primary Healthcare Center Visitors’ in an Urban Area of Alexandria in Egypt

2020 ◽  
Author(s):  
Rehab A. Rayan
Keyword(s):  
Smoking Cessation ◽  
Urban Area ◽  
Primary Healthcare ◽  
Health Hazard ◽  
Single Point ◽  
Cross Sectional Study ◽  
P Value ◽  
Sectional Study ◽  
Cross Sectional ◽  
Stop Smoking

For improving accomplished attempts to stop smoking, it is necessary to learn about the qualities of individuals who can willingly stop smoking. This study seeks to discover the willingness degree and associated determinants to stop smoking between adult visitors of a primary healthcare centre in an urban area of Alexandria in Egypt. In this single point and descriptive cross-sectional study, a semi-structured questionnaire was distributed to a sample of 53 adults aged ≥18 years in May 2019. Descriptive statistical analyses were conducted to evaluate the determinants influencing the willingness to stop smoking. Of the 53 respondents (with a mean age of 38.7 years old), 41.5% of them were males. Almost 18.9% of the respondents were ongoing smokers (36.4% of males and 6.5% of females), though 83.7% of those smokers were willing to stop smoking. The number of male smokers was significantly greater than female smokers (Pearson Chi-Square = 7.52, p-value = 0.006). Determinants, which can favourably influence the willingness to stop smoking, were believing that smoking is a health risk to them (100%) and the others around (94.3%). A bulk of participants (56.6%) doubted the need for nicotine supplements to help in smoking cessation. Smoker respondents were willing to stop smoking. Understanding that smoking is a health hazard for both smokers and the others around can motivate smoking cessation. Relying on nicotine supplements alone might not add favourably to a strong smoking cessation decision. Tailoring campaigns to raise awareness about smoking health hazards’ would support and sustain smoking cessation.

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