Non-destructive Diagnostic Technique Research Articles

Multitemporal Thermal Imagery Acquisition and Data Processing on Historical Masonry: Experimental Application on a Case Study

The recent improvement of infrared image quality has increased the use of thermography as a non-destructive diagnostic technique. Amongst other applications, thermography can be used to monitor historic buildings. The present work was carried out within the framework of the Horizon 2020 European project SHELTER, which aims to create a management plan for cultural heritage subject to environmental and anthropogenic risk. Among the chosen case studies is the Santa Croce Complex in Ravenna (Italy), which is exposed to different hazards, including flooding. The church has a peculiar architecture that develops below the street level, so the internal walls are affected by the deterioration caused by rising humidity. In such a case of advanced degradation, passive thermography cannot be used to its full potential. For this reason, an innovative methodology involving active thermography was first developed and validated with laboratory tests. Secondly, we conducted its first application to a real case study. With this purpose, an active thermography survey with forced ventilation was carried out to enhance different stages of material degradation by means of automatic classification of multitemporal data. These experiments have resulted in a method using an active thermal survey in a high moisture content environment to detect masonry degradation.

Micro-Raman spectroscopy study of blood samples from myocardial infarction patients

Acute myocardial infarction (MI) is found to be a major causative factor for global mortality and morbidity. This situation demands necessity of developing efficient and rapid diagnostic tools to detect acute MI. Raman spectroscopy is a non-destructive optical diagnostic technique, which has high potential in probing biochemical changes in clinical samples during initiation and progress of diseases. In this work, blood was taken as the sample to examine inflammation in acute MI patients using Raman spectroscopy. Ratio of Raman peak intensities that corresponds to phenylalanine (1000 cm−1) and tyrosine (825 cm−1) can facilitate indirect information about tetrahydrobiopterin (BH4) availability, which can indicate inflammatory status in patients. This ratio obtained was higher for MI patients in comparison with control subjects. The decrease in phenylalanine and tyrosine ratio (Phe-Tyr ratio) is attributed to the prognosis of standard of care (medications like antiplatelets including aspirin, statin and revascularisation) leading to inflammation reduction. Phe-Tyr ratio estimated from the Raman spectra of blood can be exploited as a reliable method to probe inflammation due to MI. The method is highly objective, require only microliters of sample and minimal sample preparation, signifying its clinical utility.

Laser fluorescence spectroscopy in predicting the formation of a keloid scar: preliminary results and the role of lipopigments.

Keloid scars, in contrast to other scar types, significantly reduce the patient's quality of life. To develop a nondestructive optical diagnostic technique predicting the keloid scars formation in vivo, laser-induced fluorescence spectroscopy (LFS) was used to study the autofluorescence in skin of patients with various types of head and neck cicatricial deformities. The unexpected results were obtained for the endogenous fluorescence of lipofuscin. Significantly reduced autofluorescence of lipofuscin was registered both in the intact and in the keloid scar tissues in comparison with the intact and scar tissues in patients with hypertrophic and normotrophic scars. Sensitivity and specificity achieved by LFS in keloid diagnosis are 81.8% and 93.9% respectively. It could take place due to the changes in the reductive-oxidative balance in cells, as well as due to the proteolysis processes violation. Therefore, we suppose that the evaluation of the lipofuscin autofluorescence in skin before any surgical intervention could predict the probability of the subsequent keloid scars formation.

Study of a collimation method as a nondestructive diagnostic diagnostic technique by PGNAA for salt distribution in concrete structures at RANS

To meet strong demand for realizing an effective tool to diagnose salt distribution in concrete infrastructures, we have started a development of a new technique using a prompt gamma neutron activation analysis (PGNAA) at the RIKEN accelerator-driven compact neutron source (RANS). So far, by applying PGNAA we have experimentally confirmed that neutrons from RANS can detect small enough amounts of chlorine within the marginal concentration of around 1.2 kg/m3 to involve steel corrosion. In this study, we have proposed two methods to derive the salt depth profile which is critical information of steel corrosion start. The first one utilizes a difference in the intensity ratio of two different γ-ray energies of interest, which is depending on the depth where the neutron capture reaction arises inside the concrete. The second is called the collimator method that measure γ-rays coming through a collimator around detector. Detection of γ-ray associated with 35Cl coming from the assembly of concrete has been also simulated with conditions of neutrons from RANS and a collimator. The feasibility of the method was discussed.

Use and Efficacy of Thermography for Stratigraphic Analysis of Historical Buildings

The use of thermography made it possible to investigate an ancient church viewed from a historical perspective, in order to learn more about its construction characteris­tics. This non-destructive diagnostic technique enabled a stratigraphic investigation of the structures in elevation to be conducted, resulting in the acquisition of new informa­tion and confirming the validity of its use in this complex field of application. This initial phase of knowledge acquisition provided an opportunity to propose a line of study to be conducted through the application of various instruments and tech­niques, starting with thermography, in accordance with a rational order. Instrumental results of the investigations as they are carried out, might suggest the location of points in which to continue with subsequent investigations, while at the same time defining appropriate guidelines in assessing the results.

Terahertz Amplitude Polynomial Principle Component Regression for Aramid–Basalt Hybrid Composite Laminate Inspection

As an emerging nondestructive diagnostic and monitoring technique, terahertz time-domain spectroscopy (THz-TDS) imagery is attracting more attention. In this regard, new THz image processing algorithms based on infrared thermography (IRT) concepts are greatly needed, since most IRT imagery modalities are fast for in-line industrial inspection. However, this scenario is difficult due to some physical constraints to be reached, although this idea should be followed to avoid the loss of useful information during image processing. In this paper, a novel THz amplitude polynomial principle component regression (APPCR) algorithm is proposed for the inspection of aramid–basalt hybrid composite laminates. This algorithm segments THz amplitude–frequency curves to simulate heating-up and cooling-down behaviors as in IRT; in addition, it uses an empirical orthogonal functions-based principle component regression modality to simplify the THz image analysis procedure. This experimental and analytical study shows that APPCR can, first, simplify the THz image analysis procedure, and second, enhance image contrast and spatial resolution. A theoretical analysis was conducted as experimental explanation, while the IRT imagery results were used for comparative purposes. In addition, signal-to-noise ratio analysis was used to evaluate quantitatively the image enhancement. Finally, it is possible to conclude that THz is more suitable to inspect transparent or semitransparent materials. Advantages and disadvantages of THz-TDS and IRT are summarized in the text.

Fourier Transform Infrared (FTIR) Spectroscopy Analysis of Transformer Paper in Mineral Oil-Paper Composite Insulation under Accelerated Thermal Aging

Mineral oil is the most popular insulating liquid for high voltage transformers due to its function as a cooling liquid and an electrical insulator. Kraft paper has been widely used as transformer solid insulation for a long time already. The degradation process of transformer paper due to thermal aging in mineral oil can change the physical and chemical structure of the cellulose paper. Fourier transform infrared (FTIR) spectroscopy analysis was used to identify changes in the chemical structure of transformer paper aged in mineral oil. FTIR results show that the intensity of the peak absorbance of the O–H functional group decreased with aging but the intensity of the peak absorbance of the C–H and C=O functional groups increased with aging. Changes in the chemical structure of the cellulose paper during thermal aging in mineral oil can be analyzed by an oxidation process of the cellulose paper and the reaction process between the carboxylic acids in the mineral oil and the hydroxyl groups on the cellulose. The correlation between the functional groups and the average number of chain scissions of transformer paper gives initial information that the transformer paper performance can be identified by using a spectroscopic technique as a non-destructive diagnostic technique.

Detection of Delamination in Laminate Wind Turbine Blades Using One‐Dimensional Wavelet Analysis of Modal Responses

This paper demonstrates the effectiveness of a nondestructive diagnostic technique used to determine the location and size of delamination in laminated coatings of wind turbine blades. This is realized based on results of numerical and experimental investigations obtained by the use of the finite element method (FEM) and laser scanning vibrometry (LSV). The proposed method is based on the one‐dimensional continuous wavelet transform of vibration parameters of a wind turbine blade. The investigations were conducted for a 1 : 10 scaled‐down blade of a 36 m rotor wind turbine. Glass fibres and epoxy resin were used as laminate components. For numerical studies, a simple delamination model was proposed. The results obtained by the authors were used to determine the optimal set of parameters of the continuous wavelet transform. The application of high‐quality LSV for experimental measurements allowed determining the optimal conditions of measuring procedures. At the same time the capabilities and limitations, resulting from the nature of the measurement method, were identified. In order to maximize the effectiveness of the detection method, preliminary signal processing was performed. Beside base wavelets also different waveform families were tested. The results obtained by the authors showed that it is possible to identify and localize even relatively small damage.

Detection of Local Temperature Change on HTS Cables via Time-Frequency Domain Reflectometry

High temperature superconducting (HTS) cables are drawing attention as transmission and distribution cables in future grid, and related researches on HTS cables have been conducted actively. As HTS cables have come to the demonstration stage, failures of cooling systems inducing quench phenomenon of the HTS cables have become significant. Several diagnosis of the HTS cables have been developed but there are still some limitations of the experimental setup. In this paper, a non-destructive diagnostic technique for the detection of the local temperature change point is proposed. Also, a simulation model of HTS cables with a local temperature change point is suggested to verify the proposed diagnosis. The performance of the diagnosis is checked by comparative analysis between the proposed simulation results and experiment results of a real-world HTS cable. It is expected that the suggested simulation model and diagnosis will contribute to the commercialization of HTS cables in the power grid.

Investigation of Isoelectronic Doping in p-GaN Based on the Thermal Quenching of UVL Band

In this paper, isoelectronic doping with indium (In) in p-GaN is investigated on the basis of the thermal quenching of ultraviolet luminescence (UVL) band. A phenomenological rate-equation model is proposed as a nondestructive diagnostic technique to acquire the dopant ionization energy of p-GaN. In terms of this model, we analyze the evolution of the ionization energy of p-GaN samples grown with different trimethyindium flow rate and find that isoelectronic doping with appropriate In incorporation is able to significantly reduce the ionization energy of the acceptor from 245 to 112 meV, which are consistent with the results of the variable temperature Hall-effect measurements. The comparison between the samples’ full width at half maximum of the UVL band indicates that excessive In incorporation will degenerate the conductivity of p-GaN.

Time–Frequency-Based Insulation Diagnostic Technique of High-Temperature Superconducting Cable Systems

For the electrical insulation of a high-temperature superconducting (HTS) cable, wrapped polypropylene laminated paper (PPLP) tape is typically used. Unfortunately, it is possible that unexpected faults at insulation layers will be present in the cables as a result of either a problematic manufacturing process or an incomplete installation procedure. In order to protect against operational failures of grid-connected HTS cable systems, this paper proposes a nondestructive diagnostic technique, i.e., time-frequency domain reflectometry (TFDR), and focuses on the characteristic of HTS cable that caused the local insulation defects . To verify the performance of the proposed method, detection and localization of local insulation failure via TFDR are compared with traditional time-domain reflectometry. The experiments are conducted at room temperature and under liquid nitrogen in order to check the efficacy of the proposed method in varieties of HTS cable's conditions. In addition, to improve the accuracy of detection and localization, a methodology to analyze incident signals, which are composed of upchirp and downchirp signals, is presented.

The Influence of Moisture Content in Oil-Paper Insulation System on Parameters of Return Voltage Measurement

As a non-destructive insulation diagnostic technique, the polarization spectrum method based on return voltage measurement has been employed to assess the state of insulation of the transformer. But how does the moisture content affect the parameters of RVM is not clear. In this paper, the effect of moisture content on the parameters of return voltage is studied based on experiments. The result shows that maximum value of return voltage (Urmax) and initial slope (Si) increase with the increase of moisture content in second-order function, while the central time constant (tcdom) decreases with the increase of moisture content in second-order function. The central time constant varies strongly with the change of moisture constant, so it is considered as a reliable indicator to evaluate the moisture level in oil-paper insulation system of transformer.

Using High Resolution Computed Tomography to Visualize the Three Dimensional Structure and Function of Plant Vasculature

High resolution x-ray computed tomography (HRCT) is a non-destructive diagnostic imaging technique with sub-micron resolution capability that is now being used to evaluate the structure and function of plant xylem network in three dimensions (3D) (e.g. Brodersen et al. 2010; 2011; 2012a,b). HRCT imaging is based on the same principles as medical CT systems, but a high intensity synchrotron x-ray source results in higher spatial resolution and decreased image acquisition time. Here, we demonstrate in detail how synchrotron-based HRCT (performed at the Advanced Light Source-LBNL Berkeley, CA, USA) in combination with Avizo software (VSG Inc., Burlington, MA, USA) is being used to explore plant xylem in excised tissue and living plants. This new imaging tool allows users to move beyond traditional static, 2D light or electron micrographs and study samples using virtual serial sections in any plane. An infinite number of slices in any orientation can be made on the same sample, a feature that is physically impossible using traditional microscopy methods. Results demonstrate that HRCT can be applied to both herbaceous and woody plant species, and a range of plant organs (i.e. leaves, petioles, stems, trunks, roots). Figures presented here help demonstrate both a range of representative plant vascular anatomy and the type of detail extracted from HRCT datasets, including scans for coast redwood (Sequoia sempervirens), walnut (Juglans spp.), oak (Quercus spp.), and maple (Acer spp.) tree saplings to sunflowers (Helianthus annuus), grapevines (Vitis spp.), and ferns (Pteridium aquilinum and Woodwardia fimbriata). Excised and dried samples from woody species are easiest to scan and typically yield the best images. However, recent improvements (i.e. more rapid scans and sample stabilization) have made it possible to use this visualization technique on green tissues (e.g. petioles) and in living plants. On occasion some shrinkage of hydrated green plant tissues will cause images to blur and methods to avoid these issues are described. These recent advances with HRCT provide promising new insights into plant vascular function.

A non-destructive optical diagnostic technique for measuring grain size of polycrystalline silicon produced by excimer laser crystallization

This work demonstrates a non-destructive optical diagnostic technique for determining grain size of polycrystalline silicon (poly-Si) and presents the result of melt-mediated phase transformation after excimer laser crystallization. The relationship between the average grain size of poly-Si films and transmissivity is investigated experimentally, which is found to coincide with the observation by field-emission scanning electron microscopy. This methodology can be used in association with a variety of non-destructive monitoring schemes.

Characterization of Mo/Si soft X-ray multilayer mirrors by grazing-incidence small-angle X-ray scattering

The morphology of buried interfaces plays a key role in high performing Mo/Si soft X-ray mirrors. We show that grazing-incidence small-angle X-ray scattering is a highly effective and non-destructive diagnostic technique for analysis of buried interfaces. The parameters of average interface autocorrelation function can be determined unambiguously. Additionally period thickness, roughness of interfaces and an effective number of vertically correlated periods can be extracted. The multilayer mirrors were prepared by e-beam evaporation on heated and unheated substrates, ion beam assisted e-beam evaporation, ion beam sputtering and RF magnetron sputtering. The latter three techniques produce multilayer mirrors with comparable interface roughness. The differences in lateral correlation length and Hurst parameter are found.

(3+1)-dimensional numerical simulations of femtosecond laser filaments in air: Toward a quantitative agreement with experiments

Three-dimensional numerical simulations and direct experimental measurements of the multifilamentation of femtosecond laser pulses propagating in air are quantitatively compared. Agreement is obtained in terms of the evolution of the filamentation pattern and in terms of the size and energy of the individual filaments through 12 m of propagation. These results are made possible by the combination of a massively parallel propagation code along with a nondestructive experimental diagnostic technique. Influence of the pulse duration is moreover addressed. The numerical calculations also show that single and multiple filaments exhibit almost identical spectral signature.

Non-Destructive Diagnostic Technique for Detection of Deteriorated Porcelain Shell Due to Alkali-Silica Reaction

Recently we experienced gas leak trouble of a hollow porcelain shell, which had been working in service for more than a few decades. From our investigation, it was found that an alkali-silica reaction might occur in the porcelain body over time depending on the sealing structure, the number of times the porcelain was fired, and the amount of alkali in the cement. This paper describes the mechanism of porosity change in porcelain body, the factors of such deterioration speed, FEM stress analysis results, and an Ultrasonic Test (UT) for the integrity of porcelain. In addition, the UT inspection results are shown.

Characterization of defect structures in magnetic liquid encapsulated Kyropoulos grown InP single crystals

Synchrotron White Beam X-ray Topography (SWBXT) has been used as a nondestructive diagnostic technique for the characterization of defect structures in large wafers cut from S and Fe-doped InP single-crystal boules. Wafers cut both longitudinally and laterally with respect to the growth axis were studied in order to reveal the overall defect distribution in the boules. Studies carried out on longitudinally cut S-doped crystals enabled information to be obtained on interface shape, from the observation of growth striations, as well as defect distribution. The conditions for optimal visibility of the growth striations were determined and it was found that the morphology of the growth interface was a sensitive function of local growth conditions. The formation of extensive slip bands from peripheral regions was also observed. This indicates that large thermal stresses were generated during crystal growth leading to such significant plastic deformation processes. Studies carried out on a series of laterally sliced, Fe-doped wafers cut from the same boule revealed dislocations in well-defined fourfold symmetric distributions. A finite element thermal-elastic stress analysis was performed for an intermediate growth stage to investigate the nature of the stress which causes this fourfold distribution. The calculated excess shear stress from this analysis agrees qualitatively with the observed dislocation distribution and slip system activity. The influence of an applied magnetic field on precipitate distributions in InP boules was preliminarily studied by examining a longitudinal cut, heavily Fe-doped InP wafer, which was grown in the presence of an intermittent applied field. Topographs recorded from this wafer revealed that no formation of large precipitates was discernible in either the initial or intermediate growth stages when the magnetic field was applied. On the other hand, the formation of large precipitates was observed in regions near the final stage of crystal growth when the magnetic field was turned off. Further such investigations are underway.

Nonneutral ion plasmas and crystals in Penning traps

Experimental work which uses laser-cooled ions in Penning traps is reviewed. With laser-cooling the ions are strongly coupled and exhibit spatial correlations characteristic of a liquid or crystal. In plasmas with dimensions less than 10–15 interparticle spacings, the observed correlations are strongly affected by the finite size and shape of the trapping potential. Plasmas with greater than 60 interparticle spacings should exhibit correlations characteristic of an infinite one-component plasma. Radiation pressure from a laser is also used to apply a torque to the plasma and change the plasma density. This permits access to all possible thermal equilibria, including the maximum density state where the plasma undergoes Brillouin flow. If the size of the plasma is small compared to the trap dimensions, Penning traps produce plasmas with simple shapes whose normal modes can be calculated exactly. The modes provide a nondestructive diagnostic technique for obtaining information on the plasma density and shape.

Multiple internal reflection infrared spectroscopy of silicon surface structure and oxidation process at room temperature

It is demonstrated that the multiple internal reflection infrared (IR) spectroscopy using a germanium prism is a very powerful nondestructive diagnostic technique for the study of silicon wafer surfaces in a wide range of IR irradiation region. The technique limits neither the shape of samples nor the IR range due to the absorption by silicon itself. With this technique, it is demonstrated that; (i) dangling bonds of a silicon surface treated with HF solution and de-ionized (DI) water are terminated mostly with H atoms, (ii) native oxide growth is enhanced by DI water rinsing, and the interstitial oxygen concentration in the silicon surface region increases during native oxide growth process, and (iii) DI water rinsing after HF etching replaces Si—F bonds with Si—H and Si—OH bonds on a silicon surface.