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PurposeHistorical newspaper collections provide a wealth of information about the past. Although the digitization of these collections significantly improves their accessibility, a large portion of digitized historical newspaper collections, such as those of KBR, the Royal Library of Belgium, are not yet searchable at article-level. However, recent developments in AI-based research methods, such as document layout analysis, have the potential for further enriching the metadata to improve the searchability of these historical newspaper collections. This paper aims to discuss the aforementioned issue.Design/methodology/approachIn this paper, the authors explore how existing computer vision and machine learning approaches can be used to improve access to digitized historical newspapers. To do this, the authors propose a workflow, using computer vision and machine learning approaches to (1) provide article-level access to digitized historical newspaper collections using document layout analysis, (2) extract specific types of articles (e.g. feuilletons – literary supplements from Le Peuple from 1938), (3) conduct image similarity analysis using (un)supervised classification methods and (4) perform named entity recognition (NER) to link the extracted information to open data.FindingsThe results show that the proposed workflow improves the accessibility and searchability of digitized historical newspapers, and also contributes to the building of corpora for digital humanities research. The AI-based methods enable automatic extraction of feuilletons, clustering of similar images and dynamic linking of related articles.Originality/valueThe proposed workflow enables automatic extraction of articles, including detection of a specific type of article, such as a feuilleton or literary supplement. This is particularly valuable for humanities researchers as it improves the searchability of these collections and enables corpora to be built around specific themes. Article-level access to, and improved searchability of, KBR's digitized newspapers are demonstrated through the online tool (https://tw06v072.ugent.be/kbr/).

Newspapers contain a wealth of historical information in the form of articles and illustrations. Libraries and cultural heritage institutions have been digitizing their collections for decades to enable web-based access to and retrieval of information. A number of challenges arise when dealing with digitized collections, such as those of KBR, the Royal Library of Brussels (used in this study), which contain only page-level metadata, making it difficult to extract information from specific contexts. A context-aware search relies heavily on metadata enhancement. Therefore, when using metadata at the page level, it is even more challenging to geolocalize less-known landmarks. To overcome this challenge, we have developed a pipeline for geolocalization and visualization of historical photographs. The first step of this pipeline consists of converting page-level metadata to article-level metadata. In the next step, all articles with building images were classified based on image classification algorithms. Moreover, to correctly geolocalize historical photographs, we propose a hybrid approach that uses both textual metadata and image features. We conclude this research paper by addressing the challenge of visualizing historical content in a way that adds value to humanities research. It is noteworthy that a number of historical urban scenes are visualized using rephotography, which is notoriously challenging to get right. This study serves as an important step towards enriching historical metadata and facilitating cross-collection linkages, geolocalization, and the visualization of historical newspaper images. Furthermore, the proposed methodology is generic and can be used to process untagged photographs from social media, including Flickr and Instagram.

Rephotography is the process of recapturing the photograph of a location from the same perspective in which it was captured earlier. A rephotographed image is the best presentation to visualize and study the social changes of a location over time. Traditionally, only expert artists and photographers are capable of generating the rephotograph of any specific location. Manual editing or human eye judgment that is considered for generating rephotographs normally requires a lot of precision, effort and is not always accurate. In the era of computer science and deep learning, computer vision techniques make it easier and faster to perform precise operations to an image. Until now many research methodologies have been proposed for rephotography but none of them is fully automatic. Some of these techniques require manual input by the user or need multiple images of the same location with 3D point cloud data while others are only suggestions to the user to perform rephotography. In historical records/archives most of the time we can find only one 2D image of a certain location. Computational rephotography is a challenge in the case of using only one image of a location captured at different timestamps because it is difficult to find the accurate perspective of a single 2D historical image. Moreover, in the case of building rephotography, it is required to maintain the alignments and regular shape. The features of a building may change over time and in most of the cases, it is not possible to use a features detection algorithm to detect the key features. In this research paper, we propose a methodology to rephotograph house images by combining deep learning and traditional computer vision techniques. The purpose of this research is to rephotograph an image of the past based on a single image. This research will be helpful not only for computer scientists but also for history and cultural heritage research scholars to study the social changes of a location during a specific time period, and it will allow users to go back in time to see how a specific place looked in the past. We have achieved good, fully automatic rephotographed results based on façade segmentation using only a single image.

Zinc single crystal specimens were irradiated with pulsed Nd:YAG laser in vacuum. Keeping the number of laser shots constant (10 shots), laser energy was varied from 50 to 150 mJ, whereas the corresponding laser fluence was 97 to 292 J cm−2, respectively. Using optical microscope, the dimensions (area and perimeter) of laser ablated region on the surface of each specimen were measured. Both parameters increased, in general, on increasing laser pulse energy. Examination of surface morphology by scanning electron microscope revealed formation of pores, grooves, cracks, bubbles, micron-size rods, ripples, ridges, cavities, microcones, and solid flakes, etc. Surface roughness had no systematic dependence on the laser pulse energy. Structural parameters, i.e., texture coefficient, lattice strain, and crystallite size, were determined by means of Harris analysis as well as Williamson–Hall analysis of the XRD patterns of specimens. The variation of lattice strain and crystallite size with laser fluence or laser pulse energy was alike. Surface hardness decreased on increasing laser fluence, and followed classical Hall–Petch relation.

Five W-alloy specimens, containing 8.57% Ni, 6.34% Cu, and 1.34% Mo, were bombarded with 5.2 MeV singly charged nitrogen ions. The ions dose range was 5 × 1014–1 × 1016 ions/cm2. XRD patterns portrayed diffraction peaks of pure W as well as of Cu0.4W0.6, MoNi4, and Ni4W phases. Harris analysis showed that the preferentially oriented planes depend on the nitrogen ions dose. The structural parameters, namely lattice strain and crystallite size, vary with nitrogen ions dose alike. Same pattern is followed by surface hardness and electrical resistivity. The increase in the values of all the parameters with ions dose is rapid in the range 0–1 × 1015 ions/cm2 and later on slow till the maximum ions dose 1 × 1016 ions/cm2. However, the interdependence of each parameter on the other ones was linear. Surface roughness of the specimens was found to decrease on increasing ions dose. On the other hand, surface hardness registers a rise as crystallite size increases, and hence follows Inverse Hall–Petch relation.

Impact of Cu doping on the structure, morphology, and antibacterial activity of NiO thin films has been investigated for a broad range of Cu/Ni ratios (0.1–25%). These thin films were synthesized on pre-heated glass substrates using indigenous spray pyrolysis setup. The structural analysis via X-ray diffraction technique reveals that all the thin films are of polycrystalline nature with cubic structure. All the diffraction peaks shift towards lower angle on an increase in the Cu/Ni ratio. Texture coefficient and stacking fault probability were determined by Harris analysis and Warren – Warekois formula, respectively. Crystallite size and lattice strain were valued by means of Williamson – Hall analysis, size-strain plots, Scherer and Wilson formulae. The value of crystallite size shows a decreasing trend while lattice strain increases on increasing the Cu/Ni ratio. SEM micrographs of the thin films reveal that surface morphology consists of pores, and the density of these pores decreases as the Cu/Ni ratio increases. The characteristic absorption bands exhibited by FTIR spectra of un-doped NiO and NiO:Cu thin films recorded in the range 4000–450 cm−1 were identified. Pure NiO thin film is found to be a very good antibacterial agent against the Escherichia Coli bacteria. However, its antibacterial ability gradually decreases on doping with 0.1–25% Cu.

Four specimens of W–8.57Ni–6.34Cu–1.34Mo alloy were irradiated with 5.2 MeV C+2 ions; ion doses were 0.1, 0.5, 1, and 5 × 1015 ions/cm2. XRD patterns showed the presence of Cu0.4W0.6, MoNi4, and Ni4W phases in the W – alloy specimens. More than one crystallographic planes were preferentially oriented. Nevertheless, the (310) plane was the common preferentially oriented plane in all the specimens. Crystallite size (11–15 nm) and lattice strain (−6.7 × 10−4 to −14.8 × 10−4) determined by Williamson – Hall analysis as well as surface hardness (2.45–3.18 GPa) and electrical resistivity (5.3–12.1 × 10−8 Ω m) varied with carbon ions dose in an identical manner. Both surface hardness and electrical resistivity were found to increase with the increase in crystallite size. SEM micrographs of the irradiated W – alloy specimens showed a thin layer of carbonaceous structures in the form of irregular-shape pallets on the surface of the specimens.

Sol-gel spin coating method have been used to deposit un-doped, La, and Sm-doped ZnO thin films on Si substrate. The influence of Sm and La doping content on various physical properties of ZnO thin films were investigated using x-ray diffraction, photoluminescence spectroscopy, spectroscopy ellipsometry, scanning electron microscope, and four point probe technique. X-ray diffraction analysis reveals that Sm and La ions were successfully incorporated in ZnO lattice and all the thin films are highly crystalline with hexagonal wurtzite structure. Photoluminescence spectroscopy spectra indicates that defect concentration increases on increase in Sm and La content. Refractive index, extinction coefficient and optical band gap were determined from spectroscopy ellipsometry technique. The optical bandgap of ZnO thin films shifts towards higher wavelength (red shift) on incorporating La and Sm because of which its absorption ability for visible portion of electromagnetic radiation increases. The micrographs obtained from scanning electron microscope reveals that morphology consists of wrinkle type structure; the density of the wrinkles seems to be dependent on the dopant concentration as well as on the type of dopant. Remarkable improvement in electrical conductivity have also been observed after doping. Sm- and La-doped ZnO thin films have shown better photocatalytic degradation efficiency for methylene blue under solar light irradiation.

Potentially sensitive materials have structural strength to tolerate loads be disposed to shrink dimension. the target of existing study is to associate the compressive strength of two material (AU5GT and AS7G06), which are utilized in diverse structural applications At quite few heat treatment sequences, it's problematic to conclude the compression strength of subsequent aluminum mixtures. Specimens are heat treated first as per premeditated progressions, later compression testing is implemented. Compression test is piloted in accordance with ASTM E9- 09 standard method on three samples with and bereft of heat treatment for separately sequences. Solution zing on trials is ended at perpetual period and temperature to achieve homogenization. Then, the aging treatment is conceded at diverse heats from 100 to 200 ° C (different intervals) for a particular period of your time to perceive the influence of the rigidity of the precipitation and thus increase the resistance. Sample compressive strength is decided using Universal Testing machine for every heat treatment cycle. The heat-treated AS7G06 displayed insignificant distortion, but the heat-treated model revealed enlarged AU5GT aluminum composite strength. Since slush, because it's very difficult to emerge as a rise in temperature precipitation, results in the harder areas of whole grains. Unsurprisingly, hardness also showed a rise in proportion. Analyze the fracture surface employing a stereomicroscope and a scanning microscope (SEM) to seek out the last sort of brittle, soft or transient fracture (combination of brittleness and ductility).

Nowadays, the uses of renewable energy resources are growing rapidly. Several renewable resources such as hydro, wind, solar and tidal are commonly used all over the world. Following this trend, the implementation of large area solar arrays is considered to be necessary. Several design methodologies and approaches have been accessible in order to obtain maximum efficiency of solar panel supporting structure. In this study, Finite Element Method (FEM) was established to investigate the impact of various wind loads on the structural reliability and strength of solar panel supporting structures. The wind speeds of 20 m/s, 25 m/s, 30 m/s, 35 m/s and 40 m/s were used for the analysis of solar panel supporting structure. Wind loads were also calculated by mathematical approach. The results show that solar panel structure was significantly affected by wind loads applied on the surface of solar PV module. The results obtained from the FEM analysis that total deformation and maximum equivalent stresses were increased by increasing the wind loads. The maximum value of equivalent stress can be found at joint sections of solar panel supporting structure and total deformation is higher at centre of the structure as well as at base of the structure. The maximum and minimum value of equivalent stress 62.866 Mpa and 15.75 Mpa can be found at 40 m/s and 20 m/s respectively. Similarly, maximum and minimum value of total deformation 0.3631 mm and 0.0911 mm can be found at 40 m/s and 20 m/s respectively. The knowledge of stress distribution and deformation play a vital role for structure designs, stability and strength of hydro solar panel supporting structure. &nbsp

Al:ZnO (AZO) thin films were successfully deposited on pre-heated glass substrate using organic and inorganic aluminum precursors, i.e. aluminum acetylacetonate (ac) and aluminum chloride hexa-hydrate (cl), respectively. The properties of spray pyrolysis grown AZO thin films were investigated for a wide range of Al/Zn ratio (0.2–10%) before and after annealing at 320 °C in an inert nitrogen atmosphere. There was remarkable improvement in the electrical properties of the films after annealing. The electrical conductivity also improved on doping but the magnitude of improvement on using cl was 10 times more as compared to ac. Photoluminescence spectroscopy of AZO thin films revealed that the near band edge emission (NBE) remarkably improved on increasing Al/Zn ratio using cl with concomitant reduction in blue luminesce (BL) intensity in the visible region. On using ac, the BL intensity however increased while NBE emission decreased. AZO thin films possessed more than 85% average optical transmission in the visible region. Blue shift in the optical band gap was observed using both types of Al precursors. cl based Al precursor produces pyramid like structure at higher Al/Zn ratios. X-ray diffraction studies revealed that AZO thin films possess hexagonal wurtizite structure with preferred orientation along c-axis. The value of the crystallite size decreased on increase in Al/Zn ratio for both types of precursors. These thin films possess good oxygen gas sensing ability and have potential ability to be used as oxygen sensor.

Enterprise networks usually require all the computing machines to remain accessible (switched-on) at all times regardless of the workload in order to entertain user requests at any instant. This comes at the cost of excessive energy utilization. Many solutions have been put forwarded, however, only few of them are tested in a real-time environment, where the energy saving is achieved by compromising the systems’ reliability. Therefore, energy-efficient resource utilization without compromising the system’s reliability is still a challenge. In this research, a novel architecture, “Sleep Alert”, is proposed that not only avoids the excessive energy utilization but also improves the system reliability by using Resource Manager (RM) concept. In contrary to traditional approaches, Primary and Secondary Resource Managers i.e. RMP and RMS respectively are used to avoid the single point of failure. The proposed architecture is tested on a network where active users were accessing the distributed virtual storage and other applications deployed on the desktop machines, those are connected with each other through a peer-to-peer network. Experimental results show that the solution can save considerable amount of energy while making sure that reliability is not compromised. This solution is useful for small enterprise networks, where saving energy is a big challenge besides reliability.

Spray pyrolysis technique was employed to synthesize NiO and NiO:Cu thin films (0.1–25% Cu) on soda-lime glass substrate. Optical properties, as well as electrical resistivity of these films, were investigated. UV–Visible spectrophotometer was employed to measure the optical properties. The absorption edge of the films was located within the UV range i.e. λ = 280–380 nm. The average reflectance of the films was 16.9% in the range λ = 280–900 nm. On increasing the Cu/Ni ratio, the optical band gap decreased whereas the refractive index and Urbach energy increased. Quantitatively, the measured average value of the refractive index and the value calculated from the Reddy-Ahammed empirical formula, which connects refractive index with optical band gap, were in good agreement. Optical conductivity was found to be in the range 1014–1015 s−1 while the dielectric loss was rather very low; it points to the good optical response of the films. The average oscillator energy as well as dispersion energy evaluated from Wemple–DiDomenico model decreased rapidly to begin with as Cu/Ni ratio was increased up to 5% but later on decreased rather slowly. Optical band gap values calculated by the Wemple-DiDomenico model and by Tauc relation agreed very well. The PL spectra of all the films displayed an intense peak at 403 nm and two secondary peaks at 426 nm and 365 nm. The PL intensity of each peak decreased monotonically with an increase in Cu content in NiO:Cu thin film from 0 to 3%. However, it remained almost independent of Cu content in the range of 4–25%. With an increase in Cu/Ni ratio, electrical resistivity and carrier mobility decreased whereas carrier concentration increased.

Williamson-Hall analysis of XRD patterns of Al 5086 alloy specimens (10 mm × 10 mm × 6 mm) irradiated with 100–500 KrF excimer laser pulses in air (1 bar) as well as in vacuum (10 −3 mbar) was done to evaluate structural changes on laser irradiation. Both crystallite size (30 nm–99 nm) and lattice strain (0.00043–0.00241) were found, in general, to increase with the number of laser shots first rapidly up to 200 and later on rather slowly. Also, for a given number of laser shots, the crystallite size of the specimen laser-irradiated in vacuum was higher than that of the specimens laser-irradiated in air. Harris analysis of XRD patterns revealed that the most preferentially oriented plane was (200) with texture coefficient in the range 2.359–2.982. Electrical resistivity of the specimens was measured by four-point probe technique. It was found to increase with the number of laser shots up to 200, and later on decreases monotonically. However, for a given number of laser shots, its value was higher for the specimen laser-irradiated in air than that for the specimen laser-irradiated in vacuum. On plotting combined surface hardness data for un-irradiated and laser-irradiated specimens in air as well as in vacuum as a function of inverse square-root of crystallite size, a cross over from classical Hall-Petch relation (99 nm–55 nm) to inverse Hall-Petch relation (55 nm–30 nm) occurred at about 55 nm. This is true not only for the surface hardness but also for the hardness measured at 0.5 and 1.0 mm depth below the specimen surface. The intensity of laser-hardening effect gradually diminishes as one goes down from the uniformly laser-irradiated specimen surface to a depth of 3.0 mm below it. The relationship between electrical resistivity and surface hardness was linear.

Highly c-axis oriented un-doped ZnO and Al-, Ba-, and Cd-doped ZnO thin films were successfully deposited on glass substrate employing sol-gel spin coating method. XRD analysis showed that all thin films possess hexagonal wurtzite structure with preferred orientation along c-axis. Field emission scanning electron microscope (FESEM) was used to study the morphology of thin films. The morphology consists of spherical and non-spherical shape grains. EDX analysis confirms the presence of O, Zn, Al, Ba, and Cd in the relevant thin films. The optical properties of thin films were studied using UV–Vis spectrometer. All thin films possess more than 85% optical transmittance in the visible region. Blue shift in optical band gap Eg has been observed on doping with Al, whereas doping with Ba and Cd resulted in red shift of Eg. Urbach energy Eu of all doped ZnO thin films was found to have excellent correlation with their band gap energy Eg. Moreover, Eg increases while Eu decreases on the increase in crystallite size D. Optical parameters Eg and Eu as well as structural parameters lattice strain and stacking fault probability also show excellent correlation with the B-factor or the mean-square amplitude of atomic vibrations of the dopant elements. Electrical conductivity measurement of the thin films was carried out using two-point probe method. The electrical conductivity was found to increase with the increase in crystallite orientation along c-axis.

Spin coating method was employed to deposit the thin films using redispersed nanoparticle suspensions of tin doped indium oxide (ITO). These films were then annealed in air at 450, 500, 550, 600, and 650 °C for 1 h. The effect of annealing temperature on the structural, optical, morphological, and electrical properties were studied by XRD, UV–vis spectroscopy, SEM, and four point probe technique, respectively. XRD analysis revealed that all thin films have cubic bixbyite structure with dominant (2 2 2) plane. Williamson-Hall analysis of XRD patterns showed that crystallite size increases with the rise in annealing temperature. SEM images of ITO thin film depicted spherical and non-spherical shaped particles of uneven size. The transmission spectra obtained from UV–vis spectroscopy reveals that transparency of thin films undulate with annealing temperature. With the rise in annealing temperature the optical band gap increases, while the Urbach energy and electrical resistivity decreases. The optical band gap, Urbach energy, and electrical resistivity were found to have systematic dependence on the crystallite size. The figure of merit is maximum for ITO thin film annealed at 550 °C.

Specimens of Pd80Ni20 alloy were irradiated in air with 70, 80, 90, and 100 laser shots using a Q-switched Nd-YAG laser of 1064 nm wavelength with pulse duration 10 ns, energy 50 mJ, and repetition rate 10 Hz. Surface morphology of the laser-irradiated specimens was studied with the help of a scanning electron microscope. It includes wave-like structures or ripples, dips, ridges, microcones, flakes, and fissures, etc. The X-ray diffraction patterns of un-irradiated and irradiated specimens were analyzed using the Williamson–Hall method to evaluate crystallite size and microstrain. Texture coefficient was determined by Harris analysis. The peak intensity of (111), (200), (220), (311), and (222) planes increases linearly with laser shots, which shows that the concentration of point defects (i.e., vacancies) is progressively decreased on increasing the number of laser shots due to the annealing processes. Surface hardness was measured using a Vickers hardness tester. The average surface hardness of the specimens initially decreases on irradiation with 70 laser shots and later on increases linearly with increase in laser shots up to 100. An inverse Hall-Petch relationship is observed in the crystallite size range 19–27 nm. As crystallite size decreases from 27 to 19 nm, volume fraction of amorphous phase increases progressively. The amorphous phase being softer than crystalline phase due to increased atomic spacing leads to reduction in surface hardness of the material.

The influence of calcination temperature on the photocatalytic activity of quaternary metal oxide nanocomposite i.e. gadolinium (Gd) doped cobalt tin oxide (CoSnO3) have been explored. The synthesis of nanocomposite material was completed in two steps using a novel method. The synthesized nanocomposite material was subjected to various characterization techniques like thermogravimetric analysis (TGA), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), particle size analyzer (PSA), UV–Visible and photoluminescence spectroscopy in order to investigate its thermal, structural, and optical properties. The crystallite size, particle size and optical band gap estimated via XRD, PSA and UV–Visible spectroscopy, respectively reveals an increasing trend with calcination temperature. The Gd doped CoSnO3 nanocomposite material is found to be very efficient visible light photocatalyst. The photo-degradation efficiency in the presence of sunlight in degrading methylene blue and methyl orange is more than 90%. An insight mechanism of electron/hole trapping using electronic configuration has also been explored.

Optical emission signal enhancement from palladium (Pd) plasma by magnetic field-assisted laser-induced breakdown spectroscopy (MF-LIBS) is reported. Plasma from Pd target was produced by second harmonic generation (532 nm, 5 ns) of Nd:YAG laser using fluence values in the range of 12.6–38.1 J/cm2. In the designed experiment, the magnetic field was parallel to the axis of plasma expansion direction with a maximum strength of 0.12 T at the target surface. Optical signals of the emission from the plasma were recorded in the spectral range of 200−700 nm with a LIBS2000+ spectrometer. A significant enhancement was noticed particularly at low fluence values for both atomic and singly ionized Pd lines. For the minimum fluence 12.6 J/cm2, an intensity enhancement of 3–4 fold was observed for Pd-I and Pd-II lines and dropped exponentially for the increased fluence values. At low fluence values, the trace elements viz., Ca and Mg were detected only in the presence of magnetic field. The optical signal enhancement effect of magnetic field was different for Pd, Ca, Mg, and H; suggesting that the field enhanced effect is strictly element dependent for plasma at the same conditions. The field influenced the plasma parameters; the electron number density (ne), and temperature (T) which were increased considerably compared to without field. Expectedly, these attributes come from the plasma confinement by the external magnetic field and have been explained in the framework of magneto hydrodynamic (MHD) model.

New cyclotriphosphazene compound bearing dioxyphenylcoumarin group (DCP-1) was synthesized from the reactions of 7,8-dihydroxy-3-(4-chlorophenyl)coumarin (3) containing chlorine as a side group at para position with cyclotriphosphazene (DCP). The structures of the compounds were determined using 1H, 13C APT, 31P NMR, FT-IR and elemental analysis spectroscopy methods. The organic layer was deposited onto the p-Si substrate to obtain an Al/p-si/phosphazene (DCP-1)/Al diode. The photoresponse and photocapacitance properties of the diode were analyzed under various solar light intensities. The photocurrent and photocapacitance results suggest that the studied device exhibits both photodiode and photocapacitor behavior. The diode indicates a linear photoresponse behavior. The photoswitching behavior of the diode is controlled by solar light intensity. The interface states density of the diode was found to be order of 1012 eV-1cm2. The value of interface states density indicates that the photocapacitor behavior of the diode is significant for photocapacitor applications.

Aircraft structural fatigue life prediction has important military significance and the conspicuous economic value. In development phase fatigue life of flight vehicles is generally predicted based on some historic / assumed data which may differ significantly from the actual operational usage of the vehicle. Consequently, the fatigue life of an aircraft may reduce / increase. The service fatigue life of a structure depends on both the irregular amplitude load conditions and the assumptions during fatigue test. To find the actual fatigue life of a structure we need to subject the structure in laboratory with constant / variable amplitude loadings that should be representative of actual flight loads and at the same time in a form that can be applied conveniently in the laboratory. In case of uniform loading it is easy to find the number of cycles but the real service loads are normally irregular, so defining spectrum from flight data is quite difficult which corresponds to the actual random loads applying on the aircraft. In this research study, a simple methodology is proposed to extract fatigue loads spectrum from a typical flight tests data. It involves statistical analysis of flight data, data filtering, power spectral density (PSD), averaging and data reduction for generating a representative fatigue spectrum from experimental as well as actual flight data. The derived spectrum following this approach contains information of not only the number of occurrences of each load factors but also the fluctuating loads and corresponding exposure time for each occurrence. This methodology is validated by developing a spectrum from known raw data and then same procedure is applied on original flight data to generate the flight fatigue spectrum. Statistical processing of good sample size (number of flights) provides a reasonably good representative fatigue spectrum of that particular flight vehicle type. Every flight fatigue spectrum can also be used for structural health monitoring / residual life estimation on flight to flight basis.

Off-axis pulsed laser deposition technique was used to deposit a diamond-like carbon (DLC) thin film and three multilayer DLC:Mo thin films of various compositions on p-type Si (1 1 1) substrate at room temperature keeping the DLC content constant. Excimer laser was used to ablate graphite and Mo targets in a vacuum of ∼10 −5 mbar, whereas the p-type Si (1 1 1) substrate was placed downside the target at a distance of 1 cm in off-axis PLD geometry. Morphological, structural, optical, and electrical characteristics of the deposited thin films were then investigated. SEM images of the thin films show that surface roughness increases as Mo content in the film increases. XRD patterns of DLC:Mo thin films rule out any carbide formation. Both crystallite size of Mo particles and film thickness increase whereas microstrain decreases with the increase in Mo content. Moreover, both refractive index and indirect optical band gap decrease exponentially while Urbach energy increases linearly with the increase in Mo content. Electrical resistivity of the thin films has been found to follow an exponential decay with the increase in Mo content in multilayer DLC:Mo thin films.

Available data on the temperature dependence of yield stress and of associated activation volume of high-purity NiAl single crystals between 76 and 205 K have been analyzed within the framework of a solid-solution hardening model, which is based on the concept of depinning of an edge-dislocation segment from several randomly dispersed, isolated, point defects simultaneously. The vacancies in NiAl single crystals act as point-defect obstacles to the stress-assisted thermally-activated glide of edge dislocations, and their concentration is estimated as about 10 at.%. The product of yield stress and associated activation volume (≈0.146 eV) is found to be independent of temperature and yield stress, as envisaged in the model.

Six specimens of 99.995% pure zinc were irradiated with a passive Q-switched pulsed Nd:YAG laser in a vacuum 10 -3 Torr. The specimens were irradiated with 50 to 100 laser shots with an increment of 10 shots. Williamson-Hall analysis of XRD patterns of un-irradiated and irradiated specimens was carried out to evaluate the structural parameters, namely crystallite size and micro-strain. Surface hardness of the specimens was measured using Vickers hardness tester. An inverse Hall-Petch relation for the surface hardness was observed in the 28–35 nm crystallite size range.

Al5086 alloy specimens were irradiated in a vacuum ~10−6 mbar with 2 MeV proton beam (200 nA) for different exposure times in the range 10–50 min (dose range: 0.35×1015–1.75×1015 p/cm2). Surface hardness was found to increases on irradiation for 10 min, and later on it decreases with the increase in exposure time. The electrical resistivity of the specimens measured by four-point probe technique was also found to follow the same pattern. The observed behavior has been explained in terms of relative contribution of two processes, namely defects formation and heat generation due to proton–material interaction. Structural characterization of the specimens was done by X-ray diffraction technique. Both surface hardness as well as electrical resistivity of un-irradiated and irradiated specimens is found to decrease with the increase in X-ray crystallite size. Moreover, the surface hardness follows the Hall–Petch relation, which indicates that crystallite boundaries progressively impede the motion of dislocations as the crystallite size gets smaller.

Six specimens of 99.995% pure zinc in the form of strips (15 mm × 8 mm × 0.5 mm) were irradiated with Q-switched pulsed Nd:YAG laser (λ=532nm, E =50 mJ, τ =6 ns, repetition rate=10 Hz) in vacuum∼10 -3 Torr. The specimens were irradiated with 50, 60, 70, 80, 90 and 100 laser shots; the laser fluence and laser intensity at the irradiation spot were 4.24 J/cm 2 and 7.07 × 10 8 W/cm 2 , respectively. Scanning electron microscope (SEM) examination of laser irradiated specimens revealed different features, e.g. wavelike structures, ridges, dips, micro cones, cavities, nano and micro size droplets, as well as solid flakes, etc. on the surface. These features are a result of splashing, hydrodynamic and exfoliational sputtering. Average surface roughness was measured from SEM micrographs using Nanotec software WSxM 5.0 develop 1.1. The electrical resistivity was determined by four- point probe technique. It is observed that average surface roughness and electrical resistivity vary with the number of laser shots in an identical manner, and are therefore found to be directly related to each other.

Mechanically polished 4N pure nickel specimens were irradiated in air with Nd:YAG laser for laser shots ranging from 1000 to 5000 with an increment of 1000. The structural and mechanical characterization of the specimens was done using X-ray diffractometer (XRD) and Vickers hardness tester. The XRD patterns exhibit variation in the intensity of diffraction peaks pointing to significant structural changes on laser irradiation. Crystallite size, uniform deformation energy density, lattice deformation stress, and lattice strain were determined by Williamson-Hall analysis using uniform deformation energy density model. All the four structural parameters referred to were found to increase linearly with laser shots. On laser irradiation, surface hardness of nickel first increases up to 3000 laser shots, and later on it decreases up to 5000 laser shots. Crossover from classical Hall-Petch relation to inverse Hall-Petch relation occurs at about 69 nm in the observed crystallite size range of 81 to 44 nm.

A passive Q-switched Nd:YAG pulsed laser was used to irradiate 99.99% pure Fe target in vacuum ∼10-3 Torr. The CR-39 specimens were exposed to laser produced plasma ions (40-250 keV) emitted along the normal to the Fe target surface. The flux of Fe ions was varied by varying the number of laser shots in the range 500-1500 with an increment of 250. A comparison of structural and optical properties of CR-39 polymer before and after ion implantation was made. The increase in ion flux leads to the transformation of polymer into rather more disordered amorphous state leading to the broadening of XRD peaks. The crystallite size decreases (3.547 to 1.618 nm) and Urbach energy increases (0.232 to 0.291 eV) exponentially with the increase in ion flux (0 to 6.07 × 105 ions/cm2). Indirect optical band gap is found to decrease (4.118 to 3.917 eV) linearly with the increase in ion flux (3.03×105 to 6.07×105 ions/cm2).

A passive Q-switched Nd:YAG pulsed laser was used to irradiate 99.99% pure Fe target in vacuum ~10−3 Torr. The CR-39 specimens were exposed to laser produced plasma ions (40–250 keV) emitted along the normal to the Fe target surface. The flux of Fe ions was varied by varying the number of laser shots in the range 500–1500 with an increment of 250. A comparison of structural and optical properties of CR-39 polymer before and after ion implantation was made. The increase in ion flux leads to the transformation of polymer into rather more disordered amorphous state leading to the broadening of XRD peaks. The crystallite size decreases (3.547 to 1.618 nm) and Urbach energy increases (0.232 to 0.291 eV) exponentially with the increase in ion flux (0 to 6.07×105 ions/cm2). Indirect optical band gap is found to decrease (4.118 to 3.917 eV) linearly with the increase in ion flux (3.03×105 to 6.07×105 ions/cm2).

Mechanically polished nickel specimens (99.99% purity) were irradiated in air with Nd:YAG laser for laser shots ranging from 1000 to 5000 with an increment of 1000. The structural and mechanical characterization of the specimens was done using an X-ray diffractometer (XRD) and a Vickers hardness tester. The XRD patterns exhibit variation in the intensity of diffraction peaks pointing to significant structural changes on laser irradiation. Stacking fault probability was found to increase on irradiation with laser shots up to 2000, and later on it remained constant. Crystallite size, uniform deformation energy density, lattice deformation stress, and lattice strain were determined by Williamson–Hall analysis using uniform deformation energy density model. All the four structural parameters referred to were found to increase linearly with laser shots. On laser irradiation, surface hardness of nickel first increases up to 3000 laser shots, and later on it decreases up to 5000 laser shots. Crossover from classical Hall–Petch relation to inverse Hall–Petch relation occurs at about 69 nm in the observed crystallite size range of 81–44 nm.

Six specimens of 99.995% pure zinc in the form of strips (15 mm × 8 mm × 0.5 mm) were irradiated with Q-switched pulsed Nd:YAG laser ( λ = 532 nm, E = 50 mJ, τ = 6 ns, repetition rate = 10 Hz) in vacuum ∼10 −3 Torr. The specimens were irradiated with 50, 60, 70, 80, 90 and 100 laser shots; the laser fluence and laser intensity at the irradiation spot were 4.24 J/cm 2 and 7.07 × 10 8 W/cm 2 , respectively. Surface morphology of laser irradiated specimens was examined by both optical and scanning electron microscopes. Crater area as well as heat affected area were measured by optical microscope using Motic software. Scanning electron microscope (SEM) examination revealed different features, e.g., wavelike structures, ridges, dips, micro cones, cavities, nano and micro size droplets, as well as solid flakes, etc., on the surface. These features are a result of splashing, hydrodynamic and exfoliational sputtering. Average surface roughness was measured from SEM micrographs using Nanotec software WSxM 5.0 develop 1.1. The electrical resistivity was determined by four-point probe technique. It is observed that average surface roughness and electrical resistivity vary with the number of laser shots in an identical manner, and are therefore found to be directly related to each other.

Annealed specimens of 99.99% pure iron were irradiated with 500, 750, 1000, and 1250 Nd:YAG laser shots. The laser fluence and laser intensity at the laser irradiation spot on the target surface were 4.4 × 103 J/cm2 and 4.8 × 1011 W/cm2, respectively. Vickers hardness of irradiated specimens was measured at various points separated by 0.5 mm in four different mutually perpendicular directions around the laser irradiation spot. The surface hardness profile for each irradiated specimen shows an increasing trend in surface hardness till a distance of 3.5 mm from the reference point. The average surface hardness (ASH) is found to increase up to 21% and electrical resistivity increases up to 50% as the number of laser shots is increased to 1250. A linear relationship between electrical resistivity and ASH is observed. Moreover, the ASH follows the well-known Hall-Petch relation, indicating that the crystallite boundaries impede the motion of dislocations to a greater extent as the crystallite size gets smaller.

Mechanically polished 4 N pure iron specimens were irradiated under a vacuum of 10 −3 Torr with Q-switched pulsed Nd:YAG laser for a number of laser shots ranging from 500 to 1500 with an increment of 250 shots. Surface morphology of laser irradiated specimens was examined by both optical and scanning electron microscopes. Heat affected area and its perimeter were found to increase with the increase in number of laser shots. Scanning electron micrographs revealed the formation of cracks, pits, and ripples as well as hydrodynamic and exfoliational sputtering of the material. Rose-like structure was developed on the target surface exposed to 500 laser shots due to the molten material movement caused by laser-induced plasma-recoil pressure. Substantial amorphization in the target occured on irradiation with 1000 laser shots. XRD study of the irradiated specimens revealed that crystallite size decreases while dislocation line density and microstrain increase on increasing the number of laser shots.

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The laser-produced plasma (LPP) ions of various metals (Mo, Ni, Cu, Ti and Zn) was implanted in CR-39 polymer, and their influence on its optical properties was investigated. The plasma of these metals was produced using 200 shots of a Q-switched Nd:YAG pulsed laser in a vacuum of 10−3 Torr. The CR-39 specimens were exposed to LPP ions (flux: F=8.01×109−22.14×109 ions/m2, average energy: E av=52−297 keV) emitted along the normal to the metal surface in each case. Both F and E av were found to be a function of the room temperature Debye–Waller thermal parameter B and increase with increase in B-value. The structural behavior of virgin and implanted specimens was investigated using a ultra violet (UV)–visible spectrophotometer. The value of disorder content (Urbach energy E u) was found to lie in the range of 0.287–0.377 eV. The optical band gap energy (E g) for indirect transition decreased on implantation with metallic LPP ions, whereas such a variation in the case of direct transition was negligible. It ...

Ions up to ionization state q = 4, emitted from laser produced plasma of Al, Ti, Ti50Al50 and Ti75Al25 targets ablated by Srivastava et al. (2006), are distributed angularly in the form of a cone, and for each ionization state the angular distribution has been shown to follow the cosine power-law: F = Focosn θ. It is found that the value of exponent n of cosn θ distribution function increases with the increase in ionization state. For each target, the value of exponent n of individual ionization states as well as total charge exhibits an excellent linear correlation with the room temperature Debye–Waller thermal parameter B or the mean-square amplitude of the atomic vibrations of the targets. It is further reported that the FWHM of ion distribution with Gaussian function fitting done by Srivastava et al. (2006) also depends linearly on B rather better than its dependence on the atomic mass of pure metal targets or average atomic mass in the case of their binary alloy targets. The FWHM of ion distribution for Al, Ti, Cu, Mo, W and their alloys Ti25Al75, Ti34Al66, Ti50Al50, Ti75Al25, W60Cu40, W80Cu20, W90Cu10 and Mo70Cu30 laser ablated by Srivastava and Rohr (2005) are also found to have much better correlation with the room temperature Debye–Waller thermal parameter B as compared to the atomic mass of the target.

Five metals (Zn, Cu, Ni, Ti, and Mo) were irradiated with 150 shots of a Q-switched Nd:YAG pulsed laser in a vacuum of 10 −3 torr. The ions projected out of the laser-produced plasma (LPP) plume were detected by CR-39 detectors positioned at −15°, 0°, 30°, 60°, and 90° with respect to the target-surface normal at a distance of 5 cm from the target in each case. The angular distribution of LPP ions, which is characterized by the exponent n of cos n θ distribution, is given by n = 2.5–11 for the five target metals. The value of the exponent n has no systematic correlation with the square-root of atomic mass of the target metals but exhibits systematic dependence on the room temperature Debye–Waller's thermal parameter B or the mean-square amplitude of atomic vibrations 〈 u 2 〉. Likewise, the ablation yield (atoms/shot) of the twelve target metals investigated by Thestrup et al. (2002) [8] under identical irradiation conditions is a function of the room temperature B -factor or 〈 u 2 〉.

The temperature dependence of the critical resolved shear stress (CRSS), τ, of ultra-pure tantalum single crystals (RRR ≥ 14000) observed below 250 K for a range of shear-strain rates $$ \dot{\gamma } = 2\times 10^{ - 5} - 6\times 10^{ - 3} \,{\text{s}}^{ - 1} $$ was analyzed within the framework of a kink-pair nucleation model of flow stress. The CRSS/strain-rate data follow the model formulation $$ \tau^{ 1/ 2} = C + D\,{ \ln }\dot{\gamma } $$ , where C and D are positive constants, for each deformation temperature T in the range 78–250 K. Evaluation of the various slip-parameters of flow stress points to (211) $$ [\bar{1}11] $$ slip system responsible for the yielding of ultra-pure tantalum single crystals in the so-called stress/temperature regime III (T

Nature of solute distribution in copper single crystals alloyed with 0–100 at.% Ni has been investigated via temperature dependence of the yield stress. The composition–property diagram developed and interpreted in terms of the kink-pair nucleation model of flow stress in solid–solution crystals shows that the solute distribution is statistically random in Cu–Ni single crystals with solute concentration c ≤ 14 at.% Ni, and is non-random for c between 14 and 50 at.% Ni. Similarly, the solute distribution is statistically random in Ni–Cu single crystals with c ≤ 20 at.% Cu, and deviation from statistically random distribution of solute occurs for all other values of c up to 50 at.% Cu.

Strips of 99.95 at.% Mo polycrystals annealed at 700 °C as well as the ones annealed and then aged for 6 months at room temperature were deformed in tension at various strain-rates in the range 2.1 × 10−4 to 4.2 × 10−3 s−1 till fracture. It is found that natural aging of the annealed specimens for 6 months leads to 20-30% reduction in the yield stress (YS), 18-22% reduction in the ultimate tensile strength (UTS), and 72-76% reduction in the ductility, i.e. the tensile strain emax corresponding to UTS, depending on the value of \( \dot{\upvarepsilon } \) in the tensile strain-rate range referred to. Data analysis in terms of the kink-pair nucleation model of flow stress shows that the reduction in YS of the aged Mo specimens is a consequence of lowering of the Peierls energy per interatomic spacing along the length of screw-dislocation segments trapped in the Peierls valleys on the migration of point defects to the dislocation cores during the course of natural aging. The reduction in UTS and emax is attributed to the variation in the relative contribution of the processes of dislocation multiplication and annihilation together with the reduction in the Peierls stress of the metal.

In a quest to identify more economic routes for synthesis of magnesium aluminate (MgAl2O4) spinel (MAS) thin films, dense plasma focus device was used with multiple plasma focus shots. Structural, bonding between composite films, surface morphological, compositional and hardness properties of MAS thin films were investigated by using x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive x-rays (EDX) analysis and Vickers micro hardness test respectively. In XRD graph, the presence of MgAl2O4 diffraction peaks in crystallographic orientations (222), (400) and (622) pointed out the successful formation of polycrystalline thin films of MgAl2O4 with face centered cubic structure. The FTIR spectrums showed a major common transmittance band at 697.95 cm−1 which belongs to MgAl2O4. SEM micrographs illustrated a mesh type, granular and multi layers microstructures with significant melting effects. EDX spectrum confirmed the existence of magnesium, oxygen and aluminum in MAS films. A common increasing behavior in micro-hardness of composite MgAl2O4 films by increasing number of plasma focus shots was found.

Un-doped and Li-doped ZnO thin films with high c-texture have been deposited on glass substrate using sol–gel spin coating method. The effect of Li dopant in concentration range 1–5 at.% on the structural, optical, morphological, and electrical properties of ZnO thin films were analyzed using x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–VIS spectrophotometer, field emission scanning electron microscopy (FESEM), and two point probe method, respectively. XRD analysis reveals that all thin films possess hexagonal wurtzite structure and (0 0 2) preferred orientation. X-ray diffraction intensity and crystallite size appertaining to (0 0 2) plane increases with the increase in Li concentration. FESEM micrographs shows that morphology of all thin films consist of spherical and non-spherical shaped grains. Surface roughness of the films decreases on increasing Li dopant concentration. Average transmittance in visible region is 90.6 ± 0.5 % for all Li-doped ZnO thin films. Blue shift, i.e. widening of optical band gap (E g) has been observed on doping with Li. Urbach energy (E u) was found to decrease on Li incorporation. Both E g and E u correlate well with variation in c-texture and crystallite size. The average refractive index of ZnO thin films in the visible region is decreased on doping with Li. Electrical conductivity of ZnO thin films is enhanced on increase in Li dopant concentration. The improvement in electrical conductivity also correlates well with increase in c-texture and crystallite size. FTIR spectra portray characteristic absorption bands centered at 901, 760, 602, and 568 cm−1 pertaining to metal–oxygen bonds.