Analysis Of Intensity Profiles Research Articles

Beam-shaping in laser-based powder bed fusion of metals: A computational analysis of point-ring intensity profiles

Laser-based powder bed fusion has the potential to enable manufacturing of local material properties and locally varying alloys. One promising approach under research is shaping of the applied laser beam. The current commercial standard using a Gaussian laser beam profile is associated with a high energy intensity peak and strong gradients. A potential alternative beam shape is the point-ring profile where laser energy is distributed between a central spot and an outer ring. We conduct a numerical study of beam shape impact on melt-pool shapes, surface temperatures, evaporation and flow dynamics of single-melt-tracks. To that end, we apply a Weakly Compressible Smoothed Particle Hydrodynamics solver coupled with a ray-tracing laser scheme. A point-ring profile is compared to a standard Gaussian profile. The profiles are studied at two different beam sizes to find the influence of beam size on the shape effect. We find good agreement between numerical results and experimental data for both narrow and deep, as well as wide and shallow melt-tracks. The simulation results show that beam size and thus energy density influence the effect beam-shaping has on the melt-pool dynamics. Both the distribution of evaporation and surface tension forces over the melt-pool surface are found to depend on the used beam shape. The study highlights the importance of distinguishing between size and shape effects when investigating laser beam shapes. Both energy density and its distribution need to be tuned for the desired melt-pool behavior.

Optimizing Image Enhancement: Feature Engineering for Improved Classification in AI-Assisted Artificial Retinas.

Artificial retinas have revolutionized the lives of many blind people by enabling their ability to perceive vision via an implanted chip. Despite significant advancements, there are some limitations that cannot be ignored. Presenting all objects captured in a scene makes their identification difficult. Addressing this limitation is necessary because the artificial retina can utilize a very limited number of pixels to represent vision information. This problem in a multi-object scenario can be mitigated by enhancing images such that only the major objects are considered to be shown in vision. Although simple techniques like edge detection are used, they fall short in representing identifiable objects in complex scenarios, suggesting the idea of integrating primary object edges. To support this idea, the proposed classification model aims at identifying the primary objects based on a suggested set of selective features. The proposed classification model can then be equipped into the artificial retina system for filtering multiple primary objects to enhance vision. The suitability of handling multi-objects enables the system to cope with real-world complex scenarios. The proposed classification model is based on a multi-label deep neural network, specifically designed to leverage from the selective feature set. Initially, the enhanced images proposed in this research are compared with the ones that utilize an edge detection technique for single, dual, and multi-object images. These enhancements are also verified through an intensity profile analysis. Subsequently, the proposed classification model's performance is evaluated to show the significance of utilizing the suggested features. This includes evaluating the model's ability to correctly classify the top five, four, three, two, and one object(s), with respective accuracies of up to 84.8%, 85.2%, 86.8%, 91.8%, and 96.4%. Several comparisons such as training/validation loss and accuracies, precision, recall, specificity, and area under a curve indicate reliable results. Based on the overall evaluation of this study, it is concluded that using the suggested set of selective features not only improves the classification model's performance, but aligns with the specific problem to address the challenge of correctly identifying objects in multi-object scenarios. Therefore, the proposed classification model designed on the basis of selective features is considered to be a very useful tool in supporting the idea of optimizing image enhancement.

Investigation of pulsatile flow structure in closed-type cavity

Pulsatile flow in a channel with sudden expansion and contraction, referred to as a closed-type cavity, is experimentally and numerically investigated in the range of Re = 50–1650, covering laminar and transitional flow regimes. Investigations are performed in the range of pulsation frequencies corresponding to Wo = 0.28–0.62 and at a constant pulsation amplitude. Pulsation frequency influence to time-averaged recirculation zone length and the development of recirculation zone as well as upper and corner eddies during the pulse cycle at different pulsation frequencies are investigated. A fixed amplitude from zero to maximum velocity is chosen to investigate flow behaviour throughout a whole pulsation cycle. The results show that the pulsation effect on the recirculation zone length is insignificant in the laminar flow regime at investigated frequencies. However, in the transitional flow regime, recirculation zone length was shortened, regardless of the Wo. The analysis of recirculation zone and upper eddy dynamics during the pulse cycle revealed that their growth rate depends on Wo. The development lag effect is observed at certain velocity phase angles. The analysis of shear rate and turbulence intensity profiles revealed that increased instabilities are determined by the interaction of recirculation zone, upper eddy and the forward-facing step during the pulse cycle.

Dielectric responses and stimulative optical shuttering action of self-assembly supramolecular hydrogen bond liquid crystalline formation via x- and y-types benzoic acids

Investigations of a single hydrogen bonded liquid crystals are made between alkyloxy benzoic acids (x-BOA) and alkyloxy benzoic acids (y-BOA) and are discussed in the present investigation. Type of mesogenic phases exhibited are visualized and recorded with the help of a Polarizing Optical Microscopy (POM). Conventional phases such as ‘Nematic’ (Nematic droplets, ‘Schlieren’ or threaded textures, four brush textures), ‘Smectic C’ (Schlieren and broken focal conical texture), ‘Smectic F’ (chequered board texture) and ‘Smectic G’ (multi colored smooth mosaic texture) are observed. Newly investigated textural phases viz., ‘Smectic X’ (‘worm’ like texture) is also characterized to elucidate their structure. Phase diagrams are constructed to study in detail the thermal stability, occurrence and thermal span of the phases as a function of the chemical constitution of hydrogen bonded (HB) complexes. Thermal analysis include analysis of Differential Scanning Calorimetry (DSC) thermograms, study of the order of the transition by Navard & Cox parameter and construction of the relevant phase diagrams. Electrical attempts include measurement of permittvity and dielectric loss with respect to the electrical stimulus applied and light intensity profile analysis.

Micron-scale human enamel layer characterization after orthodontic bracket debonding by intensity-based layer segmentation in optical coherence tomography images

In clinical orthodontic practice, fixed brackets are widely used for tooth movement and adjustments. Although years of research and development have improved the workability of fixed orthodontic brackets, there are still controversies regarding its plausible destructive influence on the enamel surface of tooth. This, in turn, makes the quantitative assessment of the enamel surface after specific orthodontic treatment procedures important in order to opt for the most effective treatment procedure. Through this study, we show the practical applicability of optical coherence tomography (OCT) as a non-ionizing and nondestructive assessment tool for measuring enamel loss after each step of orthodontic bracket bonding. Two-dimensional and volumetric OCT images are used for the evaluation of the tooth enamel. From the depth intensity profile analysis of cross-sectional OCT images, the changes in the individual internal layer thickness are calculated. A software algorithm was developed to evaluate the structural connectivity in the enamel for analyzing enamel loss on the tooth surface and for detecting enamel abrasion. An intensity-based layer segmentation algorithm is also developed to analyze and evaluate enamel wear in the tooth after each step. Using the proposed algorithms, the total enamel present after each treatment procedure was measured and tabulated for analysis.

Extended B-Site Vacancy Content Range and Cation Ordering in Twinned Hexagonal Perovskites Ba8Cr4-xTa4+0.6xO24.

The new 8-layer twinned hexagonal solid solution Ba8Cr4-xTa4+0.6xO24 (x = 0.0-3.0) was isolated through the aliovalent substitution of Ta5+ for Cr3+ in Ba2CrTaO6, showing the widest B-site vacancy content range among the 8-layer twinned hexagonal perovskites. Ba8Cr4-xTa4+0.6xO24 forms a simple 8-layer hexagonal perovskite structure within 0.0 ≤ x < 2.4 and a tripled 8-layer hexagonal perovskite superstructure within 2.4 ≤ x ≤ 3.0. The latter shows expanded a and b axes by times in comparison to the simple 8-layer hexagonal perovskite structure owing to the partial face-sharing octahedral (FSO) B cation ordering along the ab plane. The B-cation and vacancy distributions in the tripled superstructure were characterized by neutron and X-ray powder diffraction and further confirmed by a scanning transmission electron microscopy-high angle annular dark field imaging and intensity profile analysis. The formation of 8-layer twinned hexagonal perovskites Ba8Cr4-xTa4+0.6xO24 in an extended solid solution range can be attributed to the presence of both covalent B-B and B-O-B bonding and B-site vacancies in the FSO sites. This work provides an effective way of combining covalent B-B and B-O-B bonding and vacancy creation as well as the cationic ordering in the FSO sites to reduce electrostatic repulsion, which could further enable the stabilization of new hexagonal perovskite compounds.

Phase-Controlled 1T Transition-Metal Dichalcogenide-Based Multidimensional Hybrid Nanostructures

Phase-Controlled 1T Transition-Metal Dichalcogenide-Based Multidimensional Hybrid Nanostructures

Radiative Transfer Modeling of EC 53: An Episodically Accreting Class I Young Stellar Object

Abstract In the episodic accretion scenario, a large fraction of the protostellar mass accretes during repeated and large bursts of accretion. Since outbursts on protostars are typically identified at specific wavelengths, interpreting these outbursts requires converting this change in flux to a change in total luminosity. The Class I young stellar object EC 53 in the Serpens Main cloud has undergone repeated increases in brightness at 850 μm that are likely caused by bursts of accretion. In this study, we perform two- and three-dimensional continuum radiative transfer modeling to quantify the internal luminosity rise in EC 53 that corresponds to the factor of ∼1.5 enhancement in flux at 850 μm. We model the spectral energy distribution and radial intensity profile in both the quiescent and outburst phases. The internal luminosity in the outburst phase is ∼3.3 times brighter than the luminosity in the quiescent phase. The radial intensity profile analysis demonstrates that the detected submillimeter flux variation of EC 53 comes from the heated envelope by the accretion burst. We also find that the role of external heating of the EC 53 envelope by the interstellar radiation field is insignificant.

Can fluorescence and autofluorescence imaging be useful in diagnosis of basal cell cancer? Proposition of algorithms.

The most common non-melanoma skin carcinomas (NMSC) are basal cell carcinomas (BCC). Autofluorescence study may allow a non-invasive distinction of neoplastic lesions from benign lesions, whereas fluorescence spectroscopy enables qualification of the patient for possible photodynamic or surgical treatment. The aim of the study is to assess the suitability of autofluorescence and fluorescence imaging in the diagnosis of the stage of advancement, and the morphological type of changes in basal cell carcinoma of the skin. A group of 382 patients with 430 skin lesions of basal cell carcinoma were subjected to an autofluorescence study and a spectral imaging using a spectral camera. The acquired spectra and fluorescence images were analyzed using the Image Pro-Plus 5.0.2 software. An analysis of fluorescence intensity profiles in the long and short axis of the studied changes was carried out. The fluorescence emission observed in BCC lesions with an area of ​​up to 3 cm2 showed a statistically significantly higher level of intensity in comparison to changes in lesions exceeding 3 cm2 (#p < 0.05, ## p < 0.01). In the autofluorescence evaluation, we observed significant differences in the mean values of the Numerical Colour Value (NCV) depending on the size of the area of skin occupied by skin lesions. Based on the spatial and profile assessment of the types of BCC lesions a proposed algorithm for identifying changes was developed. Analysis of green fluorescence intensity profiles, analogous to fluorescence profiles analysis, allowed to propose an algorithm of autofluorescence evaluation in the diagnosis of BCC. Autofluorescence and fluorescence imaging allow assessment of the extent of neoplastic infiltration and distinguish types of skin lesions with BCC. The determined diagnostic algorithms may be an effective diagnostic solution in the diagnosis of skin lesions of this nature.

Nondestructive Evaluation for Detection of Voids in Sodium-Bonded Metallic Fuel Pins

Nondestructive detection of sodium-free regions (voids) in metallic fuel pins is necessary for their safe and reliable operation. Eddy current and X-radiography nondestructive evaluation techniques were employed for detection of voids in experimental fuel pins. Detailed finite element model-based investigations and radiography intensity profile analysis were carried out to understand the signatures to ensure that the signals are due to voids. In addition to enabling the detection of sodium voids in metallic fuel pins, NDE studies aided in optimizing the sodium filling process and were helpful in finding out the adequacy of the heat treatment during filling process.

3-Dimensional characterization of cortical bone microdamage following placement of orthodontic microimplants using Optical Coherence Tomography

Microimplants are being used extensively in clinical practice to achieve absolute anchorage. Success of microimplant mainly depend on its primary stability onto the cortical bone surface and the associated Microdamage of the cortical bone during insertion procedure leads to many a microimplants to fail and dislodge from the cortical bone leading to its failure. Even though, previous studies showed occurrence of microdamage in the cortical bone, they were mainly 2-dimension studies or studies that were invasive to the host. In the present study, we used a non-invasive, non-ionizing imaging technique- Optical Coherence Tomography (OCT), to image and analyze the presence of microdamage along the cortical bone surrounding the microimplant. We inserted 80 microimplants in two different methods (drill and drill free method) and in two different angulations onto the cortical bone surface. Images were obtained in both 2D and 3D imaging modes. In the images, microdamage in form of microcracks on the cortical bone surface around the bone-microimplant interface and micro-elevations of the cortical bone in angulated microimplant insertions and the presence of bone debris due to screwing motion of the microimplant on insertion can be appreciated visually and quantitatively through the depth intensity profile analysis of the images.

Breathers, solitons and rogue waves of the quintic nonlinear Schrödinger equation on various backgrounds

We investigate the generation of breathers, solitons, and rogue waves of the quintic nonlinear Schrodinger equation (QNLSE) on uniform and elliptical backgrounds. The QNLSE is the general nonlinear Schrodinger equation that includes all terms up to the fifth-order dispersion. We use Darboux transformation to construct initial conditions for the dynamical generation of localized high-intensity optical waves. The condition for the breather-to-soliton conversion is provided with the analysis of soliton intensity profiles. We discover a new class of higher-order solutions in which Jacobi elliptic functions are set as background seed solutions of the QNLSE. We also introduce a method for generating a new class of rogue waves—the periodic rogue waves—based on the matching of the periodicity of higher-order breathers with the periodicity of the background dnoidal wave.

Recombination activity of threading dislocations in GaInP influenced by growth temperature

Room-temperature non-radiative recombination is studied at single dislocations in Ga0.5In0.5P quantum wells grown on metamorphic templates using cathodoluminescence and electron channeling contrast imaging. An analysis of the light emission intensity profiles around single dislocations reveals that the average recombination strength of a dislocation decreases by a factor of four and seven as a result of decreasing growth temperature of the GaInP quantum well from 725 to 675 and 625 °C, respectively. This reduction occurs despite little change in the diffusion length, precluding the prospect of inducing carrier localization by ordering and phase separation in GaInP at lower growth temperatures. These observations are rationalized by the premise that point defects or impurities are largely responsible for the recombination activity of dislocations, and the extent of decoration of the dislocation core decreases with temperature. Preliminary evidence for the impact of the Burgers vector is also presented. The lowest growth temperature, however, negatively impacts light emission away from dislocations. Carrier recombination in the bulk and at dislocations needs to be considered together for metamorphic devices, and this work can lead to new techniques to limit non-radiative recombination.

Theoretical study on ultraviolet profile and chemical reactivity descriptors of fluorinated liquid crystals: Effect of end chain length and substituent

The electronic transitions in the ultraviolet (UV) region of nematic 4′‐(3,4,5‐trifluorophenyl)‐4‐alkylbicyclohexyl (3FPnBCH) molecules with propyl (3FP3BCH), and pentyl (3FP5BCH) have been studied. The UV spectra of these molecules have been simulated using the TDDFT/B3LYP/6-31 + G (d) method. Molecular charge distribution has analyzed based on Mulliken and Loewdin atomic charges for each molecule. The absorption spectra, HOMO and LUMO energies corresponding to the electronic transitions in the UV region have been reported. Excited states have been calculated via CI-singles (CIS) with semiempirical Hamiltonian ZINDO. Further, intensity profile analysis has been carried out to detect the highest possible absorption wavelength. Global chemical reactivity descriptors and effect of end chain length on all these parameters has been studied. Similar studies have been carried out for these molecules with respect to boron substitution (3BPnBCH; n = 3, 5). These computations offer deeper understanding in UV stability, reactivity, and kinetic stability of these molecules.

The Gelsolin Pathogenic D187N Mutant Exhibits Altered Conformational Stability and Forms Amyloidogenic Oligomers.

Gelsolin is an actin-severing protein that attains an open functional conformation in the presence of Ca2+ or low pH. Mutations (D187N/Y) in the second domain of gelsolin trigger the proteolytic pathway producing amyloidogenic fragments that form the pathological hallmark of gelsolin amyloidosis and lattice corneal dystrophy type 2 (LCD2). Here, we show that the D187N mutant gelsolin in a Ca2+ depleted, low pH-activated, open conformation could assemble into amyloidogenic oligomers without necessarily undergoing the specific proteolytic step. Although both wild-type (WT) and mutant proteins exhibit closely overlapping globular shapes at physiological conditions, the latter exhibits subjugated actin depolymerization, loss of thermodynamic stability, and folding cooperativity. Mutant gelsolin displayed aberrant conformational unwinding and formed structural conformers with high associative properties at low pH conditions. A SAXS intensity profile and Guinier analysis of these conformers showed the formation of unusual, higher order aggregates. Extended incubation at low pH resulted in the formation of thioflavin T and Congo red positive, β-sheet rich aggregates with a fibrillar, amyloid-like morphology visible under electron and atomic force microscopy. Mass spectrometric analysis of disaggregated end-stage fibrils displayed peptide fragments encompassing the entire protein sequence, indicating the involvement of full length mutant gelsolin in fibril formation. Atomistic and REMD simulations indicated a larger increase in solvent accessibility and loss of fold architecture in mutant gelsolin at low pH as compared to WT gelsolin. Our findings support the existence of a secondary oligomerization-dependent aggregation pathway associated with gelsolin amyloidosis and can pave the way for better therapeutic strategies.

Localization of optic disc and fovea in retinal images using intensity based line scanning analysis

Accurate detection of diabetic retinopathy (DR) mainly depends on identification of retinal landmarks such as optic disc and fovea. Present methods suffer from challenges like less accuracy and high computational complexity. To address this issue, this paper presents a novel approach for fast and accurate localization of optic disc (OD) and fovea using one-dimensional scanned intensity profile analysis. The proposed method utilizes both time and frequency domain information effectively for localization of OD. The final OD center is located using signal peak-valley detection in time domain and discontinuity detection in frequency domain analysis. However, with the help of detected OD location, the fovea center is located using signal valley analysis. Experiments were conducted on MESSIDOR dataset, where OD was successfully located in 1197 out of 1200 images (99.75%) and fovea in 1196 out of 1200 images (99.66%) with an average computation time of 0.52s. The large scale evaluation has been carried out extensively on nine publicly available databases. The proposed method is highly efficient in terms of quickly and accurately localizing OD and fovea structure together compared with the other state-of-the-art methods.

Position-sensitive detection of ultracold neutrons with an imaging camera and its implications to spectroscopy

Position-sensitive detection of ultracold neutrons (UCNs) is demonstrated using an imaging charge-coupled device (CCD) camera. A spatial resolution less than 15μm has been achieved, which is equivalent to a UCN energy resolution below 2 pico-electron-volts through the relation δE=m0gδx. Here, the symbols δE, δx, m0 and g are the energy resolution, the spatial resolution, the neutron rest mass and the gravitational acceleration, respectively. A multilayer surface convertor described previously is used to capture UCNs and then emits visible light for CCD imaging. Particle identification and noise rejection are discussed through the use of light intensity profile analysis. This method allows different types of UCN spectroscopy and other applications.

Optical coherence tomography use in the diagnosis of enamel defects.

Molar incisor hypomineralization (MIH) affects the permanent incisors and molars, whose undermineralized matrix is evidenced by lesions ranging from white to yellow/brown opacities to crumbling enamel lesions incapable of withstanding normal occlusal forces and function. Diagnosing the condition involves clinical and radiographic examination of these teeth, with known limitations in determining the depth extent of the enamel defects in particular. Optical coherence tomography (OCT) is an emerging hard and soft tissue imaging technique, which was investigated as a new potential diagnostic method in dentistry. A comparison between the diagnostic potential of the conventional methods and OCT was conducted. Compared to conventional imaging methods, OCT gave more information on the structure of the enamel defects as well as the depth extent of the defects into the enamel structure. Different types of enamel defects were compared, each type presenting a unique identifiable pattern when imaged using OCT. Additionally, advanced methods of OCT image analysis including backscattered light intensity profile analysis and enface reconstruction were performed. Both methods confirmed the potential of OCT in enamel defects diagnosis. In conclusion, OCT imaging enabled the identification of the type of enamel defect and the determination of the extent of the enamel defects in MIH with the advantage of being a radiation free diagnostic technique.

Morphological and magnetic analysis of Fe nanostructures on W(110) by using scanning tunneling microscopy and Lorentz microscopy

We investigated morphological features and magnetic properties of epitaxial Fe nanostructures (films, stripes and nanoparticles) on a W(110) surface with monoatomic steps preferentially along the direction. The nanostructures were prepared in ultra-high vacuum by using electron-beam evaporation and subsequent annealing at different temperatures. Scanning tunneling microscopy measurements in-situ revealed elongated Fe nanostructures with aspect ratios of up to . The observable shape and orientation (along or perpendicular to the monoatomic steps of the substrate) of the nanostructures depended substantially on the preparation parameters. By capping the system with 7 monolayers of Pt, the magnetic properties of selected Fe nanostructures could be analyzed ex-situ using Lorentz microscopy revealing diversified results. Depending on the size and shape, different magnetization structures, such as single domain, two domains and vortex, were observed. A precise intensity profile analysis demonstrated that the magnetic field values of different magnetic structures are close to each other and equal 2.4 T.

Optical coherence tomography for differentiation of parathyroid gland tissue

Optical coherence tomography (OCT) is a high-resolution imaging technique that allows the identification of microarchitectural features in real-time. Can OCT be used to differentiate parathyroid tissue from other cervical tissue entities? All investigations were carried out during cervical operations. Initially, ex vivo images were analyzed to define morphological imaging criteria for each tissue entity. These criteria were used to evaluate a first series of ex vivo images. In a second phase the practicability of the technique was investigated in vivo and in the third phase backscattering intensity measurements were analyzed employing linear discriminant analysis (LDA). In the ex vivo series parathyroid tissue could be differentiated from other tissue entities with a sensitivity and specificity of 84 % and 94 %, respectively. Parathyroid tissue was correctly identified in the in vivo series in only 69.2 %. The analysis of backscattering intensity profiles employing LDA reliably distinguished between the different tissue types. The OCT images displayed typical characteristics for each tissue entity. Due to technical problems in handling the probe the in vivo OCT images were of much poorer quality. Backscattering intensity measurements illustrated that OCT images provide an individual profile for each tissue entity independent of the defined morphological assessment criteria. The results show that OCT is fundamentally suitable for intraoperative differentiation of tissues.