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AIP Conference Proceedings [AIP Publishing 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Fes, Morocco (25–27 March 2019)] 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Powerful topographic analyzing method using fast Fourier transform for c-Si solar cells and advanced technologies
摘要： Roughness and texture analyses are an important topic for process development of high efficiency solar cells. Especially, strong improvement in Jsc was obtained by proper texturing of c-Si solar cells, which helped enhancing its infrared response. Usual pyramid size analysis relies on microscopy technique followed by image processing. One of the critical challenges to obtain an appropriate pyramid size distribution is to remove the initial contribution of background roughness, which is usually done by subtracting a polynomial background. This method holds strong limitation on physical meaning since the arbitrary chosen degree of the polynomial background will influence size distribution and can even provoke large errors. In this work, we present a method allowing to separate the contributions of different spatial frequencies and to filter the ones that need to be studied by applying Fast Fourier Transform (FFT). MountainsMap? software was used to study the roughness through a FFT treatment. A FFT spectrum was obtained in which selected frequencies were extracted to remove the noise and interferences from the initial confocal image. The resulted filtered topography image was obtained by the inverse FFT and analyzed to obtain the structural, morphological and geometrical characteristics of the surface. This methodology – applicable to several characterization methods – is particularly efficient when used with laser confocal scanning microscopy and opens the way to fast, automatic, accurate and non-destructive analysis that can be repeated at different positions of a sample with high throughput to enable statistical analysis.
关键词： topography analysis,Fast Fourier Transform,c-Si solar cells,roughness,texture
更新于2025-09-11 14:15:04
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Femtosecond laser microstructuring of alumina toughened zirconia for surface functionalization of dental implants
摘要： The continuous need for high-performance implants that can withstand mechanical loads while promoting implant integration into bone has focused recent research on the surface modification of hard ceramics. Their properties of biocompatibility, high mechanical and fatigue resistance and aesthetic color have contributed to its successful applications in dentistry. Alumina toughened Zirconia (ATZ) has been gaining attention as a material for dental implants applications due to its advanced mechanical properties and minimal degradation at body temperature. Still, in order to improve tissue response to this bioinert material, additional modifications are desirable. Improving the surface functionality of this ceramic could lead to enhanced implant-tissue interaction and subsequently, a successful implant integration. In this work, microtopographies were developed on the surface of Alumina toughened Zirconia using an ultrafast laser methodology, aiming at improving the cellular response to this ceramic. Microscale grooves and grid-like geometries were produced on ATZ ceramics by femtosecond laser ablation, with a pulse width of 150 fs, wavelength of 800 nm and repetition rate of 1 kHz. The variation of surface topography, roughness, chemistry and wettability with different laser processing parameters was examined. Cell-surface interactions were evaluated for 7 days on both microstructured surfaces and a non-treated control with pre-osteoblasts, MC3T3-E1 cells. Both surface topographies showed to improve cell response, with increased metabolic activity when compared to the untreated control and modulating cell morphology up to 7 days. The obtained results suggest that femtosecond laser texturing may be a suitable non-contact methodology for creating tunable micro-scale surface topography on ATZ ceramics to enhance the biological response.
关键词： Femtosecond laser microtexturing,Dental implants,Hard ceramics,Alumina toughened zirconia,Surface topography,Biological response
更新于2025-09-11 14:15:04
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Surface topography following pulsed laser texturing: Implications for adhesion and wettability
摘要： A model for predicting surface topography following nanosecond pulsed laser texturing of metals is applied to calculating the areal surface roughness, Sa, average ablation depth, Da, and Wenzel roughness factor or adhesion area ratio, r, for a range representative cases relating to adhesion and wettability. Optimisation of the laser scanning strategy, number of laser passes and focused spot size is performed by considering the ratio of increases in Sa and r with respect to the average ablation depth: ???? ????? values of ???? ????? focused spot size in both the scanning and lateral directions. Increases in Sa, r and ???/???? can be achieved by performing multiple laser passes, while r and ???/???? can be increased independently of Sa and ???? ????? by reducing the focused laser spot size. These results suggest that r and Sa can be optimised effectively and independently in line with a given application. Finally, laser texturing experiments are performed on AA 6082 aluminium alloy and 316L austenitic stainless steel specimens with the aim of confirming model outcomes, after which tensile tests are performed on adhesive-bonded joints prepared with the same laser treatments. Further to demonstrating the benefits of laser texturing, it is shown that optimum results are not necessarily associated with a single value of Sa or r, but are instead a compromise between maximising these parameters and limiting the ablated volume.
关键词： Adhesion,Topography,Surface Roughness,Laser Texturing,Wetting
更新于2025-09-11 14:15:04
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Role of Cerium Doping on Epitaxial Yttrium Iron Garnet Thin films
摘要： The present work discusses the growth optimization and magnetic properties of the Cerium doped Yttrium Iron Garnet (YIG) thin films grown through Pulsed Laser Deposition technique. The X-ray diffraction (XRD) reveals the highly crystalline, Single Phase, nature of films and the Atomic Force Microscopy (AFM) shows the films are very smooth, with root mean square roughness of less than 1 nm. Thickness of the films as calculated from the X-ray reflectivity (XRR) was found to be around 17, 35, 52, 70 and 122 nm. The Magnetic measurement shows the increase in the Saturation Magnetization, in the cerium doped YIG, but as the growth time increases, we observed a decrease in magnetic Saturation. The decrease in saturation magnetization arises due to the formation of residual Ce2O phase in the longer grown films. Longitudinal Spin Seebeck Voltage signal was observed in the films and the Platinum (Pt) deposited over the Cerium doped YIG film showed no sign of Pt magnetization.
关键词： Microwave technology,Surface topography,Cerium,Helmholtz coil
更新于2025-09-10 09:29:36
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Comparison of central corneal thickness measurements using optical low-coherence reflectometry, Fourier domain optical coherence tomography, and Scheimpflug camera
摘要： Purpose: To compare the results of central corneal thickness (CCT) measurements obtained using optical low-coherence reflectometry (OLCR), Fourier domain optical coherence tomography (FD-OCT), and a Scheimpflug camera (SC), combined with Placido corneal topography. Methods: A total of 25 healthy subjects were enrolled in the present study, and one eye of each subject was included. A detailed ophthalmic examination was performed in all cases following CCT measurements with OLCR, FD-OCT, and SC. The results were compared using an ANOVA test. Bland-Altman analysis was used to demonstrate agreement between methods. Intra-examiner repeatability was assessed by using intraclass correlation coefficients (ICCs). Results: Statistically significant differences were observed between the results of the CCT measurements obtained using the three different devices (p=0.009). Significant correlations were found between OLCR and FD-OCT (r=0.97; p<0.0001), FD-OCT and SC (r=0.91; p<0.0001), and OLCR and SC (r=0.95; p<0.0001). The 95% limits of agreement (LOA) obtained from Bland-Altman plots were from -7.2 μm to 28.7 μm for OLCR versus FD-OCT, from -19.2 μm to 30.4 μm for OLCR versus SC, and from -42.6 to 32.3 μm for FD-OCT versus SC. Intra-examiner repeatability was excellent for each method, with ICCs >0.98. Conclusions: Although the results of CCT measurements obtained from these three devices were highly correlated with one another and the mean differences between instruments were comparable with the reported diurnal CCT fluctuation, the measurements are not directly interchangeable in clinical practice because of the wide LOA values.
关键词： Fourier analysis,Comparative study,Observer variation,Cornea/anatomy & histology,Tomography, optical coherence/methods,Corneal topography/methods
更新于2025-09-10 09:29:36
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Hypoactivation of the Right Prefrontal Cortex Underlying Motor-Related Inhibitory Deficits in Children with Autism Spectrum Disorder: A Functional Near-Infrared Spectroscopy Study
摘要： Autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD) are believed to share the symptom of neurocognitive dysfunction in executive functions. Regarding the components of executive functions, however, dysfunction of motor-response inhibitory control in children with ASD remains unclear. Thus, using functional near-infrared spectroscopy (fNIRS), we investigated whether putative inhibitory brain dysfunctions are applicable to children with ASD by adopting a go/no-go task, which has robustly evoked activation in typically developing (TD) children but not in ADHD children. Twenty-four ASD and 24 TD children underwent a go/no-go task, and their cortical hemodynamics were assessed using fNIRS. Relative to TD participants, ASD participants showed reduced activation in the right inferior frontal gyrus and middle frontal gyrus (IFG/MFG) during go/no-go tasks. The current finding suggests that hypoactivation in the right IFG/MFG during a go/no-go task would serve as a potential biomarker for identifying children with ASD.
关键词： autism spectrum disorder,attention-deficit hyperactivity disorder,optical topography,prefrontal cortex,executive dysfunction
更新于2025-09-10 09:29:36
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Two-Photon Polymerization as a Tool for Studying 3D Printed Topography-Induced Stem Cell Fate
摘要： Geometric topographies are known to influence cellular differentiation toward specific phenotypes, but to date the range of features and type of substrates that can be easily fabricated to study these interactions is somewhat limited. In this study, an emerging technology, two-photon polymerization, is used to print topological patterns with varying feature-size and thereby study their effect on cellular differentiation. This technique offers rapid manufacturing of topographical surfaces with good feature resolution for shapes smaller than 3 μm. Human-induced pluripotent stem cells, when attached to these substrates or a non-patterned control for 1 week, express an array of genetic markers that suggest their differentiation toward a heterogeneous population of multipotent progenitors from all three germ layers. Compared to the topographically smooth control, small features (1.6 μm) encourage differentiation toward ectoderm while large features (8 μm) inhibit self-renewal. This study demonstrates the potential of using two-photon polymerization to study and control stem cell fate as a function of substrate interactions. The ability to tailor and strategically design biomaterials in this way can enable more precise and efficient generation or maintenance of desired phenotypes in vitro and in vivo.
关键词： induced pluripotent stem cells,differentiation,substrate topography,3D printing,two-photon polymerization
更新于2025-09-10 09:29:36
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Representing hydrodynamically important blocking features in coastal or riverine lidar topography
摘要： New automated methods are developed for identifying narrow landscape features that cause hydrodynamic blocking and might have critical impacts for management models of river flooding, coastal inundation, climate change, or extreme event analysis. Lidar data processed into a fine-resolution raster (1 m × 1 m) can resolve narrow blocking features in topography but typically cannot be directly used for hydrodynamic modeling. For practical applications such data are abstracted to larger scales, which can result in a loss of hydrodynamic blocking effects. The traditional approach to resolving hydrodynamic blocking features is to represent them as cell boundaries within a customized unstructured grid that is tuned to the spatial features. A new automated edge-blocking approach is developed, which allows application of an arbitrarily structured (Cartesian) mesh at coarser scales and provides contiguous representation of blocking features along Cartesian cell boundaries. This approach distorts the shape of a blocking feature (i.e., making it rectilinear along grid cell faces) but retains its critical hydrodynamic blocking height characteristics and spatial continuity within the topographic model.
关键词： coastal inundation,climate change,hydrodynamic blocking,river flooding,lidar topography,extreme event analysis
更新于2025-09-10 09:29:36
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Accuracy of 3D surface scanners for clinical torso and spinal deformity assessment
摘要： Externally visible deformities are cosmetic features of great concern for Adolescent Idiopathic Scoliosis (AIS) patients. Current assessment techniques for AIS do not fully encompass the external deformity. A non-invasive method capable of capturing superficial anatomy, such as 3D scanning, would enable better qualitative and quantitative evaluation of cosmesis. This study aimed to quantify the accuracy of commonly available scanners, in assessing posterior asymmetry in AIS. The technique of 3D surface deviation analysis was proposed as a suitable method for comparing the models created by each scanner. Eight plaster cast moulds manufactured to create braces for AIS patients were used as test samples. Four 3D scanners were selected: Solutionix RexScan CS + ; Artec Eva; Microsoft Kinect V1; iPhone with 123D Catch App. These scanners were selected from those available as representative of a range of scanning technologies. Each cast was scanned and 3D models created. A simulated rib hump measurement was obtained and the surface-to-surface deviations between the Solutionix scan and all other scans were determined. The Solutionix scanner is a metrology scanner of very high quality and so it was selected as the reference. Surface-to-surface deviations were calculated in the positive and negative directions separately to specifically identify size and volume inaccuracies created by the scans. Surface deviations showed excellent agreement between the Solutionix and the Eva with deviations of + 0.17 ± 0.17 mm (Eva regions larger) and ?0.20 ± 0.32 mm (Eva regions smaller) (mean ±SD). The Kinect showed lower agreement ( + 1.58 ± 1.50 mm and ?0.58 ± 0.58 mm). The iPhone scans were not able to be scaled to the correct size, so were excluded. Rib hump measurements with all scanners were within clinical measurement variability ( ±4.9 deg) of the known values. These commercially available 3D scanners are capable of imaging torso shape in 3D and deriving clinically relevant external deformity measures. The non-invasive 3D topographic information provided can be used to improve assessment of torso shape in spinal deformity patients.
关键词： Torso Deformity,3D Scanning,Scoliosis,Accuracy,Reproducibility of results,Surface topography,Surface Deviations
更新于2025-09-10 09:29:36
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Underlying Topography Estimation Over Forest Areas Using Single-Baseline InSAR Data
摘要： In this paper, a method for digital elevation model (DEM) extraction over forest areas from single-baseline interferometric synthetic aperture radar (InSAR) data is proposed. The main idea of this method is that some backscattering variations which are linked to the geometrical structures of forest occur during the radar acquisition. The time–frequency analysis is used to retrieve these variations by dividing the synthesized SAR image into multiple SAR images in the Fourier domain called sublook images. Then, by interferometry, the sublook images characterized by the same Doppler bandwidth and acquired from spatially separated locations at either end of a baseline are used to estimate the sublook coherences and the above backscattering variations are converted into the variations the number of InSAR of sublook coherences. As a result, observations can be increased. The sublook coherences are then interpreted by the two-layer vegetation scattering model and are assumed to follow a near-linear relationship in the complex plane. The ground phase can then be estimated by linear regression of the sublook coherences. The performance of the proposed method was validated by E-SAR L- and P-band SAR data acquired over coniferous and tropical forests. For the coniferous scenario, the underlying DEM estimated by the proposed method has a root-mean-square error (RMSE) of 4.39 m, which is slightly less accurate than the DEM (with an RMSE of 4.07 m) derived by the polarimetric line-?t (LF) method, but represents a signi?cant improvement in DEM accuracy over the HH InSAR method. For the tropical scenario, the DEMs derived by the proposed method and the polarimetric LF method are closer to the ground surface than those derived by the HH InSAR method, and their mean ground height difference is 0.62 m. The two experiments con?rm that it is feasible to extract a DEM by the proposed method, which has a comparable performance in DEM inversion to the polarimetric LF method and only requires single-polarization InSAR data.
关键词： time–frequency (TF) analysis,underlying topography,two-layer vegetation scattering model,Interferometric synthetic aperture radar (InSAR)
更新于2025-09-10 09:29:36