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Effect of build geometry and orientation on microstructure and properties of additively manufactured 316L stainless steel by laser metal deposition
摘要： The effect of build geometry and orientation on the microstructure and mechanical properties of additively manufactured AISI 316L stainless steel was studied. For this an integrated laser metal deposition system was used to build two test blocks, Block 1 and Block 2, such that Block 1 had its longest dimension parallel to the build direction while Block 2 had its longest dimension perpendicular to the build direction. Samples with different orientations with respect to the build direction were extracted from the two blocks and characterized in detail. Block 1 was found to have a coarser defect-free microstructure, while Block 2 had a finer microstructure with extensive inter-track/layer defects. The yield strengths and tensile strengths of Block 2 samples were higher than Block 1 samples, but their strain hardening capacities and ductility values were lower. These differences in microstructure and mechanical properties were shown to be an outcome of the different build rates and consequent thermal histories of the two blocks. In order to explain the variation of yield strength with sample orientation, an alternate measure for grain size called “effective grain size” was introduced, which revealed the effect of grain orientation on the mean free path for dislocation motion and hence yield/flow stress. Variation of yield strength with the effective grain size was found to follow Hall-Petch behaviour.
关键词： Anisotropy,Additive Manufacturing,Grain Size,Tensile Behaviour,Orientation
更新于2025-11-28 14:24:20
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From colloidal CdSe quantum dots to microscale optically anisotropic supercrystals through bottom-up self-assembly
摘要： The development of fabrication techniques for novel nanostructured materials is one of the key tasks of modern materials science. One pathway to successfully complete this task is the bottom-up assembly of colloidal nanoparticles into ordered superstructures, possessing both the properties of individual nanoparticles and further novel properties resulting from their interactions. However, nanoparticle self-assembly depends on a variety of parameters, which makes the precise control of this process a complicated problem. Here, the time course of quantum dot (QD) self-assembly into ordered superstructures has been analyzed, along with the evolution of their morphological and optical properties. QD self-assembly occurs through two distinct stages (homo- and hetero-geneous), leading to the formation of supercrystals with a layered morphology. Analysis of the optical properties throughout the superstructures’ growth has shown that the absorption and photoluminescence (PL) bands are blue shifted, retaining almost the same PL lifetimes as in the initial QD solution. The supercrystals formed possess a further unique optical property caused by their layered morphology; namely, a four-fold symmetry characterized by strong birefringence. Such supercrystals may be used for the fabrication of microscale optical paths with high extinction coefficients and specific polarization properties for novel optoelectronic devices.
关键词： optical anisotropy,nanostructured materials,birefringence,self-assembly,quantum dots,supercrystals
更新于2025-11-21 11:08:12
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Investigating native state fluorescence emission of Immunoglobulin G using polarized Excitation Emission Matrix (pEEM) spectroscopy and PARAFAC
摘要： Intrinsic ?uorescence spectroscopy (IFS) measurements for protein structural analysis can be enhanced by the use of anisotropy resolved multidimensional emission spectroscopy (ARMES). ARMES attempts to overcome the tryptophan (Trp) and tyrosine (Tyr) spectral overlap problem and resolve emitting components by combining anisotropy measurements with chemometric analysis. Here we investigate for the ?rst time the application of polarized excitation-emission matrix (pEEM) measurements and Parallel Factor (PARAFAC) analysis to study IFS from an Immunoglobulin G (IgG) type protein, rabbit IgG (rIgG), in its native state. Protein IFS is a non-trilinear system primarily because of F€orster resonance energy transfer (FRET). Non-trilinearity is also caused by inner ?lter effects, and Rayleigh/Raman scattering, both of which can be corrected by data pre-processing. However, IFS FRET cannot be corrected for, and thus here we carefully evaluated the impact of various different data pre-processing methods on IFS data which used for PARAFAC. Care must be taken with data pre-processing and interpolation, as both had an impact on PARAFAC modelling and the recovered anisotropy values, with residual shot noise from the Rayleigh scatter which overlapped the emission blue edge being the root cause. pEEM spectra from thawed rIgG solutions (15–35 (cid:1)C temperature range) were collected with an expectation being that this temperature range should cause suf?cient emission variation to facilitate component resolution but without major structural changes. However, the only signi?cant changes observed were of the overall intensity due to thermal motion induced quenching and this was con?rmed by the PARAFAC scores. PARAFAC resolved one major component (>99%) for the emission data (polarized and unpolarized) which mostly represented the large Tyr-to-Trp hetero-FRET process, with a second, very weak component (<1%) apparently a contribution from directly excited Trp emission. PARAFAC scores recovered from normalized pEEM data showed minimal change which was further proof for negligible structural change. The results of this study serves as the starting point for the use of PARAFAC analysis of IFS from IgG type proteins and important processes such as denaturation and aggregation.
关键词： Multidimensional,Fluorescence,PARAFAC,Anisotropy,Protein,Spectroscopy,Immunoglobulin G
更新于2025-11-14 15:32:45
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Anisotropic infrared light emission from quasi-one-dimensional layered TiS<sub>3</sub>
摘要： Atomically thin semiconductors hold great potential for nanoscale photonic and optoelectronic devices because of their strong light absorption and emission. Despite progress, their application in integrated photonics is hindered particularly by a lack of stable layered semiconductors emitting in the infrared part of the electromagnetic spectrum. Here we show that titanium trisulfide (TiS3), a layered van der Waals material consisting of quasi-one-dimensional chains, emits near infrared light centered around 0.91 eV (1360 nm). Its photoluminescence exhibits linear polarization anisotropy and an emission lifetime of 210 ps. At low temperature, we distinguish two spectral contributions with opposite linear polarizations attributed to excitons and defects. Moreover, the dependence on excitation power and temperature suggests that free and bound excitons dominate the excitonic emission at high and low temperatures, respectively. Our results demonstrate the promising properties of TiS3 as a stable semiconductor for optoelectronic and nanophotonic devices operating at telecommunication wavelengths.
关键词： infrared luminescence,transition metal trichalcogenides,titanium trisulfide,linear polarization anisotropy,layered semiconductors
更新于2025-11-14 14:32:36
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Plastic anisotropy of laser melting deposited Ti–5Al–5Mo–5V–1Cr–1Fe titanium alloy
摘要： Tensile tests of laser melting deposited Ti–5Al–5Mo–5V–1Cr–1Fe titanium alloy specimens in different orientations were conducted, which indicates significant plastic anisotropy of this material. Digital image correlation method added in-situ-tensile tests were carried out to investigate mechanical properties with respect to specified material structures. The results indicate that the plasticity properties of the thick columnar grain and that of other grains are significant different. Under the same stress level, the thick columnar grain yield firstly and bear the main plastic deformation of the whole specimen. The elasto-plastic Poisson's ratio of the thick columnar grains and that of other grains are also different. Tests on layer bands indicate that the coarser microstructures of the layer bands lead a stronger resistance to tensile plastic deformation, but a weaker resistance to shear plastic deformation. In addition, the direction of primary α laths on both sides of the layer bands may be different, and this has an obviously effect on the tensile plastic deformation of the specimen.
关键词： Digital image correlation method,Plastic anisotropy,Laser melting deposited,Titanium alloy,Mechanical properties
更新于2025-10-24 16:40:20
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Mixed Total Field/Scattered Field-Based Discontinuous Galerkin Frequency-Domain Method for Subsurface Sensing
摘要： To model the responses of electromagnetic surveys for geophysical subsurface sensing, a mixed total field/scattered field-based discontinuous Galerkin frequency-domain (TF/SF DGFD) method is proposed in this paper. The proposed TF/SF DGFD method is implemented at a subdomain level based on the domain decomposition technique. Different subdomains can employ either the TF DGFD framework or the SF DGFD framework, which are then coupled through the Riemann transmission condition. To balance the computation efficiency and accuracy for practical applications, the proposed method prefers to using the SF DGFD framework for subdomains with sources and using the TF DGFD framework for the remaining subdomains. At the interfaces between total field and scattered field subdomains, the Riemann transmission condition is slightly modified by incorporating the background fields due to the physically imposed sources in the background media. In this way, the proposed method only requires surface integrals of the background fields as extra overhead instead of elementwise integration of the scattering objects for the purely scattered field-based method, which can improve the computational efficiency. Also, it is more accurate than the purely TF DGFD method given the same mesh. Numerical examples are studied to examine the performance of the proposed method, which is proven to have better accuracy than the TF DGFD method. The TF/SF DGFD method will facilitate modeling of electromagnetic surveys under complicated geophysical environments for subsurface sensing.
关键词： scattered field,Anisotropy,domain decomposition,discontinuous Galerkin frequency-domain (DGFD) method,total field,subsurface sensing
更新于2025-09-23 15:23:52
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - The Effect of Trunks on Directional Brightness Temperatures of a Leafless Forest Using a Geometrical Optical Model
摘要： In the paper, a geometric optical model is proposed for a vegetation-trunk-soil scene. The effect of tree trunks was analyzed by comparing directional brightness temperatures (BTs) between vegetation-soil and vegetation-trunk-soil scenes. The comparison result reveals the tree trunk can cause directional BTs as a whole lower because of its shadow and shaded area. Therefore, the tree trunk should be considered when retrieving temperatures from thermal infrared observations over a leafless forest. Efforts using measured TIR data requires to be done in the future.
关键词： vegetation-trunk-soil canopy,directional anisotropy,brightness temperature
更新于2025-09-23 15:23:52
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Dynamic Magneto-optical Inversion in Magnetic Fluid using NanoMOKE
摘要： Systematic inversion of optical anisotropy with magnetic field sweep (0-5000Gauss) has been observed at a critical concentration in the monodispersed magnetic fluids using NanoMOKE III. This experimental technique is significantly novel method to investigate the optical anisotropy of magnetic nano-suspensions with the time-varying magnetic field. In this work, we report a detailed experimental investigation on the field dependent magneto-optical behaviour of dilute water dispersed Fe3O4 based magnetic fluid. Magnetic fluid shows tunable magneto-optical properties which primarily depends on parameters such as, particle concentration, composition and carrier medium. We have observed a systematic inversion in optical anisotropy at critical concentration for a Fe3O4 magnetic fluid with strong spatial dependence. The observed tuneable magneto-optical phenomena have been correlated to the net effect of the structuration process, electronic transitions and gravitational force in the presence magnetic field. This phenomenon leads to the development of two particle size distribution, negative optical activity initially and strong spatial dependence respectively. The present results provide a strong correlation with theoretical models presented to expound the dependency of various parameters on magneto-optical inversion behaviour of magnetic fluids.
关键词： ferrofluids,Magnetic fluids,optical anisotropy,magnetic Inversion,NanoMOKE
更新于2025-09-23 15:23:52
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Compensation of Distortions of Polarization Characteristics of Ring Resonators
摘要： The reasons of occurrence of polarization mode distortions and methods of their compensation are investigated. It is demonstrated that sensitivity of lasers with ring resonator to magnetic field may be reduced, if effect of induced polarization anisotropy to be compensated by means of installation of a mirror in resonator in certain position, which complies with the minimum ellipticity angle.
关键词： polarization characteristics of interference mirrors,ring optical resonators,phase anisotropy,information optics
更新于2025-09-23 15:23:52
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Highly Sensitive Polarization Photodetection Using a Pseudo-One-Dimensional Nb <sub/> (1– <i>x</i> ) </sub> Ti <sub/><i>x</i> </sub> S <sub/>3</sub> Alloy
摘要： Low-symmetry layered two-dimensional (2D) materials with strong in-plane optical anisotropy can potentially be applied for polarization photodetection. This is especially true for those 2D materials with a direct bandgap, who can efficiently absorb light with specific axial polarization. However, discovering such new anisotropic 2D materials with direct band structure is still extremely challenging. Here, we fabricate a photodetector using a pseudo-one-dimensional (pseudo-1D) Nb(1-x)TixS3 alloy device, and demonstrate that it is highly sensitive to the polarized light due to the strong in-plane optical anisotropy and direct bandgap of the alloy by combining the angle-resolved polarization Raman spectroscopy (ARPRS), azimuth-dependent reflectance difference microscopy (ADRDM), polarization-dependent absorption spectroscopy (PDAS), and hybrid functional theory calculations. As a consequence, the polarization photodetector of the Nb(1-x)TixS3 alloy shows a large photocurrent anisotropic ratio and a high photoresponse. The choice of low-symmetry layered pseudo-1D Nb(1-x)TixS3 alloy in polarization photodetection might open up new functionalities for novel optoelectronic device applications.
关键词： low-symmetry structure,in-plane optical anisotropy,pseudo-one-dimensional materials,Nb(1-x)TixS3 ternary alloy,polarization-sensitive photodetector
更新于2025-09-23 15:23:52