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- 2018
- Lorentzian influence
- optical flow
- additive white Gaussian noise
- 2D vector
- Materials characterization
- laser additive manufacturing
- selective laser sintering
- Additive manufacturing
- selective laser melting
- Optoelectronic Information Science and Engineering
- Mechanical Engineering
- University of Johannesburg
- Assumption University
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Morphology Control of Hydrothermally Grown ZnO Nanostructures by Additives and Seed Layers
摘要： We present a rational control over the morphology of hydrothermally grown ZnO nanostructures by introducing different additives, sequential seeding, and multilayer seeds. The aspect ratio of the ZnO nanorods could be tuned with different types of additives (surfactant, amine, metal salt, and polymer additives) at an appropriate concentration in solution for ZnO hydrothermal growth. Some of the metal salts induced change in both aspect ratio and coverage simultaneously. The degree of vertical alignment of the ZnO nanowires was influenced by the number of seed layers. Furthermore, hierarchical ZnO nanostructures could be fabricated for thermal annealing on a secondary seed layer. The various control parameters demonstrated in this study provide beneficial information that can be used to guide a new strategy for relevant future applications.
关键词： Seed,Additive,Morphology,Hydrothermal,Zinc Oxide
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Information and Communication Technology Robotics (ICT-ROBOT) - Busan (2018.9.6-2018.9.8)] 2018 International Conference on Information and Communication Technology Robotics (ICT-ROBOT) - Design of Air Cooling Housing for Image Sensors Using Additive Manufacturing Technology
摘要： Machine vision is widely used in industry for monitoring and inspection. In additive manufacturing technology (AM), it is especially important in that it can cover an entire 2-dimensional printed surface area instantly. Additionally, AM technologies can also be used to make a mechanical part for a machine vision system such as mount or illumination devices on a 3D printer. For the industrial 3D printer, the camera mount requires to have temperature control capabilities for the vision system. This research aims to develop a method to build a mount with cooling capability with AM technology. This paper introduces a 3D printed camera cooling housing and proposes a temperature feed-back control method based on the image sensor itself without adding a thermal sensor to increase the user friendliness and simplicity. In the demonstration, a camera cooling housing that was developed enabled a camera module to operate at 200°C in an industrial Fortus 400 (Stratasys, MN).
关键词： camera cooling system,3d printed heat exchanger,additive manufacturing,vision based thermal control
更新于2025-09-23 15:22:29
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Chemical imaging of buried interfaces in organic-inorganic devices using FIB-ToF-SIMS
摘要： Organic-inorganic hybrid materials enable the design and fabrication of new materials with enhanced properties. The interface between the organic and inorganic materials is often critical to the device’s performance and therefore chemical characterization is of significant interest. Since the interfaces are often buried, milling by focused ion beams (FIB) to expose the interface is becoming increasingly popular. Chemical imaging can subsequently be obtained using secondary ion mass spectrometry. However, the FIB milling process damages the organic material. In this study, we make an organic-inorganic test structure to develop a detailed understanding of the processes involved in FIB milling and SIMS imaging. We provide an analysis methodology that involves a “clean-up” process using sputtering with an argon gas cluster ion source to remove the FIB induced damage. The methodology is evaluated for two additive manufactured devices, an encapsulated strain sensor containing silver tracks embedded in a polymeric material and a copper track on a flexible polymeric substrate created using a novel nanoparticle sintering technique.
关键词： FIB,additive manufacturing,hybrid interfaces,ToF-SIMS,polymer,Argon cluster,milling
更新于2025-09-23 15:22:29
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Design Guidelines for printable Magnetic Shielding Films for NFC Tags on
摘要： The performance of RFID tags deteriorates when mounted on metallic objects. This is due to the induced eddy current effect on the metal which produces a magnetic field that opposes the reader/ tag field. Suitable electromagnetic screening is needed to mitigate this issue e.g. ferromagnetic films shielding the tag from the metal. This paper explores some design guidelines for ferrite films properties for additive manufacturing methods. Simulated and measured results for different ferromagnetic films and their influence on the performance of the NFC tags are investigated.
关键词： NFC,additive manufacturing,ferromagnetic films,RFID
更新于2025-09-23 15:22:29
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Application of Aerosol Jet 3D Printing with Conductive and Non-Conductive Inks for Manufacturing mm-Wave Circuits
摘要： In this paper, an application of Aerosol Jet 3D printing with conductive and non-conductive inks for the realization of mm-wave circuits well above 30 GHz is presented and investigated. The Optomec 5X aerosol jet 3D printing system is used together with polyimide and silver inks to fully-additive manufacture various microstrip circuits. A section of microstrip transmission line with a transition to a via-less conductor backed coplanar waveguide was designed together with a T-junction and a branch-line coupler. These circuits were designed to operate within the Ka and V frequency bands. The measured thickness of the polyimide dielectric substrate is 20.7 ± 1.35 μm while the silver traces are 2.6 ± 1.35 μm. A section of the transmission line with the developed transitions was measured up to the W-band, exhibiting a total loss of 0.65 dB/mm at 100 GHz. The T-junction power divider yielded a total loss at its center frequency of 34 GHz of 0.55 dB. The 3-dB branch line coupler yielded a loss at its center frequency at 42 GHz of 1.1 dB. The experimental results demonstrate the application of this approach for fast and high-resolution mm-wave circuit fabrication.
关键词： circuit fabrication,additive manufacturing,mm-wave circuits,aerosol jet printing,3D printing
更新于2025-09-23 15:22:29
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Experimental investigation and thermo-mechanical modelling for tool life evaluation of photopolymer additively manufactured mould inserts in different injection moulding conditions
摘要： There is a growing interest for integrating additive manufacturing (AM) technology in different manufacturing processes such as injection moulding (IM) due to the possibility of achieving shorter manufacturing times and increased cost effectiveness. This paper evaluates IM inserts fabricated by the AM vat photopolymerisation method. The inserts are directly manufactured with a photopolymer material, integrated on an injection moulding tool and subsequently used for IM. Therefore, particular attention has to be paid in order to develop the soft tooling process chain and the IM experimental procedure as detailed in this study. Different combinations of IM parameters are investigated in this work in order to determine the influence of the various process settings on the inserts’ performance (lifetime, crack propagation, consistency of the mould surface features). The mould inserts were analysed by three-dimensional optical metrology and evaluated with regard to the different surface features that were affected by the IM process. A three-dimensional thermo-mechanical with phase change model for the analysis of the effects of the IM process on the additive manufactured tools was accomplished in the FE software COMSOL Multiphysics. The potential causes for the insert failure are identified both by means of the IM experiments and the numerical model. The developed model could also predict the thermally induced deformations produced in the mould and identify where this phenomenon would eventually lead to defects in the shape of the parts. The influence of three different temperatures of the insert at 25 °C, 50 °C and 100 °C on the failure of the insert was investigated. Also a detailed discussion about the solidification and temperature changes is given.
关键词： Finite element modelling,Vat photopolymerization,Injection moulding,Soft tooling,Additive manufacturing
更新于2025-09-23 15:22:29
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Rheological and Curing Behavior of Acrylate-Based Suspensions for the DLP 3D Printing of Complex Zirconia Parts
摘要： The present study demonstrates the possibility of fabricating zirconia parts with a complex shape and internal architecture using a low-cost stereolithography-based technique. One of the critical steps in ceramics stereolithography is the preparation of a photo-curable slurry with properties that fulfil specific requirements, such as having a low viscosity, high solids loading and appropriate curing characteristics. Slurries with different acrylic monomers and ceramic fillers were studied concerning their rheological and curing behavior. New formulations based on mono- and tri-functional acrylic monomers revealed the following excellent rheological properties: The viscosity of the mono-/tri-acrylate-based slurry with 75 wt.% of zirconia was 1.6 Pa·s at 30 s?1. Zirconia stabilized with 3 mol.% yttria was found to be more favorable than zirconia with 8 mol.% yttria for slurry preparation, because of its lower surface area and higher tapped density. It was shown that the cure depth of the suspensions was suitable for printing objects with a 50 μm layer thickness, good interlayers connection and surface finishing.
关键词： ceramic,digital light processing,additive manufacturing,zirconia,stereolithography
更新于2025-09-23 15:22:29
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Realization of modified Luneburg lens antenna using quasi-conformal transformation optics and additive manufacturing
摘要： We demonstrate a new method for realizing modified Luneburg lens antennas with nearly continuously graded permittivity profiles in three-dimensions. The method used a quasi-conformal transformation optics (QCTO) approach to modify the geometry and permittivity of a spherical Luneburg lens to have a flat surface for convenient integration of antenna feeds. The modified lens was then fabricated using Fused Deposition Modeling (FDM) printing with an effective media approach that employs space-filling curves. The method was validated by designing and fabricating a modified Luneburg lens antenna designed to operate in the Ka-band. The antenna performance of the sample was measured experimentally and shown to compare well to predicted results using full wave simulations. The device was able to achieve a reasonably high degree of beam steering (ie, ?55° to +55°) over the entire Ka-band. We believe this new approach provides a cost-effective and scalable means of realizing practical passive beam steering lenses that operate over a broad range of frequencies.
关键词： additive manufacturing,beamscanning,beamforming,fused deposition modeling,Luneburg lens,transformation optics
更新于2025-09-23 15:22:29
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Noise Estimation for Image Sensor Based on Local Entropy and Median Absolute Deviation
摘要： Noise estimation for image sensor is a key technique in many image pre-processing applications such as blind de-noising. The existing noise estimation methods for additive white Gaussian noise (AWGN) and Poisson-Gaussian noise (PGN) may underestimate or overestimate the noise level in the situation of a heavy textured scene image. To cope with this problem, a novel homogenous block-based noise estimation method is proposed to calculate these noises in this paper. Initially, the noisy image is transformed into the map of local gray statistic entropy (LGSE), and the weakly textured image blocks can be selected with several biggest LGSE values in a descending order. Then, the Haar wavelet-based local median absolute deviation (HLMAD) is presented to compute the local variance of these selected homogenous blocks. After that, the noise parameters can be estimated accurately by applying the maximum likelihood estimation (MLE) to analyze the local mean and variance of selected blocks. Extensive experiments on synthesized noised images are induced and the experimental results show that the proposed method could not only more accurately estimate the noise of various scene images with different noise levels than the compared state-of-the-art methods, but also promote the performance of the blind de-noising algorithm.
关键词： additive white Gaussian noise,local gray statistic entropy,image sensor,Poisson-Gaussian noise,noise estimation,local median absolute deviation
更新于2025-09-23 15:22:29
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Cladding of Stellite-6/WC Composites Coatings by Laser Metal Deposition
摘要： This study aims to investigate the microstructure and hardness of multi-layered Stellite-6/WC metal-matrix composites coatings on metallic substrates cladded by laser metal deposition (LMD) for improvement of wear and corrosion resistances. As coating materials, Stellite-6 and WC-12wt.%Co powders were selected. Powder mixtures having various mixing-ratios of Stellite-6 and WC-12wt.%Co were provided vertically on S45C substrates by controlling powder feeding rates of the two powder feeders, individually. Stellite-6/WC composites which consist of three layers with different compositions were cladded on the S45C substrates by laser melting. Cross-sectional microstructure observation was carried out by using an optical microscope (OM). Vickers microhardness tests were conducted to evaluate hardness of the cladding layers and substrates. The experimental results demonstrate that hard multi-layered Stellite-6/WC metal-matrix composites coatings were successfully cladded on the S45C substrates. Property gradients in the Stellite-6/WC composites could be made due to the position-dependent chemical composition and microstructure made by controlling powder feeding rates of an LMD system.
关键词： Cladding,Additive Manufacturing (AM),Metal Matrix Composites (MMC),Laser Metal Deposition (LMD),Hard Materials
更新于2025-09-23 15:22:29