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Design of Chemical Surface Treatment for Laser Textured Metal Alloy to Achieve Extreme Wetting Behavior
摘要： Extreme wetting activities of laser-textured metal alloys have received significant interest due to their superior performance in a wide range of commercial applications and fundamental research studies. Fundamentally, extreme wettability of structured metal alloys depends on both surface structure and surface chemistry. However, compared with the generation of physical topology on the surface, the role of surface chemistry is less explored for the laser texturing processes of metal alloys to tune the wettability. This work introduces a systematic design approach to modify the surface chemistry of laser textured metal alloys to achieve various extreme wettabilities, including superhydrophobicity/superoleophobicity, superhydrophilicity/superoleophilicity, and co-existence of superoleophobicity and superhydrophilicity. Microscale trenches are first created on the aluminum alloy 6061 surfaces by nanosecond pulse laser surface texturing. Subsequently, the textured surface is immersion-treated in several chemical solutions to attach target functional groups on the surface to achieve the final extreme wettability. Anchoring fluorinated groups (-CF2- and -CF3) with very low dispersive and non-dispersive surface energy leads to superoleophobicity and superhydrophobicity, resulting in repelling both water and diiodomethane. Attachment of polar nitrile (-C≡N) group with very high non-dispersive and high dispersive surface energy achieves superhydrophilicity and superoleophilicity by drawing water and diiodomethane molecules in the laser textured capillaries. At last, anchoring fluorinated groups (-CF2- and -CF3) and polar sodium carboxylate (-COONa) together lead to very low dispersive and very high non-dispersive surface energy components. It results in the co-existence of superoleophobicity and superhydrophilicity, where the treated surface attracts water but repels diiodomethane.
关键词： Design,chemical modification,laser texturing,superhydrophilicity,superoleophobicity,superhydrophobicity
更新于2025-09-23 15:21:01
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[IEEE NAECON 2019 - IEEE National Aerospace and Electronics Conference - Dayton, OH, USA (2019.7.15-2019.7.19)] 2019 IEEE National Aerospace and Electronics Conference (NAECON) - In Situ Process Monitoring for Laser-Powder Bed Fusion using Convolutional Neural Networks and Infrared Tomography
摘要： Additive Manufacturing (AM) is a growing field for various industries of avionics, biomedical, automotive and manufacturing. The onset of Laser Powder Bed Fusion (LPBF) technologies for metal printing has shown exceptional growth in the past 15 years. Quality of parts for LPBF is a concern for the industry, as many parts produced are high risk, such as biomedical implants. To address these needs, a LPBF machine was designed with in-situ sensors to monitor the build process. Image processing and machine learning algorithms provide an efficient means to take bulk data and assess part quality, validating specific internal geometries and build defects. This research will analyze infrared (IR) images from a Selective Laser Melting (SLM) machine using a Computer Aided Design (CAD) designed part, featuring specific geometries (squares, circles, and triangles) of varying sizes (0.75-3.5 mm) on multiple layers for feature detection. Applying image processing to denoise, then Principal Component Analysis (PCA) for further denoising and applying Convolution Neural Networks (CNN) to identify the features and identifying a class which does not belong to a dataset, where a dataset are created from CAD images. Through this automated process, 300 geometric elements detected, classified, and validated against the build file through CNN. In addition, several build anomalies were detected and saved for end-user inspection.
关键词： Laser Powder Bed Fusion (LPBF),Principal Component Analysis (PCA),infrared image (IR),Convolution Neural Networks (CNN),Additive Manufacturing (AM),Computer Aided Design (CAD)
更新于2025-09-23 15:21:01
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Multicore Multimode Fiber-A New Type of Fiber Using Coupled-Core Structures
摘要： A new type of multimode fiber, multicore multimode fiber (MCMMF), which uses coupled multicore structure is proposed. The fiber has a large number of single mode cores with optimized coupling to achieve high bandwidth. A theoretical model for analyzing the MCMMF is developed. The effect of fiber parameters, such as index contrast, core radius, and core spacing on the bandwidth is systematically studied. Numerical simulations show that the bandwidth of a MCMMF can be optimized by choosing correct ratio of core spacing to core radius for a given profile design. In addition, mode coupling among the super-modes can further increase the bandwidth due to the small spacing in effective indices in coupled core structures. A MCMMF with 165 cores is fabricated. High bandwidth of 8.4 GHz·km in the 850 nm window is achieved. Using this fiber and a VCSEL-based 25 Gb/s SR transceiver, error free transmission though 150 m fiber is demonstrated.
关键词： fiber characterization,fiber bandwidth,data center,multimode fiber,Coupled multicore fiber,fiber design,fiber fabrication
更新于2025-09-23 15:21:01
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Acceptora??donora??acceptor type molecules for high performance organic photovoltaics a?? chemistry and mechanism
摘要： The study of organic photovoltaics (OPVs) has made great progress in the past decade, mainly attributed to the invention of new active layer materials. Among various types of active layer materials, molecules with A–D–A (acceptor–donor–acceptor) architecture have demonstrated much great success in recent years. Thus, in this review, we will focus on A–D–A molecules used in OPVs from the viewpoint of chemists. Notably, the chemical structure–property relationships of A–D–A molecules will be highlighted and the underlying reasons for their outstanding performance will be discussed. The device stability correlated to A–D–A molecules will also be commented on. Finally, an outlook and challenges for future OPV molecule design and device fabrication to achieve higher performance will be presented.
关键词： chemical structure–property relationships,device stability,organic photovoltaics,acceptor–donor–acceptor,molecule design
更新于2025-09-23 15:21:01
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Design Guidelines on LED Costumes for Dance Performances
摘要： We present design guidelines on light emitting diode (LED) costumes for dance performances assuming repetitive use during concerts. We used LED costumes more than 120 times for large concerts of well-known artists at venues of approximately 50,000 capacity that were commercially successesful and we updated the LED costume design twice based on our experiences during these concerts. Through analyzing the position of broken LEDs and the types of breakage and the problems that occurred during actual performances, we devised 17 design guidelines on LED costumes for dance performances. Thanks to these design guidelines, the LEDs on the costume are more difficult to break and we can prepare for any contingencies that may occur during a performance. We fabricated an improved LED costume based on our design guidelines and conducted endurance tests involving dancing. Throughout the endurance tests, the LEDs did not break, and other factors that cause LED breakage were found. We participated in two exhibitions to conduct special LED dance performances.
关键词： dance performance,wearable computing,design guideline,costume,LED
更新于2025-09-23 15:21:01
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Suggestions on Efficiency Droop of GaN-based LEDs
摘要： InGaN/GaN-based light-emitting diodes (LEDs) are widely used in modern society and industry among different areas. However, InGaN/GaN LEDs suffer from an efficiency droop issue: The internal efficiency decreases during high current injection. The efficiency droop significantly affects the development of GaN-based LEDs devices in efficiency and light-output areas. Therefore, the improvement of the droop phenomenon has become a significant topic. This paper introduces several possible mechanisms of droop phenomenon based on different hypotheses including Auger Recombination, Carrier Delocalization and Electron Leakage. Furthermore, some proposals to mitigate efficiency droop, including semipolar LEDs, electron blocking layer(EBL), quaternary alloy and chip design will be discussed and analyzed. Also, it will provide some suggestions for the further optimization of droop phenomenon in each proposal.
关键词： electron blocking layer,semipolar LEDs,GaN-based LEDs,Auger Recombination,chip design,quaternary alloy,Carrier Delocalization,Electron Leakage,efficiency droop
更新于2025-09-23 15:21:01
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[IEEE 2019 European Space Power Conference (ESPC) - Juan-les-Pins, France (2019.9.30-2019.10.4)] 2019 European Space Power Conference (ESPC) - Electrostatic Discharge Tests for JUICE Photovoltaic Assembly
摘要： A nominally circular 2-D broadband acoustic array of 1.3-m diameter, comprising 508 sensors and associated electronics, was designed, built, and tested for ambient noise imaging (ANI) potential in Singapore waters. The system, named Remotely Operated Mobile Ambient Noise Imaging System (ROMANIS), operates over 25–85 kHz, streaming real-time data at 1.6 Gb/s over a fiber optic link. By using sensors that are much larger than half-wavelength at the highest frequency of interest, so with some directionality, good beamforming performance is obtained with a small number of sensors compared to a conventional half-wavelength-spaced array. A data acquisition system consisting of eight single-board computers enables synchronous data collection from all 508 sensors. A dry-coupled neoprene cover is used to encapsulate the ceramic elements as an alternative to potting or oil filling, for easier maintenance. Beamforming is performed in real-time using parallel computing on a graphics processing unit (GPU). Experiments conducted in Singapore waters yielded images of underwater objects at much larger ranges and with better resolution than any previous ANI system. Although ROMANIS was designed for ANI, the array may be valuable in many other applications requiring a broadband underwater acoustic receiving array.
关键词： broadband array design,Ambient noise imaging (ANI),data acquisition,underwater acoustics
更新于2025-09-23 15:21:01
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Brazing, Laser, and Electron-Beam Welding of Additively Manufactured GRCop-84 Copper for Phased Array Lower Hybrid Launchers
摘要： Recent advances in selective laser melting 3-D printing technology allow additive manufacturing of lower hybrid current drive (LHCD) RF launchers from a new material, Glenn Research Copper 84 (GRCop-84), a Cr2Nb (8 at. % Cr, 4 at. % Nb) precipitation hardened alloy, in configurations unachievable by conventional machining. Cr2Nb crystals pin grain boundaries within the copper matrix resulting in high tensile strength and resistance to annealing at elevated temperatures. Brazing, laser, and electron-beam welding (EBW) techniques are explored for joining a thin-walled GRCop-84 waveguide with zero porosity and minimal internal surface roughness. GRCop-84 wets well with the silver solder, CuSil, and Cusil-ABA brazes, once the durable surface oxide is mechanically removed. GRCop-84 melt pool size and flow during EBW is reduced compared to oxygen-free copper (OFC). Pulsed laser and e-beam welding maintains the Cr2Nb precipitate size; precipitate coarsening occurs in conduction mode e-beam welding.
关键词： joining processes,fusion reactor design,magnetic confinement,Annealing,tokamaks,copper alloys,melt processing,materials processing,phased arrays,waveguide
更新于2025-09-23 15:21:01
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Semi-supervised deep learning based framework for assessing manufacturability of cellular structures in direct metal laser sintering process
摘要： In recent years, metal cellular structures have drawn attentions in various industrial sectors due to their design freedoms and abilities to achieve multi-functional mechanical properties. However, metal cellular structures are dif?cult to fabricate due to their complex geometries, even with modern additive manufacturing technologies such as the direct metal laser sintering (DMLS) process. Assessing the manufacturability of metal cellular structures via a DMLS process is a challenging task as the geometric features of the structures are complex. Besides, via a DMLS process, the manufacturability also depends on the cumulative deformation of the layers during the manufacturing process. Existing methods on Design for Additive Manufacturing (DFAM) provide design guidelines that are based on past successful printed designs. However, they are not effective in predicting the manufacturability of metal cellular structures. In this paper, we propose a semi-supervised deep learning based manufacturability assessment (SSDLMA) framework to assess whether a metal cellular structure can be successfully manufactured from a given DMLS process. To enable ef?cient learning, we represent the complex cellular structures as 3D binary arrays with a simple yet ef?cient voxelisation method. We then train a deep learning based classi?er using only a small amount of experimental data by adopting a semi-supervised learning approach. By running real experiments and comparing with existing DFAM methods and machine learning models, we demonstrate the advantages of the proposed SSDLMA framework. The proposed framework can be extended to predict the manufacturability of various other complex geometries beyond cellular structure in a reliable way even with a small number of training data.
关键词： Design for additive manufacturing,Manufacturability analysis,Direct metal laser sintering,Semi-supervised deep learning,Cellular structures
更新于2025-09-23 15:21:01
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Optimizing the light delivery of linear-array-based photoacoustic systems by double acoustic reflectors
摘要： Although linear transducer arrays have been intensely used in photoacoustic imaging, their geometrical shape constrains light illumination. Today, most linear array based photoacoustic systems utilize side-illumination geometry, which consists of two line fiber bundles attached to the side of the probe. The angled light illumination increases the light travel distance in deep tissue, consequently limiting the imaging depth. This issue was partially addressed by adding a right angle prism in front of the transducer. While this design makes the light illumination and acoustic detection co-axial, the transducer and the fiber bundles are orthogonal to each other, making the system inconvenient for handheld use. To overcome this limitation, here we propose a double-reflector design, in which the second reflector redirects the acoustic signals by another 90°, so that the transducer and the fiber bundle are now parallel to each other. In this design, both the transducer and fiber bundle output are fitted into a compact housing for convenient handheld imaging. To evaluate the efficiency of our design, we performed various phantom and human in vivo experiments. Our results demonstrate that the double-reflector design indeed provides deeper imaging depth and it also allows for easy imaging of objects with uneven surfaces.
关键词： handheld imaging,photoacoustic imaging,co-axial illumination,double-reflector design,linear transducer arrays
更新于2025-09-23 15:21:01