Chor Yen Yap (叶佐元)

A research team headed by Professor Jongmin Choi from the Department of Energy Science and Engineering at Daegu Gyeongbuk Institute of Science and Technology has successfully developed a “PbS quantum dot” capable of quickly improving the electrical conductivity of solar cells. This collaborative effort involved Professor Changyong Lim of the Department of Energy Chemical Engineering at Kyungpook National University, led by President Wonhwa Hong, and Professor Jongchul Lim from the Department of Energy Engineering at Chungnam National University, under the leadership of President Jeongkyoum Kim. The team identified a method to enhance electrical conductivity through the use of “pulse-shaped” light, which generates substantial energy in a concentrated manner at regular intervals. This method could replace the heat treatment process, which requires a significant amount of time to achieve the same result. This approach is expected to facilitate the production and commercialization of PbS quantum dot solar cells in the future. PbS quantum dots are nanoscale semiconductor materials that are being actively researched for the development of next-generation solar cells. They can absorb a wide range of wavelengths of sunlight, including ultraviolet, visible light, near-infrared, and shortwave infrared, and have low processing costs because of solution processing and excellent photoelectric properties. The fabrication of PbS quantum dot solar cells involves several process steps. Until recently, the heat treatment process was considered an essential step as it effectively coats a layer of quantum dots onto a substrate and heat-treats the material to further increase its electrical conductivity. However, when PbS quantum dots are exposed to light, heat, and moisture, the formation regarding defects on their surface can be accelerated, leading to charge recombination and deterioration of device performance. This phenomenon makes it challenging to commercialize these materials. The research team’s proposed “pulse-type heat treatment technique” overcomes the shortcomings of the existing method by using strong light to complete the heat treatment process in a few milliseconds. This results in the suppression of surface defects and the extension of the traveling life of charges (electrons, holes) that generate electric current. Furthermore, it achieves high efficiency. Full Article: https://lnkd.in/gE9GkXZH #Energy #SolarCells #QuantumMechanics

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Manifolds gone wild! One of the three hands-on projects in our semester long design for additive manufacturing (DfAM) course at The University of Auckland is for students to redesign a solid block manifold into one with both minimal part material and minimal support material (the two of which are often in conflict with each other). This semester we had just over 100 students doing this exercise and, as part of the project, the students had to design their manifold, generate supports in #Magics to verify that it used minimal support material (and if it used too much, go back and reiterate on their design), and to undertake all the post-processing of their manifolds themselves. In most cases, the students did a great job and, in theory, many of the manifolds would have been printable with little to no support material other than a bit to weld it to the build plate. However, being the nice guy that I am, and because I believe it is character building to remove support material (😊), for the actual build I put on way more support than was strictly needed. I also did this to avoid having one bad design crash the print and ruin all the others. But seriously, it is only once a student experiences the joy of removing steel support material that they truly understand why we try to design to minimize support material if at all possible. Here's a pic of the first 32 printed manifolds still attached to the build plate. The 2nd batch is printing today, and the 3rd batch will print tomorrow. The manifolds are printed in maraging steel (18Ni300) on an EOS M290 metal powder bed fusion system. #cdamlab #CAMMD  #uoa #manifolds #3dprinting #additivemanufacturing #EOS #dfam ASTM Additive Manufacturing Center of Excellence Wohlers Associates, Powered by ASTM International 

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When panic struck Japan in the Fukushima Dai-ichi reactor crisis, I decided to stick with my suddenly becalmed Tokyo business and ride out the crisis. If nothing else, I had more time to research nuclear risks. One of the more embarrassing moments for nuclear came when the outer containment dome of one of the reactors blew off, creating a mushroom cloud. Some even thought that the core had blown up. It was like pulling teeth to get people to understand that the "failure" was by design: The dome was only strong enough to contain hydrogen detonations that wouldn't damage the core. The dramatic loss of the dome was actually a case of a safety measure working. To be sure, in any repeat (unlikely) of an accident like Fukushima Dai-ichi, this innovation might only have the effect of causing such a dome-blowoff sooner, if anything. But it is at least an example of how nuclear could be made yet safer, as the least-bad source of power for industrial societies. I'm still on the fence about whether a more rapid build-out of renewables is the better path for now, in a world where climate tipping points could loom out of the fog at any time--this year or the next. Nuclear has long lead times before the first delivered watt. But in the longer run, nuclear still seems the better way to go. Certainly better in the developing world, where coal power is being built out hand over fist, but also where the effects of climate change will be much worse than in the richer nations. https://lnkd.in/gVdm_c59

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Question for the additive geeks. Does anyone know what data set is used to create the tensile requirements in ASTM standards for additive metals? ASTM F3001 for example. How many tensile bars from how many prints are required to generate the minimum tensile properties? I have been googling for 20 mins and i figure the LinkedIn hive mind is more efficient!

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🔦Let's #unbox the amazing #Optris Xi 400 🌡️📸 #thermal #camera, courtesy of Mr. Christian Linhart from Optris whom I met at the 🔺Dewesoft #MC2024, where it was connected to a SIRUS #DAQ System Join me as I delve into the #features of this incredible device, and explore the principles of non-contact #temperature #measurement, and demonstrate some #experiments. https://lnkd.in/dkQc3Tbb In #infrared imaging, the Optris Xi Compact Line shines with its capacity for non-contact temperature measurement. Operating within a broad infrared #wavelength range, this forward-looking infrared imager captures data beyond the visible #spectrum, allowing for accurate surface temperature measurements. - Industrial imager with 382 x 288 pixels resolution - Distance-to-spot-size ratio up to 390:1 - Monitoring of fast processes with a framerate of 80 Hz 👉 More info and details of the camera here https://lnkd.in/d2AceGDh I learned how the Optris Xi 400 thermal camera can measure temperatures up to 900°C and the fascinating differences in how materials like metal and glass reflect infrared radiation. By using the PIX Connect #software, I was able to visualize temperature variations in real time, revealing intriguing insights into thermal properties and measurement techniques. Stay tuned for more applications and experiments in upcoming videos! Don't forget to subscribe for more content! 0:00 - 📦 Unboxing the Optris Xi 400 Thermal Camera 0:32 - 📚 Overview of Non-Contact Temperature Measurement 1:05 - 💻 Setting Up and Using the PIX Connect Software 1:37 - 🖐️ Demonstration: Measuring Various Surfaces 2:02 - 🧪 Experiments with Different Materials 3:13 - 📏Tips for Accurate Temperature Measurement 3:35 - 🔦 Upcoming Video Teasers

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Dr. Jacob Rome, a visionary in the area of in-space assembly and manufacturing (ISAM), presented at the 2nd ASME SSDM and gave a passionate speech about the need to advance ISAM technologies. Manufacturing space vehicles in space will enable greater flexibility and could result in more efficient space vehicles than if they were launched from the ground, not to mention, these vehicles are not constrained by the fairing volume. Looking forward to seeing these technologies come to to fruition within the next decade. We are also accepting papers in the area of ISAM at the AIAA Scitech Conference: https://lnkd.in/g5tHyumN Title: An Architecture for Orbital Manufacturing in Support of the Future Space Enterprise Abstract: Research and development for in-space servicing, assembly, and manufacturing (ISAM) is ongoing to support future national space enterprise efforts. Many government entities, non-profit organizations, and commercial companies are engaging actively in ISAM research while supporting and sharing knowledge through consortiums such as the Consortium for Space Mobility and ISAM Capabilities (COSMIC) and Consortium for Execution of Rendezvous and Servicing Operations (CONFERS). Research and advancements are being made in the area of manufacturing, assembly, servicing, life extension, refueling, repairing, on-orbit debris removal, orbital transfers, maneuvering, and more. The objective of this presentation is to provide an architecture for orbital manufacturing in support of the future space enterprise. Research on specific aspects of the roadmap, specifically, manufacturing of electrical components within a backbone structure, inspection of manufactured components, and autonomous assembly of snap-fit parts are being conducted. While the OSF (orbit satellite factory) has been a catalyst in spawning new research and making advancements that support ISAM, the current OSF concept needs to be expanded and to be re-evaluated in the context of the capabilities being sought by governent and industry (e.g., refueling, lunar manufacturing, etc.) As part of the OSF effort, existing & future capabilities were studied and evaluated. The roadmap has helped to identify high-value opportunities for orbital manufacturing that would complement the ISAM technological landscape. For example, rather than a stand-along factory building free-flying satellites, an orbital manufacturing outpost could produce replacement parts for satellite upgrades. Another opportunity would be to focus on building large structures that would be assembled at another location by robots or humans. In short, the manufacturing roadmap will be expanded to address many other use cases where orbital manufacturing can add value to space missions of all types.

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Concurrent Design - Need of the hour to be alternative supply chain to China Design using various software has become faster and lot of savings in terms of efforts taken in physical mock ups and feel. 3D printing in non metallics and metals also helps in reducing development time. Over a period of time we have collected lot of material data and its properties and processes by which it can be enhanced, or change form. While these benefits are used for optimisation of designs and manufacturing processes it also helps in better visualisation for assembly and testing. As we know every activity or process has limitations like material cutting, welding, forming, machining can introduce stresses which are not considered by designers when he is designing product for its environmental or service conditions. Super imposing processing related stresses may aggravate the situation. It is good to have a staggering and if required change of process sequence to avoid failure. Very few design software today are able to predict such stress risers and hence concurrent engineering practices being followed earlier are required to be meticulously followed. In PDR CDR STAGE itself having a cross functional team will help in understanding what Raw materials and processes that we need to select and what impact it is going to have on final product. Inspection and testing team also can analyse at what stage it best to inspect as some of the areas may not be accessible later on or is it better to inspect on the machine? Thus working together and performing PFMEA or concurrent engineering practices shall be welcomed. Do not assume that your simulation is able to do analysis of the forces and environmental conditions and also process and raw material limitations. Earlier days since we were doing physical trials mock ups or test samples this aspect was never missed out. Earlier products were long lasting not they were over designed but they had good practices and involvement of all in approving product for production. Today to be competitive we are claiming to have optimised solution but that is commercial decision and not quality decision. This way we are also eroding our environment very fast as defective unserviceable parts or products are thrown and need not get recycled. Jaihind

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Swapping a material card does not a #composite design make. To truly take advantage of all the benefits of #composites and minimize their weaknesses requires an entirely different #design philosophy from metals. In the early days of #advancedmanufacturing, sometimes designers would take an existing metallic design and simply change the material to #carbon. These were termed "black aluminum" or "black titanium" and usually created fabrication and/or quality issues. Composite parts need to be designed as composites from the start and the surrounding and interfacing structure needs to be considered as a holistic system to ensure optimal designs that are both producible and structurally efficient. #LaminateLife #advancedmaterials

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📢 📢 📢 📢 New Publication Alert 📢 📢 📢 📢 Our, then PhD student, now officially a colleague, Lequn Chen, did an exquisite job in capturing the current state of affairs in all-things-process-monitoring related to Laser-based Additive Manufacturing. Free access to the publication in the comments below (valid for 50 days). Click to have a look on how Sensors and Machine Learning can be deployed to enhance quality in 3D printing. #AdditiveManufacturing #MachineLearning #ProcessMonitoring #QualityAssurance #AI

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Proper Design for Additive Manufacturing (DfAM) requires that a designer considers all aspects of the AM processing lifecycle and specific project requirements. These considerations can change based on the AM process, material, feedstock, geometry, and post-processing. In a recent study, we explored the fabrication of microchannels using laser powder directed energy deposition (LP-DED) with the NASA HR-1 (Fe-Ni-Cr) hydrogen-resistant alloy. Despite the benefits of AM for components with complex internal features, the challenge of rough surfaces remains. To address this, we evaluated different surface enhancement techniques and conducted flow tests to compare their performance. Balancing factors such as flow performance (pressure drop), heat transfer, fatigue life, corrosion, processing economics, and aesthetics is crucial in DfAM, especially for critical components like heat exchangers. Our results indicate surfaces can be tailored for specific applications based on end-use requirements. Read the full article here: https://lnkd.in/e9spTNe9 Thank you to my co-authors and promotors Angelo and Piero.  #AdditiveManufacturing #3DPrinting #Rockets #Aerospace #Power #Propulsion #NASA #Technology #DED NASA - National Aeronautics and Space Administration

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The composites series continues. In Module 5 we learn how to post process ply by ply stresses and strains and compare results across three different modeling techniques 3D vs 2D (https://lnkd.in/geqEGEEx). Module 6 discusses the famous ABD matrix and how the shell loads relate to mid surface strains and curvatures. We compare results from an Excel code to finite elements for a simple problem (https://lnkd.in/gyK-vAy2). We even provide the ABD matrix directly to the software to see how results compare to hand calculations. In Module 7 we learn about various failure theories via the simulation of a hypothetical wing structure under flight conditions (https://lnkd.in/gCiN4j3X). In Module 8 we learn about the benefits of sandwich structures and perform buckling and bending calculations to show their superior performance over laminates (https://lnkd.in/ga_Y4Jmm) and (https://lnkd.in/gvpQ8DSQ). And stay tuned because next we show how to optimize and tailor the stacking sequence for composites under various loading conditions!

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“A Review of Research Needs in Nondestructive Evaluation for Quality Verification in Electric Vehicle Lithium-Ion Battery Cell Manufacturing” by Megan McGovern, PhD et al. highlights several key areas where nondestructive evaluation (NDE) can enhance the manufacturing process of lithium-ion batteries. These areas include evaluating post-calendering coating thickness and defects, inspecting electrode stacking during cell assembly, and monitoring the electrolyte saturation and formation quality. Key findings include: 🔹Post-Calendering Coating Thickness: The review suggests exploring new in-line NDE methods for inspecting sub-surface defects like mechanical stresses and cracks that can arise from calendering. Existing methods like laser micrometers are limited to small scan areas and require advancements for broader applications. 🔹Electrode Stacking in Cell Assembly: Conventional visual inspections are used for checking alignment and detecting physical defects. However, more sophisticated techniques like in-line computed tomography (CT) could enhance defect detection without damaging the cells. 🔹Electrolyte Saturation: The review mentions the potential of ultrasound-based technologies which uses machine learning analytics to estimate electrolyte wetting quality rapidly and accurately without damaging the cell. UT & XCT is crucial in nondestructive evaluation (NDE) for lithium-ion battery cell manufacturing, particularly for inspecting the internal structure of battery cells without damaging them. XCT offers high-resolution images that can identify defects like cracks, misalignments & inconsistencies in density. This technology is essential for ensuring the safety and reliability of batteries, especially as electric vehicles (EVs) depend heavily on the quality of their batteries. XCT is valuable for: 🔹Internal structure visualization: XCT can scan the interior of battery cells to visualize and analyze the arrangement and integrity of internal components. 🔹Defect detection: It helps detect manufacturing defects that might not be visible through other testing methods. 🔹Quality control: Provides a thorough assessment of battery cell quality throughout the manufacturing process. The research underlines that while there have been significant advances in NDE technologies, substantial opportunities remain to develop methods that can provide real-time, high-resolution insights without disrupting the manufacturing process. Such advancements could significantly reduce manufacturing defects & improve the safety and performance of Li-Ion batteries for EVs. For further details on the specific methodologies & findings, you can read more from the primary sources. <Link 🔗 https://lnkd.in/evnKGT7B> #ElectricVehicles #Batteries #LithiumIon #NondestructiveTesting #ManufacturingInnovation #SustainableTechnology #XCT #QualityControl #EV #GigaFactories #Manufacturing #NDE Waygate Technologies #Inspection

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Zero- to ultralow-field nuclear magnetic resonance and its applications Open Journal Review "MRI is a widely used non-invasive technique for materials research and medical diagnosis. Because the image quality improves with magnetic field strength, conventional clinical scanners use fields as high as 1–3 T. However, traditional MRI instruments are immobile and expensive, and have long been inaccessible to patients with pacemakers. In addition, high-field MRI is not applicable to metallic materials because of the short penetration depth of radiofrequency radiation. One solution to these difficulties is to perform MRI at an ultralow field of the order of microtesla. In particular, ultralow-field MRI instruments can be constructed at a significantly lower cost, can be more portable, and can have many other advantages, including higher contrast to anomalies and absence of susceptibility artifacts." Authors Jiang Min a b c, Bian Ji a b c, Li Qing a b c, Wu Ze a b c, Su Haowen a b c, Xu Minxiang a b c, Wang Yuanhong a b c, Wang Xin a b c, Xinhua Peng a b c a Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China b CAS Key Laboratory of Microscale Magnetic Resonance, University of Science and Technology of China, Hefei 230026, China c Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China

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I recently discussed mesh errors, computer specifications, and the differences between laminar and turbulent flows in CFD with my students during an online 4-week CFD course. We covered methods for solving turbulent flows, including RANS, URANS, DES, LES, and DNS, with a major emphasis on achieving mesh independence and its crucial role in verification and validation. Link for course: https://lnkd.in/duWzYkJx

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AM Friends, Check out these nice tungsten parts build by Electron Beam Powder Bed Fusion (E-PBF) at Oak Ridge National Laboratory. I found the original paper from early 2023 downloadable for free here: https://lnkd.in/drQRDekS E-PBF lends itself very well to tungsten fabrication, thanks to the hot powder bed preventing crack formation, and the high vacuum environment preventing oxygen pickup. Tungsten has numerous potential applications hidden in its high density, excellent heat resistance and superior x-ray shielding properties. In the past, solid pieces of tungsten have been made by powder metallurgy methods only, without melting the tungsten itself. Casting tungsten ingots has not been commercially feasible. With the ongoing E-PBF development, we are approaching a tungsten manufacturing revolution! ***This post was written without AI*** #tungsten #additivemanufacturing #3dprinting #epbf #freemelt

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The page is from the wonderful recent open access paper In situ observation and reduction of hot-cracks in laser additive manufacturing Yunhui Chen, Duyao Zhang, Patrick O’Toole, Dong Qiu, Marc Seibold, Klaus. Schricker, Jean-Pierre Bergmann, Alexander Rack & Mark Easton (NATURE) Communications Materials volume 5, Article number: 84 (2024) https://lnkd.in/ecJd_kW5 This recent (May 2024) paper, using sophisticate and expensive experimental tools like synchrotron radiation facilities, needed to couple process history - time - with materials parameters. In my much simpler case if one would like - maybe just for a preliminar evaluation of solidification cracking of a specific metallic material - it could be wise to use the approach by prof. Sindo Kou, which recently he proved to be comparable to RDG Rappaz Drezet Gremaud. In such a "static preview" the 9 formulas reported here are (preliminarly) substitued by one (numerical derivative) One point in favour of this approach is that the data(bases) that one uses in "my" case are of thermodynamic origin, they could be commercial, such in this case, or open. In both cases hypotheses may be tested; for instance, plotting the numerical derivative of the Scheil curve, relating Temperature T ( first column of the Excel files, here in K degrees) to the solid fraction fs ( which is usually reported from 0 - all liquid - to 1 - all solid) third column of the Excel files . The Sindo Kou approach may be viewed in the the Excel files; the square root of solid fraction fs is at column AZ, while the (-) derivative of the temperature with the square root of the solid fraction fs is at column BA For my students Excel files relevant to the two Al metallic alloys here AA6061 and AlSi10Mg, with calculations using Computherm Pandat 2018 and PanAl2014 thermodynamic database are respectively at my "private" teaching site for this 2024 (Computational) Metallurgy Course The files are Respectively AA6061 https://lnkd.in/dY9VHjeC and AlSi10Mg https://lnkd.in/dQBxwGGA Do not download them directly from Linkedin, but (assuming the site is secure!) copy and past the link, just if you would like... Yet probably your browser will qualify even those Excel files as "insecure", never mind, in the remote case someone would be interested, one can still require them by email at metallurgia24 at gmail dot com Sorry, I do not have secretaries or assistants for making this specific task... more troubleless

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