Project description:Miniaturized pixel sizes in near-eye digital displays lead to pixel emission patterns with large divergence angles, necessitating efficient beam collimation solutions to improve the light coupling efficiency. Traditional beam collimation optics, such as lenses and cavities, are wavelength-sensitive and cannot simultaneously collimate red (R), green (G), and blue (B) light. In this work, we employed inverse design optimization and finite-difference time-domain (FDTD) simulation techniques to design a collimator comprised of nano-sized photonic structures. To alleviate the challenges of the spatial incoherence nature of micro-LED emission light, we developed a strategy called dual-task optimization. Specifically, the method models light collimation as a dual task of color routing. By optimizing a color router, which routes incident light within a small angular range to different locations based on its spectrum, we simultaneously obtained a beam collimator, which can restrict the output of the light emitted from the routing destination with a small divergence angle. We further evaluated the collimation performance for spatially incoherent RGB micro-LED light in an FDTD using a multiple-dipole simulation method, and the simulation results demonstrate that our designed collimator can increase the light coupling efficiency from approximately 30% to 60% within a divergence angle of ±20° for all R/G/B light under the spatially incoherent emission.
Project description:Compared with the forward design method through the control of geometric parameters and material types, the inverse design method based on the target stress-strain curve is helpful for the discovery of new structures. This study proposes an optimization strategy for mechanical metamaterials based on a genetic algorithm and establishes a topology optimization method for energy-absorbing structures with the desired stress-strain curves. A series of structural mutation algorithms and design-domain-independent mesh generation method are developed to improve the efficiency of finite element analysis and optimization iteration. The algorithm realizes the design of ideal energy-absorbing structures, which are verified by additive manufacturing and experimental characterization. The error between the stress-strain curve of the designed structure and the target curve is less than 5%, and the densification strain reaches 0.6. Furthermore, special attention is paid to passive pedestrian protection and occupant protection, and a reasonable solution is given through the design of a multiplatform energy-absorbing structure. The proposed topology optimization framework provides a new solution path for the elastic-plastic large deformation problem that is unable to be resolved by using classical gradient algorithms or genetic algorithms, and simplifies the design process of energy-absorbing mechanical metamaterials.
Project description:It is known that the stretching and bending deformations will be coupled together for the unsymmetric composite laminates under in-plane force and/or out-of-plane bending moment. Although Green's functions for unsymmetric composite laminates with elliptical elastic inclusions have been obtained by using Stroh-like formalism around 10 years ago, due to the ignoring of inconsistent rigid body movements of matrix and inclusion, the existing solution may lead to displacement discontinuity across the interface between matrix and inclusion. Due to the multi-valued characteristics of complex logarithmic functions appeared in Green's functions, special attention should be made on the proper selection of branch cuts of mapped variables. To solve these problems, in this study, the existing Green's functions are corrected and a simple way to correctly evaluate the mapped complex variable logarithmic functions is suggested. Moreover, to apply the obtained solutions to boundary element method, we also derive the explicit closed-form solution for Green's function of deflection. Since the continuity conditions along the interface have been satisfied in Green's functions, no meshes are required along the interface, which will save a lot of computational time and the results are much more accurate than any other numerical methods.
Project description:Bayesian optimization (BO) can accelerate material design requiring time-consuming experiments. However, although most material designs require tuning of multiple properties, the efficiency of multi-objective (MO) BO in time-consuming experimental material design remains unclear, due to the complexity of handling multiple objectives. This study introduces MO BO method that efficiently achieves predefined goals and shows that by focusing on achieving the goals, BO can efficiently accelerate realistic MO design problems with small efforts. Benchmarks showed that the proposed BO method dramatically reduced the number of experiments needed to achieve goals relative to a baseline method. Virtual MO inverse design experiments with realistic material design problems were also performed, during which the proposed method could achieve goals within only around ten experiments in average and showed over 1000-fold acceleration relative to the random sampling for the most difficult case. The introduction of goal-oriented BO will precede real-world application of BO.
Project description:Morphing technologies use large, seamless changes in the shape of a structure to enable multi-functionality and reconfigurability. Several industrial sectors could benefit from morphing structures, including medical, energy and aerospace which require lightweight, simple and reliable solutions. Composite materials are key to lightweight morphing technologies due to their increased strength- and stiffness-to-mass ratios, stiffness tailorability and excellent fatigue properties, all of which reduce the mass and complexity of these types of structures. By accounting for thermal effects in their analytical description, we enhance the viability of multi-stable composite helical structures. This consideration improves predictions of existing analytical models in comparison with experiments, while also vastly expanding the design space to include antisymmetric and non-symmetric flange lay-up sequences. The developed analytical model is presented and verified using both finite-element models and experiments. By including thermal effects, we show that beneficial new morphing behaviours can be obtained.
Project description:The development of information technology urgently requires ultrafast, ultra-low energy consumption and ultra-high-capacity data computing abilities. Traditional computing method of electronic chips is limited by the bottleneck of Moore's Law. All-optical computing of photonic chips provides a promising way to realize such high-performance data computing abilities. Until now, it is still a huge challenge to realize all-optical four arithmetic operations at the same time on a photonic chip. Here, we propose a new encoding scheme for all-optical binary computation, including n-bit addition, subtraction, multiplication and division. We theoretically present n-bit calculation and experimentally demonstrate 1 bit calculation. The computation part includes a half binary adder and a shifter, whose feature sizes are only 2 μm × 19.5 μm and 4 μm × 9 μm, respectively. The half binary adder and shifter consist of three low-loss basic devices through inverse design method. The distance between two adjacent basic devices is smaller than 1.5 μm, within wavelength magnitude scale. The response time is the propagation time of the signal light in a single device, within 100 fs. The threshold energy consumption is within 10 fJ/bit. Our results provide a new method to realize ultrafast, ultra-low energy consumption and ultra-high-capacity data processing abilities all-optical n-bit binary computing.
Project description:This work presents a high-efficiency achromatic meta-lens based on inverse design with topology optimization methodology. The meta-lens design with high numerical aperture values (NA = 0.7, NA = 0.8, and NA = 0.9) optimized along wavelength range starts from 550 to 800 nm, then the direct solver along the full extended wavelength band from 400 to 800 nm that applied to the final optimized structures under the three conditions of the high numerical apertures have high focusing efficiency for the all conditions. The optimization problem is based on Kreisselmeier-Steinhauser (k-s) objective function, leading to approximately stable response over the broadband bandwidths of the three designs.
Project description:Background: Tigecycline (TGC) is a recently developed antibiotic to battle resistant bacteria. The procedures outlined in the literature for analyzing TGC involve chemical solvents that could be hazardous. Therefore, this study aimed to create a sustainable and stable HPLC technique for quantifying Tigecycline in lyophilized powder. The powerful chemometric tool, experimental design (ED), will be applied to analyze the variables' interaction and impact on the selected analytical target profiles. Response surface methodology provides a tutorial on using the central composite design with three levels of variables and quadratic programming to optimize the design space of the developed method. Methods: The New HPLC method consisted of an aqueous buffer and ethanol as a green mobile phase run on a reversed-phase symmetry C18 column. A full resolution between the Tigecycline and its degradation product peaks was achieved in a short analytical runtime. Results: Further, the specificity, accuracy, precision, robustness and stability indicating power of the proposed approach were verified through stress degrading testing. Conclusions: Finally, the analytical eco-scale and the green Analytical Procedure Index (GAPI) were utilized to determine how environmentally friendly the recommended method was compared to other published approaches.
Project description:The realization of acoustic devices analogous to electronic systems, like diodes, transistors, and logic elements, suggests the potential use of elastic vibrations (i.e., phonons) in information processing, for example, in advanced computational systems, smart actuators, and programmable materials. Previous experimental realizations of acoustic diodes and mechanical switches have used nonlinearities to break transmission symmetry. However, existing solutions require operation at different frequencies or involve signal conversion in the electronic or optical domains. Here, we show an experimental realization of a phononic transistor-like device using geometric nonlinearities to switch and amplify elastic vibrations, via magnetic coupling, operating at a single frequency. By cascading this device in a tunable mechanical circuit board, we realize the complete set of mechanical logic elements and interconnect selected ones to execute simple calculations.
Project description:Flexible Unidirectional (UD) composite laminates are commonly being used for ballistic-resistant body armor. These laminates comprise UD layers, each constructed by laminating thin layers of high-performance fibers held in place using very low modulus binder resins, with the fibers in each layer oriented parallel to each other. As these materials are used in body armor, it is important to investigate their long-term reliability, particularly with regards to exposure to temperature and humidity as these are known causes of degradation in other commonly used body armor materials. This work investigates the tensile behavior of a poly(p-phenylene terephthalamide), or PPTA flexible UD laminate aged for up to 150 d at accelerated conditions of 70 °C and 76 % relative humidity (RH). Tests were performed at three different crosshead displacement rates and three different gauge lengths. The effect of ageing on the mechanical properties of the material resulted in less than 10 % degradation in tensile strength, with a more significant reduction in longer specimens when tested at slower rates.