Origin Energy (Australia)

Adaptive Dynamic Programming (ADP) aims to solve nonlinear control problems without explicitly solving complex equations, while still providing Lyapunov-based stability guarantees. Moreover, ADP offers a systematic framework for approximating near-opt

This study presents temperature measurements inside a gH2/gO2 single-element model rocket combustor using H2 chirped-probe-pulse coherent anti-Stokes Raman scattering (CPP fs CARS) thermometry. The model rocket combustor features large optical access at all four sides of the chamber, which enables spatially resolved temperature measurements over large radial distances from the injector axis. The rocket combustor operates at a mean chamber pressure of 1 MPa with an O/F ratio of 3.0. Single-shot H2 CARS spectra were collected at 5 kHz and agreed well with the theoretical model. The probe volume was scanned along the vertical axis at 44.45 mm downstream of the injector at various radial locations. The results show asymmetrical temperature distribution along the vertical axis of the combustor, with a peak temperature near 2500 K at the positive side of the axis. This observation is further confirmed by high-speed chemiluminescence images taken at 70 kHz. Overall, these results provide quantitative data to support the validation of numerical models and enhance the understanding of combustion dynamics in gas-gas rocket combustor.

Abstract The manufacturing industry is evolving and has started using model-based definition (MBD). MBD is an approach to product development and design that emphasizes the use of 3D digital models as the commanding source of information for defining a product’s characteristics, specifications, and requirements. The industry is using MBD as a way to transition away from traditional paper-based drawings and documentation due to their immense drawbacks and limitations. MBD replaces or supplements these drawings with annotated 3D models that contain all the necessary information to define the product. MBD establishes a common information model that is populated with data that are common amongst different models in different stages of the product lifecycle becoming the source authority that drives all engineering activities, from design inception, prototyping, manufacturing, inspection and quality control to complete product realization. This paper supports MBD as the necessary model across all industries and as such, its implementation in engineering curricula is vital. This will assure education, training and smooth transition of our future workforce to industry. Geometric Dimensioning and Tolerancing (GD&T) datum schema is a significant portion of the common information model of MBD. Although, GD&T has now been in existence for decades and strives to bring unique interpretation of the embedded design intent in the CAD, the traditional paper-based 2D drawing print is still susceptible to misinterpretation. Misinterpretations can occur if not everyone involved in the design, manufacturing, and inspection process has a thorough understanding of GD&T principles. A detailed case study is presented on how a 2D engineering drawing print interpretation and seemingly unequivocal GD&T datum reassignment by manufacturing and later by quality inspection lead to an engineering fiasco. Further, the case study also details how the implementation of MBD provides a fool-proof and fail-safe approach to the same design and wouldn’t allow any automatic modification to the product manufacturing information (PMI). This case study would usher the motivation for implementing MBD in engineering courses like, freshmen and sophomore engineering design, machine design, manufacturing processes, senior capstone design, etc. Further, the case study would also reinforce the understanding of the basic GD&T design principles for tolerance and datum assignments and its unambiguous interpretation across the board – Design, Manufacturing, Quality/Inspection.

Laser damage of optical components can be a limiting factor in scaling the energetics of high-peak and average power laser systems. Specifically for optical coatings, damage under nanosecond pulsed irradiation is initiated by pre-existing defects in the coating layers, including those that cause discontinuities in the structure, like craze lines. Crazing or cracking in a multilayer dielectric optical coating is induced when the overall coating stress is sufficiently tensile, and is an occasionally observed issue when employing more porous deposition techniques like electron-beam evaporation. In this study, electron-beam high-reflectors were fabricated utilizing process parameters that are known to induce crazing based on prior processing history to systematically evaluate the impact of crazing on reflector damage performance for 1064 and 355nm lasers. The crazing that was observed was apparently nucleated at nodular defects. When the cross-section of these nodules was investigated, it was observed that there were cracks into the fused silica substrate of approximately 5µm in depth. The craze lines were irradiated with 1064 and 355nm light at fluences slightly above the onset of damage initiation fluence of the coating. The 1064nm irradiated sub-apertures exhibit laser damage but with no spatial correlation with the craze line, whereas the 355nm irradiated area exhibited many damage sites along the craze line. Finite-difference time-domain electric-field simulations were conducted, and ∼2× field amplification in hafnia was observed for the 355nm wavelength case. The laser damage can be attributed to a slight electric-field intensification coincidental with an area where UV damage-prone precursors are known to occur. The 355nm laser damage in uncoated fused silica substrates has been previously correlated to initiate through localized UV absorption at the broken silica bonds in the tips of fractures.

The rapid development of generative models has significantly advanced font generation. However, limited exploration has been devoted to the evaluation and interpretability of graphical fonts. Existing quality assessment models can only provide basic visual analyses, such as recognizing clarity and brightness, without in-depth explanations. To address these limitations, we first constructed a large-scale multimodal dataset named the Diversity Font Dataset (DFD), comprising 135,000 font-text pairs. This dataset encompasses a wide range of generated font types and annotations, including language descriptions and quality assessments, thus providing a robust foundation for training and evaluating font analysis models. Based on this dataset, we developed a font agent built upon a Vision-Language Model (VLM) aiming to enhance font quality assessment and offer interpretable question-answering capabilities. Alongside the original visual encoder in VLM, we integrated an Edge-Aware Traces (EAT) module to capture detailed edge information of font strokes and components. Furthermore, we introduced a Dynamic Direct Preference Optimization (D-DPO) strategy to facilitate efficient model fine-tuning. Experimental results demonstrate that Font-Agent achieves state-of-the-art performance on the established dataset. To further evaluate the generalization ability of our algorithm, we conducted additional experiments on several public datasets. The results highlight the notable advantage of Font-Agent in both assessing the quality of generated fonts and comprehending their content.

In this study, we look at the effect of radiation heat transfer on combustion dynamics in unstable and stable liquid rocket engine simulations. Radiation heat transfer is not typically included in these types of analysis due to the significant additional cost and complexity of incorporating full non-gray radiative properties and radiative transfer equation solvers into the CFD simulations. A novel dual-mesh approach is used where the reacting flowfield and radiation heat transfer are solved on different overset grids. This approach allows a coarser grid to be used for the radiation heat transfer thereby reducing the overall computational cost. Two radiation heat transfer models are examined, an optically thin model, and the more accurate, and spherical harmonics P1 model with Full-spectrum k-distributions for nongray combustion gases. For the particular unstable combustor examined in this work, we find that the overall impact of radiation heat transfer on the combustion dynamics was not significant. As expected, the optically thin model over-predicts the effect of the radiation but even that does not result in altering the combustion dynamics.