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Characterization and commissioning of a new collaborative multi-modality radiotherapy platform

Abstract Purpose: TaiChi, a new multi-modality radiotherapy platform that integrates a linear accelerator, a focusing gamma system, and a kV imaging system within an enclosed O-ring gantry, was introduced into clinical application. This work aims to assess the technological characteristics and commissioning results of the TaiChi platform. Methods: The acceptance testing and commissioning were performed following the manufacturer’s customer acceptance tests (CAT) and several AAPM Task Groups (TG) reports/guidelines. Regarding the linear accelerator(linac), all applicable validation measurementsrecommended by the MPPG 5.a (basic photon beam model validation, intensity-modulated radiotherapy (IMRT)/volumetric-modulated arc therapy (VMAT) validation, end-to-end(E2E) tests, and patient-specific quality assurance (QA)) were performed. For the focusing gamma system, the absorbed doses were measured using a PTW31014 ion chamber (IC) and PTW60016 diode detector. EBT3 films and a PTW60016 diode detector were employed to measure the relative output factors (ROFs). The E2E tests were performed using PTW31014 IC and EBT3 films. The coincidences between the imaging isocenter and the linac/gamma treatment isocenter were investigated using EBT3 films. The image quality was evaluated regarding the contrast-to-noise ratio (CNR), spatial resolution, and uniformity. Results: All tests included in the CAT met the manufacturer’s specifications. All MPPG 5.a measurements complied with the tolerances. The confidence limits for IMRT/VMAT point dose and dose distribution measurements were achieved according to TG-119. The point dose differences were below 1.68% and gamma passing rates were above 95.9% for the linac E2E tests. All plans of patient-specific QA had point dose differences below 1.79% and gamma passing rates above 96.1% using the 3%/2 mm criterion suggested by TG-218. For the focusing gamma system, the differences between the calculated and measured absorbed doses were below 1.86%. The ROFs calculated by the TPS were independently confirmed within 2% using EBT3 films and a PTW60016 detector. The point dose differences were below 2.57% and gamma passing rates were above 95.3% using the 2%/1 mm criterion for the E2E tests. The coincidences between the imaging isocenter and the linac/gamma treatment isocenter were within 0.5 mm. The image quality parameters fully complied with the manufacturer’s specifications regarding the CNR, spatial resolution, and uniformity. Conclusion: The multi-modality radiotherapy platform complies with the CAT and AAPM commissioning criteria. The commissioning results demonstrate that this platform performs well in mechanical and dosimetry accuracy.

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Anatomy of a 20 MW Electrified Aircraft: Metrics and Technology Drivers

Development of electric, hybrid and turboelectric propulsion technologies for electrified aircraft propulsion system is essential for improving fuel consumption, reducing emissions and noise pollution, lowering maintenance costs and improving reliability of the air transportation systems. The future needs and key benefits of aircraft electrification has made it a highly persuaded common technology trend across the aerospace industry ranging from very large airplanes to small aircrafts, all alike. For very high power (20MW) propulsion system, with the inadequacies of current and near future state-of-the art of electric energy storage technologies, all electric aircraft solution faces enormous technology gaps that needs to be bridged. Advanced turbo-electric technology offers potential solutions towards successful realization of the benefits of electrification of aircrafts. However, this represent a grand challenge in many fronts to realize electric drivetrain (EDT) designs that would significantly improve fuel burn reduction, design flexibility, and operational improvements in next generation of aircrafts. This work focuses on the underlying technological elements to enable such high power turbo-electric aircraft. A preliminary study is carried out to find that to achieve the key benefits of electrifications, the ETD system efficiency has to be > 93% and the specific power density of the system is required to be > 7.5 kW/kg. Furthermore, it is found that that to achieve such system level performances, the EDT components is required to be ≥ 99% and with specific power densities > 40 kW/kg to achieve the 7.5 kW/kg target. These necessitates orders of magnitude of improvements at all technological fronts and requires radical improvement in design and integration methodologies. Major technologies and design trades for various components and system architectures are presented to provide guidelines and framework to address this grand challenge. Key results are provided to support the design study.

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Parallel Hybrid Propulsion & Secondary Power System Architecture Exploration and Evaluation

The parallel hybrid turbofan propulsion (PHTF) system, with a high and low spool connected motor/generator, applied to a single aisle aircraft, has been study extensively and been shown to provide both gas turbine level and aircraft level benefits. With significant electrification of the propulsion system, the degree of subsystem electrification should also be considered. Thus this current study focuses on the PHTF, considering not only the PHTF operating modes but also the secondary power subsystems (electric, hydraulic, and pneumatic) which interface with the propulsion system. Secondary power subsystem options range from hydraulic or electric for actuation to pneumatic or electric for the environmental control system. Each combination has been explored and evaluated within the UTRC aircraft systems integrated model (ASIM) – architecture exploration and evaluation (AEE) framework to identify the aircraft subsystem architecture that best complements the preferred hybrid propulsion system, where the hybrid propulsion system encompasses low and high spool machine size, usage scenario, and boost power source. Energy cost reduction and technology risk are evaluated for each design space architecture. The results show that a mild PHTF, using a low level of stored electric energy is preferred with a combination of electric and hydraulic actuation, electric wing anti-ice, and electric engine accessories. A bleed and electric based pneumatic system, each pared with an ECS optimized for the type of pneumatic system show similar energy cost performance.

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Structural Material Property Tailoring of Dual Phase Titanium Alloy Microstructures Using Deep Neural Networks

Machine intelligence can enable businesses to improve performance by reducing errors and improving sensitivity, quality, speed, and in some cases achieving outcomes that go beyond current resource capabilities. The explosive increase in the power of numerical analytics combined with tensor algebra manifold optimization has been driven by breakthroughs in computational algorithms, machine learning and, to a large degree, deep neural networks (a.k.a. deep learning), enabling us to automate and learn from ever more complex datasets and engineer efficient rapid response algorithms in areas of practical relevance. These areas may include new product architecture design, rapid material characterization, life-cycle management and can be tied with a digital strategy that will enable efficient development from cradle to grave. Collectively, these technologies have been used to address fundamental challenges in materials engineering e.g. automated classification and quantification of microstructure images. In this work, a total of 19 different Ti-6Al-4V microstructures were produced by varying heat treat parameters such as solution temperature, cooling rate, aging times and temperatures. Over 14,000 images were collected and used to train models for microstructure classification, quantification, and synthetic image generation. A framework is proposed to enable rapid material design space exploration, property prediction and optimization that takes into account real-time decision cycles and trade-offs between speed and accuracy.

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