Confidence Testing of Shell 405 and S-405 Catalysts in a Monopropellant Hydrazine Thruster

As part of the transfer of catalyst manufacturing technology from Shell Chemical Company (Shell 405 catalyst manufactured in Houston, Texas) to Aerojet (S-405 manufactured in Redmond, Washington), Aerojet demonstrated the equivalence of S-405 and Shell 405 at beginning of life. Some US aerospace users expressed a desire to conduct a preliminary confidence test to assess end-of-life characteristics for S-405. NASA Marshall Space Flight Center (MSFC) and Aerojet entered a contractual agreement in 2004 to conduct a confidence test using a pair of 0.2-lbf MR-103G monopropellant hydrazine thrusters, comparing S-405 and Shell 405 side by side. This paper summarizes the formulation of this test program, explains the test matrix, describes the progress of the test, and analyzes the test results. This paper also includes a discussion of the limitations of this test and the ramifications of the test results for assessing the need for future qualification testing in particular hydrazine thruster applications

A study exploring learners' informal learning space behaviors, attitudes, and preferences

What makes a successful informal learning space is a topic in need of further research. The body of discourse on informal space design is drawn from learning theory, placemaking and architecture, with a need for understanding of the synergy between the three. Findings from a longitudinal, quantitative and qualitative study at Sheffield Hallam University, explore learners' behaviours, attitudes and preferences towards informal learning spaces in higher education, within and outside of the context of the academic library. The learning spaces study contributes to the discourse on informal learning spaces design by producing a typology of nine learning space preference attributes which address aspects of learning theory, placemaking and architecture. The typology can be used to evaluate existing spaces and inform redevelopment of informal learning spaces in higher education institutions. Implementing the typology will be subject to localised conditions, but at Sheffield Hallam University the key conclusions have included developing a portfolio of discrete, interrelated learning environments, offering spaces with a clear identity and encouraging students to translate their learning preferences into space selection

Atlantic Ocean Observing Networks: Cost and feasibility study

Results of a cost and feasibility study of the present and planned integrated Atlantic Ocean Observing System, including assessing the readiness and feasibility of implementation of different observing technologie

The Dangers of Living with an X (bugs hidden in your Verilog

The semantics of X in Verilog RTL are extremely dangerous as RTL bugs can be masked, allowing RTL simulations to incorrectly pass where netlist simulations can fail. Such X-bugs are often missed because formal equivalence checkers are configured to ignore them, which is a particular concern given that equivalence checking is fast replacing netlist simulations. This paper gives examples of such problems in order to raise awareness of X issues in many different parts of the design flow, which are often poorly understood by RTL designers and EDA vendors alike. It gives practical advice on how to overcome X issues in new designs (including good coding styles) and techniques to investigate them in existing designs (including automated formal proofs). New terminology is introduced to differentiate subtle interpretations of X by EDA tools, along with recommendations to avoid problems. In particular, this paper describes how to change the default settings of equivalence checkers to find hidden bugs (that are otherwise far too sneaky to detect). In short, if you are using EDA tools for simulation, codecoverage, synthesis or equivalence checking, you must be aware of the problems and solutions described in this paper

Table of Contents

This paper first introduces a generic methodology to perform sequential equivalence checking, using a property checker rather than a dedicated equivalence checking tool. Sequential equivalence checking itself has many useful applications in the development of an RTL design, e.g. binary/gray-code/one-hot recoding, pipeline retiming, and IP configuration checking. This paper goes on to describe a novel, yet elegantly simple, solution to a number of X issues in Verilog. The technique sounds like a waste of time: sequentially comparing a design with itself! However, outputs can be non-equivalent due to dangerous X’s lurking inside the design. This approach allows a design to be optimized (via synthesis don’t-cares and smaller non-reset flipflops) without compromising verification due to different semantic interpretations of X

The need for measurement science in digital pathology

Background: Pathology services experienced a surge in demand during the COVID-19 pandemic. Digitalisation of pathology workflows can help to increase throughput, yet many existing digitalisation solutions use non-standardised workflows captured in proprietary data formats and processed by black-box software, yielding data of varying quality. This study presents the views of a UK-led expert group on the barriers to adoption and the required input of measurement science to improve current practices in digital pathology. Methods: With an aim to support the UK’s efforts in digitalisation of pathology services, this study comprised: (1) a review of existing evidence, (2) an online survey of domain experts, and (3) a workshop with 42 representatives from healthcare, regulatory bodies, pharmaceutical industry, academia, equipment, and software manufacturers. The discussion topics included sample processing, data interoperability, image analysis, equipment calibration, and use of novel imaging modalities. Findings: The lack of data interoperability within the digital pathology workflows hinders data lookup and navigation, according to 80% of attendees. All participants stressed the importance of integrating imaging and non-imaging data for diagnosis, while 80% saw data integration as a priority challenge. 90% identified the benefits of artificial intelligence and machine learning, but identified the need for training and sound performance metrics.Methods for calibration and providing traceability were seen as essential to establish harmonised, reproducible sample processing, and image acquisition pipelines. Vendor-neutral data standards were seen as a “must-have” for providing meaningful data for downstream analysis. Users and vendors need good practice guidance on evaluation of uncertainty, fitness-for-purpose, and reproducibility of artificial intelligence/machine learning tools. All of the above needs to be accompanied by an upskilling of the pathology workforce. Conclusions: Digital pathology requires interoperable data formats, reproducible and comparable laboratory workflows, and trustworthy computer analysis software. Despite high interest in the use of novel imaging techniques and artificial intelligence tools, their adoption is slowed down by the lack of guidance and evaluation tools to assess the suitability of these techniques for specific clinical question. Measurement science expertise in uncertainty estimation, standardisation, reference materials, and calibration can help establishing reproducibility and comparability between laboratory procedures, yielding high quality data and providing higher confidence in diagnosis