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Cyber-physical systems (CPS) increasingly require real-time, high bandwidth data communication and processing. To address this, Time Sensitive Networking (TSN) provides latency-bounded data trans- mission at one or more gigabits-per-second throughput. However, it does not commonly connect directly to I/O devices, such as sensors and ac- tuators. In contrast, Universal Serial Bus (USB) is ubiquitous for device I/O, but has yet to be widely adopted for host-to-host networking. This paper considers the use of a common USB software stack for both device I/O and host-to-host communication. We compare against a sys- tem using USB for device I/O and TSN for host-level networking. Our findings show that a unified approach using USB results in reduced soft- ware complexity, simplified bus coordination, and more effective miti- gation of priority inversion when transferring data across multiple bus segments. Experiments show that end-to-end latency is within expected delay bounds, and is reduced if the same USB software stack is used for all communication with a given host. This suggests that bridging chal- lenges exist in current systems, which are solved by either extending a high-bandwidth bus such as TSN to support device I/O, or enhancing USB with improved networking capabilities. 

Cyber-physical systems (CPS) increasingly require real-time, high bandwidth data communication and processing. To address this, Time Sensitive Networking (TSN) provides latency-bounded data transmission at one or more gigabits-per-second throughput. However, it does not commonly connect directly to I/O devices, such as sensors and actuators. In contrast, Universal Serial Bus (USB) is ubiquitous for device I/O, but has yet to be widely adopted for host-to-host networking. This paper considers the use of a common USB software stack for both device I/O and host-to-host communication. We compare against a system using USB for device I/O and TSN for host-level networking. Our findings show that a unified approach using USB results in reduced software complexity, simplified bus coordination, and more effective mitigation of priority inversion when transferring data across multiple bus segments. Experiments show that end-to-end latency is within expected delay bounds, and is reduced if the same USB software stack is used for all communication with a given host. This suggests that bridging challenges exist in current systems, which are solved by either extending a high-bandwidth bus such as TSN to support device I/O, or enhancing USB with improved networking capabilities. 

Poly- and Perfluorinated alkyl substances (PFAS) pose environmental and public health concerns. While incineration remains the most common PFAS remediation method, the complete combustion and pyrolysis mechanism of PFAS is unknown. This study aims to expand our understanding of the kinetics of gas-phase PFAS incineration by measuring the effect of difluoromethane (CHF) on propane ignition delay times (IDTs). The ignition delay times were measured by OH* emission and end-wall pressure time histories behind the reflected shock wave. Different concentrations of CH2F2 were mixed with fuel-lean propane-oxygen mixtures diluted in argon. Experiments were conducted at a nominal reflected shock pressure of P5 = 1 atm and reflected shock temperatures of 1200 < T5 < 1800 K. A new detailed chemical kinetic mechanism is presented. 135 new rate constants were computed using RRKM/ME theory, based upon stationary points computed using ANL0. The new mechanism is in excellent agreement with the measured ignition delay time. A novel sensitivity analysis helps to explain the elementary steps by which CH2F2 increases the ignition delay time. 

Multicore PC-class embedded systems present an opportunity to consolidate separate microcontrollers as software-defined functions. For instance, an automotive system with more than 100 electronic control units (ECUs) could be replaced with one or, at most, several multicore PCs running software tasks for chassis, body, powertrain, infotainment, and advanced driver assistance system (ADAS) services. However, a key challenge is how to handle real-time device input and output (I/O) and host-level networking as part of sensor data processing and control. A traditional microcontroller would commonly feature one or more Controller Area Network (CAN) buses for real-time I/O. CAN buses are usually absent in PCs, which instead feature higher bandwidth Universal Serial Bus (USB) interfaces. This article shows how to achieve real-time device I/O and host-to-host communication over USB, using suitably written device drivers and a time-aware POSIX-like “tuned pipe” abstraction. This allows developers to establish task pipelines spanning one or more hosts, with end-to-end latency and throughput guarantees for sensor data processing, control, and actuation. 

Previous generations of halocarbon refrigerants and flame suppressants cause intolerable levels of ozone depletion and global warming, motivating the search for environmentally-friendly alternatives, but the complex flammability of proposed halocarbon compounds has proven to be a challenge. Because the combustion chemistry of these greener halocarbon refrigerants and suppressants is very condition-dependent, the flammability of potential alternatives need to be screened under a variety of operational conditions prior to marketing and further product development. To facilitate this screening, kinetic models can be generated automatically in Reaction Mechanism Generator (RMG) to predict the flammability. RMG, a software package that automates the generation of detailed reaction mechanisms, has recently been extended to predict the chemical kinetics involved in halocarbon combustion. Full kinetic mechanisms with kinetic, thermodynamic, and transport properties generated from RMG are then evaluated with Cantera to predict laminar flame speeds under different reacting conditions. Recent work developed an RMG model of flame suppressant 2-BTP (CH2=CBrCF3) in methane flames. Current work has advanced RMG’s 2-BTP model to achieve improved quantitative agreement with experimental flame speeds. We also use RMG to generate models of binary halocarbon blends to determine the importance of “cross reactions” that are not accounted for through simple concatenation of individual combustion mechanisms. Flame speeds of RMG-generated blend models and blend models comprised of concatenated mechanisms are compared, along with experimental flame speeds found in literature. As demonstrated in current and previous work, automating the generation of full halocarbon kinetic models through RMG expedites screening for the next generation of environmentally-friendly refrigerants and suppressants, a task that would be both time- and cost-intensive if conducted without automation. 

Previous generations of halocarbon refrigerants and flame suppressants cause intolerable levels of ozone depletion and global warming, motivating the search for environmentally-friendly alternatives, but the complex flammability of proposed halocarbon compounds has proven to be a challenge. Because the combustion chemistry of these greener halocarbon refrigerants and suppressants is very condition-dependent, the flammability of potential alternatives need to be screened under a variety of operational conditions prior to marketing and further product development. To facilitate this screening, kinetic models can be generated automatically in Reaction Mechanism Generator (RMG) to predict the flammability. RMG, a software package that automates the generation of detailed reaction mechanisms, has recently been extended to predict the chemical kinetics involved in halocarbon combustion. Full kinetic mechanisms with kinetic, thermodynamic, and transport properties generated from RMG are then evaluated with Cantera to predict laminar flame speeds under different reacting conditions. Recent work developed an RMG model of flame suppressant 2-BTP (CH2=CBrCF3) in methane flames. Current work has advanced RMG’s 2-BTP model to achieve improved quantitative agreement with experimental flame speeds. We also use RMG to generate models of binary halocarbon blends to determine the importance of “cross reactions” that are not accounted for through simple concatenation of individual combustion mechanisms. Flame speeds of RMG-generated blend models and blend models comprised of concatenated mechanisms are compared, along with experimental flame speeds found in literature. As demonstrated in current and previous work, automating the generation of full halocarbon kinetic models through RMG expedites screening for the next generation of environmentally-friendly refrigerants and suppressants, a task that would be both time- and cost-intensive if conducted without automation.