An instrumentation channel is designed, implemented, and tested in a 0.5-μm SiGe BiCMOS process. The circuit features a reconfigurable Wheatstone bridge network that interfaces an assortment of ...external sensors to signal processing circuits. Also, analog sampling is implemented in the channel using a flying capacitor configuration. The analog samples are digitized by a low-power multichannel A/D converter. Measurement results show that the instrumentation channel supports input signals up to 200 Hz and operates across a wide temperature range of -180°C to 125°C. This work demonstrates the use of a commercially available first generation SiGe BiCMOS process in designing circuits suitable for extreme environment applications.
This paper presents an extreme environment capable Distributed Motor Controller (DMC) module suitable for operation with a distributed architecture of future spacecraft systems. This motor controller ...is designed to be a bus-based electronics module capable of operating a single Brushless DC motor in extreme space environments: temperature (-120°C to +85°C required, -180°C to +100°C stretch goal); radiation (>;20K required, >;100KRad stretch goal); >;360 cycles of operation. Achieving this objective will result in a scalable modular configuration for motor control with enhanced reliability that will greatly lower cost during the design, fabrication and ATLO phases of future missions. Within the heart of the DMC lies a pair of cold-capable Application Specific Integrated Circuits (ASICs) and a Field Programmable Gate Array (FPGA) that enable its miniaturization and operation in extreme environments. The ASICs are fabricated in the IBM 0.5μm Silicon Germanium (SiGe) BiCMOS process and are comprised of Analog circuitry to provide telemetry information, sensor interface, and health and status of DMC. The FPGA contains logic to provide motor control, status monitoring and spacecraft interface. The testing and characterization of these ASICs have yielded excellent functionality in cold temperatures (-135°C). The DMC module has demonstrated successful operation of a motor at temperature.
The trouble with shear stress Yager, Elowyn M.; Venditti, Jeremy G.; Smith, Heidi J. ...
Geomorphology (Amsterdam, Netherlands),
12/2018, Letnik:
323
Journal Article
Recenzirano
Predicted bedload fluxes often have large errors partly because calculations usually do not include spatial and temporal flow variability. Sediment motion is driven by a temporal distribution of ...applied fluid forces, which are often simplified into time-averaged flow velocities or shear stresses in sediment transport equations. Spatial variations in these flow parameters are also often neglected. Given the nonlinearities in the relation between flow and sediment flux, the reach-averaged sediment flux calculated with an average velocity or shear stress will not necessarily equal the measured spatially averaged bedload flux. Such spatial and temporal flow variations are ignored with the commonly used reach-averaged shear stress (τds) that is a function of the flow depth and channel slope. To demonstrate the uncertainties with using reach-averaged shear stresses, and even local shear stresses, to predict bedload transport rates, we have three goals. First, we outline the derivations and assumptions involved with commonly used estimates of shear stress. Second, we summarize the literature on the uncertainties involved with using shear stress, and other space- and time-averaged flow parameters, to predict sediment flux. Third, we use a new data set from experiments to add further support to a growing body of literature that suggests τds may not be linked to the mechanics of bedload transport. We show considerable uncertainties exist in estimating a reach-averaged shear stress, by comparing τds and near-bed shear stresses calculated from velocity profiles, Reynolds stresses, and local turbulence. For example, τds was systematically greater than these near-bed stresses even for experiments without large bed roughness. We also find that correlations between local time-averaged sediment fluxes and local Reynolds stresses or turbulence intensities are relatively poor. The near-bed, time-averaged local flow velocity has the strongest relation with the time-averaged local bedload flux because it is closely related to the forces that actually drive sediment transport. However, sediment transport rates in individual experiments could still vary by orders of magnitude for a given value of this flow velocity, suggesting that additional work is needed to identity a parameter, or distributions of parameters, that will best predict sediment fluxes.
Objective: The objective of this study was to identify factors associated with the occurrence and severity of depressive mood states among graduate-level allied health students. Participants: ...Students (N = 77) completed this study. Methods: Participants completed a series of self-reported surveys measuring moods, lifestyle behaviors, trait mental and physical energy and fatigue, and objective assessments of Trail-Making Test Part-B, and muscle oxygen consumption. Multiple backwards linear regression models were fitted to identify factors associated with depressive mood states. Results: When accounting for all subjects, increased severity of depressive mood states was associated with worse sleep quality (SQ), increased sitting time (ST), and trait physical fatigue (TPF). When examining subjects reporting depressive mood states, increased severity of depressive mood states was associated with worse SQ, increased ST, decreased mental workload on non-school days, and trait physical energy (TPE). Conclusion: Adjustments in lifestyle factors such as sleep, mental workload, and ST, may ameliorate depressive mood states.
Cushion plant dominated peatlands are key ecosystems in tropical alpine regions of the Andes in South America. The cushion plants have formed peat bodies over thousands of years that fill many valley ...bottoms, and the forage produced by the plants is critical for native and nonnative domesticated mammals. The sources and flow paths of water supporting these peatlands remain largely unknown. Some studies have suggested that glacier meltwater streams support some peatlands, and that the ongoing loss of glaciers and their meltwaters could lead to the loss or diminishment of peatlands. We analysed the hydrologic regime of 10 peatlands in four mountain regions of Bolivia and Peru using groundwater monitoring. Groundwater levels in peatlands were relatively stable and within 20 cm of the ground surface during the rainy season, and many sites had water tables 40–90 cm below the ground surface in the dry season. Topographic and groundwater elevations in the peatlands demonstrated that the water source of all 10 peatlands was hillslope groundwater flowing from lateral moraines, talus, colluvium, or bedrock aquifers into the peatlands. There was little to no input from streams, whether derived from glacier melt or other sources, and glacier melt could not have recharged the hillslope aquifers supporting peatlands. We measured the stable water isotopes in water samples taken during different seasons, distributed throughout the catchments, and the values are consistent with this interpretation. Our findings indicate that peatlands in the study region are recharged by hillslope groundwater discharge rather than stream water and may not be as vulnerable to glacial decline as other studies have indicated. However, both glaciers and peatlands are susceptible to changing thermal and precipitation regimes that could affect the persistence of peatlands.
Unintentional window falls represent a preventable source of injury and death in children. Despite major campaigns in some larger cities, there continue to be unintentional falls from windows ...throughout the United States. We aimed to identify risk factors and trends in unintentional window falls in the pediatric population in a national and regional sample.
A retrospective analysis of annual emergency department (ED) visits from the National Electronic Injury Surveillance System using product codes specific to windows, as well as patient encounters for unintentional window falls from January 2007 to August 2017 using site-specific trauma registries from 10 tertiary care children's hospitals in New England. National and state-specific census population estimates were used to compute rates per 100,000 population.
There were 38,840 ED visits and 496 regional patients who unintentionally fell from a window across the study period between 0 and 17 years old. The majority of falls occurred in children under the age of 6 and were related to falls from a second story or below. A decreased trend in national ED visits was seen, but no change in rates over time for regional trauma center encounters. A high number of falls was found to occur in smaller cities surrounding metropolitan areas and from single family residences.
Falls from windows represent a low proportion of overall types of unintentional sources of injury in children but are a high risk for severe disability. These results provide updated epidemiologic data for targeted intervention programs, as well as raise awareness for continued education and advocacy.
The radiation robustness of a newly designed Wilkinson analog-to-digital converter (ADC) is being investigated. The ADC is a front-end design block within a cold capable, analog sense, ...application-specific integrated circuit (ASIC) manufactured using the IBM 0.5 μm silicon germanium (SiGe) BiCMOS 5HP process. The ASIC is part of a next-generation, cold capable, distributed motor controller architecture, which is a candidate for the next generation of Mars rovers. Its main function is to interface with various sensor types to monitor motor health (i.e., temperature, mechanical stress, pressure). While relatively well-hardened against total ionizing dose and destructive single-event latchup, the ADC showed some SEU (SET) sensitivity that is heavily dependent on its input channel configuration. For this study, we used a combination of experiments (pulsed-laser) and Cadence mixed-mode SEE simulations to explain the heavy ion irradiation results. We concluded that ADC input impedance configuration should be carefully controlled in the design of radiation-hardened systems for space.
PURPOSE: To determine the effects of DOX treatment on rat hind-limb gait mechanics, with specific focus on the acceleration of the limb and spatiotemporal characteristics of gait. METHODS: Fifteen ...adult male Sprague-Dawley rats were randomly assigned and injected with saline, 10 mg/kg DOX, 12.5 mg/kg DOX, or 15 mg/kg DOX delivered as a bolus i.p. injection. Retro-reflective markers were positioned on the left hind-limb at the knee, ankle and foot. RESULTS: Spatiotemporal measures were not significantly altered by DOX injections (Lambda*=0.59, F sub(3,10) =2.31, p=0.14). However, DOX injections did affect limb accelerations (Lambda*=0.08, F sub(3,10) =6.96, p=0.02). Follow-up Helmert contrasts revealed decreased accelerations in ankle vertical motion (-13%, p=0.002, ES=1.07), foot horizontal motion (-5%, p=0.04, ES=0.27), and foot vertical motion (-14%, p=0.001, ES=0.97) for all dose groups compared to the saline group. However, dose magnitude had no effect beyond the baseline comparison (p > 0.25 for all contrasts).
This paper describes a rapid, high-throughput flow-through membrane immunoassay (FMIA) platform. A nitrocellulose membrane was spotted in an array format with multiple capture and control reagents ...for each sample detection area, and assay steps were carried out by sequential aspiration of sample and reagents through each detection area using a 96-well vacuum manifold. The FMIA provides an alternate assay format with several advantages over ELISA. The high surface area of the membrane permits high label concentration using gold labels, and the small pores and vacuum control provide rapid diffusion to reduce total assay time to ~30 min. All reagents used in the FMIA are compatible with dry storage without refrigeration. The results appear as colored spots on the membrane that can be quantified using a flatbed scanner. We demonstrate the platform for detection of IgM specific to lipopolysaccharides (LPS) derived from Salmonella Typhi. The FMIA format provides analytical results comparable to ELISA in less time, provides integrated assay controls, and allows compensation for specimen-to-specimen variability in background, which is a particular challenge for IgM assays.
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