The objectives, instrumentation, methods and data leading up to launch of the NASA Living With a Star (LWS) Space Environment Testbed (SET) payload onboard the Air Force Research Laboratory ...Demonstration and Science Experiments (DSX) spacecraft are described. The experiments characterize the space radiation environment and how it affects hardware performance. The payload consists of a compact space weather instrument and a carrier containing four board experiments.
Existing Internet protocols assume persistent end-to-end connectivity, which cannot be guaranteed in disruptive and high-latency space environments. To operate over these challenging networks, a ...store-carry-and-forward communication architecture called Delay/Disruption Tolerant Networking (DTN) has been proposed. This work provides the first examination of the performance and robustness of Contact Graph Routing (CGR) algorithm, the state-of-the-art routing scheme for space-based DTNs. To this end, after a thorough description of CGR, two appealing satellite constellations are proposed and evaluated by means of simulations. Indeed, the DtnSim simulator is introduced as another relevant contribution of this work. Results enabled the authors to identify existing CGR weaknesses and enhancement opportunities.
Microspheres have been proposed for different medical applications, such as the delivery of therapeutic proteins. The first step, before evaluating the functionality of a protein delivery system, is ...to evaluate their biological safety. In this work, we developed chitosan/Tween 80 microspheres loaded with magnetite nanoparticles and evaluated cell damage. The formation and physical-chemical properties of the microspheres were determined by FT-IR, Raman, thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDS), dynamic light scattering (DLS), and SEM. Cell damage was evaluated by a full set of in vitro assays using a non-cancerous cell line, human erythrocytes, and human lymphocytes. At the same time, to know if these microspheres can load proteins over their surface, bovine serum albumin (BSA) immobilization was measured. Results showed 7 nm magnetite nanoparticles loaded into chitosan/Tween 80 microspheres with average sizes of 1.431 µm. At concentrations from 1 to 100 µg/mL, there was no evidence of changes in mitochondrial metabolism, cell morphology, membrane rupture, cell cycle, nor sister chromatid exchange formation. For each microgram of microspheres 1.8 µg of BSA was immobilized. The result provides the fundamental understanding of the in vitro biological behavior, and safety, of developed microspheres. Additionally, this set of assays can be helpful for researchers to evaluate different nano and microparticles.
An approach aiming at estimating the error rates of integrated circuits, early in the design phase, is presented. It combines static SBU cross-sections predicted from MUSCA SEP3 (Multi-Scales Single ...Event Phenomena Predictive Platform) and results of fault-injection performed at netlist level thanks to NETFI method (NETlist Fault Injection). This approach was applied to predict dynamic cross-sections for two different circuits: the 8051 microcontroller and Leon2 processor. The good correlation between predictions and measures puts in evidence the efficiency of the proposed MUSCA SEP3/NETFI approach and tools.
A novel design technique is proposed for storage elements which are insensitive to radiation-induced single-event upsets. This technique is suitable for implementation in high density ASICs and ...static RAMs using submicron CMOS technology.
Radiation tests with 15-MeV neutrons were performed in a COTS SRAM including a new memory cell design combining SRAM cells and DRAM capacitors to determine if, as claimed, it is soft-error free and ...to estimate upper bounds for the cross-section. These tests led to cross-section values two orders of magnitude below those of typical CMOS SRAMs in the same technology node. MUSCA SEP3 simulations complement these results predicting that only high-energy neutrons ( > 30 MeV) can provoke bit flips in the studied SRAMs. MUSCA SEP3 is also used to investigate the sensitivity of the studied SRAM to radioactive contamination and to compare it with the one of standard CMOS SRAMs. Results are useful to make predictions about the operation of this memory in environments such as avionics.
Increasing design complexity for current and future generations of microelectronic technologies leads to an increased sensitivity to transient bit-flip errors. These errors can cause unpredictable ...behaviors and corrupt data integrity and system availability. This work proposes new solutions to detect all classes of faults, including those that escape conventional software detection mechanisms, allowing full protection against transient bit-flip errors. The proposed solutions, particularly well suited for low-cost safety-critical microprocessor-based applications, have been validated through exhaustive fault injection experiments performed on a set of real and synthetic benchmark programs. The fault model taken into consideration was single bit-flip errors corrupting memory cells accessible to the user by means of the processor instruction set. The obtained results demonstrate the effectiveness of the proposed solutions.
This paper investigates an approach to study the effects of upsets on the operation of microprocessor-based digital architectures. The method is based on the injection of bit-flips, randomly in time ...and location by using the capabilities of typical application boards. Experimental results, obtained on programs running on two different digital boards, built around an 80C51 microcontroller and a 320C50 Digital Signal Processor, illustrate the potentialities of this new strategy.
Abstract
Augmented Lagrangian (AL) algorithms are very popular and successful methods for solving constrained optimization problems. Recently, global convergence analysis of these methods has been ...dramatically improved by using the notion of sequential optimality conditions. Such conditions are necessary for optimality, regardless of the fulfillment of any constraint qualifications, and provide theoretical tools to justify stopping criteria of several numerical optimization methods. Here, we introduce a new sequential optimality condition stronger than previously stated in the literature. We show that a well-established safeguarded Powell–Hestenes–Rockafellar (PHR) AL algorithm generates points that satisfy the new condition under a Lojasiewicz-type assumption, improving and unifying all the previous convergence results. Furthermore, we introduce a new primal–dual AL method capable of achieving such points without the Lojasiewicz hypothesis. We then propose a hybrid method in which the new strategy acts to help the safeguarded PHR method when it tends to fail. We show by preliminary numerical tests that all the problems already successfully solved by the safeguarded PHR method remain unchanged, while others where the PHR method failed are now solved with an acceptable additional computational cost.
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