Publications

Results 1501–1525 of 96,771

Search results

Jump to search filters

Drop Interactions with the Conical Shock Structure Generated by a Mach 4.5 Projectile

AIAA Journal

Guildenbecher, Daniel R.; Delgado, Paul M.; White, Glen W.; Reardon, Sam M.; Stauffacher, Howard L.; Beresh, Steven J.; Daniel, Kyle

This work presents measurements of liquid drop deformation and breakup time behind approximately conical shock waves and evaluates the predictive capabilities of low-order models and correlations developed using planar shock experiments. A conical shock was approximated by firing a bullet at Mach 4.5 past a vertical column of water drops with a mean initial diameter of 192 µm. The time-resolved drop position and maximum transverse dimension were characterized using backlit stereo images taken at 500 kHz. The gas density and velocity fields experienced by the drops were estimated using a Reynolds-averaged Navier-Stokes simulation of the bullet. Classical correlations predict drop breakup times and deformation in error by a factor of 3 or more. The Taylor analogy breakup (TAB) model predicts deformed drop diameters that agree within the confidence bounds of the ensemble-averaged experimental values using a dimensionless constant C2 = 2 compared to the accepted value C2 = 2/3. Results demonstrate existing correlations are inadequate for predicting the drop response to the three-dimensional relaxation of the flowfield downstream of a conical-like shock and suggest the TAB model results represent a path toward improved predictions.

More Details
TYPE Journal Article YEAR 2023
DOIOSTIScopus

Switch leakage mitigation through differential cancellation

Forbes, T.

High speed analog-to-digital converters (ADC), switched-capacitor delay elements, and pulsed radio frequency (RF) systems all require switches in the signal path operating at high switching speeds, providing low resistance when enabled, and providing high signal isolation when disabled. In semiconductor technologies such as CMOS, the enabled state resistance directly scales with the sizing of the switch device, where a larger width switch provides a lower enabled state resistance. As the device width is increased, so is the capacitance formed between the gate, drain, and source of the device.

More Details
TYPE Other Report YEAR 2023
DOIOSTI

Defender Policy Evaluation and Resource Allocation With MITRE ATT&CK Evaluations Data

IEEE Transactions on Dependable and Secure Computing

Outkin, Alexander V.; Schulz, Patricia V.; Schulz, Timothy; Tarman, Thomas D.; Pinar, Ali P.

Protecting against multi-step attacks of uncertain start times and duration forces the defenders into indefinite, always ongoing, resource-intensive response. To allocate resources effectively, the defender must analyze and respond to an uncertain stream of potentially undetected multiple multi-step attacks and take measures of attack and response intensity over time into account. Such response requires estimation of overall attack success metrics and evaluating effect of defender strategies and actions associated with specific attack steps on overall attack metrics. We present a novel game-theoretic approach GPLADD to attack metrics estimation and demonstrate it on attack data derived from MITRE's ATT&CK Framework and other sources. In GPLADD, the time to complete attack steps is explicit; the attack dynamics emerges from attack graph and attacker-defender capabilities and strategies and therefore reflects 'physics' of attacks. The time the attacker takes to complete an attack step is drawn from a probability distribution determined by attacker and defender strategies and capabilities. This makes time a physical constraint on attack success parameters and enables comparing different defender resource allocation strategies across different attacks. We solve for attack success metrics by approximating attacker-defender games as discrete-time Markov chains and show evaluation of return on detection investments associated with different attack steps. We apply GPLADD to MITRE's APT3 data from ATT&CK Framework and show that there are substantial and un-intuitive differences in estimated real-world vendor performance against a simplified APT3 attack. We focus on metrics that reflect attack difficulty versus attacker ability to remain hidden in the system after gaining control. This enables practical defender optimization and resource allocation against multi-step attacks.

More Details
TYPE Journal Article YEAR 2023
DOIOSTIScopus

Designing Resilient Communities: A Consequence-Based Approach for Grid Investment Report Series (Final Report)

Broderick, Robert J.

As part of the project “Designing Resilient Communities (DRC): A Consequence-Based Approach for Grid Investment,” funded by the United States (US) Department of Energy’s (DOE) Grid Modernization Laboratory Consortium (GMLC), Sandia National Laboratories (Sandia) partnered with a variety of government, industry, and university participants to develop and test a framework for community resilience planning focused on modernization of the electric grid. This report provides a summary of the development, description, and demonstration of the resulting Resilient Community Design Framework.

More Details
TYPE SAND Report YEAR 2023
DOIOSTI
Results 1501–1525 of 96,771
Results 1501–1525 of 96,771