General Dynamics

About: General Dynamics is a company organization based out in Fairfax, Virginia, United States. It is known for research contribution in the topics: Signal & Propellant. The organization has 5722 authors who have published 5819 publications receiving 85768 citations. The organization is also known as: GD & General Dynamics Corporation.

Inviscid transonic flow over airfoils

Abstract: A procedure is presented to calculate steady supercritical planar flows over lifting airfoils using an unsteady approach, where the steady flow is obtained as the asymptotic flow for large times. The unsteady flow is generated by impulsively imposing the airfoil boundary condition in an initially uniform flow. The resulting flow is calculated by a finite difference analogue to the unsteady Euler equations using a diffusing second-order difference scheme. Here an artificial viscosity appears by which shock waves acquire a steep profile. The procedure is used to calculate the flows over one of the nonlifting symmetrical shockless profiles derived by Nieuwland, using the hodograph method, and over a lifting NAG A 64A-410 profile. Results agree well with experiments, with local differences accountable by a BusemannGuderley instability in the first case, and by viscous effects in the second case.

Fault tolerant computer system

Abstract: A fault tolerant computer system is disclosed which uses redundant voting at the hardware clock level to detect and to correct single event upsets (SEU) and other random failures. In one preferred embodiment, the computer (30) includes four or more commercial processing units (CPUs) (32) operating in strict "lock-step" and whose outputs (33, 37) to system memory (46) and system bus (12) are voted by a gate array (50) which may be implemented in a custom integrated circuit (34). A custom memory controller (18) interfaces to the system memory (46) and system bus (12). The data and address (35, 37) at each write to and read from memory (46) within the computer (30) are voted at each CPU clock cycle. A vote status and control circuit (38) "reads" the status of the vote and controls the state of the CPUs using hardware and software. The majority voted signals (35) are used by the agreeing CPUs 32 to continue processing operations without interruption. The system logic selects the best chance of recovering from a detected fault by resynchronizing all CPUs (32), powering down a faulty CPU or switching to a spare computer (30), resetting and re-booting the substituted CPUs (32).

Racial and Ethnic Disparities in Rates of COVID-19-Associated Hospitalization, Intensive Care Unit Admission, and In-Hospital Death in the United States From March 2020 to February 2021.

Abstract: Importance: Racial and ethnic minority groups are disproportionately affected by COVID-19. Objectives: To evaluate whether rates of severe COVID-19, defined as hospitalization, intensive care unit (ICU) admission, or in-hospital death, are higher among racial and ethnic minority groups compared with non-Hispanic White persons. Design, Setting, and Participants: This cross-sectional study included 99 counties within 14 US states participating in the COVID-19-Associated Hospitalization Surveillance Network. Participants were persons of all ages hospitalized with COVID-19 from March 1, 2020, to February 28, 2021. Exposures: Laboratory-confirmed COVID-19-associated hospitalization, defined as a positive SARS-CoV-2 test within 14 days prior to or during hospitalization. Main Outcomes and Measures: Cumulative age-adjusted rates (per 100 000 population) of hospitalization, ICU admission, and death by race and ethnicity. Rate ratios (RR) were calculated for each racial and ethnic group compared with White persons. Results: Among 153 692 patients with COVID-19-associated hospitalizations, 143 342 (93.3%) with information on race and ethnicity were included in the analysis. Of these, 105 421 (73.5%) were 50 years or older, 72 159 (50.3%) were male, 28 762 (20.1%) were Hispanic or Latino, 2056 (1.4%) were non-Hispanic American Indian or Alaska Native, 7737 (5.4%) were non-Hispanic Asian or Pacific Islander, 40 806 (28.5%) were non-Hispanic Black, and 63 981 (44.6%) were White. Compared with White persons, American Indian or Alaska Native, Latino, Black, and Asian or Pacific Islander persons were more likely to have higher cumulative age-adjusted rates of hospitalization, ICU admission, and death as follows: American Indian or Alaska Native (hospitalization: RR, 3.70; 95% CI, 3.54-3.87; ICU admission: RR, 6.49; 95% CI, 6.01-7.01; death: RR, 7.19; 95% CI, 6.47-7.99); Latino (hospitalization: RR, 3.06; 95% CI, 3.01-3.10; ICU admission: RR, 4.20; 95% CI, 4.08-4.33; death: RR, 3.85; 95% CI, 3.68-4.01); Black (hospitalization: RR, 2.85; 95% CI, 2.81-2.89; ICU admission: RR, 3.17; 95% CI, 3.09-3.26; death: RR, 2.58; 95% CI, 2.48-2.69); and Asian or Pacific Islander (hospitalization: RR, 1.03; 95% CI, 1.01-1.06; ICU admission: RR, 1.91; 95% CI, 1.83-1.98; death: RR, 1.64; 95% CI, 1.55-1.74). Conclusions and Relevance: In this cross-sectional analysis, American Indian or Alaska Native, Latino, Black, and Asian or Pacific Islander persons were more likely than White persons to have a COVID-19-associated hospitalization, ICU admission, or in-hospital death during the first year of the US COVID-19 pandemic. Equitable access to COVID-19 preventive measures, including vaccination, is needed to minimize the gap in racial and ethnic disparities of severe COVID-19.