Highly integrated digital electronic control: Digital flight control, aircraft model identification, and adaptive engine control

The highly integrated digital electronic control (HIDEC) program at NASA Ames Research Center, Dryden Flight Research Facility is a multiphase flight research program to quantify the benefits of promising integrated control systems. McDonnell Aircraft Company is the prime contractor, with United Technologies Pratt and Whitney Aircraft, and Lear Siegler Incorporated as major subcontractors. The NASA F-15A testbed aircraft was modified by the HIDEC program by installing a digital electronic flight control system (DEFCS) and replacing the standard F100 (Arab 3) engines with F100 engine model derivative (EMD) engines equipped with digital electronic engine controls (DEEC), and integrating the DEEC's and DEFCS. The modified aircraft provides the capability for testing many integrated control modes involving the flight controls, engine controls, and inlet controls. This paper focuses on the first two phases of the HIDEC program, which are the digital flight control system/aircraft model identification (DEFCS/AMI) phase and the adaptive engine control system (ADECS) phase

Fractional differential equations and numerical methods

The increasing use of Fractional Calculus demands more accurate arid efficient methods for the numerical solution of fractional differential equations. We introduce the concepts of Fractional Calculus and give the definitions of fractional integrals and derivatives in the Riemann-Liouville and Caputo forms. We explore three existing Numerical Methods of solution of Fractional Differential Equations. 1. Diethelm's Backward Difference Form (BDF) method. 2. Lubich's Convolution Quadrature method. 3. Luchko and Diethelm's Operational Calculus (using the Mittag-Lefner function) method. We present useful recursive expressions we developed to compute the Taylor Series coefficients in the Operational Calculus method. These expressions are used in the calculation of the convolution and starting weights. We compare their accuracy and performance of the numerical methods, and conclude that the more complex methods produce the more accurate results

Emission control system

Methods and apparatus utilizing hydrogen peroxide are useful to reduce SOx and mercury (or other heavy metal) emissions from combustion flue gas streams. The methods and apparatus may further be modified to reduce NOx emissions. Continuous concentration of hydrogen peroxide to levels approaching or exceeding propellant-grade hydrogen peroxide facilitates increased system efficiency. In this manner, combustion flue gas streams can be treated for the removal of SOx and heavy metals, while isolating useful by-products streams of sulfuric acid as well as solids for the recovery of the heavy metals. Where removal of NOx emissions is included, nitric acid may also be isolated for use in fertilizer or other industrial applications

Cervical Screening at Age 50-64 Years and the Risk of Cervical Cancer at Age 65 Years and Older: Population-Based Case Control Study

This work was supported by Cancer Research UK [C8162/10406 and C8162/12537]

Design, theory, and measurement of a polarization insensitive absorber for terahertz imaging

We present the theory, design, and realization of a polarization-insensitive metamaterial absorber for terahertz frequencies. We derive geometrical-independent conditions for effective medium absorbers in general, and for resonant metamaterials specically. Our fabricated design reaches and absorptivity of 78% at 1.145 ThzComment: 6 Pages, 5 figures; figures update

Tax Professional Internships And Subsequent Professional Performance

How do internships influence the socialization and performance of accounting students employed in the tax department of a CPA firm?  Previous research on accounting internships primarily focuses on auditing personnel.  There is evidence in the literature that indicates audit and tax professionals have different work cultures.  This paper examines the relationship between internships and subsequent professional performance of tax professionals as measured by promotion velocity and employee turnover.  The human resource department, from seven regional CPA firms with similarly structured internship programs, provided performance, promotion and turnover data on employees who completed internships and employees who did not complete internships.  The results of the study indicate that internships positively affect performance evaluations, promotions, and employee retention of tax professionals

Cryosat-2 significant wave height in polar oceans derived using a semi-analytical model of synthetic aperture radar 2011-2019

This paper documents the retrieval of significant ocean surface wave heights in the Arctic Ocean from CryoSat-2 data. We use a semi-analytical model for an idealised synthetic aperture satellite radar or pulse-limited radar altimeter echo power. We develop a processing methodology that specifically considers both the Synthetic Aperture and Pulse Limited modes of the radar that change close to the sea ice edge within the Arctic Ocean. All CryoSat-2 echoes to date were matched by our idealised echo revealing wave heights over the period 2011–2019. Our retrieved data were contrasted to existing processing of CryoSat-2 data and wave model data, showing the improved fidelity and accuracy of the semi-analytical echo power model and the newly developed processing methods. We contrasted our data to in situ wave buoy measurements, showing improved data retrievals in seasonal sea ice covered seas. We have shown the importance of directly considering the correct satellite mode of operation in the Arctic Ocean where SAR is the dominant operating mode. Our new data are of specific use for wave model validation close to the sea ice edge and is available at the link in the data availability statement