Cancerphobia: Electromagnetic Fields and Their Impact on Residential Loan Values

This article provides a matrix representation of the adjustment grid estimator. From this representation, one can invoke the Gauss-Mrkov theorem to examine the efficiency of ordinary least squares (OLS) and the grid estimator that uses OLS estimates of the adjustments (the "plug-in" grid method). In addition, this matrix representation suggests a generalized least squares version of the grid method, labeled herin as the total grid estimator. Based on the empirical experiments, the total grid estimator outperformed the plug-in grid estimator, which in turn outperformed the OLS.

Thermal control surfaces experiment flight system performance

The Thermal Control Surfaces Experiment (TCSE) is the most complex system, other than the LDEF, retrieved after long term space exposure. The TCSE is a microcosm of complex electro-optical payloads being developed and flow by NASA and the DoD including SDI. The objective of TCSE was to determine the effects of the near-Earth orbital environment and the LDEF induced environment on spacecraft thermal control surfaces. The TCSE was a comprehensive experiment that combined in-space measurements with extensive post flight analyses of thermal control surfaces to determine the effects of exposure to the low earth orbit space environment. The TCSE was the first space experiment to measure the optical properties of thermal control surfaces the way they are routinely measured in a lab. The performance of the TCSE confirms that low cost, complex experiment packages can be developed that perform well in space

Aircraft interior noise reduction by alternate resonance tuning

Model problem development and analysis continues with the Alternate Resonance Tuning (ART) concept. The various topics described are presently at different stages of completion: investigation of the effectiveness of the ART concept under an external propagating pressure field associated with propeller passage by the fuselage; analysis of ART performance with a double panel wall mounted in a flexible frame model; development of a data fitting scheme using a branch analysis with a Newton-Raphson scheme in multiple dimensions to determine values of critical parameters in the actual experimental apparatus; and investigation of the ART effect with real panels as opposed to the spring-mass-damper systems currently used in much of the theory

Good jobs, bad jobs, and trade liberalization

Globalization threatens "good jobs at good wages", according to overwhelming public sentiment. Yet professional discussion often rules out such concerns a priori. We instead offer a framework to interpret and address these concerns. We develop a model in which monopolistically competitive firms pay efficiency wages, and these firms differ in both their technical capability and their monitoring ability. Heterogeneity in the ability of firms to monitor effort leads to different wages for identical workers - good jobs and bad jobs - as well as equilibrium unemployment. Wage heterogeneity combines with differences in technical capability to generate an equilibrium size distribution of firms. As in Melitz (2003), trade liberalization increases aggregate efficiency through a firm selection effect. This efficiency-enhancing selection effect, however, puts pressure on many "good jobs", in the sense that the high-wage jobs at any level of technical capability are the least likely to survive trade liberalization. In a central case, trade raises the average real wage but leads to a loss of many "good jobs" and to a steady-state increase in unemployment

The continuing materials analysis of the thermal control surfaces experiment (S0069)

The long term effects of the natural and induced space environment on spacecraft surfaces are critically important to future spacecraft - including Space Station Freedom. The damaging constituents of this environment include thermal vacuum, solar ultraviolet radiation, atomic oxygen, particulate radiation, and the spacecraft induced environment. The behavior of materials and coatings in the space environment continues to be a limiting technology for spacecraft and experiments. The Thermal Control Surfaces Experiment (TCSE) was flown on the National Aeronautics and Space Administration (NASA) Long Duration Exposure Facility (LDEF) to study these environmental effects on surfaces-particularly on thermal control surfaces. The TCSE was a comprehensive experiment that combined in-space measurements with extensive pre- and post-flight analyses of thermal control surfaces to determine the effects of exposure to the low Earth orbit space environment. The TCSE is the first space experiment to directly measure the total hemispherical reflectance of thermal control surfaces in the same way they are routinely measured in the laboratory. The trend analyses of selected coatings performed as part of the continuing post-flight analysis of the TCSE are described. A brief description of the TCSE and its mission on LDEF are presented. There are several publications available that describe the TCSE, it's mission on LDEF, and initial results in greater detail. These are listed in the TCSE Bibliography

Aircraft interior noise reduction by alternate resonance tuning

Existing interior noise reduction techniques for aircraft fuselages perform reasonably well at higher frequencies, but are inadequate at lower, particularly with respect to the low blade passage harmonics with high forcing levels found in propeller aircraft. A method is being studied which considers aircraft fuselages lines with panels alternately tuned to frequencies above and below the frequency to be attenuated. Adjacent panels would oscillate at equal amplitude, to give equal source strength, but with opposite phase. Provided these adjacent panels are acoustically compact, the resulting cancellation causes the interior acoustic modes to become cut off and therefore be non-propagating and evanescent. This interior noise reduction method, called Alternate Resonance Tuning (ART), is currently being investigated both theoretically and experimentally. This new concept has potential application to reducing interior noise due to the propellers in advanced turboprop aircraft as well as for existing aircraft configurations. This program summarizes the work carried out at Duke University during the third semester of a contract supported by the Structural Acoustics Branch at NASA Langley Research Center

Dynamic analysis of geared rotors by finite elements

A finite-element model of a geared rotor system on flexible bearings was developed. The model includes the rotary inertia of shaft elements, the axial loading on shafts, flexibility and damping of bearings, material damping of shafts and the stiffness and the damping of gear mesh. The coupling between the torsional and transverse vibrations of gears were considered in the model. A constant mesh stiffness was assumed. The analysis procedure can be used for forced vibration analysis of geared rotors by calculating the critical speeds and determining the response of any point on the shaft to mass unbalances, geometric eccentricities of gears and displacement transmission error excitation at the mesh point. The dynamic mesh forces due to these excitations can also be calculated. The model has been applied to several systems for the demonstration of its accuracy and for studying the effect of bearing compliances on system dynamics