Ergonomics in the Workplace: Is It Time for an OSHA Standard?

Improper ergonomic design of jobs is one of the leading causes of work-related illness, accounting for perhaps a third of employers’ costs under state workers’ compensation laws. Due to the wide variety of circumstances, however, any comprehensive standard would probably have to be complex and costly, while scientific understanding of the problem is not complete

Moving to high quality of life

The U.S. population has been migrating to places with high perceived quality of life. A calibrated general-equilibrium model shows that such migration follows from broad-based technological progress. Rising national wages increase demand for consumption amenities. Under a baseline parameterization, a place with amenities for which individuals would pay 5 percent of their income grows 0.3 percent faster than an otherwise identical place. Productivity is shown to be a decreasingly important determinant of local population. The faster growth of high-amenity places is considerably strengthened if they have low initial equilibrium population density underpinned by low relative productivity. Places with identical amenities asymptotically converge to an identical population density, regardless of their relative productivity levels. An implication is that the high growth rates of high-amenity localities should eventually taper off.>Consumption (Economics) ; Quality of life

Constant directions of the Riccati equation

A constant direction of the Riccati equation associated with a class of singular discrete-time optimization problems is defined. The set of constant directions is completely characterized using a control viewpoint. Constant directions are used to reduce the computational complexity of the optimal system. Application to optimal filtering in colored noise is given

Consumption amenities and city crowdedness

Crowdedness varies widely among U.S. cities. A simple, static general equilibrium model suggests that plausible differences in metro areas’ consumption amenities can account for much of the observed variation. Under a baseline calibration, differences in amenities valued at 30 percent of average consumption expenditures suffice to support a twenty-fold difference in population density. Empirical results confirm that amenities help support crowdedness and suggest that they are becoming a more important determinant of where people choose to live. But for the moment, local productivity appears to be the more important cause of local crowdedness.Productivity ; Consumption (Economics)

Origin of chaos in the Prometheus–Pandora system

We demonstrate that the chaotic orbits of Prometheus and Pandora are due to interactions associated with the 121:118 mean motion resonance. Differential precession splits this resonance into a quartet of components equally spaced in frequency. Libration widths of the individual components exceed the splitting resulting in resonance overlap which causes the chaos. A single degree of freedom model captures the essential features of the chaotic dynamics. Mean motions of Prometheus and Pandora wander chaotically in zones of width 1.8 deg yr^−1 and 3.1 deg yr^−1, respectively

FOOD TRANSPORTATION

Agribusiness,

Formation of Short-Period Binary Pulsars in Globular Clusters

We present a new dynamical scenario for the formation of short-period binary millisecond pulsars in globular clusters. Our work is motivated by the recent observations of 20 radio pulsars in 47 Tuc. In a dense cluster such as 47 Tuc, most neutron stars acquire binary companions through exchange interactions with primordial binaries. The resulting systems have semimajor axes in the range \~0.1-1 AU and neutron star companion masses ~1-3 Msun. For many of these systems we find that, when the companion evolves off the main sequence and fills its Roche lobe, the subsequent mass transfer is dynamically unstable. This leads to a common envelope phase and the formation of short-period neutron star - white dwarf binaries. For a significant fraction of these binaries, the decay of the orbit due to gravitational radiation will be followed by a period of stable mass transfer driven by a combination of gravitational radiation and tidal heating of the companion. The properties of the resulting short-period binaries match well those of observed binary pulsars in 47 Tuc.Comment: To appear in ApJ Letters, slightly abbreviated version with only minor change

73 GHz Wideband Millimeter-Wave Foliage and Ground Reflection Measurements and Models

This paper presents 73 GHz wideband outdoor foliage and ground reflection measurements. Propagation measurements were made with a 400 Megachip-per-second sliding correlator channel sounder, with rotatable 27 dBi (7 degrees half- power beamwidth) horn antennas at both the transmitter and receiver, to study foliage-induced scattering and de-polarization effects, to assist in developing future wireless systems that will use adaptive array antennas. Signal attenuation through foliage was measured to be 0.4 dB/m for both co- and cross-polarized antenna configurations. Measured ground reflection coefficients for dirt and gravel ranged from 0.02 to 0.34, for incident angles ranging from 60 degrees to 81 degrees (with respect to the normal incidence of the surface). These data are useful for link budget design and site-specific (ray-tracing) models for future millimeter-wave communication systems.Comment: 6 pages, 4 figures, 2015 IEEE International Conference on Communications (ICC), ICC Workshop