3,903 research outputs found
Apparatus for aiding a pilot in avoiding a midair collision between aircraft
An apparatus for aiding a pilot in avoiding a midair collision between aircraft is described. A protected aircraft carries a transmitter, a transponder, a receiver, and a data processor; and an intruding cooperating aircraft carries a transponder. The transmitter of the protected aircraft continuously transmits a signal to the transponders of all intruding aircraft. The transponder of each of the intruding aircraft adds the altitude of the intruding aircraft to the signal and transmits it back to the receiver of the protected aircraft. The receiver selects only the signal from the most hazardous intruding aircraft and applies it to the data processor. From this selected signal the data processor determines the closing velocity between the protected and intruding aircraft, the range between the two aircraft, their altitude difference and the time to a possible collision
Phase modulating with odd and even finite power series of a modulating signal
Method and apparatus is presented for producing a phase-modulated waveform having a high degree of linearity between the modulating signal and the phase of the modulated carrier signal. Two signals representing finite odd and even power series transformations of the modulating signal are produced and multiplied with two quadrature components of the input carrier signal, respectively. One of the multiplied signals is subtracted from the other and the resulting signal is hard-limited to produce a phase-modulated output signal. The means for producing the two signals representing the odd and even power series of the modulating signal includes means for varying the coefficients of the two power series. By means of an existing computer program, the coefficients of the two power series are selected such that there is an extremely high degree of linearity between the modulating signal and the phase of the modulated carrier signal
Wide deviation phase modulator
Modulator produces phase-modulated waveform having high modulating linearity. Technique is inherently wideband with respect to carrier frequency and can operate over decade carrier frequency range without adjustments. Circuit performance is both mathematically predictable and highly reproducible
Evaluation of Ventilation Designs for Increasing Local Exhaust Ventilation Performance in Traditional Settings and Concrete Dowel Drilling
Over 2 million workers are potentially exposed to respirable crystalline silica with the overwhelming majority in the construction industry. Occupational exposure to respirable crystalline silica can lead to silicosis, lung cancer, and other adverse diseases. The present research evaluated novel designs in both traditional ventilation and local exhaust ventilation for a concrete dowel drill to reduce occupational exposures such as silica. The first study investigated traditional ventilation novel designs to increase capture velocities without increasing fan speeds or power consumption. The second and third study focused on improving a concrete dowel drill local exhaust ventilation design to reduce potential respirable crystalline silica exposures during large concrete construction project such as airport runways. Previous research indicated that the manufacturer’s local exhaust ventilation system reduced respirable crystalline silica exposures by over 90 percent but the system was susceptible to filter and hose clogging which reduced performance. In the second study, a laboratory study evaluated two novel local exhaust ventilation hoods, one commercially available hood, and the dowel drill manufacturer’s hood for hood efficiency and airflow characteristics. The novel design hoods increased hood coefficient of entry from 0.59 for the manufacturer’s hood to 0.64 indicating increased efficiency. Novel simple hood analysis found an average hood coefficient of entry of 0.81 indicating further improvements can be made. In the third study, simulated workplace conditions were used to evaluate the best performance hood identified in laboratory testing along with other local exhaust ventilation modifications such as replacing the manufacturer’s corrugated hose with smooth-bore hose and including a cyclone pre-separator to reduce the dust transport burden within the exhaust system. The most effective local exhaust ventilation configuration consisted of the novel design hood, smooth-bore hose, and cyclone which reduced average accumulated hose weight (manufacturer’s configuration = 0.3 pounds per trial vs. most effective configuration = 0.05 pounds per trial) and increased average cleanout bucket capture (0.95 pounds per trial to 6.30 pounds per trial). These metrics indicated potential concrete dowel drill ventilation system efficiency and capture performance increases that address the ventilation system limitations indicated by previous research.PhDEnvironmental Health SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/133420/1/couchjr_1.pd
Public policies for the working poor: The earned income tax credit versus minimum wage legislation
This paper documents the declining relationship between low hourly wages and low household income over the last half-century and how this has reduced the share of minimum wage workers who live in poor households. It then compares recent and prospective increases in the earned income tax credit (EITC) and the minimum wage as methods of increasing the labor earnings of poor workers. Data from the Current Population Survey (CPS) are used to simulate the effects of both programs. Increases in the EITC between 1989 and 1992 delivered a much larger proportion of a given dollar of benefits to the poor than did increases in the minimum wage from 4.25. Scheduled increases in the EITC through 1996 will also do far more for the working poor than raising the minimum wage.
Dissipative transformation of non-nucleated dwarf galaxies into nucleated systems
Recent photometric observations by the {\it Hubble Space Telescope (HST)}
have revealed the physical properties of stellar galactic nuclei in nucleated
dwarf galaxies in the Virgo cluster of galaxies. In order to elucidate the
formation processes of nucleated dwarfs, we numerically investigate gas
dynamics, star formation, and chemical evolution within the central 1 kpc of
gas disks embedded within the galactic stellar components of non-nucleated
dwarfs. We find that high density, compact stellar systems can be formed in the
central regions of dwarfs as a result of dissipative, repeated merging of
massive stellar and gaseous clumps developed from nuclear gaseous spiral arms
as a result of local gravitational instability. The central stellar components
are found to have stellar masses which are typically 5% of their host dwarfs
and show very flattened shapes, rotational kinematics, and central velocity
dispersions significantly smaller than those of their host dwarfs. We also find
that more massive dwarfs can develop more massive, more metal-rich, and higher
density stellar systems in their central regions, because star formation and
chemical enrichment proceed more efficiently owing to the less dramatic
suppression of star formation by supernovae feedback effects in more massive
dwarfs. Based on these results, we suggest that gas-rich, non-nucleated dwarfs
can be transformed into nucleated ones as a result of dissipative gas dynamics
in their central regions. We discuss the origin of the observed correlations
between physical properties of stellar galactic nuclei and those of their host
galaxies.Comment: 13 pages, 4 figures (1 color), ApJL in pres
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