1,522 research outputs found
How (In)accurate Are Demand Forecasts in Public Works Projects? The Case of Transportation
This article presents results from the first statistically significant study
of traffic forecasts in transportation infrastructure projects. The sample used
is the largest of its kind, covering 210 projects in 14 nations worth US$59
billion. The study shows with very high statistical significance that
forecasters generally do a poor job of estimating the demand for transportation
infrastructure projects. The result is substantial downside financial and
economic risks. Such risks are typically ignored or downplayed by planners and
decision makers, to the detriment of social and economic welfare. For nine out
of ten rail projects passenger forecasts are overestimated; average
overestimation is 106 percent. This results in large benefit shortfalls for
rail projects. For half of all road projects the difference between actual and
forecasted traffic is more than plus/minus 20 percent. Forecasts have not
become more accurate over the 30-year period studied. If techniques and skills
for arriving at accurate demand forecasts have improved over time, as often
claimed by forecasters, this does not show in the data. The causes of
inaccuracy in forecasts are different for rail and road projects, with
political causes playing a larger role for rail than for road. The cure is
transparency, accountability, and new forecasting methods. The challenge is to
change the governance structures for forecasting and project development. The
article shows how planners may help achieve this.Comment: arXiv admin note: text overlap with arXiv:1302.2544, arXiv:1303.6571,
arXiv:1302.364
Detection of molecular microwave transitions in the 3 mm wavelength range in comet Kohoutek (1973f)
Observations of comet Kohoutek made with a 3-mm line receiver mounted on the 11-m NRAO radio dish at Kitt Peak are presented. The detection of line transitions of hydrogen cyanide and methyl cyanide is reported and discussed along with the variability of neutral gas jets. Microwave transitions in molecules of cometary origin are also examined
Conserving All the Pollinators: Variation in Probability of Pollen Transport among Insect Taxa
As concern about declining pollinator populations mounts, it is important to understand the range of insect taxa that provide pollination services. We use pollen transport information acquired over three years in two habitats at Badlands National Park, South Dakota, USA, to compare probabilities of pollen transport among insect taxa and between sexes of bees. Sampling was conducted on 1-ha plots, eight in sparse vegetation (May–October samples; N = 74 surveys) and 12 in wheatgrass prairie vegetation (June–July samples; N = 87 surveys). Insects contacting reproductive parts of flowers were netted, placed individually into tubes charged with ethyl acetate, then transferred to individual labeled glassine envelopes for transport to the lab. Pollen was removed from insect bodies with fuchsin jelly cubes which were then mounted on microscope slides for identification. The probability of taxa transporting only conspecific pollen (with respect to the plant species upon which it was collected), mixed pollen, only non-conspecific, or no pollen was estimated with multinomial logistic regression. Bees were the most commonly captured flower visitor and carried by far the most pollen (females \u3e10× as much as males), but they were most likely to carry mixed pollen loads. Flies, beetles, and wasps were also common flower visitors and beetles were most likely to carry only conspecific pollen. Ants and diurnal lepidopterans were unlikely to carry any pollen. Bees, beetles, flies, and wasps varied in the timing and habitat in which they were most likely to transport pollen, suggesting that all played a role in providing robust pollination services
A search for interstellar molecules in the spectra of highly reddened stars
A total of ten stars were observed with cameras of the International Ultraviolet Explorer (IUE) in both high and low dispersion. One star, X Persei (HD 24534, 6.0 BE), was analyzed in detail. Ultraviolet observations of the column densities of CO match those derived from the radio to within a factor of 4, with the difference probably due to the larger beam size of the radio measurement and the assumption of a thermal population in the rotational levels of CO. Upper limits are given to the log column densities for OH, HCl, and CH2 of 14.0, 12.3 and 12.8. The carbon abundance was found to be about solar with a possible depletion of about a factor of 2. With precautions concerning both noise and correct background, the IUE can be used for studies of interstellar molecules
Satellite Time -Dilation Measurement
Contains a report on a research project.National Aeronautics and Space Administration (Contract NASw-143)Lincoln Laboratory (Purchase Order B-00306)United States ArmyUnited States NavyUnited States Air Force (Contract AF19(604)-5200
Sudbury project (University of Muenster-Ontario Geological Survey): Summary of results - an updated impact model
In 1984 the Ontario Geological Survey initiated a research project on the Sudbury structure (SS) in cooperation with the University of Muenster. The project included field mapping (1984-1989) and petrographic, chemical, and isotope analyses of the major stratigraphic units of the SS. Four diploma theses and four doctoral theses were performed during the project (1984-1992). Specific results of the various investigations are reported. Selected areas of the SS were mapped and sampled: Footwall rocks; Footwall breccia and parts of the sublayer and lower section of the Sudbury Igneous Complex (SIC); Onaping Formation and the upper section of the SIC; and Sudbury breccia and adjacent Footwall rocks along extended profiles up to 55 km from the SIC. All these stratigraphic units of the SS were studied in substantial detail by previous workers. The most important characteristic of the previous research is that it was based either on a volcanic model or on a mixed volcanic-impact model for the origin of the SS. The present project was clearly directed toward a test of the impact origin of the SS without invoking an endogenic component. In general, our results confirm the most widely accepted stratigraphic division of the SS. However, our interpretation of some of the major stratigraphic units is different from most views expressed. The stratigraphy of the SS and its new interpretation is given as a basis for discussion
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