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781.
A combined observational-modeling study was conducted to investigate turbulence mixing, and the relation to surface forcing, in the surface boundary layer (SBL) of a tropical, high-altitude, freshwater reservoir. A suite of vertical profiles of temperature microstructure, collected at three different stations of one-day duration each, provided estimates of dissipation rates of turbulence kinetic energy, , and temperature variance, χ. Numerical simulations of and χ, using state-of-the-art, public domain, two-equation turbulence closure models, compared favorably with the observations and reproduced the dynamics of daytime wind mixing as well as the vertical and temporal turbulence structure during nighttime convective conditions.Two independent estimates of vertical eddy diffusivities in the stably stratified (daytime) SBL, computed from the microstructure measurements, agreed closely, and the near surface heat and buoyancy fluxes, computed from the diffusivities, were similar to those computed independently from surface meteorology. Model generated eddy diffusivities agreed closely with the observed values, except those generated by K profile parameterization (KPP) model simulations. The good agreement provides confidence that nutrient fluxes in the SBL may be accurately computed from the models when forced with regularly measured surface meteorological parameters. The consequences are important for estimation of daily primary productivity rates in the euphotic zone and the ability to predict algal blooms such as those observed in the present reservoir. 相似文献
782.
P. Bolzern F. Cheli G. Falciola F. Resta 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1999,31(1):23-34
The paper discusses the application to real data of an identification procedure based on an Extended Kalman Filter, for estimating the equivalent non-linear suspension tyre cornering forces of a road vehicle from a single standard manoeuvre. In particular, both the steady-state and the dynamic handling characteristics can be evaluated. 相似文献
783.
Realistic predictions of the likely safety performance of advanced transport systems will need to draw on the knowledge accumulated from a large number of safety evaluations which have already been undertaken for existing transport systems. In particular, safety evaluations of future technologies must avoid the methodological pitfalls experienced in extensively researched areas, such as road safety, if such evaluations are to be meaningful. This paper reviews the use of exposure for a broad range of road safety studies, and concludes that unsatisfactory treatment of exposure is a common failing in past evaluations of the effectiveness of road accident countermeasures. Whilst a broad range of safety analyses is discussed, the use of exposure in site safety studies is emphasized. A follow-up paper will extend the discussion to other aspects of accident exposure including exposure measures for large groups of transport system users. 相似文献
784.
785.
G. Levikov 《Maritime Policy and Management》1988,15(3):247-254
In light of the Reveiw Conference on the UN Code of Conduct for Liner Conferences to be in November 1988, this paper highlights some of the Major problems impinging upon the universal acceptability of the Code. These include the reservation (known as the Brussels Package) by EC and certain other OECD countries that discriminates aganist developing and Socialist countries; reservations of a controversial nature with regard to the establishment of joint shipping lines established on the basis of intergovernmental bilateral agreement; and the question of compctition by non-conference lines that diminishes the share of cargo available to National Lines by virtue of the Code. 相似文献
786.
This paper undertakes a comparative analysis of the stock market perception of risk in US listed water transportation companies and seven other main sectors, air transportation; rail transportation; trucks; electricity; gas; petroleum refining; and real estate over the period July 1984-June 1995. This is done by employing the Capital Asset Pricing Model (CAPM) to model the stock returns of each industry and hence compare their betas (systematic risk). Multiequation Regression Models are used for estimation. The findings suggest that the water transportation industry exhibits significantly lower market risk than the average stock and the rail transportation industry, significantly higher systematic risk than the real estate industry, while its systematic risk is insignificantly different from the rest of the industries. These results are useful to investors basing their decisions on relative market exposures to risk in different industries. 相似文献
787.
G. F. Mazepova 《Journal of Marine Systems》1998,15(1-4)
This describes a study of the pelagic zone of Lake Baikal with particular reference to copepods. In addition the cycling of matter and energy in lacustrine basins is described. 相似文献
788.
Paratransit services bridge the gap between static fixed route transit and the flexible automobile travel. Paratransit services provide personalized public trapsportation by responding to the needs of individual markets and users. Unfortunately, fragmentation of the paratransit sector and institutional and regulatory constraints have prevented or complicated realization of paratransit's full potential. The orientation in this paper is not primarily to identify promising paratransit applications. Rather, it is to examine basic characteristics of paratransit services, fundamental issues unique to paratransit, existing problems that are constraining paratransit development, and ways to overcome or minimize existing difficulties. A taxonomy of paratransit services is proposed so that these systems can be better related to each other. The institutional environment of paratransit is examined from the viewpoints of planning, operations and regulation. A primary focus is on integration of various paratransit services and of paratransit and conventional fixed route services. Several proposals are made relating to improvements in existing services, new service concepts, new institutional arrangements and service integration. 相似文献
789.
An experimental technique for exploring the sensitivity of transportation plan evaluations to forecasting and community value uncertainties is described. Three kinds of uncertainty — goal-achievement impacts, costs, and goal-weights — are included. Within a cost-effectiveness evaluation framework, an on-line capability for interactively and iteratively testing plan comparisons is outlined. A series of user-oriented computer instructions is developed to test plan comparison outcomes according to a wide variety of user-selected changes in impact forecasts, goal weights, and cost forecasts. A sample, hypothetical application of the technique is described. The technique is currently under further development by the San Diego Region Comprehensive Planning Organization. 相似文献
790.