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1.
The paper discusses the geo dimensions of the new world order, with particular emphasis on the increasing role of geoeconomics, and its impact on US national strategy. While the paper uses the US experience to illustrate the growing importance of geoeconomic considerations, the issues raised have direct bearing on many other nations throughout the world.US post Cold War strategy is determined by its three geo challenges. The most important is the geoeconomic challenge caused by the tri-polar division of the world along trading bloc lines, instant global communication and other technologies overcoming the constraints of physical geography, transnational corporations (TNCS) that are becoming supranational in character, and the emergence of a well educated global labor force. The geopolitical challenge is characterized by America's declining relative economic power and its traditional military allies having become economic competitors, while religious, ethnic, and regional tensions threaten its global interests. The third challenge is the military geography issue of effectively projecting power over distance, within the constraints of greatly reduced budgets and loss of overseas bases. 相似文献
2.
Elizabeth J. Botha Brigitte Leblon Bernie Zebarth James Watmough 《International Journal of Applied Earth Observation and Geoinformation》2007,9(4):360-374
Optimizing nitrogen (N) fertilization in crop production by in-season measurements of crop N status may improve fertilizer N use efficiency. Hyperspectral measurements may be used to assess crop N status by estimating leaf chlorophyll content. This study evaluated the ability of the PROSAIL canopy-level reflectance model to predict leaf chlorophyll content. Trials were conducted with two potato cultivars under different N fertility rates (0–300 kg N ha−1). Canopy reflectance, leaf area index (LAI) and leaf chlorophyll and N contents were measured. The PROSAIL model was able to predict leaf chlorophyll content with reasonable accuracy later in the growing season. The low estimation accuracy earlier in the growing season could be due to model sensitivity to non-homogenous canopy architecture and soil background interference before full canopy closure. Canopy chlorophyll content (leaf chlorophyll content × LAI) was predicted less accurately than leaf chlrophyll content due to the low estimation accuracy of LAI for values higher than 4.5. 相似文献
3.
Bernie D. Shizgal 《Planetary and Space Science》2004,52(10):915-922
There are numerous situations in laboratory experiments and in atmospheric science that are characterized by distributions of energetic neutral species with extended high-energy tails. This paper provides a detailed analysis of the relaxation of such isotropic nonequilibrium distributions of neutral species. We consider a minor constituent, referred to as the test-particle dilutely dispersed in a second component that acts as a heat bath at equilibrium. A hard sphere cross section is assumed for the collisions of the test particles and the heat bath particles, and collisions between test particles are not included in the analysis. We study the approach to equilibrium with a finite difference method of solution of the Boltzmann equation. The solution of the Boltzmann equation is also presented as an expansion in the eigenfunctions of the Boltzmann collision operator. The main objective of the paper is the calculation of the energy-dependent relaxation times for the distribution function. It is anticipated that these relaxation times will not exhibit a strong energy dependence owing to the energy-independent hard sphere cross section. This relaxation behaviour is important in the characterization of nonthermal populations of energetic atoms in aeronomy. The results are compared with a similar analysis for Coulomb collisions described in the preceeding paper. 相似文献
4.
D. J. Bernie E. Guilyardi G. Madec J. M. Slingo S. J. Woolnough J. Cole 《Climate Dynamics》2008,31(7-8):909-925
Coupled ocean atmosphere general circulation models (GCM) are typically coupled once every 24 h, excluding the diurnal cycle from the upper ocean. Previous studies attempting to examine the role of the diurnal cycle of the upper ocean and particularly of diurnal SST variability have used models unable to resolve the processes of interest. In part 1 of this study a high vertical resolution ocean GCM configuration with modified physics was developed that could resolve the diurnal cycle in the upper ocean. In this study it is coupled every 3 h to atmospheric GCM to examine the sensitivity of the mean climate simulation and aspects of its variability to the inclusion of diurnal ocean-atmosphere coupling. The inclusion of the diurnal cycle leads to a tropics wide increase in mean sea surface temperature (SST), with the strongest signal being across the equatorial Pacific where the warming increases from 0.2°C in the central and western Pacific to over 0.3°C in the eastern equatorial Pacific. Much of this warming is shown to be a direct consequence of the rectification of daily mean SST by the diurnal variability of SST. The warming of the equatorial Pacific leads to a redistribution of precipitation from the Inter tropical convergence zone (ITCZ) toward the equator. In the western Pacific there is an increase in precipitation between Papa new guinea and 170°E of up to 1.2 mm/day, improving the simulation compared to climatology. Pacific sub tropical cells are increased in strength by about 10%, in line with results of part 1 of this study, due to the modification of the exchange of momentum between the equatorially divergent Ekman currents and the geostropic convergence at depth, effectively increasing the dynamical response of the tropical Pacific to zonal wind stresses. During the spring relaxation of the Pacific trade winds, a large diurnal cycle of SST increases the seasonal warming of the equatorial Pacific. When the trade winds then re-intensify, the increase in the dynamical response of the ocean leads to a stronger equatorial upwelling. These two processes both lead to stronger seasonal basin scale feedbacks in the coupled system, increasing the strength of the seasonal cycle of the tropical Pacific sector by around 10%. This means that the diurnal cycle in the upper ocean plays a part in the coupled feedbacks between ocean and atmosphere that maintain the basic state and the timing of the seasonal cycle of SST and trade winds in the tropical Pacific. The Madden–Julian Oscillation (MJO) is examined by use of a large scale MJO index, lag correlations and composites of events. The inclusion of the diurnal cycle leads to a reduction in overall MJO activity. Precipitation composites show that the MJO is stronger and more coherent when the diurnal cycle of coupling is resolved, with the propagation and different phases being far more distinct both locally and to larger lead times across the tropical Indo-Pacific. Part one of this study showed that that diurnal variability of SST is modulated by the MJO and therefore increases the intraseasonal SST response to the different phases of the MJO. Precipitation-based composites of SST variability confirm this increase in the coupled simulations. It is argued that including this has increased the thermodynamical coupling of the ocean and atmosphere on the timescale of the MJO (20–100 days), accounting for the improvement in the MJO strength and coherency seen in composites of precipitation and SST. These results show that the diurnal cycle of ocean–atmosphere interaction has profound impact on a range of up-scale variability in the tropical climate and as such, it is an important feature of the modelled climate system which is currently either neglected or poorly resolved in state of the art coupled models. 相似文献
5.
James W. Beletic Sean Adkins Barry Burke Robert Reich Bernie Kosicki Vyshnavi Suntharalingham Charlie Bleau Ray DuVarney Richard Stover Jerry Nelson Francois Rigaut 《Experimental Astronomy》2005,19(1-3):103-109
All of the extremely large telescopes (ELTs) will utilize sodium laser guide star (LGS) adaptive optics (AO) systems. Most of these telescopes plan to use the Shack-Hartmann approach for wavefront sensing. In these AO systems, the laser spots in subapertures at the edge of the pupil will suffer from spot elongation due to the 10 km extent of the sodium layer and the large separation from the projection laser. This spot elongation will severely degrade the performance of standard geometry wavefront sensing systems. In this paper, we present a CCD with custom pixel morphology that aligns the pixels of each subaperture with the radial extension of the LGS spot. This CCD design will give better performance than a standard geometry CCDs for continuous wave lasers. In addition, this CCD design is optimal for a pulsed sodium laser. The pixel geometry enables each subaperture to follow a laser pulse traversing the sodium layer, providing optimal sampling of a limited number of detected photons. In addition to novel pixel layout, this CCD will also incorporate experimental JFET sense amplifiers and use CMOS design approaches to simplify the routing of biases, clocks and video output. This CCD will attain photon-noise limited performance at high frame rates, and is being incorporated in the plans for the Thirty Meter Telescope (TMT). 相似文献
6.
Bernie D. Shizgal 《Planetary and Space Science》2004,52(10):923-933
Nonequilibrium distributions of space plasmas are often characterized by extended high-energy tails. This paper provides a detailed analysis of the relaxation of such isotropic nonequilibrium plasmas. We consider an energetic charged species dilutely dispersed in a fully ionized plasma, which acts as a heat bath at equilibrium. The minor constituent is referred to as a “test particle” and collisions between test particles are not included. We study the approach to equilibrium with a finite difference method of solution of the Fokker-Planck equation appropriate for collisions between charged particles. The solution of the Fokker-Planck equation is also presented formally as an expansion in the eigenfunctions of the Fokker-Planck operator. The main objective of the paper is the calculation of the energy-dependent relaxation times of the distribution function. A strong energy dependence for these relaxation times is anticipated since, for Coulomb collisions, the Rutherford cross-section varies with relative speed g as g−4. Analogous results for neutral species are presented for comparison in the following paper. 相似文献
7.
B. E. Burke J. A. Gregory R.W. Mountain B. B. Kosicki E. D. Savoye P. J. Daniels V. S. Dolat T. L. Lind A. H. Loomis D. J. Young G. A. Luppino J. L. Tonry 《Experimental Astronomy》1998,8(1):31-40
We describe recent work in the area of large, back-illuminated CCD imagers at M.I.T. Lincoln Laboratory as well as new technology applicable to astronomy. We completed in 1995 the development of a 2560 x 1960-pixel frame-transfer imager that filled a 100-mm wafer and several back-illuminated versions of this device were completed. More recently we have begun the development, in collaboration with the U. of Hawaii, of a three-side abuttable 2k x 4k CCD for a multi-chip focal plane. In the unused chord area of the wafer layout, we added test imagers as development vehicles for blooming control and for the demonstration of a CCD that is capable of charge transfer in all four directions. We expect the latter to find application as an electronic means of performing tip-tilt correction to compensate for atmospheric turbulence. 相似文献
8.
Kristina A. Brown Eric R. McGreer Bernie Taekema Jay T. Cullen 《Aquatic Geochemistry》2011,17(6):821-839
A field and laboratory study of the accuracy of a method commonly used to determine free sulphide concentrations in the porewater
of marine sediments is presented. The method uses an ion-selective electrode (ISE), sensitive to the sulphide ion (S2−), in sediments buffered to high pH (>12) and is commonly used in regulatory monitoring programs to assess the impacts of
open net-pen finfish aquaculture on local marine habitats. Here we report that on the timescale of field measurements, the
accepted protocol can lead to significant bias of free sulphide measurements, with orders of magnitude higher concentration
detected in the buffered sediment–porewater slurry than in porewater samples isolated and analysed separately. Laboratory
experiments with model marine sediments and analysis of sediment composition indicate that this bias is likely introduced
by the dissolution of particulate sulphides and/or sulphur present in the sediments under the intense alkaline conditions
of the protocol. Recommendations for the modification and continued use of this commonly applied field methodology are discussed. 相似文献
9.
Land-use change in urbanizing areas can significantly alter the hydrology of a watershed and can have serious impacts on wetland water balances, downstream flooding, and groundwater recharge. Most currently available models used in determining the hydrologic impacts of urbanization are not well suited to long-term hydrologic analysis or are too complex and data intensive for widespread practical application. The Long-Term Hydrologic Impact Assessment (LTHIA) model run on a Geographic Information System (GIS) is a relatively simple, user-friendly model that uses the Curve Number method to estimate changes in surface runoff between different stages of development. Application of the model to a large, rapidly urbanizing watershed near Indianapolis, Indiana, suggests that average annual runoff depths increased by more than 60% from 1973 to 1991, with even greater increases for some individual sub-basins. These results are consistent with runoff changes estimated from historical stream flow data in the watershed. A sensitivity analysis to determine minimum data requirements shows that a precipitation record length of 15 years or more is required to produce consistent results with LTHIA and that the highest possible resolution land-use and soils data should be used. The LTHIA model is now available on the Internet at http://www.ecn.purdue.edu/runoff. [Key words: hydrology, urbanization, modeling, GIS.] 相似文献
10.
Denis A Wiesenburg James M Brooks Bernie B Bernard 《Geochimica et cosmochimica acta》1985,49(10):2069-2080
The composition of light hydrocarbon gases in the Orca Basin, an anoxic, hypersaline intraslope depression on the continental slope of the northern Gulf of Mexico, indicates that both methane and ethane are biogenic in nature with a ratio of 730 and a δ13C of methane of ?73%. relative to the PDB standard. The concentrations of methane (750 mM) and ethane (1300 mM) in the Orca Basin brine are higher than any other marine anoxic basin. These high levels result not from high rates of productivity, but from the long residence time of the brine in the basin, due to its high stability toward mixing with overlying seawater (). Both methane and ethane show well mixed distributions in the brine. These distributions probably result from convective mixing of the isohaline brine pool due to normal heat flow from the basin sediments. Methane and ethane maxima above the pycnocline at the brine/seawater interface reflect in situ production and/or consumption in the aerobic water column. Concurrent maxima in suspended particulate material distributions in this region suggest methane may be produced there in anaerobic microenvironments associated with the suspended matter. Reduced rates of anaerobic decomposition (including sulfate reduction) in the brine sediments are inferred from preserved Sargassum fronds in the sediments, vertical sulfate profiles in most cores, and the sediment organic carbon content which is two to three times higher in sediments below the high salinity brine than in the normal Gulf sediments nearby. 相似文献