Discovery of co2 ice and leading-trailing spectral asymmetry on the uranian satellite ariel

New 0.8- to 2.4-μm spectral observations of the leading and trailing hemispheres of the uranian satellite Ariel were obtained at IRTF/SpeX during 2002 July 16 and 17 UT. The new spectra reveal contrasts between Ariel’s leading and trailing hemispheres, with the leading hemisphere presenting deeper H₂O ice absorption bands. The observed dichotomy is comparable to leading-trailing spectral asymmetries observed among jovian and saturnian icy satellites. More remarkably, the trailing hemisphere spectrum exhibits three narrow CO₂ ice absorption bands near 2 μm. This discovery of CO₂ ice on one hemisphere of Ariel is its first reported detection in the uranian system.     

PIV measurements of hull wake behind a container ship model with varying loading condition

Flow characteristics of the hull wake behind a container ship model were investigated under different loading conditions (design and ballast loadings) by employing the particle image velocimetry (PIV) technique. Measurements were made at four transverse locations and two longitudinal planes for three Reynolds numbers (Re) (=U₀Lpp/ν, where U₀ is the freestream velocity, Lpp is the length between two perpendiculars of the ship model and ν is the kinematic viscosity) of 5.08×10⁵, 7.60×10⁵, and 1.01×10⁶. It was observed that symmetric, large-scale, longitudinal counter-rotating vortices (with respect to centerline) of nearly the same strength were formed in the near wake. For the ballast-loading condition, the vortices appear at propeller plane below the propeller-boss. The vortex center exhibits a significant upward shift near the propeller-boss as the Reynolds number increase, and as the flow moves downstream. Under the design-loading condition, the vortices first appear at a further downstream location than that for the ballast-loading condition above the propeller-boss. This difference in the flow structure can significantly change the inflow conditions to the propeller blades, such as the streamwise mean velocity profiles and turbulence intensity distributions at the propeller plane. In particular, under the ballast-loading condition, asymmetric inflow may weaken the propulsion and cavitation performance of the marine propeller.     

Design of an integrated shallow water wave experiment

The experimental design and instrumentation for an integrated shallow-water surface gravity wave experiment is discussed. The experiment required the measurement of the water surface elevation, meteorological parameters, and directional spectra at a number of locations on a shallow lake. In addition, to acquire data under a wide range of conditions, an experimental period of three years was required. A system of telephone and radio modem links were installed to enable real-time monitoring of instrument performance at eight separate measurement locations on the lake. This system also enabled logging sessions to be optimized to ensure the maximum possible data return from this extended experiment     

Potential conflict in the South China sea and environs

There are many territorial disputes in Asia — both on continental Asia and in the surrounding seas. These disputes are often extensions of wider ethnic, historical and ideological rivalries. A relatively new development in disputes over island territories and EEZ boundaries is the economic dimension that has been added to old disputes and rivalries: the disputing nations, aware of the benefits that offshore oil and minerals, as well as fishing, can provide to their economies, have a clear financial incentive to pursue their claims as strongly as they dare. National pride and wider political and ideological conflicts with their rival claimants further reduce the prospects for compromise. Tensions are increased by the possibility that a military conflict in pursuit of a claim could lead to escalation, drawing the USA and the USSR into the dispute. This article outlines some of the major tension points in the area of the South China Sea.     

Indicator kriging for unit vectors: Rock joint orientations

Indicator kriging (IK) is extended to analyze three-dimensional random unit vectors and evaluate the local probability distribution of rock joint orientations in geological formations. The pole vector representing joint orientations is regionalized and projected on a plane normal to the mean attitude of the joint family and centered at the mean. A two-dimensional cutoff system is developed to define the indicator variable, and corresponding indicator variograms and indicator kriging. The cutoff system defines probability regions similar to those of a bivariate distribution, concentric rings sliced into radial sectors. A case study made on an open pit mine proved positively the efficiency of IK and encourages its applications to localized probabilistic structural modeling for geotechnical or geohydrological analysis and oil and gas reservoir analysis.     

Observing and Calibration Strategies for FIR Imaging with SIRTF

We present data from a 16×32 array of unstressed Ge:Gadetectors, showing the long time constant responses and hook effectcharacteristic of these devices. This array is half the size of the70 m imaging array planned for MIPS, the Multiband ImagingPhotometer for SIRTF. We present simulations of the FIR (farinfrared) sky as viewed by a MIPS array, including realistic noiseeffects and extraction of point sources with a standard photometrypackage, showing that the photometric goals of MIPS are attainablewith the current array performance and using standard analysistechniques. Previous calculations by Heim et al. (1998) haddetermined that MIPS would achieve 5- detections of 1 mJy at 70 m in 2000 s; the simulations presented hereobtain results consistent with those calculations.