An Objective Analysis Technique for Constructing Three-Dimensional Urban-Scale Wind Fields

An objective analysis procedure for generating mass-consistent, urban-scale three-dimensional wind fields is presented together with a comparison against existing techniques. The algorithm employs terrain following coordinates and variable vertical grid spacing. Initial estimates of the velocity field are developed by interpolating surface and upper level wind measurements. A local terrain adjustment technique, involving solution of the Poisson equation, is used to establish the horizontal components of the surface field. Vertical velocities are developed from successive solutions of the continuity equation followed by an iterative procedure which reduces anomalous divergence in the complete field. Major advantages of the procedure are that it is computationally efficient and allows boundary values to adjust in response to changes in the interior flow. The method has been successfully tested using field measurements and problems with known analytic solutions

Clinical and Radiographic Assessment of Lumbar Spine Total Disc Replacement in Athletes with Two Year Follow Up

The purpose of the study was to evaluate the consequences of athletic activity on the clinical and radiographic outcomes of lumbar spine total disc replacement (TDR) patients. The data for this study is drawn secondarily from a prospective randomized study evaluating the Prodisc prosthesis at Yale New Haven Hospital. Athletic activities prior to the onset of spinal injury, after the onset of spinal injury, and post lumbar spine total disc replacement (TDR) surgery were assessed. Athletic activity was classified into three groups. These were contact/vigorous, moderate, and light, based on effect on the involved spinal segments. Outcomes were assessed both clinically and radiographically. Out of 195 patients enrolled in the Prodisc study at Yale, 82 qualified for inclusion and fulfilled all follow-up criteria. In these 82 patients 120 disc replacements were performed. The average reduction from pre-operative visual analog pain scale was 44 (std dev 30.1) at a minimum of 2 years follow up. The average reduction in Oswestry disability index was 38% (std dev 23). 74/82 patients returned to athletic activity following TDR. 19 (23%) patients returned to pre-injury athletic activity levels, 47 (57%) returned to athletic activity but not to pre-injury levels, 14 (17%) patients reported activity levels that were unchanged since surgery, and 2 (3%) had activity levels become more impaired since surgery. Of those that returned to athletic activity, 4/74 complained of radiculopathy symptoms during athletic participation. Overall, 14 of 82 patients reported persistent back pain and 8 of these patients reported radiculopathy symptoms. Segmental flexion and extension at the levels of the implant, and the levels adjacent, revealed that the goal of physiologic motion was not reached at either the level of the implant, nor at the superior or inferior adjacent segments. Three L5/S1 subluxations occurred in heavy weight lifters and were the only radiographic complications. Athletic activities of varying degrees appear to be well-tolerated following lumbar TDR surgery in single and multi-level cases. Contact-vigorous athletic activities do not appear to result in high levels of clinical or radiographic complications in the lumbar TDR patients except for heavy weight lifting activities in patients who have undergone L5/S1 Prodisc surgery in which we experienced 3 implant subluxations. Further biomechanical and clinical studies are necessary before general recommendations can be made

Use of models to establish source-receptor relationships and estimate relative source contributions of NO_x to air quality problems

A basic objective of the Technical Symposium on the Implications of a Low NO_x Vehicle Emission Standard is to examine the need for and technical feasibility of a low NO_x emission standard for future light-duty motor vehicles. A major component of this assessment is to estimate the changes in air quality that would result from the imposition of a low NO_x vehicle emission standard. Such an assessment requires a method for relating emission to air quality changes, i.e. a so-called air quality model. In this summary, we focus on those air quality models that may be used to estimate the impact of changes in the NO_x emission levels from motor vehicles

Identification of Remaining Oil Resource Potential in the Frio Fluvial/Deltaic Sandstone Play, South Texas

The Frio Fluvial/Deltaic Sandstone (Vicksburg Fault Zone) oil play of South Texas has produced nearly 1 billion stock tank barrels (BSTB) of oil, yet still contains about 1.2 BSTB of unrecovered mobile oil and an even greater amount of residual oil resources (1.5 BSTB). More than half of the reservoirs in this depositionally complex play have been abandoned, and large volumes of oil may remain unproduced unless advanced characterization techniques are applied to define incompletely drained and untapped reservoirs as suitable targets for near-term recovery. Interwell-scale geological facies models of Frio fluvial/deltaic reservoirs will be combined with engineering assessments and geophysical evaluations to characterize Frio fluvial/deltaic reservoir architecture, flow unit boundaries, and the controls that these characteristics exert on the location and volume of unrecovered mobile and residual oil. These results will lead directly to the identification of specific opportunities to exploit these heterogeneous reservoirs for incremental recovery by recompletion and strategic infill drilling. Reservoir attribute data were statistically analyzed from oil and gas fields throughout the geographic area covered by the Frio Fluvial/Deltaic Sandstone oil play. General reservoir attributes analyzed in detail included porosity, initial water saturation, residual oil saturation, net pay, reservoir area, and fluid characteristics. Statistical analysis of variance demonstrated no difference between oil reservoir attributes and gas reservoir attributes, indicating that oil and gas reservoirs are subsets of a larger genetically similar population. Probability functions that describe attribute frequency distributions were determined for use in risk-adjusting resource calculations. Different functions were found to be most applicable for the various petrophysical reservoir attributes.Bureau of Economic Geolog

Cavity optoelectromechanical regenerative amplification

Cavity optoelectromechanical regenerative amplification is demonstrated. An optical cavity enhances mechanical transduction, allowing sensitive measurement even for heavy oscillators. A 27.3 MHz mechanical mode of a microtoroid was linewidth narrowed to 6.6\pm1.4 mHz, 30 times smaller than previously achieved with radiation pressure driving in such a system. These results may have applications in areas such as ultrasensitive optomechanical mass spectroscopy

Convective Downmixing of Plumes in a Coastal Environment

This paper describes the results of an atmospheric tracer study in which sulfur hexafluoride (SF_6) was used to investigate the transport and dispersion of effluent from a power plant located in a coastal environment. The field study demonstrated that material emitted into an elevated stable layer at night can be transported out over the ocean, fumigated to the surface, and then he returned at ground level by the sea breeze on the next day. At night when cool stable air from the land encounters the warmer ocean convective mixing erodes the stable layer forming an internal boundary layer. When the growing boundary layer encounters an elevated plume the pollutant material, entrained at the top of the mixed layer, can be rapidly transported in ∼20 min to the surface. Various expressions for the characteristic downmixing time (λ = Z_i/w_*) are developed utilizing the gradient Richardson number, the Monin-Obukhov length and turbulence intensifies. Calculations using these expressions and the field data are compared with similar studies of convective mixing over the land

Validity and Accuracy of Atmospheric Air Quality Models

Effective evaluation of air pollution control strategies requires the use of validated and reliable mathematical models that can relate pollutant emissions to atmospheric air quality. The derivation and use of such models, at least for inert and linearly decaying pollutants such as CO and SO_2, has received a great deal of attention. Much less work has been devoted to assessing how the model predictions are related to actual atmospheric concentrations. The objectives of this paper are to formulate the concepts of validity and accuracy and to suggest and describe some experiments that can be performed to assess these features