bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Impact of Doppler Lidar Wind Observations on a Single-Level Meteorological Analysis
Authors: Riishøjgaard L. P. , Atlas R. , Emmitt G. D. 
Published: May 2004

AbstractThrough the use of observation operators, modern data assimilation systems have the capability to ingest observations of quantities that are not themselves model variables but are mathematically related to those variables. An example of this is the so-called line-of-sight (LOS) winds that a spaceborne Doppler wind lidar (DWL) instrument would provide. The model or data assimilation system ideally would need information about both components of the horizontal wind vectors, whereas the observations in this case would provide only the projection of the wind vector onto a given direction. The estimated or analyzed value is then calculated essentially as a weighted average of the observation itself and the model-simulated value of the observed quantity. To assess the expected impact of a DWL, it is important to examine the extent to which a meteorological analysis can be constrained by the LOS winds. The answer to this question depends on the fundamental character of the atmospheric flow fields that are analyzed, but, just as important, it also depends on the real and assumed error covariance characteristics of these fields. A single-level wind analysis system designed to explore these issues has been built at the NASA Data Assimilation Office. In this system, simulated wind observations can be evaluated in terms of their impact on the analysis quality under various assumptions about their spatial distribution and error characteristics and about the error covariance of the background fields. The basic design of the system and experimental results obtained with it are presented. The experiments were designed to illustrate how such a system may be used in the instrument concept definition phase.
The Australian Air Quality Forecasting System. Part II: Case Study of a Sydney 7-Day Photochemical Smog Event
Authors: Hess G. D. , Tory K. J. , Cope M. E. , Lee S. , Puri K. , Manins P. C. , Young M. 
Published: May 2004

Abstract
The performance of the Australian Air Quality Forecasting System (AAQFS) is examined by means of a case study of a 7-day photochemical smog event in the Sydney region. This was the worst smog event for the 2000/ 01 oxidant season, and, because of its prolonged nature, it provided the opportunity to demonstrate the ability of AAQFS to forecast situations involving recirculation of precursors and remnant ozone, fumigation, and complex meteorological dynamics. The forecasting system was able to successfully predict high values of ozone, although at times the peak concentrations for the inland stations were underestimated. The dynamics for the Sydney region require a sensitive balance between the synoptic and mesoscale flows. Often high concentrations of ozone were advected inland by the sea breeze. On two occasions the system forecast a synoptic flow that was too strong, which blocked the inland advancement of the sea breeze. The peak ozone forecasts were underpredicted at the inland stations on those occasions. An examination of possible factors causing forecast errors has indicated that the AAQFS is more sensitive to errors in the meteorological conditions, rather than in the emissions or chemical mechanism in the Sydney region.
Quartic moveout coefficient for a dipping azimuthally anisotropic layer
Authors: Pech Andrés , Tsvankin Ilya 
Published: May 2004

Interpretation and inversion of azimuthally varying nonhyperbolic reflection moveout requires accounting for both velocity anisotropy and subsurface structure. Here, our previously derived exact expression for the quartic moveout coefficient A4is applied to P‐wave reflections from a dipping interface overlaid by a medium of orthorhombic symmetry.The weak‐anisotropy approximaton for the coefficient A4in a homogeneous orthorhombic layer is controlled by the anellipticity parameters η(1), η(2), and η(3), which are responsible for time processing of P‐wave data. If the dip plane of the reflector coincides with the vertical symmetry plane [x1, x3], A4on the dip line is proportional to the in‐plane anellipticity parameter η(2)and always changes sign for a dip of 30○. The quartic coefficient on the strike line is a function of all three η–parameters, but for mild dips it is mostly governed by η(1)—the parameter defined in the incidence plane [x2, x3]. Whereas the magnitude of the dip line A4typically becomes small for dips exceeding 45○, the nonhyperbolic moveout on the strike line may remain significant even for subvertical reflectors. The character of the azimuthal variation of A4depends on reflector dip and is quite sensitive to the signs and relative magnitudes of η(1), η(2), and η(3). The analytic results and numerical modeling show that the azimuthal pattern of the quartic coefficient can contain multiple lobes, with one or two azimuths of vanishing A4between the dip and strike directions.The strong influence of the anellipticity parameters on the azimuthally varying coefficient A4suggests that nonhyperbolic moveout recorded in wide‐azimuth surveys can help to constrain the anisotropic velocity field. Since for typical orthorhombic models that describe naturally fractured reservoirs the parameters η(1,2,3)are closely related to the fracture density and infill, the results of azimuthal nonhyperbolic moveout analysis can also be used in reservoir characterization.
Migration velocity analysis in factorized VTI media
Authors: Sarkar Debashish , Tsvankin Ilya 
Published: May 2004

One of the main challenges in anisotropic velocity analysis and imaging is simultaneous estimation of velocity gradients and anisotropic parameters from reflection data. Approximating the subsurface by a factorized VTI (transversely isotropic with a vertical symmetry axis) medium provides a convenient way of building vertically and laterally heterogeneous anisotropic models for prestack depthmigration.The algorithm for P‐wave migration velocity analysis (MVA) introduced here is designed for models composed of factorized VTI layers or blocks with constant vertical and lateral gradients in the vertical velocity VP0. The anisotropic MVA method is implemented as an iterative two‐step procedure that includes prestack depth migration (imaging step) followed by an update of the medium parameters (velocity‐analysis step). The residual moveout of the migrated events, which is minimized during the parameter updates, is described by a nonhyperbolic equation whose coefficients are determined by 2D semblance scanning.For piecewise‐factorized VTI media without significant dips in the overburden, the residual moveout of P‐wave events in image gathers is governed by four effective quantities in each block: (1) the normal‐moveout velocity Vnmoat a certain point within the block, (2) the vertical velocity gradient kz, (3) the combination kx[Formula: see text] of the lateral velocity gradient kxand the anisotropic parameter δ, and (4) the anellipticity parameter η. We show that all four parameters can be estimated from the residual moveout for at least two reflectors within a block sufficiently separated in depth. Inversion for the parameter η also requires using either long‐spread data (with the maximum offset‐to‐depth ratio no less than two) from horizontal interfaces or reflections from dipping interfaces.To find the depth scale of the section and build a model for prestack depth migration using the MVA results, the vertical velocity VP0needs to be specified for at least a single point in each block. When no borehole information about VP0is available, a well‐focused image can often be obtained by assuming that the vertical‐velocity field is continuous across layer boundaries. A synthetic test for a three‐layer model with a syncline structure confirms the accuracy of our MVA algorithm in estimating the interval parameters Vnmo, kz, kx, and η and illustrates the influence of errors in the vertical velocity on the image quality.
Volume Change Measurement of Soil Specimen in Triaxial Test
Authors: Leong EC , Agus SS , Rahardjo H 
Published: May 2004

Abstract
Measuring the volume change of a soil specimen during a test has become a standard routine in laboratory testing. Accurate volume change measurement does not depend solely on the resolution of the measurement devices used but also on other factors such as the measurement method, cell pressure, temperature fluctuations, system creep, and system compliance. This paper examines volume change measurement inferred from the volume of the confining water in a triaxial cell. In particular, the effects of stiffness of the pressure cell and temperature fluctuations on the accuracy of the volume change measurements are investigated. A method to correct for temperature effects on the volume of water in a triaxial pressure cell for providing a more reliable measurement of the volume change of a soil specimen is suggested. The suggested method can also be applied in triaxial apparatuses using double cells.
Determination of the Soil Water Characteristic Curve of Highly Compressible Materials: Case Study of Pulp and Paper By-Product
Authors: Cabral AR , Planchet L , Marinho FA , Lefebvre G 
Published: May 2004

Abstract
A technique was developed for the determination of various points of the soil-water characteristic curve (SWCC)—including the air entry value (AEV)—of compressible materials from one single test. The testing setup, which employs the axis-translation technique, is presented and the testing methodology, explained. With the proposed methodology, it is possible to determine the volume of the sample at various stages of the desaturation process, thus making it possible to determine the degree of saturation and volumetric water content for each level of suction applied. The results of some tests performed on deinking residues (DR), a fibrous and highly compressible industrial by-product used in geoenvironmental works, are presented and discussed. It is shown that if volume changes that samples undergo during desaturation are not considered, the volumetric water content and degree of saturation of the sample is underestimated at all suction values. One important consequence is that lower hydraulic conductivities are obtained from mathematical models based on the SWCC.
Frequency Domain Determination of G Using Bender Elements
Authors: Greening PD , Nash DFT 
Published: May 2004

Abstract
Methods for determination of shear wave velocity (vs) with bender elements using frequency domain techniques are reviewed. An enhanced method is proposed, which is quicker and provides more information than existing techniques. The method can be implemented using a spectrum analyzer—a common piece of hardware.
The validity of the method is demonstrated by means of a series of bench top tests on a reconstituted clay sample. The results are compared both with existing frequency domain practice and with established time-domain techniques.
The results reveal that the system comprising benders elements and soil sample is dispersive. The relationship between velocity and frequency is established in detail for several propagation paths through the sample, allowing some insight to be gained into the factors influencing the dispersion characteristics.
A Physical Model for Sloping Capillary Barriers
Authors: Tami D , Rahardjo H , Leong E-C , Fredlund DG 
Published: May 2004

Abstract
A physical capillary barrier model has been developed to study the mechanism and the effectiveness of a capillary barrier for slope stabilization purposes. A sloping two-layer capillary barrier model consisting of a relatively fine soil layer over a relatively coarse soil layer was constructed inside a specially designed apparatus. Simulated rainfalls of different intensities and durations representative of tropical climatic conditions were applied through a rainfall simulator. Various instruments consisting of tensiometers for pore-water pressure measurement, time domain reflectometry (TDR) for water content measurement, magnetic flow meter and electronic weight balances for water balance measurements were used in the experiment. The results obtained from various types of instrumentation were in good agreement. The experimental results show that the performance of the capillary barrier under the influence of a high precipitation rate is primarily governed by the storage capacity of the relatively fine soil of the capillary barrier.
Transition Toughness Modeling of Steels Since RKR
Authors: Kirk MT , Natishan MAE , Wagenhofer M 
Published: May 2004

AbstractIn this paper we trace the development of transition fracture toughness models from the landmark paper of Ritchie, Knott, and Rice in 1973 up through the current day. While such models have become considerably more sophisticated since 1973, none have achieved the goal of blindly predicting fracture toughness data. In this paper we suggest one possible way to obtain such a predictive model.
The Power of the Denominator: A Proposal for More Comprehensive Modeling of Risk Factors in Ice Hockey Injuries
Authors: Stuart MJ , Smith AM , Larson DR 
Published: May 2004

Abstract
In the sport of ice hockey, the incidence of injury has been investigated at multiple levels of participation based on collective player exposure, which assumes equal playing time among participants. However, playing time varies enormously between individual players on a given team because of variability in the number and length of shifts. Individual player monitoring, although laborintensive, more accurately identifies risk factors for sustaining injuries. Specific player exposure data are necessary for detailed analysis of factors such as style of play, illegal activities, equipment, player size, and officiating. In addition, prospective, uniform and accurate collection of exposure data may permit meaningful comparison of injury rates between levels of participation in ice hockey and also among different sports. Refinement of data collection tools that determine individual player injury exposure will increase the power of the denominator and facilitate prevention of ice hockey injuries.
Modeling Variability in Service Loading Spectra
Authors: Socie DF , Pompetzki MA 
Published: May 2004

Abstract
This paper describes a methodology for statistically extrapolating a single measured service loading history to the expected long-term service usage spectra. The measured time history first is processed into a rainflow counted histogram. Nonparametric kernel smoothing techniques are employed to convert the rainflow histogram of cycles into a probability density histogram. Once the probability density histogram is obtained, Monte Carlo methods are used to produce a rainflow histogram of any desired number of cycles. A new loading history then is reconstructed from the expected rainflow histogram, which can be combined with a probabilistic fatigue analysis to obtain an estimate of the durability of a structure. Obtaining an estimate of the loading spectra for a ground vehicle is difficult because there are many users, each with different service usage. The extrapolating methodology is extended to combine data from several users to obtain loading spectra that represent more severe users in the population.
Effect of Individual Component Life Distribution on Engine Life Prediction
Authors: Zaretsky EV , Hendricks RC , Soditus SM 
Published: May 2004

Abstract
The effect of individual engine component life distributions on engine life prediction was determined. A Weibull-based life and reliability analysis of the NASA Energy Efficient Engine was conducted. The engine's life at a 95 and 99.9 % probability of survival was determined based on the engine manufacturer's original life calculations and assumed values of each of the component's cumulative life distributions as represented by a Weibull slope. The lives of the high-pressure turbine (HPT) disks and blades also were evaluated individually and as a system in a similar manner. Knowing the statistical cumulative distribution of each engine component with reasonable engineering certainty is a condition precedent to predicting the life and reliability of an entire engine. The life of a system at a given reliability will be less than the lowest-lived component in the system at the same reliability (probability of survival). Where Weibull slopes of all the engine components are equal, the Weibull slope had a minimal effect on engine L0.1 life prediction. However, at a probability of survival of 95 % (L5 life), life decreased with increasing Weibull slope.
Wear and Structural Fatigue Simulation of Crosslinked Ultra-High Molecular Weight Polyethylene for Hip and Knee Bearing Applications
Authors: Wang A , Manley M , Serekian P 
Published: May 2004

Abstract
There have been increasing concerns about the structural fatigue resistance of crosslinked UHMWPE devices due to deterioration of certain mechanical properties. However, due to the lack of clear correlation between specific mechanical properties and clinical performance, these concerns remain theoretical. In order to evaluate the potential benefits and risks of various crosslinked polyethylene materials for hip and knee bearing applications, two clinically relevant worst-case scenarios were simulated on functional devices. In the first worst-case scenario, cemented all-poly patellar components were tested under simulated stair-climbing conditions with rotational misalignment. In the second worst-case scenario, metal-backed thin acetabular liners were tested in a hip joint simulator under rim-loading conditions. Various types of crosslinked UHMWPE were prepared according to published process descriptions of commercial materials. While significant levels of volumetric wear reduction were confirmed by both the patellar and hip simulator tests, mixed results were obtained on the structural integrity of the devices. The latter was more significantly affected by the post-irradiation thermal treatment history than by the total dose of irradiation. Re-melting following irradiation led to catastrophic fractures of both rim-loaded liners and rotational-malaligned patellar pegs. The key mechanical property that was positively identified to correlate with the structural fatigue performance of crosslinked polyethylene materials was the ultimate tensile strength, whereas tensile elongation within 250% and 400% range had no effect on structural integrity. However, the results presented in this study should not be misconstrued with respect to the potential clinical performance of irradiation crosslinked and re-melted polyethylene liners with proper designs. In fact, the true outcome of all the crosslinked materials can only be revealed by long-term clinical follow-up.
Parametric Study on Cement Grout and Aggregate Media for Preplaced Aggregate Grouting
Authors: Zhang J , Swaddiwudhipong S , Lee SL 
Published: May 2004

Abstract
Experimental programs were designed carefully and appropriate testing materials were selected for the parametric study on the flow of cement grout through aggregate media during the preplaced aggregate grouting process in concrete construction. Experimental investigations include the testing and evaluation of the viscosity of cement grout, the intrinsic permeability coefficient, and the porosity of the aggregate media. The time dependency and shear history dependency of the rheological properties of the cement grout are incorporated in the viscosity tests so as to be able to simulate more accurately the grouting process. The average shear rate of the flow is estimated from the flow velocity by determining the average nominal radius of the imaginary flow channel from the permeability testing. The resulting parameters include the yield stress and plastic viscosity of the cement grout and their time dependency, intrinsic permeability and porosity of the aggregate media, and the average nominal radius of the imaginary flow channel.
Toughness Characterization of Fiber-Reinforced Concrete: Which Standard to Use?
Authors: Banthia N , Mindess S 
Published: May 2004

Abstract
The major advantage of fiber-reinforced concrete (FRC) over its plain counterpart is in its improved energy absorption capability, or ‘toughness.’ There are currently several standard test methods available to characterize the toughness of fiber-reinforced concrete, but little is known of the relationship between the toughness results they produce for a given fiber-reinforced concrete. An attempt is made here to compare the results produced by three of these techniques: ASTM C 1018, ASTM C 1399, and JSCE SF-4 for the same concrete and to assess the subjectivity encountered in toughness characterization. It was found that there is no firm and reliable correlation between these three procedures; they would rank different FRCs differently. Only a weak correlation exists between the toughness parameters generated by the C 1399 and the SF-4 standards, and the correlation is highly dependent on the fiber type. The ASTM C 1018 procedure is the least reliable of all and produces Toughness Indices and RM,N values that are very difficult to interpret.
Geotechnical Properties of Compressible Materials Used for Induced Trench Construction
Authors: McAffee RP , Valsangkar AJ 
Published: May 2004

Abstract
Results of a testing program to measure the compressibility and shear strength parameters of compressible fill materials commonly used for induced trench construction are presented. The geotechnical properties of sawdust, wood chips, and hay have been determined. A large-scale consolidometer and direct shear testing apparatus were used to perform the tests. To resolve strain compatibility issues, the mobilized friction angle corresponding to an appropriate shear displacement value is reported. The experimental results are compared to geotechnical properties of several other compressible materials reported in the literature that also have been used in induced trench applications. The results presented in this paper can be used to perform numerical modeling of induced trenches where these compressible materials are commonly used.
Inverted duplication of 15q with terminal deletion in a multiple malformed newborn with intrauterine growth failure and lethal phenotype
Authors: Rita Genesio , Daniele De Brasi , Anna Conti , Annamaria Borghese , Pasqua Di Micco , Pasquale Di Costanzo , Dario Paladini , Paola Ungaro , Lucio Nitsch 
Published: May 2004

AbstractWe describe the cytogenetic and molecular characterization of an inverted duplication of chromosome 15q with evidence of a terminal deletion of the same rearranged chromosome. The proband was a multiple congenital malformed female with a prenatal diagnosis of trisomy 15q and an extremely severe clinical course. The phenotype of the patient was characterized by marked intrauterine growth retardation, congenital heart defect, “horseshoe” kidney, hand contractures, and clubfeet. The exitus came at 20 days because of progressive cardio‐respiratory impairment. Overall, the clinical phenotype appeared more severe than usual trisomy 15q syndrome. Postnatal cytogenetic and molecular studies unraveled a “de novo” inverted duplication of 15q (q21.3→q26.3), associated with the deletion of the 15q telomere and part of the band 15q26.3. A single copy region spanning approximately 600 kb between the duplicated segments was present. Correlation between the clinical findings of the patient and the phenotype of trisomy 15q reported in literature is also provided. © 2004 Wiley‐Liss, Inc.