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  • 1
    Call number: ZSP-201-89/10
    In: CRREL Report, 89-10
    Description / Table of Contents: In early fall 1984, a questionnaire was sent to over 325 general aviation airports in cold regions. The results from over 200 responses were compiled and evaluated and over 20 airport managers were contacted for additional details. Site visits were made to 36 airports to obtain additional information. The most common pavement problems identified in the study were associated with non-traffic-related phenomena and include 1) pre-existing cracks reflecting through asphalt concrete overlays (in two years less), 2) thermal cracking, and 3) longitudinal cracking (at a construction joint). Most of the airports experienced 1) water pumping up through cracks and joints in the pavements during spring thaw, or 2) additional roughness due to differential frost heave in the winter, or both problems. Many airport managers reported that debris was generated at cracks during the winter and spring. Many pavement problems can be traced to the evolutionary history of general aviation airports and the lack of consideration for site drainage. Based on the recognition of these problems, several future research programs are identified.
    Type of Medium: Series available for loan
    Pages: v, 147 Seiten , Illustrationen
    Series Statement: CRREL Report 89-10
    Language: English
    Note: CONTENTS Abstract Preface Introduction Statement of the problem Purpose and scope Background - the physical environment and airport pavements Physical environment of study area Comparison of highway and general aviation airport pavements Types of pavements and surface treatments Pavement distress and condition rating Surveys of airport pavement distress Airport pavement performance problems in cold regions Cracking Distortion and pavement faulting Disintegration Inadequate skid resistance Improper maintenance Stripping Statement of research needs Basis for statement of research needs Performance of overlays Recycling/reconstructing airport pavements Drainage of airport pavement structures Eliminating/accommodating differential frost heave Evaluation of adequacy of design procedures Maintenance products and performance Control of transverse cracking Additives for asphalt concrete Performance documentation Wildlife conservation vs aircraft safety Literature cited Appendix A: Questionnaire and listing of airports contacted Appendix B: Summary listing of questionnaire responses Appendix C: Narrative summary of site visits
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  • 2
    Call number: ZSP-201-86/18
    In: CRREL Report, 86-18
    Description / Table of Contents: Findings from a six-year yield and laboratory program of frost action research in four principal areas are summarized. Research on the first topic, frost susceptibility index tests, led to selection of the Corps of Engineers frost design soil classification system as a useful method at the simplest level of testing. At a much more complex level, a new freezing test combined with a CBR test after thawing is recommended as an index of susceptibility to both frost heave and thaw weakening. Under the second topic, a soil column and dual gamma system were developed and applied to obtain soil data used in improving and validating a mathematical model of frost heave, the objective of the third research topic. The model was effectively improved, a probabilistic component was added, and it was successfully tested against field and laboratory measurements of frost heave. A thaw consolidation algorithm was added, which was shown to be useful in predicting the seasonal variation in resilient modulus of granular soils, the objective of the fourth topic. A laboratory testing procedure was developed for assessing the resilient modulus of thawed soil at various stages of the recovery process, as a function of the applied stress and the soil moisture tension, which increases as the soil gradually desaturates during recovery. The procedure was validated by means of appropriate analyses of deflections measured on pavements by a falling-weight deflectometer. Frameworks for implementing findings from the principal research topics are outlined. Keywords: Airfields, Freezing thawing, Frost heave, Frozen soil, Resilient modulus, Roads.
    Type of Medium: Series available for loan
    Pages: v, 52 Seiten , Illustrationen
    Series Statement: CRREL Report 86-18
    Language: English
    Note: Contents Abstract Preface Introduction Field test sites Frost-susceptibility index testing Index tests selected Laboratory test results Conclusions Soil column and dual gamma system Design features Test results Mathematical model of frost heave and thaw settlement Model development Numerical approach Probabilistic concepts Model verification Discussion Seasonal variation in the resilient modulus of granular soils Characterization by laboratory testing Field verification Summary of predictive approach Simulating frost heave and pavement deflection Method of evaluation Results and discussion Summary of findings Frost-susceptibility index tests Soil column and dual gamma system Mathematical model of frost heave and thaw settlement Seasonal variation in resilient modulus of granular soils Implementation of research findings Corps of engineers frost design soil classification system New laboratory freeze-thaw test Frost-heave model Repeated-load triaxial test on frozen and thawed soil Evaluation of seasonal variation of resilient modulus Literature cited
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  • 3
    Call number: ZSP-201-80/10
    In: CRREL Report, 80-10
    Description / Table of Contents: A mathematical model of coupled heat and moisture flow in soils has been developed. The model includes algorithms for phase change of soil moisture and frost heave and permits several types of boundary and initial conditions. The finite element method of weighted residual (Galerkin procedure) was chosen to simulate the spatial regime and the Crank-Nicholson method was used for the time domain portion of the model. To facilitate evaluation of the model, the heat and moisture fluxes were essentially decoupled; moisture flux was then simulated accurately, as were heat flux and frost heave in a laboratory test. Comparison of the simulated and experimental data illustrates the importance of unsaturated hydraulic conductivity. It is one parameter which is difficult to measure and for which only a few laboratory test results are available. Therefore, unsaturated hydraulic conductivities calculated in the computer model may be a significant source of error in calculations of frost heave. The algorithm incorporating effects of surcharge and overburden was inconclusively evaluated. Time-dependent frost penetration and frost heave in laboratory specimens were closely simulated with the model. After 10 days of simulation, the computed frost heave was about 2.3 cm vs 2.0 cm and 2.8 cm in two tests. Frost penetration was computed as 15 cm and was measured at 12.0 cm and 12.2 cm in the two laboratory samples after 10 days.
    Type of Medium: Series available for loan
    Pages: v, 49 Seiten , Illustrationen
    Series Statement: CRREL Report 80-10
    Language: English
    Note: CONTENTS Abstract Preface Introduction One-dimensional equations of simultaneous heat and moisture flux Moisture transport Heat transport Phase change Coupling effects Frost heave algorithm Development of computer model Finite difference vs finite element method Finite element formulation Time domain solution Evaluation of the mathematical model Heat flux Moisture flux Numerical dispersion Frost heave of homogeneous laboratory samples Conclusions Recommended studies to refine the model Literature cited Appendix A. Work plan, staffing and instrumentation requirements for correlating results oflaboratory frost susceptibility tests with field performance Appendix B. Proposed investigation of thaw weakening of subgrade soil and granular unboundbase course Appendix C. Derivation of finite element system matrices
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  • 4
    Call number: ZSP-201-80/19
    In: CRREL Report, 80-19
    Description / Table of Contents: During the period 1975-1978 the Federal Highway Administration sponsored a series of environmental engineering in­vestigations along the Yukon River to Prudhoe Bay Haul Road. In 1976 the Department of Energy joined these in­vestigations with a series of ecological projects which continue to the present. Both agencies research efforts were con­ducted on a cooperative basis with CRREL’s in-house research program. The objectives of the research focused on 1) an evaluation of the performance of the road, 2) an assessment of changes in the environment associated with the road, 3) documentation of flora and vegetation along the 577-km-long transect, 4) methodologies for revegetation and restoration, and 5) an assessment of biological parameters as indicators of environmental integrity. In support of these objectives, specific studies were undertaken that investigated the climate along the road, thaw and subsidence beneath and adjacent to the road, drainage and side slope performance, distribution and properties of road dust, vegetation distribution, vegetation disturbance and recovery, occurrence of weeds and weedy species, erosion and its control, revegetation and restoration, and construction of the fuel gas line. This report presents background, information on the region, detailed results of the road thaw subsidence and dust investigations, and summaries of revegetation, fuel gas line, vegetation distribution, soil, and weed studies.
    Type of Medium: Series available for loan
    Pages: xv, 187 Seiten , Illustrationen
    Series Statement: CRREL Report 80-19
    Language: English
    Note: CONTENTS Abstract Preface Summary Introduction Chapter 1. The road and its environment Introduction General physiography Regional climate Surficial and bedrock geology Permafrost and ground ice General biota Vegetation Floristic survey Vegetation mapping Soils and mapping Chapter 2. Roadbed performance and associated investigations Roadbed investigations Roadbed performance Performance of drainage features Performance of sideslopes Conclusions from road, drainage and sideslope performance studies Fuel gas line construction Chapter 3. Distribution and properties of road dust along the northern portion of the Haul Road Introduction Methods Results of wind direction and velocity measurements Dust load and distribution Particle size analyses of dust Chemical composition properties of dust and related samples Soil cation composition Dust impacts on vegetation Discussion and conclusions Chapter 4. Revegetation and restoration investigations Introduction Revegetation approaches Alyeska erosion control and revegetation program Weeds and weedy plants Performance of revegetation Alyeska willow cutting program CRREL restoration experiments Conclusions Revegetation recommendations General report recommendations Literature cited Appendix A: General environmental guidelines applicable to subarctic and arctic road construction Appendix B: University-based studies along the Yukon River-Prudhoe Bay Haul Road Appendix C: CRREL maps of Haul Road showing locations of all study Sites Appendix D: Additional Haul Road cross-sectional profiles Appendix E: Clay mineralogy of road-related materials Appendix F: List of reports in the Joint State/Federal Fish and Wildlife Ad­visory Team series
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  • 5
    Publication Date: 2017-07-01
    Print ISSN: 1369-8478
    Electronic ISSN: 1873-5517
    Topics: Geography , Psychology
    Published by Elsevier
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  • 6
  • 7
    Publication Date: 2008-04-15
    Description: Warfarin is an effective, commonly prescribed anticoagulant used to treat and prevent thrombotic events. Because of historically high rates of drug-associated adverse events, warfarin remains underprescribed. Further, interindividual variability in therapeutic dose mandates frequent monitoring until target anticoagulation is achieved. Genetic polymorphisms involved in warfarin metabolism and sensitivity have been implicated in variability of dose. Here, we describe a novel variant that influences warfarin requirements. To identify additional genetic variants that contribute to warfarin requirements, screening of DNA variants in additional genes that code for drug-metabolizing enzymes and drug transport proteins was undertaken using the Affymetrix drug-metabolizing enzymes and transporters panel. A DNA variant (rs2108622; V433M) in cytochrome P450 4F2 (CYP4F2) was associated with warfarin dose in 3 independent white cohorts of patients stabilized on warfarin representing diverse geographic regions in the United States and accounted for a difference in warfarin dose of approximately 1 mg/day between CC and TT subjects. Genetic variation of CYP4F2 was associated with a clinically relevant effect on warfarin requirement.
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 8
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