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1

Evaluation Model for Pavement Surface Distress on 3d Point Clouds from Mobile Mapping System  

Science.gov (United States)

This paper proposes a methodology to evaluate the pavement surface distress for maintenance planning of road pavement using 3D point clouds from Mobile Mapping System (MMS). The issue on maintenance planning of road pavement requires scheduled rehabilitation activities for damaged pavement sections to keep high level of services. The importance of this performance-based infrastructure asset management on actual inspection data is globally recognized. Inspection methodology of road pavement surface, a semi-automatic measurement system utilizing inspection vehicles for measuring surface deterioration indexes, such as cracking, rutting and IRI, have already been introduced and capable of continuously archiving the pavement performance data. However, any scheduled inspection using automatic measurement vehicle needs much cost according to the instruments' specification or inspection interval. Therefore, implementation of road maintenance work, especially for the local government, is difficult considering costeffectiveness. Based on this background, in this research, the methodologies for a simplified evaluation for pavement surface and assessment of damaged pavement section are proposed using 3D point clouds data to build urban 3D modelling. The simplified evaluation results of road surface were able to provide useful information for road administrator to find out the pavement section for a detailed examination and for an immediate repair work. In particular, the regularity of enumeration of 3D point clouds was evaluated using Chow-test and F-test model by extracting the section where the structural change of a coordinate value was remarkably achieved. Finally, the validity of the current methodology was investigated by conducting a case study dealing with the actual inspection data of the local roads.

Aoki, K.; Yamamoto, K.; Shimamura, H.

2012-07-01

2

Pavement distress detection and severity analysis  

Science.gov (United States)

Automatic recognition of road distresses has been an important research area since it reduces economic loses before cracks and potholes become too severe. Existing systems for automated pavement defect detection commonly require special devices such as lights, lasers, etc, which dramatically increase the cost and limit the system to certain applications. Therefore, in this paper, a low cost automatic pavement distress evaluation approach is proposed. This method can provide real-time pavement distress detection as well as evaluation results based on the color images captured from a camera installed on a survey vehicle. The entire process consists of two main parts: pavement surface extraction followed by pavement distress detection and classification. In the first part, a novel color segmentation method based on a feed forward neural network is applied to separate the road surface from the background. In the second part, a thresholding technique based on probabilistic relaxation is utilized to separate distresses from the road surface. Then, by inputting the geometrical parameters obtained from the detected distresses into a neural network based pavement distress classifier, the defects can be classified into different types. Simulation results are given to show that the proposed method is both effective and reliable on a variety of pavement images.

Salari, E.; Bao, G.

2011-03-01

3

Digital image processing as a tool for pavement distress evaluation  

Science.gov (United States)

The information obtained through accurate condition assessment of pavement surface distress data is needed as an essential input to any decision making process concerning pavement management policy. At the same time technological advances in automated inspection systems provide the opportunity to automate the collection and evaluation of the pavement surface condition. In this paper a method developed jointly by the Laboratories of Highway Engineering and Photogrammetry of the National Technical University of Athens is described and proposed. The method involves digital image processing techniques to provide suitable digital imagery as input to specialised software developed especially for this project. This software determines objectively and fully automatically the type, the extent and the severity of surface crackings for flexible road pavements. The proposed method presenten substantial agreement, when compared with systematic visual ratings of existing pavement crackings carried out according to the internationally accepted requirements for airfield and road pavement of the Federal Aviation Administration (FAA).

Georgopoulos, A.; Loizos, A.; Flouda, A.

4

A Novel Pavement Distress Image Filtering Algorithm  

Directory of Open Access Journals (Sweden)

Full Text Available Combined the Nonsubsampled Contourlet Transform (NSCT with compressed sensing de-noising theory, this study proposed a compressed sensing image filtering algorithm in the NSCT transform domain. This algorithm adopted the transform domain filtering method. Firstly, the NSCT was used to do multi-scale and multi-directional transform on the input noisy pavement distress Image which was mapped to the transform domain. Then the compressed sensing theory was used to filter the high-frequency sub-band coefficients. The experiment results show that this algorithm improves the effectiveness and timeliness of the pavement distress image filtering.

Feng Xin

2013-01-01

5

LDPE and CRMB Utilization in Bituminous Concrete Pavement Surfaces  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The road traffic and the traffic intensity are also increasing. Thus the load bearing capacities of the road is to be increased. There are two types of roads - flexible pavements (bitumen roads) and rigid pavements (concrete roads). Flexible pavements (bitumen roads) comprise of the major portion of all surfaced roads. In India, bituminous surfaced flexible pavements comprise of majority of the roads. Distress symptoms, such as cracking, rutting, etc., are being increasingly caused earlier by...

Payal Bakshi

2013-01-01

6

Pavement thickness, surface evenness and construction practice  

Science.gov (United States)

The structural performance and the riding quality of a road are strongly influenced by the accurate and uniform laying of the pavement materials to the appropriate design thickness. The effectiveness of level control procedures used in road construction to achieve the required thicknesses and surface regularity is investigated. Surface profile and of thickness of pavement were measured during construction on 38 randomly selected 100-meter lengths from two flexible and three rigid roads. Measurements analysis showed that the mean layer thicknesses were generally at or near the required thickness but that layer thickness varied considerably along the test lengths, particularly for the concrete pavements. On flexible roads, the results showed that the profiles of the lower layers influenced the evenness of the finished surface. On rigid construction the evenness of the finished surfaces was independent of the profile of the subbase.

McLellan, J. C.

1982-01-01

7

Performance of recycled asphalt concrete airport pavement surfaces  

Science.gov (United States)

The objective of this research was to make an assessment of the relative performance of recycled versus new asphalt concrete pavement surfaces constructed for airport facilities. To make this assessment, pavement condition index (PCI) surveys and tests on core samples from the hot-mix recycled pavements located on the airports at Needles, California, and Valley City, North Dakota were conducted. Both pavements have a condition rating of very good. The survey and test data were compared with those for recycled highway and virgin material Navy airfield pavements. The recycle pavement at Needles is performing as good as those Navy pavements constructed with virgin material. The recycled pavement at Valley City has a higher deterioration rate than the Navy pavements but this could be attributed to the harsh climate found in North Dakota. The results of this study show that hot-mix recycling was successful at these airports but additional studies are required to determine the applicability of Asphalt Concrete (AC) recycling for reconstruction at all airports.

Cline, G. D.; Hironaka, M. C.

1986-10-01

8

Thin, applied surfacing for improving skid resistance of concrete pavements  

Science.gov (United States)

The use of select aggregate in a thin wearing surface of portland cement mortar to prolone or restore a concrete pavement's ability to develop high friction was accomplished. Two fine aggregates, blast furnace slag and lightweight expanded shale were found to exhibit skid resistance greater than the other aggregates evaluated. The British polishing wheel was used in the laboratory evaluation of aggregate to simulate wear. The need for a method of restoring friction to a worn, but otherwise sound concrete pavement led to a field evaluation of several different techniques for placing a very thin overlay. The successful method was a broomed, very thin layer of mortar, 3 mm thick.

Scholer, C. F.

1980-12-01

9

Propagation Mechanisms for Surface Initiated Crackingin Composite Pavements  

Directory of Open Access Journals (Sweden)

Full Text Available The primary objective of this study was to identify the mechanisms for the development and propagation of longitudinal cracks that initiate at the surface of composite pavement. In this study the finite element program ANSYS version (5.4 was used and the model worked out using this program has the ability to analyze a composite pavement structure of different layer properties. Also, the aim of this study was modeling and analyzing of the composite pavement structure with the physical presence of crack induced in concrete underlying layer. The results obtained indicates that increasing the thickness of the asphalt layer tends to decrease the stress intensity factor, which may be attributed to the rapidly decrease of horizontal tensile stress in the asphalt layer. The cracks initiate at the surface due to high vertical stress and shear stress from wheel loads tends to propagate downward due tensile stress generated at the bottom of the asphalt layer or near crack tip, and the whole process occur at the same location of the existing cracks in underlying concrete layer rather than travel up from existing crack. As the load position varies from the crack zone, this result in tensile stresses or tension at the crack tip, leading to increase the stress intensity factor and intern result in crack propagation further into the depth of the pavement.

Duraid Ali Al Khafagy

2009-01-01

10

Development and evaluation of the model for the surface pavement temperature prediction  

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Full Text Available This paper examines the existing models for predicting pavement temperatures and formulates a new one using a regression equation to predict the minimum and maximum pavement surface temperatures depending on the air temperature. Also, the paper presents a model for pavement temperature prediction according to the Superpave methodology and conducts the validation of the model for measured temperatures.

B. Mati?

2012-07-01

11

Evaluation of the Cost-Effectiveness of Pavement Surface Maintenance Activities  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study covers pavement surface maintenance on three surface types: rigid, flexible and composite (asphalt overlay on rigid pavement). It addresses 3 main issues as follows: 1) Do routine maintenance activities make a difference in terms of pavement serviceability? If yes, how much? 2) Are chip and sand seal coating cost-effective? What is their optimal timing? 3) What management criteria should be used as a guide to make seal coating decisions on specific roadways? In resolving Issue #1, ...

Mouaket, Ibrahim Moussa; Al-mansour, Abdullah; Sinha, Kumares C.

1990-01-01

12

Pavement Aging Model by Response Surface Modeling  

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Full Text Available In this work, surface course aging was modeled by Response Surface Methodology (RSM. The Marshall specimens were placed in a conventional oven for time and temperature conditions established on the basis of the environment factors of the region where the surface course is constructed by AC-20 from the Ing. Antonio M. Amor refinery. Volatilized material (VM, load resistance increment (?L and flow resistance increment (?F models were developed by the RSM. Cylindrical specimens with real aging were extracted from the surface course pilot to evaluate the error of the models. The VM model was adequate, in contrast (?L and (?F models were almost adequate with an error of 20 %, that was associated with the other environmental factors, which were not considered at the beginning of the research.

Manzano-Ramírez A.

2011-10-01

13

Statistical analysis of acoustic measurements for assessing pavement surface condition  

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This work presents a method for assessing pavement surface condition using measurements from a microphone mounted underneath a moving vehicle. Such measurements will include tire-generated sound, which carries much information about the road condition, as well as noise generated by the wind and vehicle. The proposed method uses Principal Component Analysis (PCA) to extract the tire-generated sound from the noisy measurements. The analysis begins with acoustic pressure measurements made over constant and known road conditions. Fourier transforms are taken over various time windows and a PCA is performed over the resulting vectors, yielding to a set of principal component vectors for that road condition. Each road condition is characterized by a set of principal component vectors. These vector sets are used to analyze measurements from a road with unknown road conditions by finding the vector set that best represents the acoustic measurements from that road. Successful applications of this method are demonstrated by accurate estimations of the mean texture depth (MTD) of pavement directly from acoustic measurements.

Zhang, Yiying; Ma, Xin; McDaniel, J. Gregory; Wang, Ming L.

2012-04-01

14

Application of a three-surface kinematic hardening model to the repeated loading of thinly surfaced pavements  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Little effort has been made to apply the Critical State Soil Mechanics concept to the prediction of pavement response. The aim of this research is to apply soil mechanics principles, particularly the kinematic hardening concept, to the prediction of the response of lightly trafficked pavements to repeated loading. For this purpose, the finite element critical state program CRISP is used. A comparison is made between the predictions given by the three-surface kinematic hardening (3-SKH) mo...

Hau, Kah Wai

2003-01-01

15

Indirect diagnosis of pavement structural damages using surface GPR reflection techniques  

Science.gov (United States)

The safety and operability of road networks is, in part, dependent on the quality of the pavement. It is known that pavements suffer from many different structural problems which can lead to damage to the pavement surface. To minimize the effect of these problems programmed policies for pavement management are required. Additionally a given local anomaly on the road surface can affect the safety of the road to various degrees according to the category of the road, so it is possible to set up different programmes of repair according to the different standards of road. Programmed policies for pavement management are required because of the wide structural damage which occurs to pavements during their normal operating life. This has consequences for the safety and operability of road networks. During the last decade, road networks suffered from great structural damage. The damage occurs for different reasons, such as the increasing traffic or the lack of means for routine maintenance. Many forms of damage, originating in the bottom layers are invisible until the pavement cracks. They depend on the infiltration of water and the presence of cohesive soil greatly reduces the bearing capacity of the sub-asphalt layers and underlying soils. On the basis of an in-depth literature review, an experimental survey with Ground Penetrating Radar (GPR) was carried out to calibrate the geophysical parameters and to validate the reliability of an indirect diagnostic method of pavement damage. The experiments were set on a pavement under which water was injected over a period of several hours. GPR travel time data were used to estimate the dielectric constant and the water content in the unbound aggregate layer, the variations in water content with time and particular areas where rate of infiltration decreases. A new methodology has been proposed to extract the hydraulic permittivity fields in sub-asphalt structural layers and soils from the moisture maps observed with GPR. It is effective at diagnosing the presence of clay or cohesive soil that compromises the bearing capacity of sub-base and induces damage.

Benedetto, A.; Pensa, S.

2007-06-01

16

Methods to Use Surface Infiltration Tests in Permeable Pavement Systems to Determine Maintenance Frequency  

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Currently, there is limited guidance on selecting test sites to measure surface infiltration rates in permeable pavement systems to determine maintenance frequency. The ASTM method (ASTM C1701) for measuring infiltration rate of in-place pervious concrete suggest to either (1) p...

17

Mobile acoustic system for the detection of surface-breaking cracks in pavement  

Science.gov (United States)

Monitoring the structural condition of road and airport pavement is an extremely critical task to ensure the safety and efficiency of teh transportation. The topic is relevant to both civil and military transportation infrastructure. The presence of damage in pavement, including surface cracking, depressions, swells, and wear, is inevitable due to the sever environmental and service loads that these structures must be subject to. Existing NDE techniques aimed at assessing the structural condition of pavement include Falling Weight Deflectometer, Ground Penetrating Radar, and acoustic methods based on surface waves. This paper presents improvements to the traditional surface-wave method for the detection of surface-breaking cracks in pavement. The advances include 1) the modeling of the problem as dipsersive waves propagating in a multilayer system, 2) the inclusion of post-processing algorithms based on the Wavelet Transform to improve the sensitivity and accuracy of the inspection, and 3) the use of non-contact, air-coupled acoustic detectors to enhance the mobility of the inspection unit. The crack detection procedure consists of first generating a dispersive wave with an impulse hammer, and then measuring the changes in velocity, amplitude and/or frequency content as the wave travels across the flaw with the aid of the Continuous Wavelet Transform. Multilayer wave propagation modeling provides a better understanding of the experimental results by predicting how the various frequencies interact with cracks of different depths. The results of field tests will be presented for both rigid (concrete-based) and flexible (bitumen-based) pavement with surface cracks.

Marzani, Alessandro; Rizzo, Piervincenzo; Lanza di Scalea, Francesco; Benzoni, Gianmario

2004-07-01

18

Analysis of Load Stress for Asphalt Pavement of Lean Concrete Base  

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The study revealed that whether it is early distresses in asphalt pavement or not depends largely on working performance of base. In the field of asphalt pavement, it is widely accepted that lean concrete base, compared with the general semi-rigid base, has better working performance, such as high strength and good eroding resistance. Problem of early distresses in asphalt pavement, which caused by more traffic loadings, can be settled effectively when lean concrete is used in asphalt pavement. Traffic loading is important parameter used in the analysis of the new pavement design. However, few studies have done extensive and intensive research on the load stress for asphalt pavement of lean concrete base. Because of that, it is necessary to study the load stress for the asphalt pavement. In the paper, first of all, three-dimension finite element model of the asphalt pavement is created for the aim of doing mechanical analysis for the asphalt pavement. And then, the two main objectives of this study are investigated. One is analysis for load stress of lean concrete base, and the other is analysis for load stress of asphalt surface. The results show that load stress of lean concrete base decreases, decrease and increase with increase of base's thickness, surface's thickness and ratio of base's modulus to foundation's modulus respectively. So far as the asphalt surface is concerned, maximum shearing stress, which is caused by load, is evident in asphalt surface which is located in transverse contraction joint of lean concrete base of asphalt pavement. Maximum shearing stress decrease, decrease, decrease and increase respectively with increase of the surface's modulus, the surface's thickness, base's thickness and ratio of base's modulus to foundation's modulus.

Lijun, Suo; Xinwu, Wang

19

DRAINAGE AND FLEXIBLE PAVEMENT PERFORMANCE  

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Full Text Available Providing adequate drainage to a pavement system has been considered as an important design consideration to prevent premature failures due to water related problems such as pumping action, loss of support, and rutting, among others. Most water in pavements is due to rainfall infiltration into unsaturated pavement layers, throughjoints, cracks, shoulder edges, and various other defects, especially in older deteriorated pavements. Water also seep upward from a high groundwater table due to capillary suction or vapour movements, or it may flow laterally from the pavement edges and side ditches. Providing adequate drainage to a pavement system has been considered as an important design consideration to ensure satisfactory performance of the pavement, particularly from the perspective of life cycle cost and serviceability. To minimize premature pavement distresses and to enhance the pavement performance, it is imperative to provide adequate drainage to allow infiltrated water to drain out from the base and sub-base, thus avoiding saturation of base and subgrade soils. This paper deals with the analysis of the impact of subsurface drainage on pavement system performance. The requirement ofeffective subsurface drainage for pavement performance is also discussed.

SIDDHARTHA ROKADE

2012-04-01

20

EFFECTS OF PAVEMENT SURFACE TEMPERATURE ON THE MODIFICATION OF URBAN THERMAL ENVIRONMENT  

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Full Text Available Urban centres continue to experience escalating average summer temperature over the last fifty years. Temperature in the urban core cites have been rising due to rapid growth of urbanization in the latter half of the twentieth century (Akbari et al., 1989. Outdoor experiments were conducted to investigate the effects of different movement of materials on the urban thermal environment. Meteorological conditions such as air temperature, pavement surface temperature, Relative humidity and wind velocity were recorded to determine temperature differences among Asphalt/concrete, interlocking bricks and grass surfaces.

SARAT, Adebayo-Aminu

2012-01-01

 
 
 
 
21

Evaluation of Surface Infiltration Testing Procedures in Permeable Pavement Systems  

Science.gov (United States)

The ASTM method (ASTM C1701) for measuring infiltration rate of in-place pervious concrete provides limited guidance on how to select testing locations, so research is needed to evaluate how testing sites should be selected and how results should be interpreted to assess surface ...

22

Improving rutting resistance of pavement structures using geosynthetics: an overview.  

Science.gov (United States)

A pavement structure consists of several layers for the primary purpose of transmitting and distributing traffic loads to the subgrade. Rutting is one form of pavement distresses that may influence the performance of road pavements. Geosynthetics is one type of synthetic materials utilized for improving the performance of pavements against rutting. Various studies have been conducted on using different geosynthetic materials in pavement structures by different researchers. One of the practices is a reinforcing material in asphalt pavements. This paper intends to present and discuss the discoveries from some of the studies on utilizing geosynthetics in flexible pavements as reinforcement against permanent deformation (rutting). PMID:24526919

Mirzapour Mounes, Sina; Karim, Mohamed Rehan; Khodaii, Ali; Almasi, Mohammad Hadi

2014-01-01

23

Fast simulated annealing inversion of surface waves on pavement using phase-velocity spectra  

Science.gov (United States)

The conventional inversion of surface waves depends on modal identification of measured dispersion curves, which can be ambiguous. It is possible to avoid mode-number identification and extraction by inverting the complete phase-velocity spectrum obtained from a multichannel record. We use the fast simulated annealing (FSA) global search algorithm to minimize the difference between the measured phase-velocity spectrum and that calculated from a theoretical layer model, including the field setup geometry. Results show that this algorithm can help one avoid getting trapped in local minima while searching for the best-matching layer model. The entire procedure is demonstrated on synthetic and field data for asphalt pavement. The viscoelastic properties of the top asphalt layer are taken into account, and the inverted asphalt stiffness as a function of frequency compares well with laboratory tests on core samples. The thickness and shear-wave velocity of the deeper embedded layers are resolved within 10% deviation from those values measured separately during pavement construction. The proposed method may be equally applicable to normal soil site investigation and in the field of ultrasonic testing of materials. ?? 2006 Society of Exploration Geophysicists.

Ryden, N.; Park, C. B.

2006-01-01

24

Visual surveying platform for the automated detection of road surface distresses  

Science.gov (United States)

Road distresses, such as potholes and edge cracks, are not only a source of frustration to drivers but also negatively impact the economy due to damage to motor vehicles and costly ro6ad repairs. Regular and rapid pavement inspection and maintenance is vital to preventing pothole formation and growth. To improve the efficiency of maintenance and reduce the cost thereof, the Visual Surveying Platform (VSP) is being developed that will automatically detect and analyse road distresses. The VSP consists of a vehicle mounted sensor system, consisting of a high speed camera and a Global Positioning System (GPS) receiver, and an analysis and visualization software suite. The system extracts both a visual image and the coordinates of a detected road defect from recorded video and presents it in an interactive interface for use by technical experts and maintenance schedulers. The VSP automatically detects and classifies road distresses using a two-stage artificial neural network framework. Video frames first undergo hue, saturation and value (HSV) colour space conversion as well as a spatial frequency transformation before being used as inputs to the neural networks. A road detector neural network first classifies which section of the image contains the road, after which a distress detector neural network identifies those road regions containing defects. Although the VSP can be adapted to detect any type of road distress it has been trained to specifically detect potholes. An initial prototype of the VSP was designed and constructed. The prototype was also trained and tested on real-world data collected from provincial roads.

Naidoo, Thegaran; Joubert, Deon; Chiwewe, Tapiwa; Tyatyantsi, Ayanda; Rancati, Bruno; Mbizeni, Asanda

2014-06-01

25

Summary and recommendations for the implementation of rigid pavement design, construction and rehabilitation techniques  

Science.gov (United States)

In order to explain observations of significantly different performances for many of the rigid pavements in Texas, a quantitative evaluation was required to relate distress mechanisms to distress manifestation and to develop better predictions of performance. The CTR staff had previously derived underlying principles concerning the mechanistic behavior of composite materials. Maintenance and rehabilitation studies were performed concurrently using information collected from condition survey and surface profile measurements. This information was analyzed in depth in the development of distress prediction models and suitable criteria for use in rehabilitation decision making. The implementation of several innovative rehabilitation techniques is also described.

McCullough, B. F.; Hudson, W. R.; Noble, C. S.

1981-03-01

26

Some experience using noncontact sensors on airport pavements  

Science.gov (United States)

The Swedish National Road Administration has been using a laser based system for assessing pavement surface characteristics for over a decade. Typically, important distress data like roughness and rutting are being sampled at speeds up to 25 meters per second. Other parameters include textures and geometric data, such as cross slope and curvature. The Royal Swedish Fortifications Administration has just recently looked into these techniques for airfield pavements. The objectives are similar but not exactly the same as for highway pavements. A promising aspect is using data for building terrain models of the surface so that overlay design procedures can take place in a computerized environment. The objectives are similar but not exactly the same as for highway pavements. A promising aspect is using data for building terrain models of the surface so that overlay design procedures can take place in a computerized environment. Two different ways of treating the data for this purpose was tried. One model uses several parallel continuous longitudinal profiles. The other consists of snap-shot transverse profiles at five meter intervals. The former model yields good assessment of the volumetric needs of either filling or milling operations. The latter is better for identifying features on the surface. The present paper describes some of experiences obtained with the two methods. However, in both cases the most advantageous aspect of using the non-contact devices is the short time needed for collecting the data.

Lenngren, Carl A.

1996-11-01

27

Weak interlayers in flexible and semi-flexible road pavements: Part 1  

Scientific Electronic Library Online (English)

Full Text Available SciELO South Africa | Language: English Abstract in english Weak layers, interlayers, laminations and/or interfaces in the upper structural layers of road pavements are specifically prohibited in most road-building specifications. However, such layers are extremely common and often lead to premature pavement distress. In Part 1 of this two-part set of papers [...] , it is shown that from experience with heavy vehicle simulator (HVS) and dynamic cone penetrometer (DCP) testing, the presence of such layers and/or conditions at any depth in the structural layers of a flexible or semi-flexible pavement is far more deleterious than is commonly appreciated. In Part 2 the effects of these weak layers are further modelled and discussed using various examples based an HVS testing and mechanistic pavement analyses. In particular, a weak upper base course of a cemented pavement under a thin bituminous surfacing may lead to severe surfacing (and upper base) failure within a matter of weeks to months after opening to traffic, not excluding failure even during construction. In this paper (Part 1), the causes of weak layers, interlayers, laminations and/or interfaces, together with simple methods for their detection during construction and analyses of their effects on the structural capacity of flexible and semi-rigid (cemented) road pavements, are briefly discussed.

F, Netterberg; M, de Beer.

2012-04-01

28

Weak interlayers in flexible and semi-flexible road pavements: Part 1  

Directory of Open Access Journals (Sweden)

Full Text Available Weak layers, interlayers, laminations and/or interfaces in the upper structural layers of road pavements are specifically prohibited in most road-building specifications. However, such layers are extremely common and often lead to premature pavement distress. In Part 1 of this two-part set of papers, it is shown that from experience with heavy vehicle simulator (HVS and dynamic cone penetrometer (DCP testing, the presence of such layers and/or conditions at any depth in the structural layers of a flexible or semi-flexible pavement is far more deleterious than is commonly appreciated. In Part 2 the effects of these weak layers are further modelled and discussed using various examples based an HVS testing and mechanistic pavement analyses. In particular, a weak upper base course of a cemented pavement under a thin bituminous surfacing may lead to severe surfacing (and upper base failure within a matter of weeks to months after opening to traffic, not excluding failure even during construction. In this paper (Part 1, the causes of weak layers, interlayers, laminations and/or interfaces, together with simple methods for their detection during construction and analyses of their effects on the structural capacity of flexible and semi-rigid (cemented road pavements, are briefly discussed.

F Netterberg

2012-04-01

29

Weak interlayers in flexible and semi-flexible road pavements: Part 1  

Scientific Electronic Library Online (English)

Full Text Available SciELO South Africa | Language: English Abstract in english Weak layers, interlayers, laminations and/or interfaces in the upper structural layers of road pavements are specifically prohibited in most road-building specifications. However, such layers are extremely common and often lead to premature pavement distress. In Part 1 of this two-part set of papers [...] , it is shown that from experience with heavy vehicle simulator (HVS) and dynamic cone penetrometer (DCP) testing, the presence of such layers and/or conditions at any depth in the structural layers of a flexible or semi-flexible pavement is far more deleterious than is commonly appreciated. In Part 2 the effects of these weak layers are further modelled and discussed using various examples based an HVS testing and mechanistic pavement analyses. In particular, a weak upper base course of a cemented pavement under a thin bituminous surfacing may lead to severe surfacing (and upper base) failure within a matter of weeks to months after opening to traffic, not excluding failure even during construction. In this paper (Part 1), the causes of weak layers, interlayers, laminations and/or interfaces, together with simple methods for their detection during construction and analyses of their effects on the structural capacity of flexible and semi-rigid (cemented) road pavements, are briefly discussed.

F, Netterberg; M, de Beer.

30

The Impact of Cloud Type on Surface Radiation and Road Pavement Temperature  

Science.gov (United States)

Forecast systems provide decision support for end-users ranging from the solar energy industry to municipalities concerned with winter road maintenance. The racing community also relies on racetrack pavement temperature forecast systems because tire friction decreases as temperature increases, affecting vehicle performance. Race crews perform vehicle maintenance (e.g., tire pressure and suspension adjustments) to maximize traction given a forecasted racetrack temperature. Many forecast systems suffer from inaccurate radiation forecasts resulting in part from a lack of information relating radiation to cloud types. This research seeks to improve the forecasts by determining how cloud type impacts the amount of solar radiation reaching the surface. Cloud type information was obtained from the Naval Research Laboratory Cloud Classifier algorithm and radiation data were obtained from a Davis Weather Station. A theoretical maximum solar radiation distribution was calculated. Cloud type-radiation distribution analyses from Salisbury, North Carolina during May-June 2012 indicated that low clouds allowed approximately 20% of the maximum possible radiation to reach the surface, mid level clouds 32%, high clouds 40% and cumuliform types 34%. A categorical regression analysis revealed 33% of the variation in solar radiation on cloudy case days can be explained by cloud type. Inclusion of clear case days with apparent variability lowered this to 7% suggesting another influence on radiation. A similar bulk statistical analysis is in progress on a much larger data set obtained from the Oklahoma Mesonet. This work lays the foundation for use of satellite cloud type information in order to improve the output of forecast systems. Distribution of mean solar radiation measured at the surface for all nine case studies, sorted by cloud type height characteristics, where n represents the sample size.

Walker, C. L.; Anderson, A.; Chapman, M.; Drobot, S.

2012-12-01

31

Limestone Pavement  

...herb robert, wood sorrel and common dog-violet. The high proportion...with mosses and liverworts are common residents.Limestone pavement is noted...as the Irish hare, stoat, common lizard, skylark, wren, wheatear and...

32

Experimental pavement delineation treatments  

Science.gov (United States)

Visibility and durability of materials used to delineate shoulders and medians adjacent to asphalt pavements were evaluated. Materials evaluated were polysulfide and coal tar epoxies, one and two component polyesters, portland cement, acrylic paints, modified-alkyd traffic paint, preformed plastic tape, and thermoplastic markings. Neat applications, sand mortars, and surface treatments were installed in several geometric patterns including cross hatches, solid median treatments, and various widths of edge lines. Thermoplastic pavement markings generally performed very well, providing good visibility under adverse viewing conditions for at least 4 years. Thermoplastic 4 in. wide edge lines appear to provide adequate visibility for most conditions.

Bryden, J. E.; Lorini, R. A.

1981-06-01

33

76 FR 67018 - Notice to Manufacturers of Airport In-Pavement Stationary Runway Weather Information Systems  

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...Manufacturers of Airport In-Pavement Stationary Runway...150/5220-30, Airport Winter Safety and...recommends that in-pavement runway sensor systems...become mandatory for airports using AIP grant funds, an in-pavement runway surface...

2011-10-28

34

Mechanistic interpretation of nondestructive pavement testing deflections  

Science.gov (United States)

A method is proposed for the backcalculation of material properties in flexible pavements based on the interpretation of surface deflection measurements. ILLI-PAVE, a stress dependent finite element pavement model, was used to generate data for developing algorithms and nomographs for deflection basin interpretation. Over 11,000 deflection measurements for 24 different flexible pavement sections were collected and analyzed. Deflections were measured using the Benkelman Beam, the IDOT Road Rater, the Falling Weight Deflectometer, and an accelerometer to measure deflections under moving trucks. Loading mode effects on pavement response were investigated using dynamic and viscous pavement models. The factors controlling the pavement response to different loading modes were explained and identified. Correlations between different devices were developed. The proposed evaluation procedure is illustrated for three different flexible pavements using deflection data collected on several testing dates.

Hoffman, M. S.

1980-06-01

35

Technical and Economic Sustainability of Concrete Pavements  

Directory of Open Access Journals (Sweden)

Full Text Available Economic evaluation of road pavements is as important as their technical and structural design: often only initial construction costs are calculated to assess economic project sustainability. Instead, forgetting maintenance costs exposes society to unacceptable risks of expensive and incorrect decisions. Road pavements design and construction solutions affect maintenance works during service life, which not only entail economical and financial expenditures, but also damage service regularity for users and affect environmental impact. The analysis of pavement distress and the study of its evolution during service life can contribute to find the financially most advantageous solution. This paper shows a software program developed to analyze structural, functional and financial performances of road concrete pavements both doweled slabs and continuously reinforced.

Laura Moretti

2014-04-01

36

New Method for Pavement Rutting Prediction  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In recent years, pavement rutting rate has increased significantly due to constant traffic intensity increment. These solicitations affect the bituminous layers that can quickly attain their permanent deformation limit resistance. This phenomenon can lead to a pavement depression, located in the tyre-road contact surface. The purpose of this paper is to present a methodology to estimate the rutting of bituminous pavements and to predict the rutting risk considerin...

Rodriguez, M.; Ould-henia, M.; Dumont, A. -g

2006-01-01

37

An experience on street pavement maintenance program in small region- (Bafq city  

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Full Text Available This paper reports an experience on Pavement Maintenance plan of the Research Team of the Islamic Azad University- Bafq Branch. The City of Bafq streets are failing at a growing rate, despite all the efforts of Pavement Management, improved efficiencies in street maintenance operations, contracted work and sharing equipment with other agencies. Pavements in this range show some form of distress or wear that requires more than a life extending achievement. In this group, a well-designed pavement will have served at least 75% of its life and the authority of the pavement has dropped by about 40%.

Khabiry Mehdi

2009-05-01

38

Pavement management and rehabilitation of portland cement concrete pavements  

Science.gov (United States)

Pavement management and rehabilitation projects and techniques are discussed. The following topics are discussed: economic analyses and dynamic programming in resurfacing project selection; implementation of an urban pavement management system; pavement performance modeling for pavement management; illustration of pavement management: from data inventory to priority analysis; rehabilitation of concrete pavements by using portland cement concrete overlays; pavement management study: Illinois tollway pavement overlays; resurfacing of plain jointed-concrete pavements; design procedure for premium composite pavement; model study of anchored pavement; prestressed concrete overlay at O'Hare International Airport: in-service evaluation; and, bonded portland cement concrete resurfacing.

Zegeer, C. V.; Agent, K. R.; Rizenbergs, R. L.; Curtayne, P. C.; Scullion, T.; Pedigo, R. D.; Hudson, W. R.; Roberts, F. L.; Karan, M. A.; Haas, R.

39

Monitoring the condition of roads pavement surfaces: proposal of methodology using hyperspectral images / Monitoramento das condições das superfícies de pavimentos rodoviários: proposta de metodologia utilizando imagens hiperespectrais  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese No atual sistema de concessões rodoviária do Brasil ambos, concessionárias e agências reguladoras têm a missão de melhorar a qualidade dos pavimentos rodoviários no País. Tal situação requer a pesquisa e a identificação de novas ferramentas que facilitem o levantamento das condições dos pavimentos r [...] odoviários num tempo e custos menores que os métodos usuais. Recentemente, se verificou um grande aumento da disponibilidade de imagens de sensoriamento remoto com alta resolução espacial, seguindo uma tendência do mercado de novos satélites de sensoriamento remoto, e de sensores aerotransportados. De forma similar, imagens multi e hiperespectrais estão disponíveis tanto comercialmente quanto para a pesquisa científica. O artigo apresenta uma nova metodologia para a identificação das condições do asfalto em superfícies pavimentadas e uma classificação dos tipos de defeitos identificáveis a partir de imagens hiperespectrais adquiridas por sensores aerotransportados. O objetivo do artigo é o de mostrar que índices das condições das superfícies dos pavimentos asfaltados gerados via imagens hiperespectrais podem ser comparados com os indicadores vigentes, utilizados pela agência reguladora nacional. Abstract in english With the current system of concession roads in Brazil, both concessionaires and regulatory agents have been charged with improving the quality of the pavement on Brazilian highways. This situation requires the search for new tools that can facilitate the survey of pavement conditions in less time an [...] d at a lower cost than traditional methods. Recently, an increasing number of high-resolution spatial images have become available on the world market following the development of new remote sensing satellites and airborne sensors. Similarly, multispectral images and even hyperspectral images are now available commercially and for scientific research. The paper presents a new methodology for the identification of asphalted pavement surfaces condition and the classification of the main types of asphalt defects using hyperspectral images from airborne digital sensors. The objective of this study was to generate indexes of pavement conditions from images that can be compared with the indicators of pavement surface conditions already used by national regulatory agencies.

Marcos Ribeiro, Resende; Liedi Legi Bariani, Bernucci; José Alberto, Quintanilha.

2014-04-01

40

Permeable Pavement Research - Edison, New Jersey  

Science.gov (United States)

This presentation provides the background and summary of results collected at the permeable pavement parking lot monitored at the EPA facility in Edison, NJ. This parking lot is surfaced with permeable interlocking concrete pavers (PICP), pervious concrete, and porous asphalt. ...

 
 
 
 
41

Psychological Distress  

Science.gov (United States)

... 08, rev. 06 11 PATIENT / FAMILY TEACHING SHEET Psychological Distress What is psychological distress? Uneasy feelings of anxiety or depression in ... harm What are the signs and symptoms of psychological distress? ? Feelings of anxiety, sadness, anger. Wanting to ...

42

MODELING PAVEMENT DETERIORATION PROCESSES BY POISSON HIDDEN MARKOV MODELS  

Science.gov (United States)

In pavement management, it is important to estimate lifecycle cost, which is composed of the expenses for repairing local damages, including potholes, and repairing and rehabilitating the surface and base layers of pavements, including overlays. In this study, a model is produced under the assumption that the deterioration process of pavement is a complex one that includes local damages, which occur frequently, and the deterioration of the surface and base layers of pavement, which progresses slowly. The variation in pavement soundness is expressed by the Markov deterioration model and the Poisson hidden Markov deterioration model, in which the frequency of local damage depends on the distribution of pavement soundness, is formulated. In addition, the authors suggest a model estimation method using the Markov Chain Monte Carlo (MCMC) method, and attempt to demonstrate the applicability of the proposed Poisson hidden Markov deterioration model by studying concrete application cases.

Nam, Le Thanh; Kaito, Kiyoyuki; Kobayashi, Kiyoshi; Okizuka, Ryosuke

43

Energy equivalents for selected pavement materials: Their production and placement  

Science.gov (United States)

Energy requirements for selected pavement surfaces are discussed. Energy requirements for hot-mixed bituminous recycling and portland cement concrete recycling projects are presented along with conventional pavement methods. Energy requirements for conventional thin surface treatments are also discussed. Environmental analyses involving both air and noise quality measurement are included for various recycling and conventional paving options.

Lane, K. R.

1981-03-01

44

Hybrid green permeable pave with hexagonal modular pavement systems  

Science.gov (United States)

Modular permeable pavements are alternatives to the traditional impervious asphalt and concrete pavements. Pervious pore spaces in the surface allow for water to infiltrate into the pavement during rainfall events. As of their ability to allow water to quickly infiltrate through the surface, modular permeable pavements allow for reductions in runoff quantity and peak runoff rates. Even in areas where the underlying soil is not ideal for modular permeable pavements, the installation of under drains has still been shown to reflect these reductions. Modular permeable pavements have been regarded as an effective tool in helping with stormwater control. It also affects the water quality of stormwater runoff. Places using modular permeable pavement has been shown to cause a significant decrease in several heavy metal concentrations as well as suspended solids. Removal rates are dependent upon the material used for the pavers and sub-base material, as well as the surface void space. Most heavy metals are captured in the top layers of the void space fill media. Permeable pavements are now considered an effective BMP for reducing stormwater runoff volume and peak flow. This study examines the extent to which such combined pavement systems are capable of handling load from the vehicles. Experimental investigation were undertaken to quantify the compressive characteristics of the modular. Results shows impressive results of achieving high safety factor for daily life vehicles.

Rashid, M. A.; Abustan, I.; Hamzah, M. O.

2013-06-01

45

Fracture of highway and airport pavements  

Science.gov (United States)

Existing solutions for the stresses in a cracked slab containing a crack and supported by an elastic foundation are extended to obtain the stress intensity factor (SIF) for a crack in a pavement subjected to moving vehicular loads. In the existing solutions the stresses can be obtained only for a uniform bending stress (before the crack occurs) along the crack surface. For pavements subjected to moving vehicular loads, the stress distribution along the crack surface is not uniform and the approximation of a uniform stress is often unsatisfactory. The present work extends the above solutions to cover more realistic loading of highway and airport pavements. This facilitates the application of the principles of fracture mechanics to the fatigue crack propagation and fracture of pavements. Beginning with a part-through semi-elliptical starter crack, the crack is assumed to grow under load and the SIF is presented at various stages of crack growth, from the starter crack into a short through-crack that eventually becomes a very long through-crack. Some examples of the fracture of typical rigid and flexible highway and airport pavements are presented to show the need to consider fracture in the design of pavements.

Ramsamooj, D. V.

1993-03-01

46

FUEL CONSUMPTION & ENERGY DISSIPATION THROUGH ROAD PAVEMENT CHARACTERISTIC  

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Full Text Available This thesis estimates the effect of pavement characteristic on energy dissipation of a rolling vehicle tyre. On objective of this study is to compare the relative amount of energy dissipated in pavement by the rolling depending on the pavement materials surface condition & environmental condition also. The study also assesses the effect of the vertical deflection, induced by the tyre, on overall energy dissipation in pavement. A comprehensive literature was carried out to prove a wide background for the study. Field measures and laboratory tests were discussed to provide basis for analyses. Results indicate that energy dissipated in pavement significantly depend on the characteristic of pavement. An obvious influence of speed on energy dissipation can be found only when the stiffness in a low level.

Dipanjan Mukherjee

2014-06-01

47

RIGID PAVEMENT PUMPING: (1) SUBBASE EROSION AND (2) ECONOMIC MODELING (SUBDRAINAGE, REHABILITATION, RIGID PAVEMENTS)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Pumping of rigid pavements is a major contributor to rigid pavement failure. Fines can be removed through pore water pressure buildup in the subbase or through surface erosion of subbase and shoulder materials. A number of studies have been conducted since the 1940s, and a number of remedies have been implemented, viz., granular, stabilized, open-graded, and lean concrete subbases. The effectiveness of these measures varied. Stabilized layers, although reducing pumping, do not eliminate pumpi...

Wijk, Adriaan Jacobus

1985-01-01

48

Field Evaluation of Nondestructive Tests in Measuring the Pavement Layers Density  

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Full Text Available The aim of this study was field evaluation of nondestructive devices in measuring the density of road layers. Density may be considered as a reliable criterion for evaluating pavement quality and has a high level of importance in that it can ensure the proper performance of pavement at least prior the period of life-time. At present time, the most current and also accurate method to determine in-situ density of asphalt mixture is core sample method, however it has some disadvantages. As well as being costly and time consuming, core sample method causes some distress on the pavement surface and it is not possible to repeat the test for a specific location. In view of this, some attempts were made to develop new methods as alternatives for core sample method. And as such, nondestructive tests have grown into a huge area over the last few years. These tests including nuclear and nonnuclear nondestructive tests do not have the limitations of core sample method. In this study, field evaluation in a new constructed part of a highway was conducted using pavement quality indicator (PQI301 and Troxler nuclear gauge (Model HS-5001EZ. According to the results of validation tests for nondestructive devices (PQI and Nuclear devices, PQI device has sufficient reliability to determine density of asphalt mixture layer but Nuclear device is not reliable to determine density. The obtained results from validation of nuclear device revealed that it has sufficient reliability to determine density of soil layers. Also it was found that the role of calibration procedure in obtaining correct readings From PQI device is highly critical.

H. Divandary

2010-01-01

49

Weak interlayers in flexible and semi-flexible road pavements: Part 1  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Weak layers, interlayers, laminations and/or interfaces in the upper structural layers of road pavements are specifically prohibited in most road-building specifications. However, such layers are extremely common and often lead to premature pavement distress. In Part 1 of this two-part set of papers, it is shown that from experience with heavy vehicle simulator (HVS) and dynamic cone penetrometer (DCP) testing, the presence of such layers and/or conditions at any depth in the structural layer...

Netterberg, F.; Beer, M.

2012-01-01

50

Dynamic pavement deflection  

Science.gov (United States)

Dynamic pavement deflection measurements for bituminous concrete pavements of two and three-quarter, five and seven-eights, and seven and one-half inches in thickness under moving axle loads of 15,000, 18,000, and 22,000 pounds were obtained at speeds of 10, 25 and 45 miles per hour. The results were analyzed and compared to Benkelman beam measurements. The data indicate that slow moving loads have greater adverse effect (larger deflections) on the pavement than the high speed loads. The results also show that the bituminous pavement undergoes numerous vertical fluctuations and bending as the front and rear axles approached the point of measurement. The magnitude of the vertical displacement was measured via the means of an accelerometer and double integrator. When values of the dynamic deflections were in the magnitude of 0.07 through 0.10 inches, there was evidence of pavement failure. When the deflection values were above 0.10 inches pavement failures were distinct.

Rand, D. W.; Jacobs, K. M.

1981-06-01

51

Classificação híbrida: pixel a pixel e baseada em objetos para o monitoramento da condição da superfície dos pavimentos rodoviários / Hybrid classification: pixel by pixel and object based to monitor the surface conditions of road pavements  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Monitorar a condição de uso de toda a extensão das rodovias brasileiras é tarefa dispendiosa e demorada. Este trabalho trata de novas técnicas que permitem o levantamento da condição da superfície dos pavimentos rodoviários de forma ágil utilizando imagens hiperespectrais de sensor digital aeroembar [...] cado. Nos últimos anos, um número crescente de imagens de alta resolução espacial tem surgido no mercado mundial com o aparecimento dos novos satélites e sensores aeroembarcados de sensoriamento remoto. Propõe-se uma metodologia para identificação dos pavimentos asfálticos e classificação das principais ocorrências dos defeitos na superfície do pavimento. A primeira etapa da metodologia é a identificação da superfície asfáltica na imagem, utilizando uma classificação híbrida baseada inicialmente em pixel e depois refinada por objetos. A segunda etapa da metodologia é a identificação e classificação das ocorrências dos principais defeitos nos pavimentos flexíveis que são observáveis nas imagens de alta resolução espacial. Esta última etapa faz uso intensivo das novas técnicas de classificação de imagens baseadas em objetos. O resultado final é a geração de índices da condição da superfície do pavimento a partir das imagens que possam ser comparados com os indicadores vigentes da condição da superfície do pavimento já normatizados pelos órgãos competentes no país. Abstract in english Monitoring every Brazilian road use condition is an expensive and time consuming task. This research deals with new techniques which will yield a quick survey of road surface pavement condition by using hyperspectral images from airborne remote sensing. Recently, an increasing number of images with [...] high spatial resolution has emerged on the world market with the advent of new remote sensing satellites and airborne sensors. Hyperspectral images from digital airborne sensor have been used in this work. A new identification methodology for a pavement surface and also for classification of the main defects of the surface has been devised. The first step of the methodology is the identification of the asphalt surface in the image, by using hybrid classification based on pixel initially and then improved by objects. The second step of the methodology is the identification and classification of the main defects of pavement surface that are observable in high spatial resolution imagery. This step makes intensive use of new techniques for classification of images based on objects. The goal is the generation of pavement surface condition index from the images which can be compared to quality index of pavement surface already managed by the regulatory agency in the country.

Marcos Ribeiro, Resende; Liedi Légi Barianni, Bernucci; José Alberto, Quintanilha.

2012-09-01

52

Measurement and effects of segregated hot mix asphalt pavement  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Asphalt mixture segregation is the nonuniform distribution of coarse and fine aggregate components. Because of segregation, early distress of asphalt pavement results. A test that identifies asphalt mixture segregation would be a significant contribution to asphalt technology.^ There are several factors that lead to segregation. Segregation can occur during stockpiling and handling of aggregate, and during mixing, storage, transport, and laydown of the asphalt mixture. Sometimes segregatio...

Williams, Ronald Christopher

1996-01-01

53

Pavement Evaluation and Maintenance Decisions Based on Fuzzy Inference Systems  

Directory of Open Access Journals (Sweden)

Full Text Available The remaining service life and maintenance decisions of existing pavements are highly dependent on stiffness and deterioration conditions throughout their operation. A non-conventional fuzzy logic based methodology is proposed in this work to address the stiffness-deterioration condition and conservation decisions, by means of three Fuzzy Inference Systems. Analysis were conducted using a database gathered from field tests performed on three and four layer pavement systems, that included traditional layer structuring and pavements having a subbase stiffer than their granular base. Information about layer thicknesses, magnitude and severity of structural distresses, and parameters and indicators derived from deflection testing by impulse load devices were used. The developed systems, allowed representing expert knowledge and linguistic variables of subjective and qualitative nature, commonly used to describe the severity levels of deterioration; thus they can be involved into structural characterization of pavements. Results were also expressed linguistically, to facilitate their interpretation and understanding. Based on the high quality of results obtained, it seems reasonable to conclude that the proposed systems could be used confidently for assessing and making decisions about pavement conservation, with low computational cost.

Beltrán-Calvo Gloria Inés

2014-07-01

54

Pavement Snow Melting  

Energy Technology Data Exchange (ETDEWEB)

The design of pavement snow melting systems is presented based on criteria established by ASHRAE. The heating requirements depends on rate of snow fall, air temperature, relative humidity and wind velocity. Piping materials are either metal or plastic, however, due to corrosion problems, cross-linked polyethylene pipe is now generally used instead of iron. Geothermal energy is supplied to systems through the use of heat pipes, directly from circulating pipes, through a heat exchanger or by allowing water to flow directly over the pavement, by using solar thermal storage. Examples of systems in New Jersey, Wyoming, Virginia, Japan, Argentina, Switzerland and Oregon are presented. Key words: pavement snow melting, geothermal heating, heat pipes, solar storage, Wyoming, Virginia, Japan, Argentina, Klamath Falls.

Lund, John W.

2005-01-01

55

A real-time 3D scanning system for pavement distortion inspection  

International Nuclear Information System (INIS)

Pavement distortions, such as rutting and shoving, are the common pavement distress problems that need to be inspected and repaired in a timely manner to ensure ride quality and traffic safety. This paper introduces a real-time, low-cost inspection system devoted to detecting these distress features using high-speed 3D transverse scanning techniques. The detection principle is the dynamic generation and characterization of the 3D pavement profile based on structured light triangulation. To improve the accuracy of the system, a multi-view coplanar scheme is employed in the calibration procedure so that more feature points can be used and distributed across the field of view of the camera. A sub-pixel line extraction method is applied for the laser stripe location, which includes filtering, edge detection and spline interpolation. The pavement transverse profile is then generated from the laser stripe curve and approximated by line segments. The second-order derivatives of the segment endpoints are used to identify the feature points of possible distortions. The system can output the real-time measurements and 3D visualization of rutting and shoving distress in a scanned pavement

56

Pervious Pavement System Evaluation  

Science.gov (United States)

Pervious pavement is a low impact development stormwater control. The Urban Watershed Management Branch of the U.S. Environmental Protection Agency in Edison, NJ, is evaluating concrete pavers as a popular implementation. The pollutant removal of a bench-scale permeable interlo...

57

Pavement and Soil Characteristics.  

Science.gov (United States)

The papers in the Record contain information on soil characteristics useful for pavement design. They are of interest to soil engineers and highway designers. These papers include a presentation of an estimate of the contribution of the subgrade to the to...

C. L. Monismith

1975-01-01

58

Validation of procedures for pavement design on expansive soils  

Science.gov (United States)

This report documents site investigations and design recommendations for airport pavements on expansive soils at three sites. The methods used were developed previously in an FAA-sponsored research project. The design procedure involves soil characterization, determination of surface characteristics and evaluation of soil-pavement interaction. Investigations at three airports are reported; they are Murdo, South Dakota, Mesquite, Texas, and Love Field, Dallas, Texas. Soils data are used along with climatic information to obtain estimates of the equivalent thickness of pavement required for each site. The work at Love Field was somewhat different than the other sites since NMERI was not directly conducting the investigation. Results are reported in the form of pavement thickness required to adequately perform, in terms of surface roughness, on the soil surface characteristics predicted for each site. Recommendations are included for consideration in rehabilitation of each site since all were experiencing surface roughness at the time of the investigations. These results confirm that methods developed for evaluating airport pavements on expansive soils provide useful information for pavement design.

McKeen, R. G.

1985-07-01

59

Cost-effectiveness evaluation of highway flexible pavement routine maintenance  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This dissertation deals with three major issues related to routine maintenance of highway flexible pavements in Indiana. First is the evaluation of roadway and shoulder maintenance activity expenditures. The second issue is the evaluation of the impact of various individual and groups of maintenance activities on pavement surface condition. The third issue involves the analysis of cost-effectiveness of different maintenance scenarios.^ The first issue included the analysis of total routine...

Al-mansour, Abdullah Ibrahim

1991-01-01

60

A model for the pavement temperature prediction at specified depth using neural networks  

Directory of Open Access Journals (Sweden)

Full Text Available Earlier researches have established that the ambient temperature is one of the most important factors for pavement temperature analysis.This paper examines the existing models for predicting pavement temperatures at specified depth and formulates a new one using neural networks depending on the surface pavement temperature and depth. It was also conducted the validation of the model comparing predicted with measured temperatures.

B. Mati?

2014-10-01

 
 
 
 
61

Cloud Impacts on Pavement Temperature in Energy Balance Models  

Science.gov (United States)

Forecast systems provide decision support for end-users ranging from the solar energy industry to municipalities concerned with road safety. Pavement temperature is an important variable when considering vehicle response to various weather conditions. A complex, yet direct relationship exists between tire and pavement temperatures. Literature has shown that as tire temperature increases, friction decreases which affects vehicle performance. Many forecast systems suffer from inaccurate radiation forecasts resulting in part from the inability to model different types of clouds and their influence on radiation. This research focused on forecast improvement by determining how cloud type impacts the amount of shortwave radiation reaching the surface and subsequent pavement temperatures. The study region was the Great Plains where surface solar radiation data were obtained from the High Plains Regional Climate Center's Automated Weather Data Network stations. Road pavement temperature data were obtained from the Meteorological Assimilation Data Ingest System. Cloud properties and radiative transfer quantities were obtained from the Clouds and Earth's Radiant Energy System mission via Aqua and Terra Moderate Resolution Imaging Spectroradiometer satellite products. An additional cloud data set was incorporated from the Naval Research Laboratory Cloud Classification algorithm. Statistical analyses using a modified nearest neighbor approach were first performed relating shortwave radiation variability with road pavement temperature fluctuations. Then statistical associations were determined between the shortwave radiation and cloud property data sets. Preliminary results suggest that substantial pavement forecasting improvement is possible with the inclusion of cloud-specific information. Future model sensitivity testing seeks to quantify the magnitude of forecast improvement.

Walker, C. L.

2013-12-01

62

Toward the acoustical characterization of asphalt pavements: analysis of the tire/road sound from a porous surface.  

Science.gov (United States)

Sound level in close proximity to the contact patch of the tire and road (L(CPtr)) is analyzed as a function of the vehicle speed in the acoustic frequency range, showing different behavior depending on frequency. At least two regions are observed; one at low frequencies, where the variation in sound with speed (coefficient B) increases with frequency, and the other at higher frequencies, where such sound/speed variation does not increase significantly with frequency. The dependence of B at low frequencies seems to be correlated with the high sound absorption of this porous surface. PMID:19173385

Paje, S E; Bueno, M; Viñuela, U; Terán, F

2009-01-01

63

Geotextiles in Flexible Pavement Construction  

Science.gov (United States)

People everywhere in the developed world regularly drive on paved roads. Learning about the construction techniques and materials used in paving benefits technology and construction students. This article discusses the use of geosynthetic textiles in pavement construction. It presents background on pavements and describes geotextiles and drainage…

Alungbe, Gabriel D.

2004-01-01

64

Respiratory Distress  

Science.gov (United States)

The University of Miami School of Medicine asked the Research Triangle Institute for assistance in improvising the negative pressure technique to relieve respiratory distress in infants. Marshall Space Flight Center and Johnson Space Center engineers adapted this idea to the lower-body negative-pressure system seals used during the Skylab missions. Some 20,000 babies succumb to respiratory distress in the U.S. each year, a condition in which lungs progressively lose their ability to oxygenate blood. Both positive and negative pressure techniques have been used - the first to force air into lungs, the second to keep infant's lungs expanded. Negative pressure around chest helps the baby expand his lungs and maintain proper volume of air. If doctors can keep the infant alive for four days, the missing substance in the lungs will usually form in sufficient quantity to permit normal breathing. The Skylab chamber and its leakproof seals were adapted for medical use.

1976-01-01

65

Stormwater quality of spring-summer-fall effluent from three partial-infiltration permeable pavement systems and conventional asphalt pavement.  

Science.gov (United States)

This study examined the spring, summer and fall water quality performance of three partial-infiltration permeable pavement (PP) systems and a conventional asphalt pavement in Ontario. The study, conducted between 2010 and 2012, compared the water quality of effluent from two Interlocking Permeable Concrete Pavements (AquaPave(®) and Eco-Optiloc(®)) and a Hydromedia(®) Pervious Concrete pavement with runoff from an Asphalt control pavement. The usage of permeable pavements can mitigate the impact of urbanization on receiving surface water systems through quantity control and stormwater treatment. The PP systems provided excellent stormwater treatment for petroleum hydrocarbons, total suspended solids, metals (copper, iron, manganese and zinc) and nutrients (total-nitrogen and total-phosphorus) by reducing event mean concentrations (EMC) as well as total pollutant loadings. The PPs significantly reduced the concentration and loading of ammonia (NH4(+)+NH3), nitrite (NO2(-)) and organic-nitrogen (Org-N) but increased the concentration and loading of nitrate (NO3(-)). The PP systems had mixed performances for the treatment of phosphate (PO4(3-)). The PP systems increased the concentration of sodium (Na) and chloride (Cl) but EMCs remained well below recommended levels for drinking water quality. Relative to the observed runoff, winter road salt was released more slowly from the PP systems resulting in elevated spring and early-summer Cl and Na concentrations in effluent. PP materials were found to introduce dissolved solids into the infiltrating stormwater. The release of these pollutants was verified by additional laboratory scale testing of the individual pavement and aggregate materials at the University of Guelph. Pollutant concentrations were greatest during the first few months after construction and declined rapidly over the course of the study. PMID:24681366

Drake, Jennifer; Bradford, Andrea; Van Seters, Tim

2014-06-15

66

Analysis of Pavement for National Highway-N.H.1  

Directory of Open Access Journals (Sweden)

Full Text Available Rigid pavements are those which posses note worthy flexural strength or flexural rigidity. The stresses are not transferred from grain to grain to the lower layers as in the ease of flexible pavements layers the rigid pavements are made of Portland cement concrete-either plain, reinforced or prestressed concrete[1]. This paper shows the required to evaluate the strength characteristics of the soil subgrade, this helps the designer to adopt the suitable values of the strength parameter for design purposes and in case this supporting layer does not come upto the expectations, the same is treated or conditioned to suit the requirementsThe plain cement concrete slabs are expected to take up about 40 kg/cm2 flexural stress. As the rigid pavements slab has tensile strength, tensile stresses are developed due to the bending of the slab under wheel load and temperature variations thus the type of stress develop and their distribution within the cement concrete slab are quit different. The rigid pavement does not get deformed to the shape of the lower surface as it can bridge the minor variation of lower layer[2].

Arvind Dewangan

2012-02-01

67

Design of Rigid and Flexible Pavements by Various Methods & Their Cost Analysis of Each Method  

Directory of Open Access Journals (Sweden)

Full Text Available Highway and pavement design plays an important role in the DPR projects. The satisfactory performance of the pavement will result in higher savings in terms of vehicle operating costs and travel time, which has a bearing on the overall economic feasibility of the project. This paper discusses about the design methods that are traditionally being followed and examines the “Design of rigid and flexible pavements by various methods & their cost analysis by each method”. Flexible pavement are preferred over cement concrete roads as they have a great advantage that these can be strengthened and improved in stages with the growth of traffic and also their surfaces can be milled and recycled for rehabilitation. The flexible pavements are less expensive also with regard to initial investment and maintenance. Although Rigid pavement is expensive but have less maintenance and having good design period. The economic part are carried out for the design pavement of a section by using the result obtain by design method and their corresponding component layer thickness. It can be done by drawing comparisons with the standard way and practical way. This total work includes collection of data analysis various flexible and rigid pavement designs and their estimation procedure are very much useful to engineer who deals with highways.

Saurabh Jain

2013-09-01

68

Image Preprocessing Methods to Identify Micro-cracks of Road Pavement  

Directory of Open Access Journals (Sweden)

Full Text Available Standards of highway conservation and maintenance are improved gradually following the improvement of requirements of road service. Before obvious damage such as obvious cracking (block?transverse, longitudinal and rutting emerge, inconspicuous distress (micro-cracks, polishing, pockmarked is generated previously. These inconspicuous distresses may provide basis and criteria for pavement preventive maintenance. Currently most of preventive conservation measures are determined by experienced experts in maintenance and repair of road after site visits. Thus method is difficult in operation, and has a certain amount of instability as it is based on experience and personal knowledge. In this paper, camera and laser were used for automated high-speed acquisition images. Methods to preprocess pavement image are compared. The pretreatment method suitable for analyze micro-cracks picture is elected, an effective way to remove shadow is also proposed.

Hui Wang

2013-06-01

69

Pervious Pavement System Evaluation-Poster  

Science.gov (United States)

Pervious pavement is a low impact development stormwater control. The Environmental Protection Agency's Urban Watershed Management Branch is evaluating interlocking concrete pavingstone pervious pavement systems. The pavingstones themselves are impermeable, but the spaces between...

70

Recycling of Asphalt Pavements with Asphalt Rubber  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Pavement recycling has been an important rehabilitation technique to deal with reclaimed materials from old pavements which are usually sent to landfills. The application of this technique contributes to: i) the accomplishment of the requirements defined by the European legislation for the amount of material sent to landfills; ii) the reduction in the use of new raw materials used to produce pavement layers. The reduction of materials to be used in pavement rehabilitation has also been possib...

Pais, Jorge; Pereira, Paulo; Minhoto, Manuel; Baptista, Anto?nio

2008-01-01

71

High Performance Concrete Pavement in Indiana  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Until the early 1990s, curling and warping of Portland cement concrete pavement did not concern pavement engineers in many transportation agencies. Since beginning construction of the interstate system in the United States in the late 1950s through the late 1980s, the performance of Portland cement concrete pavement has been associated with properties of concrete as a pavement material. In those years developed standards and design guidelines emphasized better concrete materials and construct...

Nantung, Tommy E.

2011-01-01

72

Use of ground penetrating radar data in pavement rehabilitation strategy selection and pavement condition assessment  

Science.gov (United States)

The Fort Worth District of the Texas Department of Transportation (TxDOT) has used Ground Penetrating Radar (GPR) data extensively for pavement condition assessment and pavement rehabilitation type selection. GPR is a non- destructive testing technique that can determine pavement layer thicknesses as well as the presence of excessive moisture or excessive air voids in pavement layers. This paper describes four case studies where TxDOT personnel used GPR data to make pavement rehabilitation and assessment decisions.

Wimsatt, Andrew J.; Scullion, Thomas; Ragsdale, John; Servos, Stacia

1998-03-01

73

Making "Magic" Sidewalks of Pervious Pavement  

Science.gov (United States)

Students use everyday building materialsâsand, pea gravel, cement and waterâto create and test pervious pavement. They learn what materials make up a traditional, impervious concrete mix and how pervious pavement mixes differ. Groups are challenged to create their own pervious pavement mixes, experimenting with material ratios to evaluate how infiltration rates change with different mix combinations.

Water Awareness Research and Education (WARE) Research Experience for Teachers (RET),

74

Reducing Your Cost for Asphalt Pavements  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This session will discuss of how local government decision-makers can achieve greater value without sacrificing quality or service life. The session will touch upon use of Higher Recycled Asphalt Pavement (RAP), Recycled Asphalt Shingles (RAS), Asphalt Mix Design for Heavy Traffic vs. Light Traffic, Speed of Construction, Perpetual Pavement and Pavement Rehabilitation Strategies.

Evans, Alvin

2012-01-01

75

Development of Performance Models for a Typical Flexible Road Pavement in Nigeria  

Directory of Open Access Journals (Sweden)

Full Text Available The results of a study conducted to facilitate the development of road pavement performance models that are appropriate for Nigeria and similar developing countries andcould predict the rate of deterioration over their lifespan have been presented. Comprehensive investigations were carried out on the expressway linking Lagos (the economic nerve centre of Nigeria with Ibadan (the largest city in West Africa - apparently one of the most heavily trafficked roads in the country. Data relating to traffic characteristics, pavement condition ratings, distress types, pavement thickness, roughness index, rainfall and temperature, were collected. Models were developed to determine Pavement Condition Score (PCS and International Roughness Index (IRI. Stepwise Regression was used to analyse the data and quantify the impact of key input parameters on the PCS and IRI. Parameters such as depth of ruts and area of pot holes were found to be statistically significant in predicting PCS while number of patches, length of longitudinal cracks and depth of ruts were statistically significant in predicting IRI. The models can be used for planning road maintenance programs, thus minimizing the need for comprehensive data collection on pavement condition before the maintenance exercise, which is costly and time consuming.

Adebayo Oladipo Owolabi

2012-09-01

76

Use of noncontact sensors for paving operations on airport pavements  

Science.gov (United States)

The Swedish National Road Administration has been using a laser range finder system for assessing longitudinal and transversa profiles of pavements for a number of years. The Civil Administration has expressed interest in trying automated methods for surveying airfield runways. Regardless of sampling method, the data re used as input for computer aided design of new pavement surfaces. Typically, the output will consist of tables and maps of where to pave and mill the old pavement surface. Adjusting an old surface to perfectly smooth standards may require continuously changing the new pavement layer thickness. Traditionally, this was often carried out with mechanical devices, usually in direct touch with a wire. Some manufacturers now offer non-contact devices for pavers such as ultra sound sensors as an alternative to the mechanical sensors thus eliminating the need for setting up sires. The method was tested in late 1997 after the output data were converted for a design to be read directly by a paver control unit. A larger test was done in the summer of 1998. The results were promising and the Royal Swedish Fortifications Administration decided to try the method on a taxiway in 1999. The present paper describes some of the experiences obtained with this method and computer controlled equipment in general.

Lenngren, Carl A.

1999-01-01

77

Desert Pavement Process and Form: Modes and Scales of Landscape Stability and Instability in Arid Regions  

Science.gov (United States)

Desert pavements are recognized in arid landscapes around the world, developing via diminution of constructional/depositional landform relief and creating a 1-2 stone thick armor over a "stone free" layer. Surface exposure dating demonstrates that clasts forming the desert pavements are maintained at the land surface over hundreds of thousands of years, as aeolian fines are deposited on the land surface, transported into the underlying parent material and incorporated into accretionary soil horizons (e.g., the stone free or vesicular [Av] horizon). This surface armor provides long-term stability over extensive regions of the landscape. Over shorter time periods and at the landform-element scale, dynamic surficial processes (i.e., weathering, runoff) continue to modify the pavement form. Clast size reduction in comparison to underlying parent material, along with armoring and packing of clasts in pavements contribute to their persistence, and studies of crack orientations in pavement clasts indicate physical weathering and diminution of particle size are driven by diurnal solar insolation. Over geologic time, cracks form and propagate from tensile stresses related to temporal and spatial gradients in temperature that evolve and rotate in alignment with the sun's rays. Observed multimodal nature of crack orientations appear related to seasonally varying, latitude-dependent temperature fields resulting from solar angle and weather conditions. Surface properties and their underlying soil profiles vary across pavement surfaces, forming a landscape mosaic and controlling surface hydrology, ecosystem function and the ultimate life-cycle of arid landscapes. In areas of well-developed pavements, surface infiltration and soluble salt concentrations indicate that saturated hydraulic conductivity of Av horizons decline on progressively older alluvial fan surfaces. Field observations and measurements from well-developed desert pavement surfaces landforms also yield significantly lower infiltration rates, enhanced rates of overland flow characterized by high water:sediment ratios and reduced production of desert ecosystems. Consequently, regionally extensive pavement and significantly decreased infiltration over geologic time have resulted in widespread overland flow, elaborate drainage networks on alluvial and eolian-mantled bedrock landscapes, and channel incision and regional dissection of the pavement-mantled landforms. However, these once stable landscapes become progressively unstable with time, serving as sediment source areas for younger alluvial deposits (i.e., geologic life-cycle). Thus, regional dissection (instability) of these desert landscapes can be influenced by the intrinsic properties of pavement-mantled landscapes and not necessarily to external forces of climate change and tectonics.

Wells, Stephen G.; McFadden, Leslie D.; McDonald, Eric V.; Eppes, Martha C.; Young, Michael H.; Wood, Yvonne A.

2014-05-01

78

Geo synthetic-reinforced Pavement systems  

International Nuclear Information System (INIS)

Geo synthetics have been used as reinforcement inclusions to improve pavement performance. while there are clear field evidence of the benefit of using geo synthetic reinforcements, the specific conditions or mechanisms that govern the reinforcement of pavements are, at best, unclear and have remained largely unmeasured. Significant research has been recently conducted with the objectives of: (i) determining the relevant properties of geo synthetics that contribute to the enhanced performance of pavement systems, (ii) developing appropriate analytical, laboratory and field methods capable of quantifying the pavement performance, and (iii) enabling the prediction of pavement performance as a function of the properties of the various types of geo synthetics. (Author)

79

Comparative Study on Pavement Temperature Features of Bridge Deck and Road Pavement  

Directory of Open Access Journals (Sweden)

Full Text Available The objective of this study was to comparatively analyze the difference of pavement temperature of bride deck and road pavement. The asphalt pavement temperature of road pavement and bride deck were tested in Guozigou area of Xinjiang, China. And the air temperature, wind speed, humidness and sunlight radiation were collected. Further, the distribution features of asphalt pavement of bridge deck and road pavement were comparatively analyzed. At last, the predictive model of pavement temperature field for bridge deck and road pavement was set up. The results show that the pavement temperature and air temperature change synchronously. The pavement temperature of bridge deck is usually 66~13ºC higher than the air temperature and keeps close to it in winter. Compared with road pavement temperature, the temperature of bridge deck is characterized by being higher lowest-temperatures in winter, greater in temperature changes and lasting for longer time when it keeps its high temperature in summer. The predictive model of pavement temperature field for bridge deck and road pavement is proposed utilized linear function with five factors, namely air temperature, wind speed, humidness, sunlight radiation and pavement depth. The developed model was proved to be more accurate and closer to the measured temperature compared with LTPP and SHRP model.

Yueqin Hou

2013-12-01

80

The Concrete and Pavement Challenge  

Science.gov (United States)

The modern world is characterized by the extensive use of concrete and asphalt pavement. Periodically, these materials are replaced and the old materials disposed of. In this challenge, students will be asked to develop ways to reuse the old materials. It is important for students to understand how concrete and asphalt are made and applied, as…

Roman, Harry T.

2012-01-01

 
 
 
 
81

Cooler reflective pavements give benefits beyond energy savings: durability and illumination  

International Nuclear Information System (INIS)

City streets are usually paved with asphalt concrete because this material gives good service and is relatively inexpensive to construct and maintain. We show that making asphalt pavements cooler, by increasing their reflection of sunlight, may lead to longer lifetime of the pavement, lower initial costs of the asphalt binder, and savings on street lighting and signs. Excessive glare due to the whiter surface is not likely to be a problem

82

Cooler reflective pavements give benefits beyond energy savings: durability and illumination  

Energy Technology Data Exchange (ETDEWEB)

City streets are usually paved with asphalt concrete because this material gives good service and is relatively inexpensive to construct and maintain. We show that making asphalt pavements cooler, by increasing their reflection of sunlight, may lead to longer lifetime of the pavement, lower initial costs of the asphalt binder, and savings on street lighting and signs. Excessive glare due to the whiter surface is not likely to be a problem.

Pomerantz, Melvin; Akbari, Hashem; Harvey, John T.

2000-06-01

83

Validation of theoretical models through measured pavement response  

DEFF Research Database (Denmark)

Most models for structural evaluation of pavements are of the analytical-empirical type. An analytical model, derived from solid mechanics, is used to calculate stresses or strains at critical positions, and these stresses or strains are then used with empirical relationships to predict pavement performance. The analytical models are based on a number of simplifications with respect to reality and must be verified experimentally.Different pressure gauges were installed in a sand, assumed to be a semi-infinite halfspace. The surface of the sand was loaded by a Falling Weight Deflectometer (FWD) at different lateral positions with respect to the gauges. An integration of the stresses measured at the plane of the gauges showed that the total load recorded by the gauges was close to the loade imposed by the FWD, cofirming the reliability of the gauges. The theoretical stress calculated using continuum mechanics was quite different from the measured stress, the peak theoretical value being only half of the measured value.On an instrumented pavement structure in the Danish Road Testing Machine, deflections were measured at the surface of the pavement under FWD loading. Different analytical models were then used to derive the elastic parameters of the pavement layeres, that would produce deflections matching the measured deflections. Stresses and strains were then calculated at the position of the gauges and compared to the measured values. It was found that all analytical models would predict the tensile strain at the bottom of the asphalt layer reasonably well, but that the vertical strain at the top of the subgrade could only be predicted with some degree of accuracy if the subgrade was treated as a non-linear elastic material.

Ullidtz, Per

1999-01-01

84

Ground-penetrating radar for airfield pavement evaluations  

Science.gov (United States)

A ground penetrating radar (GPR) system has been developed and implemented for the U.S. Air Force's pavement evaluation teams. This tool can be used to rapidly, continuously, and non-destructively perform feature delineation, anomaly detection, and layer thickness measurements for airfield pavements. The layer thickness function has been automated. The basic GPR hardware, a Geophysical Survey Systems Inc. (GSSI) SIR-8 with three sets of antennas (500 MHz, 900 MHz, and 2.5 GHz), is mounted in a full-size van and has been extensively modified. An additional SIR-8 controller was installed to allow simultaneous operation of two antenna sets. Direct data capture, on-board digital data storage, and real-time analysis and display capability has been provided by installing a 486 computer and color printer, then connecting them directly to the antenna data lines. Distance markers are also embedded directly into the data stream. Layer thickness measurement is accomplished by combining the dielectric constant obtained from the 2.5 GHz antennas (using the surface reflectivity ratio method), with the 2-way layer travel time measured by the 900 MHz antennas. Automated layer thickness determination techniques have been developed for analyzing data from the ground-coupled antennas that provide the deeper penetration necessary on thick airfield pavements. Automatic data processing software has been developed that performs the direct data capture and calculations necessary to provide real-time output of dielectric constant and layer thickness versus distance travelled. The Air Force GPR device has been successfully used on several airfields to date, demonstrating it can be used to differentiate between pavement features of significantly different thickness, detect anomalies such as voids under pavement and water intrusion, as well as accurately measure the surface layer thickness. Several comparisons of core-measured versus radar-predicted thicknesses have been made, on both PCC and AC, with good correlation.

Adcock, Avery D.; Dass, William C.; Rish, Jeff W., III

1995-07-01

85

Improving the distribution and reducing the magnitude of pavement damage  

Science.gov (United States)

In the analysis of flexible pavement, the layered elastic theory was used to compute the pavement response. For the rigid pavement, finite difference, layered elastic theory, and Westergard procedures were used to compute tensile stresses in concrete that formed the basis for predicting allowable stress repetitions. For flexible pavement, the only effective means to reduce pavement damage was to modify the wheel assembly to reduce stress or strain at the critical locations in the pavement systems. The most effective modification would be to increase the spacing between duals. For rigid pavements, the edge effect was critical, thus suggesting that modifications to shift the loading away from the pavement edge would be effective.

Barker, W. R.; Chou, U. T.

1980-08-01

86

ELLPAG - Economics of Long-Life Pavement  

Digital Repository Infrastructure Vision for European Research (DRIVER)

One of the most important research efforts developed to date is the European Project ELLPAG (European Long-Life Pavement Group). It was founded, in 2002, as a FEHRL group to gather the European knowledge. The group has been active since then, and it has been focused on flexible, semi-rigid and rigid pavements. The advantages of this type of pavements can be very significant, either in terms of economy, serviceability or environment. However, important research needs are still required...

Bueche, N.

2008-01-01

87

Modeling the Deflection Basin of Flexible Highway Pavements by Gene Expression Programming  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, Gene Expression Programming (GEP is used in modeling the deflection basins measured on the surface of the flexible pavements. Backcalculation of the pavement layer moduli are well-accepted procedures for the evaluation of the structural capacity of pavements. The ultimate aim of the backcalculation process from Nondestructive Testing (NDT results is to estimate the pavement material properties. Using backcalculation analysis, in situ material properties can be backcalculated from the measured field data through appropriate analysis techniques. In order to backcalculate reliable moduli, deflection basin must be realistically modeled. In this study, GEP was used to model the deflection basin characteristics. Experimental deflection data groups from NDT are used to show the capability of the GEP approach in modeling the deflection bowl. This approach can be easily and realistically performed to solve the problems which do not have a formulation or function about the solution.

Serdal Terzi

2005-01-01

88

Predicting physical clogging of porous and permeable pavements  

Science.gov (United States)

SummaryPorous pavements are easily retrofitted, and effective in improving water quality and hydrology, but prone to clogging. Despite being a major determinant in the lifespan of porous pavements, there is limited information on the physical clogging processes through these systems. The aim of this study was to understand the main physical processes that govern physical clogging and develop a simple black-box model that predicts physical clogging. The key variables that were hypothesised to influence clogging were pavement design and climate characteristics. Two compressed time scale laboratory experiments were conducted over 3 years on three common porous pavement types; monolithic porous asphalt, modular Hydrapave and monolithic Permapave. Pavement design was found to be an important role in clogging. Permapave did not clog even after 26 years of operation in simulated sub-tropical Brisbane (Australia) climate while porous asphalt and Hydrapave clogged after just 12 years, from surface clogging and geotextile clogging, respectively. Each system was tested using two different dosing patterns: (1) continual wetting with no dry periods and (2) variable inflow rates with drying periods (i.e. representing more natural conditions). The latter dosing method approximately doubled the lifespan of all systems suggesting the influence of climate conditions on clogging. Clogging was found to be highly correlated with cumulative volume and flow rate. A simple black-box regression model that predicts physical clogging was developed as a function of cumulative volume and Brisbane climatic conditions. However it is very likely that the shape of this regression is general, and that it could be calibrated for different climates in the future.

Yong, C. F.; McCarthy, D. T.; Deletic, A.

2013-02-01

89

A design system for rigid pavement rehabilitation  

Science.gov (United States)

The development, use, and applicability of a rigid pavement rehabilitation design system, RPRDS, developed for use by the Texas State Department of Highways and Public Transportation is described. Like other pavement design systems, RPRDS makes use of the systems approach to incorporate a number of pavement design and analytical models into a computer program, RPRDS-1, for the generation, analysis, and comparison of numerous pavement design strategies. Basically, RPRDS generates a number of feasible overlay design strategies based on user inputs, performs a present value cost analysis on each, and then presents those which are optimal.

Seeds, S. B.; McCullough, B. F.; Hudson, W. R.

1982-01-01

90

Review of permeable pavement systems  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this review paper is to summarise the wide-range but diffuse literature on predominantly permeable pavement systems (PPS), highlight current trends in research and industry, and to recommend future areas of research and development. The development of PPS as an integral part of sustainable drainage systems is reviewed in the context of traditional and modern urban drainage. Particular emphasise is given to detailed design, maintenance and water quality control aspects. The most important target pollutants are hydrocarbons, heavy metals and nutrients (i.e. nitrogen and phosphorus). The advantages and disadvantages of different PPS are discussed with the help of recent case studies. The latest innovations are highlighted and explained, and their potential for further research work is outlined. Recent research on the development of a combined geothermal heating and cooling, water treatment, and recycling pavement system is promising. (author)

Scholz, Miklas; Grabowiecki, Piotr [Institute for Infrastructure and Environment, School of Engineering and Electronics, The University of Edinburgh, William Rankine Building, The King' s Buildings, Edinburgh EH9 3JL, Scotland (United Kingdom)

2007-11-15

91

Comparative field permeability measurement of permeable pavements using ASTM C1701 and NCAT permeameter methods.  

Science.gov (United States)

Fully permeable pavement is gradually gaining support as an alternative best management practice (BMP) for stormwater runoff management. As the use of these pavements increases, a definitive test method is needed to measure hydraulic performance and to evaluate clogging, both for performance studies and for assessment of permeability for construction quality assurance and maintenance needs assessment. Two of the most commonly used permeability measurement tests for porous asphalt and pervious concrete are the National Center for Asphalt Technology (NCAT) permeameter and ASTM C1701, respectively. This study was undertaken to compare measured values for both methods in the field on a variety of permeable pavements used in current practice. The field measurements were performed using six experimental section designs with different permeable pavement surface types including pervious concrete, porous asphalt and permeable interlocking concrete pavers. Multiple measurements were performed at five locations on each pavement test section. The results showed that: (i) silicone gel is a superior sealing material to prevent water leakage compared with conventional plumbing putty; (ii) both methods (NCAT and ASTM) can effectively be used to measure the permeability of all pavement types and the surface material type will not impact the measurement precision; (iii) the permeability values measured with the ASTM method were 50-90% (75% on average) lower than those measured with the NCAT method; (iv) the larger permeameter cylinder diameter used in the ASTM method improved the reliability and reduced the variability of the measured permeability. PMID:23434738

Li, Hui; Kayhanian, Masoud; Harvey, John T

2013-03-30

92

Infiltration Through Desert Pavements, Mojave Desert, CA, USA  

Science.gov (United States)

Desert pavements consist of a surface layer of closely packed gravel that overlies thin, gravel-poor vesicular A (Av) soil horizon. Pavements are prominent features in arid and semi-arid environments and can be found on a variety of landforms of significantly diverse ages ranging from Holocene to Tertiary. Well-developed Av profiles form distinct and highly structured prismatic peds. These fine-grained, structured soils can exhibit drastically reduced infiltration rates, rendering some localized areas nearly impermeable and greatly impacting soil development, plant and biota diversity, and groundwater recharge. We sought to study how desert pavement development can impact the hydraulic conductivity characteristics in localized areas (order of 10s of cm). Field sites were chosen at the Mojave Natural Preserve, near Kelso Dunes, CA, USA, which has been the location of considerable prior research by the second author. The sites vary by parent material, clay and silt content, surface age, and variable degree of surface clast cover. Transects were chosen that traversed pavement surfaces of variable development (well developed to poorly developed). Hydraulic conductivity was determined with a tension infiltrometer conducted at different tensions and initial water contents (to better estimate the potential for preferential flow). Sites with dry initial conditions were first analyzed at zero tensions to promote inter-ped flow. After allowing soil peds to hydrate and expand, the tests were run again at a range of soil tensions to promote matrix flow. Differences in saturated conductivities (measured and fitted) were attributed to preferential flow around desiccated peds. Soil texture and structure were measured and described, respectively, allowing for the correlation of conductivity functions to soil surface age and physical characteristics.

Young, M. H.; McDonald, E. V.; Caldwell, T. C.; Benner, S. G.

2003-04-01

93

Enhancing pavements for thermal applications  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Renewable energy combined with energy efficiency can offer a viable and influential solution to minimise the harmful consequences of both fossil fuel depletion and increases in the cost of power generation. However, in most cases renewable energy technologies require high initial investments that may deter potential users. Pavement Energy Systems (PES) potentially offer a low-cost solution to sustainable and clean energy generation by utilising the thermo-physical properties and design featur...

Keikhaei Dehdezi, Pejman

2012-01-01

94

Mathematical failure-theory (MFT methodology in pavement management system for rehabilitation and repair methods selection  

Directory of Open Access Journals (Sweden)

Full Text Available Pavement rehabilitation and repair methods selection is one of the key issues many road organizations and researchers have occupied. Not only road management cost but also road user’s cost and cost for inhabitants and community should be included in the life cycle cost in order to help infrastructure investment judgment. Thus in estimating life cycle cost, Pavement rehabilitation and repair methods selection is essential even if technological capabilities of evaluation are not sufficient. In order for Pavement Management Systems (PMS to be effective, they must be based on a reliable, statistically sound means for the rehabilitation and repair methods that are present on the system. To make sensible life cycle cost decisions in design and rehabilitation, pavement engineers must be able to account for distress phenomena and repair methods. This paper will present a Mathematical Failure-Theory (MFT methodology for incorporating statistical and probabilistically Factors into life cycle cost analysis and PMS. This approach gives the engineer the ability to statistically and probability consider different rehabilitation and repair method and statistically and probability factors in computing the life cycle costs for rehabilitation and repair methods selection.

Fereidoon Moghadas Nejad

2009-04-01

95

Preliminary evaluation of the lifecycle costs and market barriers of reflective pavements  

Energy Technology Data Exchange (ETDEWEB)

The objective of this study is to evaluate the life cycle costs and market barriers associated with using reflective paving materials in streets and parking lots as a way to reduce the urban heat island effect. We calculated and compared the life cycle costs of conventional asphalt concrete (AC) pavements to those of other existing pavement technologies with higher reflectivity-portland cement concrete (PCC), porous pavements, resin pavements, AC pavements using light-colored chip seals, and AC pavements using light-colored asphalt emulsion additives. We found that for streets and parking lots, PCC can provide a cost-effective alternative to conventional AC when severely damaged pavements must be completely reconstructed. We also found that rehabilitating damaged AC streets and intersections with thin overlays of PCC (ultra-thin white topping) can often provide a cost-effective alternative to standard rehabilitation techniques using conventional AC. Chip sealing is a common maintenance treatment for low-volume streets which, when applied using light-colored chips, could provide a reflective pavement surface. If the incremental cost of using light-colored chips is low, this chip sealing method could also be cost-effective, but the incremental costs of light-colored chips are as of yet uncertain and expected to vary. Porous pavements were found to have higher life cycle costs than conventional AC in parking lots, but several cost-saving features of porous pavements fell outside the boundaries of this study. Resin pavements were found to be only slightly more expensive than conventional AC, but the uncertainties in the cost and performance data were large. The use of light-colored additives in asphalt emulsion seal coats for parking lot pavements was found to be significantly more expensive than conventional AC, reflecting its current niche market of decorative applications. We also proposed two additional approaches to increasing the reflectivity of conventional AC, which we call the chipping and aggregate methods, and calculated their potential life cycle costs. By analyzing the potential for increased pavement durability resulting from these conceptual approaches, we then estimated the incremental costs that would allow them to be cost-effective compared to conventional AC. For our example case of Los Angeles, we found that those allowable incremental costs range from less than dollar 1 to more than dollar 11 per square yard (dollar 1 to dollar 13 per square meter) depending on street type and the condition of the original pavement. Finally, we evaluated the main actors in the pavement market and the existing and potential market barriers associated with reflective pavements. Apart from situations where lifecycle costs are high compared to conventional AC, all reflective paving technologies face a cultural barrier based on the belief that black is better. For PCC, high first costs were found to be the most significant economic barrier, particularly where agencies are cons trained by first cost. Lack of developer standards was found to be a significant institutional barrier to PCC since developers are often not held accountable for the long-term maintenance of roads after initial construction, which creates a misplaced incentive to build low first-cost pavements. PCC also faces site-specific barriers such as poorly compacted base soils and proximity to areas of frequent utility cutting.

Ting, M.; Koomey, J.G.; Pomerantz, M.

2001-11-21

96

Effects of impervious pavements on reducing runoff in an arid urban catchment  

Science.gov (United States)

The progressive urbanization of US arid and semi-arid southwestern territories has transformed undeveloped aridlands into dynamic, radially expanding metropolitan centers. As these mature, infill development further reduces undeveloped area, inversely coupling surface imperviousness to infiltration rates, with a subsequent increase in runoff generation. Intensified runoff carries undesirable environmental consequences, magnifying urban flooding events and concentrations, transport, and propagation of contaminants. Pervious pavements offer one potential solution for decreased urban infiltration. At present, the application potential of pervious pavements as an effective urban infiltration management tool exceeds its exploitation. While entirely eliminating urban Total Impervious Area is not a feasible solution, pervious pavements significantly reduce Effective Impervious Area at costs competitive with traditional Best Management Practices. Previous research into pervious pavements has largely consisted of laboratory prototypes or small-scale field experiments, with a heavy bias towards parking lots. In this study we explore the effectiveness of pervious pavements in increasing infiltration, thus decreasing runoff volume during summer monsoonal and winter convective rainfall events in an 8 ha residential catchment in Scottsdale, Arizona. Analysis focuses on the interaction dynamics between surface area of pervious pavement application and its net effect on runoff response at the catchment level. Hydrological response was modeled using MAHLERAN (Model for Assessing Hillslope-Landscape Erosion, Runoff and Nutrients), a spatially explicit, event-based model, parameterized at a spatial resolution of 0.25 sq m. Data for model parameterization was obtained from analysis of aerial imagery and field-based monitoring of surface properties. The model was tested against measurements of flow at the catchment outlet for multiple rainfall events with total event rainfall ranging from 5 mm to 25 mm. Model testing shows total event discharge simulated well, although low Nash-Sutcliffe coefficients for events indicate a poor fit between the shape and timing of the modeled and monitored hydrograph, which we attribute to poor characterization of friction factors in urban catchments. Scenario-based model analysis tested catchment response to substitution of pervious for conventional pavement by percent and pavement-function scenarios. Results are consistent with previous findings in that short duration-high intensity storms trigger threshold infiltration capacity, past which pervious pavement damping of runoff volume levels off, approaching conventional levels. However at the modeled catchment scale, this initial damping represents a significant reduction in volume, peak flow velocity, and contaminant loading potential. Urban surface drainage networks concentrate and channel flow along roads: the capacity of pervious pavements to simultaneously increase infiltration directly at location of greatest runoff and mitigate inflow effects from remote points has compelling potential as a hydrologic and urban systems engineering tool.

Epshtein, O.; Turnbull, L.; Earl, S.

2011-12-01

97

Pervious Pavement System Evaluation-Paper  

Science.gov (United States)

The use of a pervious pavement can be effective as a low impact development stormwater control. The Urban Watershed Management Branch is evaluating interlocking concrete paver systems as a type of porous pavement. Although the pavers are impermeable, the spaces between the pave...

98

Study of the Effect of Temperature Changes on the Elastic Modulus of Flexible Pavement Layers  

Directory of Open Access Journals (Sweden)

Full Text Available In general, the stiffness of flexible pavement is influenced by environmental changes, whereby temperature and rainfall affect the asphalt layer and non-asphalt layer, such as the subgrade, respectively. Normally, the effect of temperature on flexible pavement can be measured using two methods. The first is a destructive test whereby core samples are tested in a laboratory using a Universal Testing Machine (UTM. The second is a non-destructive in situ test using equipment such as a Falling Weight Deflectometer (FWD and Spectral Analysis of Surface Waves (SASW. This study was conducted to investigate the effect of temperature at different tensile levels on the Soekarno-Hatta and Purwakarta Cikampek roads in Bandung, West Java, Indonesia. It is observed that different tensile levels and testing methods result in various elastic modulus values of flexible pavement. The higher the temperature applied to the flexible pavement layer, the more the elastic modulus values decrease. In contrast, the lower the temperature imposed on the flexible pavement layer, the more the elastic modulus values increase. Different testing methods (FWD, UTM and SASW on the flexible pavement layer are also affected by temperature changes.

Mohd Raihan Taha

2013-02-01

99

23 CFR 971.208 - Federal lands pavement management system (PMS).  

Science.gov (United States)

... Federal lands pavement management system (PMS). In addition...the AASHTO's “Pavement Management Guide.” 1 1 “Pavement Management Guide,” AASHTO...nature of the transportation network. These different...

2010-04-01

100

In place recycling of granular bases of asphalt pavements  

Directory of Open Access Journals (Sweden)

Full Text Available This work presents the results of a study intended the obtaining and introduction of the auxiliary elements to assure the road pavements technological control of rehabilitation which involves the recycling in place of granular bases. This verification was made using two techniques, the CBR in place verification, through the use of DCP (Dynamic Cone Penetrometer, and the granulometric framing, through the curve of Talbot, for recycled materials. The investigations were accomplished starting from practical applications in roads which involved, in an experimental way, the pavements rehabilitation through the base course recycling, incorporating the surface layer. Through the data processing obtained in the tests, it was possible the elaboration of the technical specification proposal of the granular bases recycling.

Taís Sachet

2008-04-01

 
 
 
 
101

Global warming potential of pavements  

International Nuclear Information System (INIS)

Pavements comprise an essential and vast infrastructure system supporting our transportation network, yet their impact on the environment is largely unquantified. Previous life-cycle assessments have only included a limited number of the applicable life-cycle components in their analysis. This research expands the current view to include eight different components: materials extraction and production, transportation, onsite equipment, traffic delay, carbonation, lighting, albedo, and rolling resistance. Using global warming potential as the environmental indicator, ranges of potential impact for each component are calculated and compared based on the information uncovered in the existing research. The relative impacts between components are found to be orders of magnitude different in some cases. Context-related factors, such as traffic level and location, are also important elements affecting the impacts of a given component. A strategic method for lowering the global warming potential of a pavement is developed based on the concept that environmental performance is improved most effectively by focusing on components with high impact potentials. This system takes advantage of the fact that small changes in high-impact components will have more effect than large changes in low-impact components.

102

23 CFR 972.208 - Federal lands pavement management system (PMS).  

Science.gov (United States)

... Federal lands pavement management system (PMS). In addition...the AASHTO's “Pavement Management Guide.”2 2 “Pavement Management Guide,” AASHTO...the nature of the pavement network. These different...

2010-04-01

103

23 CFR 973.208 - Indian lands pavement management system (PMS).  

Science.gov (United States)

...208 Indian lands pavement management system (PMS). In addition...the AASHTO's “Pavement Management Guide.” 1 1 “Pavement Management Guide,” AASHTO...the nature of the pavement network. These different...

2010-04-01

104

Modelación del envejecimiento de los pavimentos asfálticos con la metodología de la superficie de respuesta / Pavement Aging Model by Response Surface Modeling  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: Spanish Abstract in spanish En la presente investigación se realizó la modelación del envejecimiento de una carpeta asfáltica por medio de la Metodología de Superficie de Respuesta (MSR). Se elaboraron muestras cilíndricas tipo Marshall, que fueron colocadas en un horno bajo las condiciones de tiempo y temperatura establecidos [...] por las condiciones ambientales de la región geográfica donde se construyen pavimentos asfálticos con el AC-20 de la Refinería Ing. Antonio M. Amor, los cuales fueron codificados en la MSR, con esto se determinaron los modelos que predicen el cambio de la estabilidad Marshall (?L) y del flujo (?F), así como la volatilización del material (VM). Además, se extrajeron muestras cilíndricas de una carpeta asfáltica piloto para determinar el error de modelación, observando que el material volatilizado predicho por el modelo VM fue muy cercano al real, no así para los modelos de ?Ly ?F, posiblemente asociado a los factores ambientales que no fueron considerados al inicio de la investigación. Abstract in english In this work, surface course aging was modeled by Response Surface Methodology (RSM). The Marshall specimens were placed in a conventional oven for time and temperature conditions established on the basis of the environment factors of the region where the surface course is constructed by AC-20 from [...] the Ing. Antonio M. Amor refinery. Volatilized material (VM), load resistance increment (?L) and flow resistance increment (?F) models were developed by the RSM. Cylindrical specimens with real aging were extracted from the surface course pilot to evaluate the error of the models. The VM model was adequate, in contrast (?L) and (?F) models were almost adequate with an error of 20 %, that was associated with the other environmental factors, which were not considered at the beginning of the research.

L.E., Chávez-Valencia; C, Hernández-Barriga; A, Manzano-Ramírez.

2011-12-01

105

Modelación del envejecimiento de los pavimentos asfálticos con la metodología de la superficie de respuesta / Pavement Aging Model by Response Surface Modeling  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: Spanish Abstract in spanish En la presente investigación se realizó la modelación del envejecimiento de una carpeta asfáltica por medio de la Metodología de Superficie de Respuesta (MSR). Se elaboraron muestras cilíndricas tipo Marshall, que fueron colocadas en un horno bajo las condiciones de tiempo y temperatura establecidos [...] por las condiciones ambientales de la región geográfica donde se construyen pavimentos asfálticos con el AC-20 de la Refinería Ing. Antonio M. Amor, los cuales fueron codificados en la MSR, con esto se determinaron los modelos que predicen el cambio de la estabilidad Marshall (?L) y del flujo (?F), así como la volatilización del material (VM). Además, se extrajeron muestras cilíndricas de una carpeta asfáltica piloto para determinar el error de modelación, observando que el material volatilizado predicho por el modelo VM fue muy cercano al real, no así para los modelos de ?Ly ?F, posiblemente asociado a los factores ambientales que no fueron considerados al inicio de la investigación. Abstract in english In this work, surface course aging was modeled by Response Surface Methodology (RSM). The Marshall specimens were placed in a conventional oven for time and temperature conditions established on the basis of the environment factors of the region where the surface course is constructed by AC-20 from [...] the Ing. Antonio M. Amor refinery. Volatilized material (VM), load resistance increment (?L) and flow resistance increment (?F) models were developed by the RSM. Cylindrical specimens with real aging were extracted from the surface course pilot to evaluate the error of the models. The VM model was adequate, in contrast (?L) and (?F) models were almost adequate with an error of 20 %, that was associated with the other environmental factors, which were not considered at the beginning of the research.

L.E., Chávez-Valencia; C, Hernández-Barriga; A, Manzano-Ramírez.

106

A comparison between linear and non-linear analysis of flexible pavements  

Energy Technology Data Exchange (ETDEWEB)

Computer pavement analysis programs, which are based on mathematical simulation models, were compared. The programs included in the study were: ELSYM5, an Elastic Linear (EL) pavement analysis program, MICH-PAVE, a Finite Element Non-Linear (FENL) and Finite Element Linear (FEL) pavement analysis program. To perform the analysis different tire pressures, pavement material properties and asphalt layer thicknesses were selected. Evaluation criteria used in the analysis were tensile strain in bottom of the asphalt layer, vertical compressive strain at the top of the subgrade and surface displacement. Results showed that FENL methods predicted more strain and surface deflection than the FEL and EL analysis methods. Analyzing pavements with FEL does not offer many advantages over the EL method. Differences in predicted strains between the three methods of analysis in some cases was found to be close to 100% It was suggested that these programs require more calibration and validation both theoretically and empirically to accurately correlate with field observations. 19 refs., 4 tabs., 9 figs.

Soleymani, H.R.; Berthelot, C.F.; Bergan, A.T. [Saskatchewan Univ., Saskatoon, SK (Canada). Dept. of Mechanical Engineering

1995-12-31

107

Effects on evaporation rates from different water-permeable pavement designs.  

Science.gov (United States)

The urban water balance can be attenuated to the natural by water-permeable pavements (WPPs). Furthermore, WPPs have a 16% higher evaporation rate than impermeable pavements, which can lead to a better urban climate. Evaporation rates from pavements are influenced by the pavement surface and by the deeper layers. By a compared evaporation measurement between different WPP designs, the grain size distribution of the sub-base shows no influence on the evaporation rates in a significant way. On the contrary, a sub-base made of a twin-layer decreases the evaporation by 16% compared to a homogeneous sub-base. By a change in the colour of the paving stone, 19% higher evaporation rates could be achieved. A further comparison shows that the transpiration-effect of the grass in grass pavers increases the evaporation rates more than threefold to pervious concrete pavements. These high evapotranspiration rates can not be achieved with a pervious concrete paving stone. In spite of this, the broad field of application of the pervious concrete paving stone increases the importance in regard to the urban climate. PMID:22049757

Starke, P; Göbel, P; Coldewey, W G

2011-01-01

108

Research on tensile strength characteristics of bridge deck pavement bonding layers  

Science.gov (United States)

As the development of the traffic in the world, the bridge deck pavement is playing a more and more important role in the whole traffic system. Big span bridge has become more and more especially cement concrete bridge, therefore the bridge deck pavement bonding layers are emphasized as an important part of bridge traffic system, which can mitigate travel impact to bridge and magnify stationary or traffic amenity. The quality and durability of deck pavement bonding layer has directly effect on traffic safety, comfort, durability and investment of bridge. It represents the first line of defence against the ingress of water, road de-icing salts and aggressive chemicals. In real project, many early age damage of bridge deck pavement has become serious disease that affecting the function of bridge. During the construction of the bridge deck, many types of asphalt binders were used, such as styrene-butadiene-styrene (SBS) modified asphalt, styrene-butadiene rubber (SBR) modified asphalt, neoprene latex asphalt, etc. In this paper UTM-25 was used to test the tensile strength of different bridge deck pavement bonding layers with the different treatment methods to inter-surface.

Wu, Shaopeng; Han, Jun

2010-03-01

109

Investigation of antenna frequency impact on assessing voids of asphalt pavements using GPR  

Science.gov (United States)

Ground Penetrating Radar (GPR) is a Non Destructive Testing (NDT) technique that has been developed and improved upon over the past 30 years. The technique is frequently utilized in order to evaluate and assess pavement structures. GPR, for pavement evaluation purposes, can be described as a remote sensing system that emits a short pulse, of electromagnetic energy, into the pavement, with a central frequency varying from 10 MHz up to 2.5GHz. The two most commonly utilized setups are air-coupled and ground-coupled antenna systems. For air-coupled systems, the antennas are suspended above the pavement surface and can operate at normal traffic speeds (up to ~ 80 Km/h). The major drawback of the air-coupled antenna is that penetration depth is limited. On the other hand, for ground-coupled systems the antennas are in direct contact with the pavement surface, providing for better signal penetration into the pavement structure; however ground coupled systems can achieve only limited operational speeds. As a generalized rule, increasing the GPR central operating frequency, increases the investigation resolution, while decreasing the overall depth of investigation In the light of the above, air-coupled systems have become increasingly popular for the evaluation of the part of the pavement structure, especially for the asphalt layers, while ground-coupled systems are utilized mostly in order to gather information from the entire pavement structure (up to ~ 3 m depth). The majority of GPR pavement studies are carried out with air-coupled horn antennas, as they can be implemented at driving speeds without need for road closures. For instance, the 1 GHz air-coupled horn antenna is commonly used for the estimation of pavement layer thickness. However signals generated by horn antenna systems must have sufficient quality to allow the performance of automated signal processing and qualitative data analysis, especially when pavement data more sensitive to the analysis parameters, such voids or moisture, is concerned. The implementation of the horn antenna method is dependent upon, amongst others, the resolution of the antenna in use. The present research work investigates the application of the GPR sensor technique to assess voids within the asphalt layers, with a focus on the air-coupled antenna penetration depth and resolution. For this purpose the dielectric properties of asphalt layer materials were estimated and related voids contents were evaluated based on data collected by an air-coupled GPR system, operating at a 1 GHz and alternatively a 2 GHz central frequency. The collected data is analyzed comparatively for the two antennas. Comparison results indicate differences between the voids determined from the 1 GHz and 2GHz antennas. These differences are further analyzed and evaluated for pavement quality control purposes. The indication of a relationship between the measured voids is also evaluated, while ground truth data is used for the validation of the GPR data analysis results. The above is presented and discussed thoroughly with the aim to assist pavement quality assurance systems

Plati, C.; Georgouli, K.; Loizos, A.

2012-04-01

110

Flying blind: designing and maintaining jointed concrete pavement without monitoring pavement pressure generation  

Science.gov (United States)

The generation of longitudinal pavement pressures or growth of jointed-rigid pavement have been recognized by many engineers for at least a century. The manifestations of this pressure/growth phenomenon, in the form of progressive pavement and bridge damage, are vivid examples of its destructive potential. Yet, only a few researchers have attempted to measure the pressures generated by this phenomenon. None, to the author's knowledge, have attempted to periodically monitor pressure generation for the purpose of either determining and describing pressure generation characteristics or predicting the probability of its abrupt final and destructive manifestations. Because the pavement/growth phenomenon occurs over such a long period of time (a decade or more), it is generally unrecognized, or if recognized, it is poorly understood. Consequently, design and maintenance of jointed rigid pavement continues to be guided more by intuition and personal judgement rather than be replicated research and professional consensus. This paper provides a speculative description of the pavement pressure/growth phenomenon. It also contains an appeal to research professionals to develop instrumentation suitable to monitor generating pavement pressures. The results of such research should finally enable the transportation profession to establish suitable background so that future pavement design and maintenance will be guided so that pressure generation will be minimized and pavement and bridge function and durability will be improved. Otherwise, transportation systems will continue to experience progressive and substantial pavement and bridge damage, commensurate repair costs, and the traveling public will continue to be exposed to occasional but abrupt manifestations of its destructive potential.

Burke, Martin P., Jr.

2001-08-01

111

Friction evaluation of concrete paver blocks for airport pavement applications  

Science.gov (United States)

The development and use of concrete paver blocks is reviewed and some general specifications for application of this type of pavement surface at airport facilities are given. Two different shapes of interlocking concrete paver blocks installed in the track surface at NASA Langley's Aircraft Landing Dynamics Facility (ALDF) are described. Preliminary cornering performance results from testing of 40 x 14 radial-belted and bias-ply aircraft tires are reviewed. These tire tests are part of a larger, ongoing joint NASA/FAA/Industry Surface Traction and Radial Tire (START) Program involving several different tire sizes. Both dry and wet surface conditions were evaluated on the two concrete paver block test surfaces and a conventional, nongrooved Portland cement concrete surface. Future test plans involving evaluation of other concrete paver block designs at the ALDF are indicated.

Yager, Thomas J.

1992-01-01

112

GPR in Nondestructive Quality Assurance of New Asphalt Pavements  

Science.gov (United States)

Mara Nord is an international cooperation project financed by Interreg IVA Nord funding program with partners from Finland, Sweden and Norway. One of the objectives in Mara Nord project has been to research the quality assurance of new asphalt pavement. Ground penetrating radar (GPR) survey is used as an alternative method for coring in quality assurance. There exist numerous advantages for the use of GPR. For example, the fluent measuring arrangements without closing the traffic on the road and the extensive continuous profile that can be constructed from the measuring data. Within the framework of Mara Nord Project field tests were organized in Seinäjoki region in Finland on August 2011. The tests were done by four consulting companies from Finland and Rovaniemi University of Applied Sciences. The aim of these tests was to compare the measured dielectric value profiles and the calculated void content profiles of the equipment. The tested equipment was GSSI manufactured SIR-20 and 1 GHz horn antennas. Void content values were calculated using the model presented by Mr. Roimela (1997). All core samples were taken from the right wheel path. The same reference core samples were used when analyzing the data of each GPR equipment. Some samples were taken right after the pavement work was completed with the rest three weeks after during the test measurements. The tests indicated that GPRs have very good repeatability in measuring dielectric changes on top surface layers of asphalt pavements. Furthermore, different GPRs locate the same detectable longitudinal dielectric changes with high accuracy. Some differences were found in the dielectric value levels, yet reproducibility of the calculated void content values was quite good. The test data was also used to evaluate the reliability of the regression model between the dielectric values measured through GPR and the void content of the pavement determined from reference cores. Test data indicated that accurate regression model could not be validated by using test data because of too wide variation. The variation of void content in core sample results was not always registered by GPR with corresponding variation in dielectric value. There was some moisture present in test conditions and this might have influenced the GPR results. There are some reference data from dry conditions which will be used later on for analyzing the influence of moisture. There was also quite wide variation in void content determined from core samples taken close to each other during field tests. However, wide variation was not seen in core samples taken right after the pavement work. It is possible that traffic load had its effect on the asphalt pavement compaction. The results indicate that when using only one survey line it should be located between wheel paths. Another option is GPR void content measurements should be done right after the pavement work.

Poikajärvi, J.; Peisa, K.; Narbro, A.

2012-04-01

113

An Innovative Strategy for Maintenance of Highway Pavement  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Highway pavement are deteriorating fast due to lack of timely maintenance, leading to higher vehicle operating costs, increasing number of accidents etc. Thus, timely maintenance of the highway pavement is essential. Because, once pavements start to deteriorate; they deteriorate rapidly beyond the point where maintenance is effective. Thus, there is an urgent need to develop a strategy for maintenance of pavement in a huge highway network. In this study, an innovative strategy for maintenance...

Sandeep Choudhary, Dr P. K. Agarwal

2013-01-01

114

Calculation method for permanent deformation of unbound pavement materials  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An analytical-mechanistic method for the calculation of permanent deformations of pavements has been developed at the Technical Research Centre of Finland (VTT) over some years by the author. The calculation method is needed in the analytical design procedure of pavements. This research concentrated on the calculation method for permanent deformations in unbound pavement materials. The calculation method was generated based on the results of full-scale accelerated pavement tests along with th...

Korkiala-tanttu, Leena

2009-01-01

115

Benefits of including hot mix recycled materials in pavement design  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Pavement recycling is becoming more acceptable among the available techniques for pavement maintenance/rehabilitation. It is based on sustainable development, by reusing materials reclaimed from the pavements and reducing the disposal of asphalt materials. Based on the results obtained from laboratory tests carried out on two bituminous mixtures, one of which including 50% of recycled asphalt, some simulations were made for the design of a pavement where those mixtures would be used as a bitu...

Oliveira, Joel; Pereira, Paulo A. A.; Pais, Jorge C.; Santos, Lui?s Picado

2005-01-01

116

Evaluation of airport pavements using NDT approaches  

Science.gov (United States)

Corrosion of airport pavements is a major problem involved with materials engineering and transportation engineering. Airport pavements frequently start to deteriorate slowly primarily, gradually progressing to failure. Such failure can be expensive in terms of both money and lives, but can also be prevented. For that reason, intelligent techniques should be suggested, with the intention of examining the condition of such engineering structures. IR thermography and ground penetrating radar are two NDT (non-destructive testing) techniques that have the ability to inspect effectively substantial areas, such as airport pavements. In this work, two different airport pavements located at the International Airport of Athens, in Greece, were investigated by the use of the above two mentioned techniques. Successful detection of cracks, voids and other imperfections appearing either from the aging of the materials or due to poor workmanship was attained. Furthermore, this paper describes the problem of deteriorated airport pavements, shows the process and the apparatus used for the in situ tests, and finally presents results obtained from the investigations.

Avdelidis, N. P.; Moropoulou, A.

2007-04-01

117

Pavement Sealcoat, PAHs, and the Environment  

Science.gov (United States)

Recent research by the USGS has identified coal-tar-based pavement sealants as a major source of polycyclic aromatic hydrocarbons (PAHs) to the environment. Coal-tar-based sealcoat is commonly used to coat parking lots and driveways and is typically is 20-35 percent coal tar pitch, a known human carcinogen. Several PAHs are suspected mutagens, carcinogens, and (or) teratogens. In the central and eastern U.S. where the coal-tar-based sealants dominate use, sum-PAH concentration in dust particles from sealcoated pavement is about 1,000 times higher than in the western U.S. where the asphalt-based formulation is prevalent. Source apportionment modeling indicates that particles from sealcoated pavement are contributing the majority of the PAHs to recent lake sediment in 35 U.S. urban lakes and are the primary cause of upward trends in PAHs in many of these lakes. Mobile particles from parking lots with coal-tar-based sealcoat are tracked indoors, resulting in elevated PAH concentrations in house dust. In a recently completed study, volatilization fluxes of PAHs from sealcoated pavement were estimated to be about 60 times fluxes from unsealed pavement. Using a wide variety of methods, the author and colleagues have shown that coal-tar-based sealcoat is a major source of PAHs to the urban environment and might pose risks to aquatic life and human health.

Van Metre, P. C.; Mahler, B. J.

2011-12-01

118

ARDS (Acute Respiratory Distress Syndrome)  

Science.gov (United States)

... on Twitter. What Is ARDS? ARDS, or acute respiratory distress syndrome, is a lung condition that leads to ... pulmonary disease (COPD) or lower mortality from acute respiratory distress syndrome (ARDS), report two studies that rigorously tested ...

119

Design of airport pavements for expansive soils  

Science.gov (United States)

Expansive soil subgrades exhibit volume changes with variation in moisture condition. These changes result in differential movement of airport pavements resting on these soils. Special design procedures must be used to account for the expansive soil activity during equilibration. In addition, special precautions are required to protect the subgrade from moisture variation with climate. Measurement of soil suction is a key step in quantifying moisture-induced soil behavior. Procedures are outlined for suction characterization of the soil and for estimating the in situ differential movement likely to occur under the pavement. Once the wavelength and amplitude characteristics of the differential movement are obtained, design calculations to select the thickness and materials for the pavement may proceed.

McKeen, R. G.

1981-01-01

120

Finite Deformation Analysis of Layered Asphalt Pavement  

Directory of Open Access Journals (Sweden)

Full Text Available Layered asphalt pavement structures are usually analyzed applying small deformation theory. In this study, finite deformation theory was employed to achieve more accurate results. The response of pavement structure under vertical and horizontal loads was investigated by three-dimensional finite element method. The calculating results, especially for deflection, on the basis of finite deformation theory are very different from that according to the small deformation theory. And the difference will increase while the stiffness of pavement structure decrease. With only vertical loads, asphalt layer is mainly under compressive stress in three directions. With horizontal loads and vertical loads, shear stress contributes to accumulated plastic deformation in the asphalt layer. Sliding between layers could occur due to the shear stress. Tensile strain can cause fatigue cracking in asphalt layer under low temperature. Due to a small modulus of resilience, there exists a large compressive strain and visible deflection in soil base.

Ming-Jian Li

2013-01-01

 
 
 
 
121

Mechanistic - empirical pavement design guide implementation and pavement preservation strategies with asphalt rubber  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Asphalt-Rubber (AR) mixtures, with their great fleld performance, have received great attention from many transportation agencies world-wide. Current pavement design procedures do not specifically address the unique engineering properties that these mixtures offer. For example, the Mechanistic-Empirical Pavement Design Guide (MEPDG) did not include asphalt-rubber mixes as part of its calibration and Implementation in the USA. This paper addresses some issues on asphalt rubber mixture...

Kaloush, Kamil; Way, George B.; Belshe, Mark; Rodezno, Maria Carolina

2011-01-01

122

Permeable pavement research ? Edison, New Jersey  

Science.gov (United States)

These are the slides for the New York City Concrete Promotional Council Pervious Concrete Seminar presentation. The basis for the project, the monitoring design and some preliminary monitoring data from the permeable pavement parking lot at the Edison Environmental Center are pre...

123

The neonate in distress  

International Nuclear Information System (INIS)

Respiratory distress is a very common and yet non-specific symptom in neonates and young infants. It may be manifested clinically in many ways, including tachypnea, apnea, periodic respiratory, grunting, retractions, nasal flaring, and cyanosis. In many instances, the chest radiograph is diagnostic or at least suggestive of the diagnosis. This fact is important in determining surgical or medical conditions that require emergency therapy. Even if the chest film is normal, valuable information can be gained. This initial normal radiograph can be used as a baseline film in the face of further developing symptoms which, likewise, may have developing radiographic findings. In any event, the chest radiograph gives the clinician ''direction'' in his or her search for the cause of the patient's respiratory distress

124

Inspection of airport runways and asphalt pavements using long-wave infrared thermography  

Science.gov (United States)

The deterioration of asphalt pavements and airport runways is one of the most serious problems concerned with materials engineering, transport engineering and transportation in general. Usually, this is done to the lack of knowledge or even in the lack of commitment, the maintaining such structures. When failure occurs in an airport runway or in an asphalt pavement, reconstruction is expensive. Therefore, cost-effective ways must be suggested, in order to see how badly deteriorated the investigated structure is. One of these cost-effective ways is the infrared thermography technique. This technique is used successfully in the detection of cracks, surface voids and other anomalies appearing from the aging of such materials. In this research work, by using an infrared thermographic system (AVIO TVS 2000 Mk II LW, wavelength 8 - 12 micrometers ), and with the aid of liquid diffusion, an investigation of asphalt pavements and airport runways situated in Greece was performed. The results of this investigation have led to the design of a monitoring and control NDT system for the inspection of the defected areas of the airport runways and asphalt pavements and consequently the appropriateness of distinctive engineering structures.

Moropoulou, Antonia; Koui, Maria; Avdelidis, Nicolas P.; Kakaras, Kostas

2000-03-01

125

Orientation patterns of stone pavements as a result of modern geomorphologic processes  

Science.gov (United States)

Stone pavements are typical surface features of climate-sensitive, arid environments. They form a tightly interlocking mosaic of clasts, covering virtually stone-free aeolian material. However, this mosaic does not generally exhibit random orientation of its constituents. Rather, there are systematic unimodal to bimodal distributions of stone length axes present. These orientation patterns may be the result of active geomorphologic processes, implying the unstable and fragile nature of this landform as well as a dominant lateral geomorphologic component, not considered in existing models of stone pavement formation. Responsible processes should be controlled by relief properties and may thus be described by topographic attributes. From three study areas (Laguna Salada, Mexico, eastern Mojave Desert and southern Sevier Basin, USA) we present measurements of pavement stone orientations and their relationship to landscape parameters. From 1 by 1 m sized plots azimuthal digital images were taken, corrected, georeferenced and length as well as orientation angle of the a- and b-axes of at least 100 stones were digitised. Subsequently, statistical parameters of circular data were calculated. From a digital elevation model relief attributes were derived to test their influence on pavement patterns. Three general types of orientation patterns were identified from all study areas: unimodal, bimodal and unoriented. These types are clustered together and may change within small lateral distance. The type of pattern is not influenced by stone dimensions or the formation character of the site (i.e. basalt flow vs. alluvial fan). Relief properties (e.g. slope length, specific catchment, inclination), controlling lateral geomorphologic processes appear to play a major role in generating orientation patterns in stone pavement surfaces. Hence, from pattern analysis the dynamic nature of these features can be drawn.

Dietze, Michael; Kleber, Arno

2010-05-01

126

23 CFR 973.208 - Indian lands pavement management system (PMS).  

Science.gov (United States)

...Indian Affairs Management Systems § 973.208 Indian lands pavement management system (PMS). In addition...AASHTO's “Pavement Management Guide.” 1 1 “Pavement...for a PMS: (1) A database and an ongoing...

2010-04-01

127

23 CFR 972.208 - Federal lands pavement management system (PMS).  

Science.gov (United States)

...Wildlife Service Management Systems § 972.208 Federal lands pavement management system (PMS). In addition...AASHTO's “Pavement Management Guide.”2 2 “Pavement...for a PMS: (1) A database and an ongoing...

2010-04-01

128

23 CFR 971.208 - Federal lands pavement management system (PMS).  

Science.gov (United States)

...Highway Program Management Systems § 971.208 Federal lands pavement management system (PMS). In addition...AASHTO's “Pavement Management Guide.” 1 1 “Pavement...for a PMS: (1) A database and an ongoing...

2010-04-01

129

23 CFR 972.208 - Federal lands pavement management system (PMS).  

Science.gov (United States)

... Federal lands pavement management system (PMS). In addition...the AASHTO's “Pavement Management Guide.”2 2 “Pavement Management Guide,” AASHTO...information; (ii) A history of project dates and...

2010-04-01

130

23 CFR 973.208 - Indian lands pavement management system (PMS).  

Science.gov (United States)

...208 Indian lands pavement management system (PMS). In addition...the AASHTO's “Pavement Management Guide.” 1 1 “Pavement Management Guide,” AASHTO...information; (ii) A history of project dates and...

2010-04-01

131

23 CFR 971.208 - Federal lands pavement management system (PMS).  

Science.gov (United States)

... Federal lands pavement management system (PMS). In addition...the AASHTO's “Pavement Management Guide.” 1 1 “Pavement Management Guide,” AASHTO...information; (ii) A history of project dates and...

2010-04-01

132

Utilize Cementitious High Carbon Fly Ash (CHCFA) to Stabilize Cold In-Place Recycled (CIR) Asphalt Pavement as Base Coarse  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this study was to evaluate the performance of cementitious high carbon fly ash (CHCFA) stabilized recycled asphalt pavement as a base course material in a real world setting. Three test road cells were built at MnROAD facility in Minnesota. These cells have the same asphalt surface layers, subbases, and subgrades, but three different base courses: conventional crushed aggregates, untreated recycled pavement materials (RPM), and CHCFA stabilized RPM materials. During and after the construction of the three cells, laboratory and field tests were carried out to characterize the material properties. The test results were used in the mechanistic-empirical pavement design guide (MEPDG) to predict the pavement performance. Based on the performance prediction, the life cycle analyses of cost, energy consumption, and greenhouse gasses were performed. The leaching impacts of these three types of base materials were compared. The laboratory and field tests showed that fly ash stabilized RPM had higher modulus than crushed aggregate and RPM did. Based on the MEPDG performance prediction, the service life of the Cell 79 containing fly ash stabilized RPM, is 23.5 years, which is about twice the service life (11 years) of the Cell 77 with RPM base, and about three times the service life (7.5 years) of the Cell 78 with crushed aggregate base. The life cycle analysis indicated that the usage of the fly ash stabilized RPM as the base of the flexible pavement can significantly reduce the life cycle cost, the energy consumption, the greenhouse gases emission. Concentrations of many trace elements, particularly those with relatively low water quality standards, diminish over time as water flows through the pavement profile. For many elements, concentrations below US water drinking water quality standards are attained at the bottom of the pavement profile within 2-4 pore volumes of flow.

Wen, Haifang; Li, Xiaojun; Edil, Tuncer; O' Donnell, Jonathan; Danda, Swapna

2011-02-05

133

Pervious Concrete: New Era For Rural Road Pavement  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Pervious concrete is a relatively new concept for rural road pavement, with increase into the problems in rural areas related to the low ground water level, agricultural problem. Pervious concrete has introduced in rural road as a road pavement material. Pervious concrete as a paving material has seen renewed interest due to its ability to allow waterto flow through itself to recharge groundwater level and minimize storm water runoff. This introduction topervious concrete pavements reviews it...

Darshan S Shah, Prof Jayeshkumar Pitroda Prof J. J. Bhavsar

2013-01-01

134

The limestone pavements of Great Asby Scar, Cumbria, UK  

Science.gov (United States)

Varied, well-developed limestone pavements are well exposed over an extensive area of the Carboniferous limestone outcrop of the Orton-Asby escarpment, Cumbria. This area is the largest expanse of limestone pavements outside the well-known Ingleborough karst of Yorkshire, and the National Nature Reserve at Great Asby Scar includes the best developed and least damaged landforms of the whole area, most of which is now protected by Limestone Pavement Orders.

Goldie, H. S.

1996-10-01

135

Non-linear dynamic analysis of flexible and rigid pavements  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Closed form analysis is commonly used to analyze pavement structures. This type of analysis assumes linear elastic material properties and static loading conditions. In reality, pavement materials are not linear elastic materials. For example, asphalt mixtures are viscoelastic materials and cohesive soils are elastic-plastic materials. Also truck loads are moving loads. The difference between the closed form analysis assumptions and the actual pavement conditions leads to significant differen...

Zaghloul, Sameh Mohamed

1993-01-01

136

Stochastic finite element applications in rigid pavement performance  

Science.gov (United States)

Rigid pavement structures have uncertainties and variability in their structural layers and components. These variations and uncertainties are seldomly included in performance assessment and evaluation in pavement systems. This paper proposes to use Stochastic Finite Element Method (SFEM) in rigid pavement faulting and load transfer efficiency. The SFEM uses random parameters, as stochastic process namely random fields. These random fields are characterized, quantitatively by spatial functions of statistical moment like the mean, variance and covariance.

Attoh-Okine, Nii O.

1999-05-01

137

The Catskill-Cairo experimental rigid pavement: A ten-year progress report  

Science.gov (United States)

The Catskill-Cairo experimental rigid pavement, open to traffic for over 10 years, shows very little change in condition. Test sections include 60-ft 10-in. slab lengths reinforced with mesh and containing load-transfer devices, 20-ft slab lengths with no mesh reinforcement but both with and without load-transfer devices, and three types of base material. All sections are in good condition, with little added roughness, little faulting, and light cracking. More important, there are no significant differences in performance of the various designs. The lack of distress and performance differences among the various designs is most likely due to the light traffic volumes carried by the test road. This situation led to the conclusion that none of the design alternatives can be eliminated based on performance of this test road after 10 years.

Vyce, J. M.; Phillips, R. G.

1981-07-01

138

Proceedings of the Continuously Reinforced Concrete Pavement workshop  

Science.gov (United States)

Design, construction, and maintenance procedures of continuously reinforced concrete pavements are dicussed. Maintenance procedures were emphasized. Polymer patching, under sealing, and flexible and rigid overlays were considered.

1980-06-01

139

Practical applications of nondestructive evaluation for airport pavement analysis  

Science.gov (United States)

This paper discusses the equipment and methodologies currently used for nondestructive testing (NDT) and nondestructive evaluation (NDE) of the structural capacity of military and civil airport pavements, including: (1) commonly used equipment and test methods for measuring pavement response to dynamic loads; (2) qualitative and quantitative evaluation of NDT data; (3) methods for back-calculating layer properties from NDT data; (4) layered elastic methods for evaluating pavement performance using processed NDT data; and (5) application of analytical results for developing pavement rehabilitation and management strategies.

McQueen, Roy D.; Guo, Edward

1995-07-01

140

Financial Distress Prediction Using Distress Score as a Predictor  

Directory of Open Access Journals (Sweden)

Full Text Available Financial distress can be the reflection of corporation's management condition. Consequently the distress scoreof corporations should be considered as a new predictor variable in predicting the financial distress.The analysis of ROC curve, among the models employed to compare the effectiveness of different statisticalmodels, is often used in the fields of psychology and bio-physics in order to summarize the discriminatory of adiagnostic test and also to compare the performance of different models for binary outcomes. Therefore,concerning the topic of this research and the use of ROC curves in predicting the financial distress ofcorporations, we use logit models to study the financial distress of the manufacturing corporations in TehranStock Exchange. We also compare the accuracy of the prediction method with financial distress score variable tothe method without this variable.Concerning the accuracy of prediction and classification, the results of this research show that the accuracy ofprediction can be enhanced by using the distressed score, gained from DEA, as a new predictor variable inpredicting the financial distress.

Maryam Sheikhi

2011-12-01

 
 
 
 
141

Relationships between laboratory measured HMA material and mixture properties and pavement performance at WesTrack  

Science.gov (United States)

For years researchers and practitioners alike in the pavements and materials industry have attempted to establish relationships between laboratory measured material and mixture properties and actual pavement performance. The ultimate goal of any highway agency is to have performance related specifications, which require such relationships. This sounds simple enough, but in reality such a task is not so simple due to the extremely complex behavior of hot mix asphalt. Due to the fact that it takes many years to evaluate new materials and methodologies, the use of accelerated loading facilities such as WesTrack for evaluation purposes becomes very advantageous. The research presented here produces multiple permanent deformation performance relationships for the WesTrack project, some of which may be extended to other environments. An attempt to develop similar fatigue performance relationships was unsuccessful due partially to the lack of fatigue distress at WesTrack to date. Additionally, mix design and some quality control data summaries are presented for the project along with an investigation into a potential cause of the premature rutting of coarse Superpave mixes. The investigation resulted in the development of precision statements for the ASTM D5821-95 coarse aggregate angularity test method and a better understanding of the sensitivity of coarse Superpave mixtures.

Hand, Adam J. T.

142

Effectiveness of transverse grooves in rigid pavement  

Science.gov (United States)

Transverse grooves were installed at 11 intersection approaches on worn rigid pavement to reduce a high rate of wet road accidents. In most cases, accident reductions were experienced only at intersections with multiple negative operational characteristics, including higher approach speeds, limited sight distances, and frequent vehicle stopping for turns or stop signs. Intersections with no more than one negative characteristic generally did not benefit from grooving.

Gurney, G. F.; Bryden, J. E.

1982-10-01

143

AN INVESTIGATION OF RECYCLING BITUMINOUS PAVEMENTS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The deplorable conditions that have developed in our highway system is one of the major problems confronting transportation agencies today. Rapidly escalating maintenance and reconstruction costs, coupled with a nearly fixed level of highway funding have contributed significantly to this problem. Asphalt pavement recycling is a viable rehabilitation method that can be used to help solve this serious problem; for recycling can be an economical, as well as an energy efficient rehabilitation alt...

Mckinney, James L.

1980-01-01

144

How Is Respiratory Distress Syndrome Treated?  

Science.gov (United States)

... Respiratory Distress Syndrome » Treatments Respiratory Distress Syndrome Explore Respiratory Distress Syndrome What Is ... Other Names Causes Who Is at Risk Signs & Symptoms Diagnosis Treatments Prevention Living With Clinical Trials ...

145

Global Cooling: Policies to Cool the World and Offset Global Warming from CO2 Using Reflective Roofs and Pavements  

Energy Technology Data Exchange (ETDEWEB)

Increasing the solar reflectance of the urban surface reduce its solar heat gain, lowers its temperatures, and decreases its outflow of thermal infrared radiation into the atmosphere. This process of 'negative radiative forcing' can help counter the effects of global warming. In addition, cool roofs reduce cooling-energy use in air conditioned buildings and increase comfort in unconditioned buildings; and cool roofs and cool pavements mitigate summer urban heat islands, improving outdoor air quality and comfort. Installing cool roofs and cool pavements in cities worldwide is a compelling win-win-win activity that can be undertaken immediately, outside of international negotiations to cap CO{sub 2} emissions. We propose an international campaign to use solar reflective materials when roofs and pavements are built or resurfaced in temperate and tropical regions.

Akbari, Hashem; Levinson, Ronnen; Rosenfeld, Arthur; Elliot, Matthew

2009-08-28

146

Airport pavement NDE research at CQEFP  

Science.gov (United States)

The Center for Quality Engineering and Failure Prevention (CQEFP) at Northwestern University is actively involved in the development of new stress-wave based non-destructive evaluation techniques for airport pavements. This paper summarizes recent accomplishments and outlines current research directions. The development of a new stress-wave source is detailed first. The stress-wave generating technique allows for a high degree of control of the input stress wave while at the same time enabling the generation of significant wave amplitudes. Experimental results on concrete specimens demonstrate the controllability and penetrating ability of the developed stress wave generation technique. Its performance is compared to that of an impact source. Experimental results from an existing stress-wave based NDE technique, the impact-echo method, are presented and limitations of that approach are demonstrated. Finally, directions of future airport pavement NDE research at CQEFP, which focus upon application of the developed stress wave generation technique to pavement NDE problems, are outlined.

Popovics, John S.; Achenbach, Jan D.

1996-11-01

147

Pavement technology for mega transportation projects  

Energy Technology Data Exchange (ETDEWEB)

This paper described the use of asphalt and concrete pavement technology for mega projects such as the Duarte Highway in the Dominican Republic, the Colombia Bogota El Dorado International Airport, Highway 407 Express Toll Route north of Toronto, the Cobequid Pass Highway in Nova Scotia and the Fredericton-Moncton Highway in New Brunswick. A mega transportation project is considered to involve more than $100 million in construction costs and use an alternative delivery method such as design-build. It must also include life cycle costing for technology evaluation, fast track construction and total quality management. This paper showed that the durability, flexibility and structural capacity of hot-mix asphalt and PCC concrete make it possible to provide economic, smooth, safe pavements for highways, airports and for heavy traffic conditions under both normal and severe operating environments. In particular, the paper focused on the practical concepts of the pavement technology and the role of contractors in meeting the fast-track technical quality requirements for mega paving projects. The paper emphasized the fact that it is possible to develop sustainable paving projects that integrate transportation infrastructure development with communities and the environment while maintaining safety and performance. 8 refs., 4 tabs., 8 figs.

Emery, J. [John Emery Geotechnical Engineering Ltd., Toronto, ON (Canada)

2001-07-01

148

Electro-optical approach to pavement deflection management  

Science.gov (United States)

A prototype continuous deflection device, referred to as a rolling weight deflectometer (RWD), has been developed as a nondestructive evaluation tool for airfield pavements. The system consists of a rigid trailer equipped with specially designed optical triangulation pavement sensors, a high-speed data acquisition system, and a high-pressure tire/load platform assembly. Pavement sensors are mounted on a rigid box beam equipped with an internal sensor system that corrects, in real time, the relative pavement height position measurements for displacements induced in the beam by mechanical vibrations, changes in temperature, or nonuniform dynamic loads at points where the beam attaches to the frame. The device produces continuous deflection profiles that show pavement response to a moving loaded wheel along the path of travel. These deflection profiles, combined with multiple passes along a lane, provide a far more detailed picture of the pavement structural integrity than has ever before been possible, because existing evaluation tools only produce response information at discrete points. Preliminary results show deflections measured by the RWD are in general agreement with the expected pavement response for various loads. A discussion of the device configuration, preliminary data, and potential as a pavement management tool is presented.

Rish, Jeff W., III; Adcock, Avery D.; Tuan, Christopher Y.; Baker, Samuel L.; Welker, Hugh W., II; Johnson, Roger F.

1995-07-01

149

Desempeño de pavimentos estabilizado con asfalto espumado en una prueba de pavimentos a escala real y carga acelerada Performance of foamed bitumen pavements in accelerated testing facility  

Directory of Open Access Journals (Sweden)

Full Text Available Uno de los objetivos claves de la gestión de pavimentos es desarrollar e implementar una estrategia de construcción y mantenimiento rentables, con el fin de alcanzar niveles requeridos de servicio y desempeño. Una técnica rentable y sustentable para la rehabilitación de pavimentos es la de estabilización o reciclado con asfalto espumado (AE. Este artículo presenta un estudio sobre el desempeño de pavimentos estabilizados con asfalto espumado en el Canterbury Accelerated Pavement Testing Indoor Facility CAPTIF. CAPTIF es un laboratorio a escala real para pavimentos ubicado en Nueva Zelandia, que permite aplicar un gran número de cargas de tráfico en un breve período de tiempo. Seis secciones de pavimentos con distintos contenidos de asfalto y cemento fueron ensayadas en CAPTIF. Los resultados del experimento mostraron que las deflexiones disminuyen en las secciones con mayor contenido de asfalto espumado. Luego de aplicar más de un millón de ciclos de carga, las secciones estabilizadas sólo con cemento, sólo con asfalto y la sección sin estabilizar mostraron un deterioro significativo en forma de ahuellamiento. Por otro lado, las secciones que fueron estabilizadas con AE y cemento mostraron un buen desempeño, demostrando que el cemento y el AE juntos mejoran significativamente el desempeño del pavimento. Los resultados de ahuellamiento fueron empleados para desarrollar modelos y describir el deterioro estable y acelerado de los pavimentos en estudio, lo que puede ser utilizado para una mejor gestión de los pavimentos estabilizados con asfalto espumado.One of the key principal goals of pavement asset management is to develop and implement cost-effective pavement construction and maintenance strategies that achieve the required levels of service and performance. A sustainable, cost-effective technique for rehabilitating pavements is foamed bitumen stabilization. This paper presents a study on the performance of foamed bitumen pavements tested in the Canterbury Accelerated Pavement Testing indoor Facility (CAPTiF, for full scale testing of pavements. Six pavement sections were tested; the variables were bitumen and cement content; one control section with the untreated unbound material was tested. Results showed that surface deflections decreased at sections with higher bitumen contents. After the application of 5,710,000 Equivalent Standard Axles (ESAs, the sections stabilised with cement only, bitumen only, and the control section all showed large amounts of rutting. Conversely, little rutting was observed in the three sections stabilised with foamed bitumen and 1.0% cement, showing that cement and FB together significantly improve pavement performance. The rutting results were used to develop models to describe the stable and unstable performance of the tested pavements. The paper concludes by outlining some of the practical benefits of utilising this technology in pavement asset management.

Alvaro Gonzalez

2012-08-01

150

Measurements of the stiffness and thickness of the pavement asphalt layer using the enhanced resonance search method.  

Science.gov (United States)

Enhanced resonance search (ERS) is a nondestructive testing method that has been created to evaluate the quality of a pavement by means of a special instrument called the pavement integrity scanner (PiScanner). This technique can be used to assess the thickness of the road pavement structure and the profile of shear wave velocity by using the principle of surface wave and body wave propagation. In this study, the ERS technique was used to determine the actual thickness of the asphaltic pavement surface layer, while the shear wave velocities obtained were used to determine its dynamic elastic modulus. A total of fifteen locations were identified and the results were then compared with the specifications of the Malaysian PWD, MDD UKM, and IKRAM. It was found that the value of the elastic modulus of materials is between 3929 MPa and 17726 MPa. A comparison of the average thickness of the samples with the design thickness of MDD UKM showed a difference of 20 to 60%. Thickness of the asphalt surface layer followed the specifications of Malaysian PWD and MDD UKM, while some of the values of stiffness obtained are higher than the standard. PMID:25276854

Zakaria, Nur Mustakiza; Yusoff, Nur Izzi Md; Hardwiyono, Sentot; Nayan, Khairul Anuar Mohd; El-Shafie, Ahmed

2014-01-01

151

Characterization of nanoparticles released during construction of photocatalytic pavements using engineered nanoparticles  

Energy Technology Data Exchange (ETDEWEB)

With the increasing use of titanium dioxide (TiO{sub 2}) nanoparticles in self-cleaning materials such as photocatalytic concrete pavements, the release of nanoparticles into the environment is inevitable. Nanoparticle concentration, particle size, surface area, elemental composition, and surface morphology are pertinent to determine the associated risks. In this study, the potential of exposure to synthetic nanoparticles released during construction activities for application of photocatalytic pavements was measured during laboratory-simulated construction activities of photocatalytic mortar overlays and in an actual field application of photocatalytic spray coat. A scanning mobility particle sizer system measured the size distribution of nanoparticles released during laboratory and field activities. Since incidental nanoparticles are released during construction activities, nanoparticle emissions were compared to those from similar activities without nano-TiO{sub 2}. Nanoparticle counts and size distribution suggest that synthetic nanoparticles are released during application of photocatalytic pavements. In order to identify the nanoparticle source, nanoparticles were also collected for offline characterization using transmission electron microscopy. However, positive identification of synthetic nanoparticles was not possible due to difficulties in obtaining high-resolution images. As a result, further research is recommended to identify nanoparticle composition and sources.

Dylla, Heather; Hassan, Marwa M., E-mail: marwa@lsu.edu [Louisiana State University, Department of Construction Management and Industrial Engineering (United States)

2012-03-15

152

Characterization of nanoparticles released during construction of photocatalytic pavements using engineered nanoparticles  

International Nuclear Information System (INIS)

With the increasing use of titanium dioxide (TiO2) nanoparticles in self-cleaning materials such as photocatalytic concrete pavements, the release of nanoparticles into the environment is inevitable. Nanoparticle concentration, particle size, surface area, elemental composition, and surface morphology are pertinent to determine the associated risks. In this study, the potential of exposure to synthetic nanoparticles released during construction activities for application of photocatalytic pavements was measured during laboratory-simulated construction activities of photocatalytic mortar overlays and in an actual field application of photocatalytic spray coat. A scanning mobility particle sizer system measured the size distribution of nanoparticles released during laboratory and field activities. Since incidental nanoparticles are released during construction activities, nanoparticle emissions were compared to those from similar activities without nano-TiO2. Nanoparticle counts and size distribution suggest that synthetic nanoparticles are released during application of photocatalytic pavements. In order to identify the nanoparticle source, nanoparticles were also collected for offline characterization using transmission electron microscopy. However, positive identification of synthetic nanoparticles was not possible due to difficulties in obtaining high-resolution images. As a result, further research is recommended to identify nanoparticle comporecommended to identify nanoparticle composition and sources.

153

New structural systems for zero-maintenance pavements. Volume 1: Analytical and experimental studies of an anchored pavement. A candidate zero-maintenance pavement  

Science.gov (United States)

The design feasibility and construction cost effectiveness of an anchored pavement concept for zero maintenance highways are investigated. An analytical model is designed to verify computer program results and to investigate construction methods for a full-scale highway section. A conventional slab and an anchored pavement in both continuous and jointed configurations were subjected to heat transfer, thermal stress, and mechanical stress analyses. The anchored pavement offers two distinct advantages over a conventional pavement. Deflections are lower and more uniform; and stresses in the soil are lower and distributed more widely by the rigid anchors. Three dimensional finite element analysis is considered to be the most efficient technique for examining the significance of environmentally induced stress.

Saxena, S. K.; Rosenkranz, W. J.; Militsopoulos, S. G.

1980-05-01

154

Asphalt mixture moisture sensitivity evaluation using surface energy parameters  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Asphalt mixture is mainly used for the construction of roads throughout the world. Large amounts of capital are spent for construction and maintenance of roads. Water is one of the major contributors towards the damage of the road structure. It is considered as the worst enemy of a pavement structure by directly causing a distress or indirectly magnifying a distress and hence damaging the road structure. Asphalt mixture loses its strength in the presence of water either through loss of cohesi...

Ahmad, Naveed

2011-01-01

155

Hypertension Awareness and Psychological Distress  

Digital Repository Infrastructure Vision for European Research (DRIVER)

There is conflicting evidence regarding the association of hypertension with psychological distress, such as anxiety and depressive symptoms. The association may be because of a direct effect of the raised blood pressure, adverse effects of treatment, or the consequences of labeling. In a representative study of 33 105 adults (aged 51.7 +/- 12.1 years; 45.8% men), we measured levels of psychological distress using the 12-item General Health Questionnaire and collected blood pressure, data on ...

Hamer, M.; Batty, G. D.; Stamatakis, E.; Kivimaki, M.

2010-01-01

156

Acute respiratory distress syndrome  

Directory of Open Access Journals (Sweden)

Full Text Available Acute respiratory distress syndrome (ARDS is characterized by non-cardiogenic pulmonary oedema and respiratoy failure. In 1994, ARDS was defined by the American – European Consensus Conference (AECC and since then issues regarding the reliability and validity of this definition have emerged. The Berlin definition was developed by a panel of experts in a convention in 2011 with an initiative of European Society of Intensive Care Medicine endorsed by American Thoracic Society, mainly focussing on feasibility, reliability and validity and objective evaluation of performance. The definition proposed three exclusive categories of ARDS based on degree of hypoxaemia, namely, mild, moderate and severe. The updated and revised Berlin definition of ARDS may serve as model to create a more accurate, evidence based critical illness syndrome and to improve clinical care, research, health services planning and resource management. The article describes clinical, aetiological and physiological basis of ARDS and summarizes how its molecular pathogenesis leads to physiologic alterations of respiratory failure. It provides a physiologic basis for understanding and implementing modern strategies for the respiratory management of patients with ARDS.

M.H. Rao

2014-04-01

157

Numerical study on the curling and warping of hardened rigid pavement slabs  

Science.gov (United States)

In-service hardened concrete pavement suffers from environmental loadings caused by curling and warping of the slab. Traditionally, these loadings are computed on the basis of treating the slab as an elastic material, and of evaluating separately the curling and warping components. This dissertation simulates temperature distribution and moisture distribution through the slabs by use of a developed numerical model that couples the heat transfer and moisture transport. The computation of environmental loadings treats the slab as an elastic-viscous material, which considers the relaxation behavior and Pickett effect of the concrete. The heat transfer model considers the impacts of solar radiation, wind speed, air temperature, pavement slab albedo, etc. on the pavement temperature distribution. This dissertation assesses the difference between documented models that aim to predict pavement temperature, highlighting their pros and cons. The moisture transport model is unique for the documented models; it mimics the wetting and drying events occurring at the slab surface. These events are estimated by a proposed statistical algorithm, which is verified by field rainfall data. Analysis of the predicted results examines on the roles of the local air RH (relative humidity), wind speed, rainy pattern in the moisture distribution through the slab. The findings reveal that seasonal air RH plays a decisive role on the slab's moisture distribution; but wind speed and its daily variation, daily RH variation, and seasonal rainfall pattern plays only a secondary role. This dissertation sheds light on the computation of environmental loadings that in-service pavement slabs suffer from. Analysis of the computed stresses centers on the stress relaxation near the surface, stress evolution after the curing ends, and the impact of construction season on the stress's magnitude. An unexpected finding is that the total environmental loadings at the cyclically-stable state divert from the thermal stresses. At such a state, the total stress at the daytime is roughly equal to the thermal stress; whereas the total stress during the nighttime is far greater than the thermal stress. An explanation for this phenomenon is that during the night hours, the decline of the slab's near-surface temperature leads to a drop of the near-surface RH. This RH drop results in contraction therein and develops additional tensile stresses. The dissertation thus argues that estimating the environmental loadings by solely computing the thermally-induced stresses may reach delusive results. It recommends that the total environmental loadings of in-service slabs should be estimated by a sophisticated model coupling both moisture component and temperature component.

Qin, Yinghong

158

An Innovative Strategy for Maintenance of Highway Pavement  

Directory of Open Access Journals (Sweden)

Full Text Available Highway pavement are deteriorating fast due to lack of timely maintenance, leading to higher vehicle operating costs, increasing number of accidents etc. Thus, timely maintenance of the highway pavement is essential. Because, once pavements start to deteriorate; they deteriorate rapidly beyond the point where maintenance is effective. Thus, there is an urgent need to develop a strategy for maintenance of pavement in a huge highway network. In this study, an innovative strategy for maintenance of highway pavement is proposed. A two stage maintenance strategy is proposed. In stage I, it is proposed to determine priority of highway sections. In Stage II, priority of various maintenance activities to be carried out on various sections will be determined. Maintenance priority of the pavement is based on importance of the road sections, present road conditions, and future road conditions. The methodology proposed in this study is illustrated with the help of example of some hypothetical highway network consisting of 4 sections. Analysis results indicated that the proposed strategy is considered to be more rational, innovative & logical. Some strategies for maintenance of urban roads are also presented in this study. Therefore, it is expected that this study will be useful for maintenance of huge highway network in India and thus will be useful for preserving huge asset of pavement infrastructure.

Sandeep Choudhary, Dr. P. K. Agarwal

2013-05-01

159

Variability of pavement noise benefit by vehicle type  

Science.gov (United States)

The Volpe Center Acoustics Facility, in support of the California Department of Transportation (Caltrans), is participating in a long-term study to assess several types of pavement for the purpose of noise abatement. On a four-mile stretch of a two-lane highway in Southern California, several asphalt pavement overlays are being examined. Acoustical, meteorological, and traffic data are collected in each pavement overlay section, where microphones are deployed at multiple distances and heights. Single vehicle pass-by events are recorded primarily for three vehicle types: automobiles, medium trucks, and heavy trucks. Data are analyzed to determine the noise benefit of each pavement as compared to the reference dense-graded asphaltic concrete (DGAC); this includes a modified Statistical Pass-By Index as well as average Lmax values for each vehicle type. In addition, 1/3-octave band data are examined. Automobiles and heavy trucks are the focus of this paper, where benefits due to pavement will be presented for three pavement types: open-graded asphaltic concrete (OGAC) of 75 mm thickness, open-graded asphaltic concrete (OGAC) of 30 mm thickness, and rubberized asphaltic concrete, Type O (open) (RAC) of 30 mm thickness. Average Lmax values and spectral data show that noise benefits due to pavement can vary by vehicle type.

Rochat, Judith L.; Read, David R.

2005-09-01

160

Development of Improved Mechanistic Deterioration Models for Flexible Pavements  

DEFF Research Database (Denmark)

The paper describes a pilot study in Denmark with the main objective of developing improved mechanistic deterioration models for flexible pavements based on an accelerated full scale test on an instrumented pavement in the Danish Road Tessting Machine. The study was the first in "International Pavement Subgrade Performance Study" sponsored by the Federal Highway Administration (FHWA), USA. The paper describes in detail the data analysis and the resulting models for rutting, roughness, and a model for the plastic strain in the subgrade.The reader will get an understanding of the work needed to be done to be succesful in establishing mechanistic models based on Accelerated Load Testing (ALT) complemented by laboratory testing.

Ullidtz, Per

1998-01-01

 
 
 
 
161

Development of Mechanistic-Empirical Flexible Pavement Design in Iran  

Directory of Open Access Journals (Sweden)

Full Text Available Recent advances in flexible pavement design have prompted agencies to move toward the development and use of Mechanistic-Empirical (M-E design procedures. Mechanistic-Empirical (M-E design combine the elements of mechanical modeling and performance observation in determining the required pavement thickness for a set of design condition. In this study, a Mechanistic-Empirical (M-E design procedures and algorithm based on KENLAYER software with regard to Iran climatic and traffic conditions is developed. This study also explores present relationships and diagrams based on effective variable on pavement design to facilitate design process.

M. Ameri

2009-01-01

162

On-site inspections of pavement damages evolution using GPR  

Science.gov (United States)

Ground-penetrating radar (GPR) is being increasingly used for pavements maintenance due to the wide range of applications spanning from physical to geometrical inspections, thereby allowing for a reliable diagnosis of the main causes of road structural damages. In this work, an off-ground GPR system was used to investigate a large-scale rural road network. Two sets of surveys were carried out in different time periods, with the main goals to i) localize the most critical sections; ii) monitor the evolution of previous damages and localize newborn deep faults, although not revealed at the pavement surface level; iii) analyze the causes of both evolution and emergence of faults by considering environmental and human factors. A 1-GHz GPR air-launched antenna was linked to an instrumented van for collecting data at traffic speed. Other support techniques (e.g. GPS data logger, odometer, HD video camera) were used for cross-checking,. Such centre frequency of investigation along with a 25-ns time window allow for a signal penetration of 900 mm, consistent with the deepest layer interfaces. The bottom of the array was 400 mm over the surface, with a minimum distance of 1200 mm from the van body. Scan length of maximum 10 km were provided for avoiding heavy computational loads. The rural road network was located in the District of Rieti, 100 km north from Rome, Italy, and mostly develops in a hilly and mountainous landscape. In most of the investigated roads, the carriageway consists in two lanes of 3.75 meters wide and two shoulders of 0.50 meters wide. A typical road section includes a HMA layer (65 mm average thickness), a base layer (100 mm average thickness), and a subbase layer (300 mm average thickness), as described by pavement design charts. The first set of surveys was carried out in two days at the beginning of spring in moderately dry conditions. Overall, 320-km-long inspections were performed in both travel directions, thereby showing a productivity of approximately 160 km/day at 40 km/h speed, on the average. After processing and first-checking, GPR profiles were divided into homogeneous sections according to the combination of different parameters (e.g. route analyzed, long distance conditions of regularity/irregularity in layers arrangement). In such context, a high consistency between surface damages, mismatches from the GPR scans, and boundary environmental conditions was demonstrated. In addition, deep mismatches were detected even for early-stage or unrevealed faults. The second set of surveys was carried out in autumn in high humidity conditions, due to recent rainfalls. 160 km of relevant routes from the same road network were investigated. Results showed a high consistency with those collected during the first-stage of surveys. Minor changes were found in those sections with low traffic loads (e.g. farther away from the biggest town of Rieti), whereas major mismatches were detected in wetlands (e.g. close to rivers), work zones, and nearby those sections already deeply damaged in the past. This work benefited from networking activities carried out within the EU funded COST Action TU1208 'Civil Engineering Applications of Ground Penetrating Radar'.

Tosti, Fabio; D'Amico, Fabrizio; Calvi, Alessandro; Benedetto, Andrea

2014-05-01

163

Time series observations of marsh recovery and pavement persistence at three Metula spill sites after 30.5 years  

International Nuclear Information System (INIS)

In 1974, the oil tanker Metula ran aground in the Strait of Magellan, Chile and spilled about 50,000 tons of light Arabian crude and 2,000 tons of Bunker C fuel. No attempt was made to recover or treat the stranded oil and the coast was left to recover by natural attenuation. Field visits to the coastal sites affected by the spill were conducted 30 years after the incident. The survey in 2005 repeated observations and measurements made in 1998 in the heavily affected Punta Espora area that documented salt marsh recovery at 2 sites, and changes in asphalt pavement at a third site. The 1998 survey also indicated that tilling was responsible for a significant increase in the number of plants that recolonized the area. A comparison of the plant counts between 1998 and 2005 showed that the number of plants in tilled plots was reduced because of fewer larger plants. A comparison of oil distribution in the west marsh from 1998 to 2005 showed that recolonization was evident. A large 550 m-long asphalt pavement on a mixed sediment beach showed very little changes in pavement area in the aftermath of the spill. However, the upper edge of the pavement showed signs of erosion by backwash action of waves during high-tide. The presence of surface oil cover continues to dominate the physical character of the upper intertidal and supratidal zones. 11 refs., 6 tabs., 3 figs

164

Time series observations of marsh recovery and pavement persistence at three Metula spill sites after 30.5 years  

Energy Technology Data Exchange (ETDEWEB)

In 1974, the oil tanker Metula ran aground in the Strait of Magellan, Chile and spilled about 50,000 tons of light Arabian crude and 2,000 tons of Bunker C fuel. No attempt was made to recover or treat the stranded oil and the coast was left to recover by natural attenuation. Field visits to the coastal sites affected by the spill were conducted 30 years after the incident. The survey in 2005 repeated observations and measurements made in 1998 in the heavily affected Punta Espora area that documented salt marsh recovery at 2 sites, and changes in asphalt pavement at a third site. The 1998 survey also indicated that tilling was responsible for a significant increase in the number of plants that recolonized the area. A comparison of the plant counts between 1998 and 2005 showed that the number of plants in tilled plots was reduced because of fewer larger plants. A comparison of oil distribution in the west marsh from 1998 to 2005 showed that recolonization was evident. A large 550 m-long asphalt pavement on a mixed sediment beach showed very little changes in pavement area in the aftermath of the spill. However, the upper edge of the pavement showed signs of erosion by backwash action of waves during high-tide. The presence of surface oil cover continues to dominate the physical character of the upper intertidal and supratidal zones. 11 refs., 6 tabs., 3 figs.

Owens, E.H. [Polaris Applied Sciences Inc., Bainbridge Island, WA (United States); Sergy, G.A. [Environment Canada, Edmonton, AB (Canada)

2005-07-01

165

STUDY ON PROPERTIES OF SKID RESISTANCE ON FREEZING PAVEMENTS AND QUANTITATIVE EVALUATION METHOD OF ANTIFREEZING EFFECTS  

Science.gov (United States)

Snow and ice control in winter roads trends to be controlled by the skid friction coefficients in North America and North European countries at present, but the measurements are not necessarily easy. We studied on a simplified measurement method based on the relationship between skid friction coefficients and the bare pavement ratio (BPR) in the laboratory tests and field tests. The factors of BPR, surface textures and antifreezing materials which affect the skid friction coefficient are reviewed by a multiple linear regression analysis and a spectrum analysis, considering different freezing surfaces. These studies indicate that conclusions induced by laboratory tests could be applied to roads in service.

Tanaka, Shunsuke; Takeichi, Kiyoshi; Masuyama, Yukiei; Takahashi, Naoto

166

Nondestructive evaluation of load transfer at rigid airport pavement joints  

Science.gov (United States)

Current design criteria for rigid pavements for commercial and military airfields assume that 25% of the load applied to an edge of a slab is transferred through the joint to an adjacent unloaded slab. A nondestructive testing technique using a falling weight deflectometer (FWD) was used to conduct field testing at a number of sites. A transfer function, developed from an analytical study, was used to estimate load transfer from the measured joint efficiency as a function of the loaded area and the radius of relative stiffness of the pavement. This procedure, although analytically sound, lacks actual field verification at an instrumented pavement site. This procedure was used to estimate load transfer at a number of commercial and military airfields for a variety of joint types, climate conditions, and pavement structures. The results of these tests indicate that the assumption of load transfer as a constant value of 25% appears to be unconservative, especially during the winter months.

Hammons, Michael I.

1995-07-01

167

Development of probabilistic rigid pavement design methodologies for military airfields  

Science.gov (United States)

The current Corps of Engineers design procedures for rigid airfield pavements is based on the Westergaard free edge stress slab theory, and a proposed procedure is based on the multilayer elastic theory. These two design procedures have been expanded to airfield pavement designs expressed in probabilistic and reliability terms. Further developments were required in these procedures to make the analysis more practicable. Two major investigations were conducted: (1) Evaluation and use of the composite modulus of elasticity for layers beneath the rigid pavement, and (2) Evaluation of the maximum tensile stress at the bottom of the slab for different aircraft types. Derivations obtained from the investigation of the composite modulus and maximum tensile stress are reported and are included in computer programs for probabilistic/reliability analysis of rigid pavements. The approximate closed form (Taylor series expansion) is utilized. Example runs of the computer program are presented.

Witczak, M. W.; Uzan, J.; Johnson, M.

1983-12-01

168

Striated clast pavements: Products of deforming subglacial sediment?  

Science.gov (United States)

Studies of modern glaciers have recently drawn attention to the importance of subglacial sediment deformation to glacier dynamics and processes. Inferences regarding the probable shear strength of this sediment imply that large clasts may in some cases sink to underlying rigid sediment, where abrasion by overlying deforming sediment could occur. This scenario provides a formative mechanism for striated clast pavements commonly described from the base of fine-grained massive diamictons associated with the late Pleistocene Laurentide ice sheet. Such a mechanism indicates that, at the time of formation of clast pavements, overlying diamictons associated with pavements had a low yield strength (?0.5 kPa) and were deforming mechanically like a debris flow. Clast pavements may therefore be an important criterion for recognition of sediments deposited by subglacial deformation transport.

Clark, Peter U.

1991-05-01

169

ANALYSIS OF GROUP MAINTENANCE STRATEGY -ROAD PAVEMENT AND SEWERAGE PIPES-  

Science.gov (United States)

Recently, it is critical to manage deteriorating sewerage and road facilities efficiently and strategically. Since the sewerage pipes are mostly installed under road pavement, the works for the replacement of the sewerage pipes are partially common to the works for the road. This means that the replacement cost can be saved by coordinating the timing of the replacements by sewerage pipe and road pavement. The purpose of the study is to develop the model based on Markov decision process to derive the optimal group maintenance policy so as to minimize lifecycle cost. Then the model is applied to case study area and demonstrated to estimate the lifecycle cost using statistical data such as pipe replacement cost, road pavement rehabilitation cost, and state of deterioration of pipes and road pavement.

Tanimoto, Keishi; Sugimoto, Yasuaki; Miyamoto, Shinya; Nada, Hideki; Hosoi, Yoshihiko

170

Performance of geotextile-gravel bed all-weather surfaces  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A cost-effective way of producing all-weather surfaces for cattle is to use a combined geotextile-gravel pad construction, which allows pavement depth to be reduced. This study sought to determine the pavement construction that would offer the least runoff, best drainage effect and highest quality runoff and drainage effluent after exposure to heavy precipitation under different manure loads in high animal density areas. The study also examined whether any pavement construction gave acceptabl...

Von Wachenfelt, Hans

2011-01-01

171

Fatigue resistance of bituminous layers incorporating reclaimed asphalt pavement  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper presents the results of an investigation into the fatigue performance of a 20mm Binder Course Asphalt Pavement Mix incorporating Recycled Asphalt Pavement (RAP). For the study, a series of binder course mixes were designed containing varying percentages of RAP. A mix made only from virgin material, was selected as the control mix for the investigation. A Circular Wheel Tracker (CWT) was developed in order to simulate the dynamic loading conditions of a rolling wheel and to st...

Tabakovic, Amir; Gibney, Amanda; Gilchrist, M. D.; Mcnally, Ciaran

2006-01-01

172

Finite Element Investigation of the Deterioration of Doweled Rigid Pavements  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The purpose of this study is to describe the failure of concrete around dowel bars in jointed rigid pavements, and the resulting effect on the pavement performance. In fact, under repetitive vehicle loading, concrete in contact with the dowel bar deteriorates, particularly at the joint face. The degradation of concrete around the dowel negatively affects the latter's performance in terms of transferring wheel loads through vertical shear action. In this context, a nonlinear ...

Ghauch, Ziad G.

2011-01-01

173

Evaluation of Common Maintenance Methods for Flexible Pavements  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Problem statement: With the increasing use and awareness of pavement management systems and the growing emphasis on asset management of pavement infrastructure, it is important to strengthen the maintenance components of these systems and particularly the preventive maintenance component. Iraqi Roads don?t receive an effective and proper maintenance during their service life until they reach the state of major failure that requires rehabilitation. Roads in Iraq are being lost. Appr...

Ibraheem, Asma T.; Gani, Suda M.

2011-01-01

174

Evaluation and Development of Pavement Scores, Performance Models and Needs Estimates for the TXDOT Pavement Management Information System - Final Report.  

Science.gov (United States)

This project conducted a thorough review of the existing Pavement Management Information System (PMIS) database, performance models, needs estimates, utility curves, and scores calculations, as well as a review of District practices concerning the three b...

A. Wimsatt, A. T. Papagiannakis, C. Chang-Albitres, C. Gurganus, I. Abdallah, J. Weissmann, N. Gharaibeh, S. Nazarian, S. Saliminejad, T. Freeman

2012-01-01

175

What Is Acute Respiratory Distress Syndrome?  

Science.gov (United States)

... usually given with a feeding tube placed Acute Respiratory Distress Syndrome (ARDS) is a life threatening problem in ... Series © 2007 American Thoracic Society What is Acute Respiratory Distress Syndrome? ? ARDS is a serious life threatening problem ...

176

Pavement macrotexture estimation using principal component analysis of tire/road noise  

Science.gov (United States)

An investigation on the prediction of macrotexture Mean Texture Depth (MTD) of pavement from a moving vehicle is conducted. The MTD was predicted by using the tire/road noise measured from a microphone mounted underneath a moving vehicle. Principal Component Analysis (PCA) is used to filter noise from microphone data prioer to estimating its energy over an optimally selected bandwidth. Energy obtained using this method is named PCA energy, hence the developed method for MTD estimation is termed as PCA Energy Method. The acoustic energy is assumed to have positive linear correlation with MTD of pavement. Moreover, PCA was used to differentiate important information about the road surface from noisy data while vehicle is moving, yielding a set of principal component vectors representing the conditions of each road section. This principal component vector was used to compute the PCA energy that is to be used for MTD prediction. The frequency band most relative to pavement macrotexture was determined to be 140 to 700 Hz through theoretical and statistical research. Then, a MTD prediction model was built based on a Taylor series expansion with two variables, PCA energy and the driving speed of the vehicle. The model parameters were obtained from an engineered track (interstate highway) with known MTD, and then applied to urban roads for the feasibility test. The accuracy of the model is 83.61% for the engineered track, which is 10% higher than the previous energy-based methods without PCA treatment. Moreover, applicability of the model is increased by the extended MTD prediction range between 0.2 and 3 mm compared to that of the engineered track having 0.4 to 1.5 mm. In addition, the MTD could be predicted every 7.8 meters and with good repeatability in the urban road test, which proves the feasibility of the proposed approach. Therefore, the PCA Energy Method is a reliable, efficient, and cost effective way to predict MTD for engineering applications as an important index for pavement friction prediction and pavement segregation identification.

Zhang, Yiying; McDaniel, J. Gregory; Wang, Ming L.

2014-04-01

177

47 CFR 80.312 - Priority of distress transmissions.  

Science.gov (United States)

... 2010-10-01 false Priority of distress transmissions...Procedures Distress, Alarm, Urgency and Safety Procedures § 80.312 Priority of distress transmissions...distress call has absolute priority over all other...

2010-10-01

178

Perfectionism, Procrastination, and Psychological Distress  

Science.gov (United States)

Using a cross-panel design and data from 2 successive cohorts of college students ( N = 357), we examined the stability of maladaptive perfectionism, procrastination, and psychological distress across 3 time points within a college semester. Each construct was substantially stable over time, with procrastination being especially stable. We also…

Rice, Kenneth G.; Richardson, Clarissa M. E.; Clark, Dustin

2012-01-01

179

Distress management. Clinical practice guidelines.  

Science.gov (United States)

The evaluation and treatment model expressed in the NCCN Distress Management Guidelines recommends that each new patient be rapidly assessed in the office or clinic waiting room for evidence of distress using a brief screening tool (the Distress Thermometer and Problem List) presented in Figure 1 (see page 369). A score of 5 or greater on the thermometer should trigger further evaluation and referral to a psychosocial service. The choice of which service should be determined by the problem areas specified on the Problem List. Patients with practical and psychosocial problems are referred to social work, emotional or psychological (excessive sadness, worry, nervousness) problems to mental health, and spiritual concerns to pastoral counselors. The primary oncology team members--doctor, nurse, and social worker--are central to making this model work. Team members collect information from the brief screening and problem list and expand it with the clinical evaluation. It is critical for at least one team member to be familiar with the mental health, psychosocial, and pastoral counseling resources available in the institution and the community. A list of the names and phone numbers for these resources should be kept in all oncology clinics and updated frequently. The first step in implementing this model is to establish a multidisciplinary committee in each institution or office responsible for 1) revising and modifying the standards of care to fit the particular clinical care setting and 2) implementing and monitoring the use of these standards. Because each institution has its own culture, standards must be implemented in ways that are compatible with each institution. The second step is to institute professional educational programs to ensure that staff is 1) aware that distress is under-recognized, 2) knowledgeable about the management of distress, and 3) aware of the resources available to treat it. It is important to have access to mental health professionals and clergy who are trained to deal with cancer-related distress. The benefits of treating distress in cancer accrue to the patients and their families, to the treating staff, and to improved efficiencies in clinic operations. Health care contracts often allow these services to "fall through the cracks" by failing to reimburse for them through either behavioral health or medical insurance. Reimbursement for services to treat psychosocial distress must be included in medical health care contracts to prevent fragmentation of services for the medically ill. For patients with cancer, integration, not separation, of mental health services and medical services is critically important. Also outcomes research studies that include quality-of-life assessment and analysis of cost-effectiveness are needed. Patients and families should be informed that management of distress is part of their total medical care. Finally, the multidisciplinary committee, office practice, or institution must be responsible for evaluating the quality of the distress management (see guidelines algorithm [page 368]), with CQI studies making an important contribution. Presently, the quality of the psychological care patients receive is not routinely monitored. Accrediting bodies have not directly examined the quality of psychosocial care, nor have they established minimal performance standards for its delivery. The panel believes that psychosocial care should and will eventually be on our institution's report cards. PMID:19761069

2003-07-01

180

Water quality and quantity assessment of pervious pavements performance in experimental car park areas.  

Science.gov (United States)

Pervious pavements have become one of the most used sustainable urban drainage system (SUDS) techniques in car parks. This research paper presents the results of monitoring water quality from several experimental car park areas designed and constructed in Spain with bays made of interlocking concrete block pavement, porous asphalt, polymer-modified porous concrete and reinforced grass with plastic and concrete cells. Moreover, two different sub-base materials were used (limestone aggregates and basic oxygen furnace slag). This study therefore encompasses the majority of the materials used as permeable surfaces and sub-base layers all over the world. Effluent from the test bays was monitored for dissolved oxygen, pH, electric conductivity, total suspended solids, turbidity and total petroleum hydrocarbons in order to analyze the behaviour shown by each combination of surface and sub-base materials. In addition, permeability tests were undertaken in all car parks using the 'Laboratorio Caminos Santander' permeameter and the Cantabrian Portable Infiltrometer. All results are presented together with the influence of surface and sub-base materials on water quality indicators using bivariate correlation statistical analysis at a confidence level of 95%. The polymer-modified porous concrete surface course in combination with limestone aggregate sub-base presented the best performance. PMID:24718346

Sañudo-Fontaneda, Luis A; Charlesworth, Susanne M; Castro-Fresno, Daniel; Andres-Valeri, Valerio C A; Rodriguez-Hernandez, Jorge

2014-01-01

 
 
 
 
181

Passive pavement-mounted acoustical linguistic drive alert system and method  

Science.gov (United States)

Systems and methods are described for passive pavement-mounted acoustical alert of the occupants of a vehicle. A method of notifying a vehicle occupant includes providing a driving medium upon which a vehicle is to be driven; and texturing a portion of the driving medium such that the textured portion interacts with the vehicle to produce audible signals, the textured portion pattern such that a linguistic message is encoded into the audible signals. The systems and methods provide advantages because information can be conveyed to the occupants of the vehicle based on the location of the vehicle relative to the textured surface.

Kisner, Roger A. (Knoxville, TN); Anderson, Richard L. (Oak Ridge, TN); Carnal, Charles L. (Cookeville, TN); Hylton, James O. (Clinton, TN); Stevens, Samuel S. (Harriman, TN)

2001-01-01

182

Diabetes distress among type 2 diabetic patients  

Directory of Open Access Journals (Sweden)

Full Text Available Background: Diabetes mellitus is being increasingly recognized as a serious global health problem and is frequently associated with co-morbid distress, contributing double burden for the individual and the society. Aim: This study documents the proportion of diabetes distress and factors associated with it. Methods: A cross-sectional study was conducted from January to June 2012. Data were collected through interview and record review of 165 adults with type 2 diabetes. Results: The proportion of diabetes distress among the study population was 48.5%, which includes 22.4% high distress and 26.1% moderate distress. The remainder had little or no distress. The Mean ± SD of total diabetes distress score was2.17 ± 0.75. The Mean ± SD for each domain score such as emotional burden, physician-related distress, regimen-related distress and interpersonal distress was (3.49 ± 1.52, (1.13 ± 0.32, (2.12 ± 0.85, (1.40± 0.65 respectively. Emotional burden was considered as the most important domain in measuring diabetes distress. The influence of age (p<0.001, occupation (p<0.05, smoking (p<0.005, BMI (p<0.001, duration since detection of diabetes mellitus (p<0.001, glycaemic status (p<0.001 treatment modalities (P<0.001, diabetic complications (p<0.001 on level of diabetes distress was statistically significant. There was a strong, positive correlation between the two variables (r=0.64, p<0.001; diabetes distress score with duration of diabetes mellitus. There was a medium, positive correlation between the two variables [r=0.43, p<0.001]; diabetes distress score with glycaemic status (HbA1c level .Conclusion: This study identified diabetes distress as a significant health problem among adult type 2 diabetes mellitus patients. This should be taken into consideration for effective management of patient.

Islam MR

2013-08-01

183

Implementation of the AASHTO pavement design procedures into MULTI-PAVE.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This thesis implements the empirical pavement design procedures for flexible as well as rigid pavement by American Association of State Highways and Transportation Officials (AASHTO) into two MATLAB modules of MULTI-PAVE. MULTI-PAVE was developed as a teaching tool that performs pavement thickness design for multiple design procedures using a common input file and a common output format. The AASHTO components were developed in accordance with the 1993 AASHTO Pavement Design Guide, and verifie...

Bekele, Abiy

2011-01-01

184

Design of Rigid and Flexible Pavements by Various Methods & Their Cost Analysis of Each Method  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Highway and pavement design plays an important role in the DPR projects. The satisfactory performance of the pavement will result in higher savings in terms of vehicle operating costs and travel time, which has a bearing on the overall economic feasibility of the project. This paper discusses about the design methods that are traditionally being followed and examines the “Design of rigid and flexible pavements by various methods & their cost analysis by each method”. Flexible pavement are...

Saurabh Jain

2013-01-01

185

Bearing capacity evaluation of rubblized concrete pavements  

Directory of Open Access Journals (Sweden)

Full Text Available The paper presents the findings of a research work performed on a real scale concrete pavement project where Rubblizing technology was used for its structural rehabilitation. Rubblizing may be defined as a fracture technique in which a concrete pavement slab is transformed in a granular base with a very high Modulus. This technique, fractures the concrete slab in angular pieces by using a concentrated dynamic load of low amplitude and high frequency. The research work was based on field study on the rehabilitation of 5 km motorway. The structural evaluations where made, before, during and after one year construction. Measurements and site evaluation where made by using DCP, Light Weight Deflectometer and FWD (on top of asphalt layer and excavating inside pits. The structural capacity of the Rubblized layer was evaluated through theoretical analysis. Because of the anisotropic properties of the Rubblized layer the results are presented using AASHTO structural layer coefficient. The structural layer coefficients recommended are between the range of 0.25 and 0.30 for concrete slabs with thickness grater than 220 mm.El trabajo presenta los resultados de un estudio a escala real de la capacidad estructural de un firme de hormigón rehabilitado utilizando la técnica de Rubblizing. La técnica de Rubblizing ha sido traducida como el pulverizado del firme de hormigón pero, es más bien un efecto combinado de trituración y fracturación de la losa de hormigón en todo su espesor para convertir esta en una base granular de alto módulo. Esta tecnica fractura la losa de hormigón en trozos angulares y entrelazados empleando una carga dinámica concentrada, de baja amplitud y alta frecuencia. La investigación se basó en el estudio de la rehabilitación de 5 km de autopista. Los estudios de la capacidad estructural fueron realizados durante, al término y un año después de la construcción. Para las mediciones y evaluaciones de terreno se utilizó, el DCP, Deflectómetro de Impacto Liviano, FWD (sobre carpeta asfáltica y excavando calicatas bajo el material triturado. La capacidad estructural del material triturado se realizó a través de un análisis teórico. Debido al las características anisotrópicas del material triturado, los resultados son presentados utilizando el coeficiente estructural AASHTO. Los resultados del estudio permiten recomendar un rango para el coeficiente estructural del pavimento sometido al proceso de Rubblizing el cual para espesores de losa superior a 22 cm está entre 0,25 a 0,30.

González, M.

2009-03-01

186

Development of ground-penetrating radar equipment for detecting pavement condition for preventive maintenance  

Science.gov (United States)

The report documents the development of a ground penetrating radar (GPR) system for locating potential maintenance problems in highway pavements. The report illustrates how GPR has the potential to detect four defects in pavements: stripping in an asphalt layer; moisture in base layer; voids or loss of support under rigid pavements; and overlay delamination.

Smith, S. S.; Scuillion, T.

1993-10-01

187

PAH volatilization following application of coal-tar-based pavement sealant  

Science.gov (United States)

Coal-tar-based pavement sealants, a major source of PAHs to urban water bodies, have recently been identified as a source of volatile PAHs to the atmosphere. We tracked the volatilization of PAHs for 1 year after application of a coal-tar-based pavement sealant by measuring gas-phase PAH concentrations above the pavement surface and solid-phase PAH concentrations in sealant scraped from the surface. Gas-phase concentrations at two heights (0.03 and 1.28 m) and wind speed were used to estimate volatilization flux. The sum of the concentrations of eight frequently detected PAHs (?PAH8) in the 0.03-m sample 1.6 h after application (297,000 ng m-3) was about 5000 times greater than that previously reported for the same height above unsealed parking lots (66 ng m-3). Flux at 1.6 h after application was estimated at 45,000 ?g m-2 h-1 and decreased rapidly during the 45 days after application to 160 ?g m-2 h-1. Loss of PAHs from the adhered sealant also was rapid, with about a 50% decrease in solid-phase ?PAH8 concentration over the 45 days after application. There was general agreement, given the uncertainties, in the estimated mass of ?PAH8 lost to the atmosphere on the basis of air sampling (2–3 g m-2) and adhered sealant sampling (6 g m-2) during the first 16 days after application, translating to a loss to the atmosphere of one-quarter to one-half of the PAHs in the sealcoat product. Combining the estimated mass of ?PAH8 released to the atmosphere with a national-use estimate of coal-tar-based sealant suggests that PAH emissions from new coal-tar-based sealcoat applications each year (~1000 Mg) are larger than annual vehicle emissions of PAHs for the United States.

Van Metre, Peter C.; Majewski, Michael S.; Mahler, Barbara J.; Foreman, William T.; Braun, Christopher L.; Wilson, Jennifer T.; Burbank, Teresa L.

2012-01-01

188

Coal-tar based pavement sealant toxicity to freshwater macroinvertebrates  

International Nuclear Information System (INIS)

Non-point-source pollution is a major source of ecological impairment in urban stream systems. Recent work suggests that coal-tar pavement sealants, used extensively to protect parking areas, may be contributing a large portion of the polycyclic aromatic hydrocarbon (PAH) loading seen in urban stream sediments. The hypothesis that dried coal-tar pavement sealant flake could alter the macroinvertebrate communities native to streams in Austin, TX was tested using a controlled outdoor laboratory type approach. The treatment groups were: control, low, medium, and high with total PAH concentrations (TPAH = sum of 16 EPA priority pollutant PAHs) of 0.1, 7.5, 18.4, and 300 mg/kg respectively. The low, medium, and high treatments were created via the addition of dried coal-tar pavement sealant to a sterile soil. At the start of the 24-day exposure, sediment from a minimally impacted local reference site containing a community of live sediment-dwelling benthic macroinvertebrates was added to each replicate. An exposure-dependent response was found for several stream health measures and for several individual taxa. There were community differences in abundance (P = 0.0004) and richness (P < 0.0001) between treatments in addition to specific taxa responses, displaying a clear negative relationship with the amount of coal-tar sealant flake. These results support the hypothesis that coal-tar pavement sealants contain bioavailable PAHs that may harm aquatic environments. - Coal-tar pavement sealants degrade stream invertebrate communities.

189

Surfactant alteration and replacement in acute respiratory distress syndrome  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract The acute respiratory distress syndrome (ARDS) is a frequent, life-threatening disease in which a marked increase in alveolar surface tension has been repeatedly observed. It is caused by factors including a lack of surface-active compounds, changes in the phospholipid, fatty acid, neutral lipid, and surfactant apoprotein composition, imbalance of the extracellular surfactant subtype distribution, inhibition of surfactant function by plasma protein leakage, incorporation of...

2001-01-01

190

Environmental Impact Assessment of Road Asphalt Pavements  

Directory of Open Access Journals (Sweden)

Full Text Available This paper deals with a versatile, synthetic, simple and user-friendly method based on Life Cycle Assessment studies which summarizes multifaceted, often competing, environmental, technical and economic aspects in road construction. In many cases just economic criteria are applied in call for tenders, because the calculation of the environmental impact of road construction is difficult. In fact, it can be referred to many available options and both the economic and the environmental suitabilities have to be considered, in order to achieve globally sustainable results about road infrastructure work. In this research, the weighted sum model of multicriteria analysis is identified as the tool to evaluate global impact of road works, to compare solutions and to choose the best one. The advantages of the proposed approach are that the local contest and the stakeholders’ objective are represented by adopting variable parameters and weights, in order to apply the method to several contexts. A case study explains potential environmental implications of using this new Road Environmental Impact Assessment to calculate effect related to the production of asphalt pavement, considering the production system for aggregates from cradle to gate, the materials transportation to road site and the works to have the road done.

Laura Moretti

2013-10-01

191

Incidence of respiratory distress syndrome  

International Nuclear Information System (INIS)

Objective: To determine the incidence of respiratory distress syndrome (RDS) in hospital born babies. Subjects and Methods: All live born infants delivered at the hospital and who fulfilled the diagnostic criteria of respiratory distress syndrome (RDS) were included in the study. Results: Ninety-four neonates developed RDS. Out of these, 88 (93.61%) were preterm and 06 (6.38%) were term infants. There was a male preponderance (65.95%). RDS was documented in 1.72% of total live births. 37.28% of preterm and 0.11% of term neonates born at the hospital. The incidence of RDS was 100% at 26 or less weeks of gestation, 57.14% at 32 weeks, and 3.70% at 36 weeks. The mortality with RDS was 41 (43.61%). Conclusion: RDS is the commonest cause of respiratory distress in the newborn, particularly, in preterm infants. It carries a high mortality rate and the incidence is more than that documented in the Western world. (author)

192

Unconventional Banking System in Distress  

Directory of Open Access Journals (Sweden)

Full Text Available AbstractWith the proliferation of banking sector problems around the world, in the last few years the empirical literature on systemic banking crises has grown significantly. This literature has frequently focused attention on the factors connected with the onset of conventional banking distress, in order to identify the determinants of the crises or to look for “early warning indicators” of difficulty. In fact a number of studies have relied on factors determining bank failures related to conventional rather than Islamic information. A lack of study and comprehension therefore has been a major challenge. Regrettably Islamic banking still remains enigmatic. The central aim of this paper is to elucidate the sense of Islamic banking distress and expose collapse. This study contributes to this ongoing debate over the Banking Distress of Islamic bank with the following distinct features. First, we pay attention to size and the factors determining bank failures for the unconventional. Second, we try to identify some cases of banks facing these problems. As mentioned below banks face difficulties in the present-day environment, and Islamic banks are no exception. Given all these constraints, it would be necessary to adopt measures to ovoid collapse which will be treated in the last part.

Wassim Rajhi

2011-08-01

193

Evaluating Functional and Structural Condition Based Maintenances of Airfield Pavements  

Directory of Open Access Journals (Sweden)

Full Text Available This study evaluates airfield pavements’ functional- and structural-condition to determine the most economical maintenance method. As a part of the analysis, Pavement Condition Index (PCI for several runways, taxiways, and aprons has been determined by MicroPAVER. Structural evaluation of airport pavements has been performed by Falling Weight Deflectometer (FWD test. Evaluation of Layer Moduli and Overlay Design (ELMOD also determines the required overlay thickness based on the E-values, i.e. FWD data analysis. Damage analysis determines the time of repeated overlay application. In addition, functional parameters have been included to determine the time of functional maintenance. Maintenance and rehabilitation alternatives have been selected to develop different program strategies. Life Cycle Cost Analysis (LCCA has been performed to determine the maintenance cost. Structural condition based maintenance cost is compared to functional condition based maintenance cost. Comparison shows that structural condition based approach yields cheaper maintenance strategies than functional condition based maintenance approach.

Tarefder R.

2013-01-01

194

Low cost pavement marking materials based on plasticized sulfur  

Science.gov (United States)

Pavement marking was made more cost effective by reducing the cost of the marking materials. A low cost marking material based on sulfur was developed. Elemental sulfur is a hard, brittle, crystalline material which, on heating, melts to a thin liquid that can be spray applied. If molten elemental sulfur is spray applied to the road as markings, it will on application solidify, crack and adhere poorly to the road. The first ten high speed trucks that ride over the markings will remove them. To make a useful sulfur based pavement marking material it was necessary to chemically modify (plasticize) the sulfur and mix it with fillers and pigments such that it had all of the characteristics desired of a pavement marking material. Yellow and white formulations were developed. For identification they were given the names YS-EIGHT and WS-EIGHT for the yellow and white formulations.

Dale, J. M.

1982-04-01

195

Geo synthetic-reinforced Pavement systems; Sistemas de pavimentos reforzados con geosinteticos  

Energy Technology Data Exchange (ETDEWEB)

Geo synthetics have been used as reinforcement inclusions to improve pavement performance. while there are clear field evidence of the benefit of using geo synthetic reinforcements, the specific conditions or mechanisms that govern the reinforcement of pavements are, at best, unclear and have remained largely unmeasured. Significant research has been recently conducted with the objectives of: (i) determining the relevant properties of geo synthetics that contribute to the enhanced performance of pavement systems, (ii) developing appropriate analytical, laboratory and field methods capable of quantifying the pavement performance, and (iii) enabling the prediction of pavement performance as a function of the properties of the various types of geo synthetics. (Author)

Zornberg, J. G.

2014-02-01

196

Airfield Rigid Pavement Structural Design—A Review of Main Aspects and Methods of Analysis  

Science.gov (United States)

Airfield pavements present a number of characteristics that make their design considerably different from that of road pavements. Apart from load magnitude and it's frequency, maintenance issues and pavement strength classification reporting are aspects that must be considered in the design phase. In the present paper, these aspects are analysed in the light of traditional and new methods of airfield pavement analysis. Parametric studies are performed in order to study the effects of different factors, such as pavement structure, layer thickness, material strength, effects of temperature, load transfer across joints and traffic characteristics.

Tiago Bonucci, Pereira

2010-05-01

197

Evaluation of Common Maintenance Methods for Flexible Pavements  

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Full Text Available Problem statement: With the increasing use and awareness of pavement management systems and the growing emphasis on asset management of pavement infrastructure, it is important to strengthen the maintenance components of these systems and particularly the preventive maintenance component. Iraqi Roads don?t receive an effective and proper maintenance during their service life until they reach the state of major failure that requires rehabilitation. Roads in Iraq are being lost. Approach: In this study, a study of the status of maintenance methods for road pavements in Iraq with special reference to flexible pavements is presented. For this purpose, open and closed questionnaires were executed in Baghdad to investigate the status of road pavement maintenance in Iraq. Road maintenance offices as (Ministry of construction and Housing, State Corporation for Roads and Bridges, Amanat Baghdad, Project office, were included in the questionnaire to arrive at the level of maintenance and techniques followed to maintain paved road in Iraq. Results: The interviews carried out reveal that maintenance in Iraq has secondary importance, apparently with no special budget allocated for such important works. In addition the maintenance methods and techniques followed do not comply the developments and modern techniques. Conclusion/Recommendations: Poor and miss-management of maintenance works and activities leading to delays and accumulation of failure in the highway network that require unusual expenditures to repair and maintain the accumulated damages. Also shortages in resources allocated for maintenance works and this leads to the diversion of significant portion of the allocated fund for maintenance works toward purchasing of new, or additional equipment to be used for the construction of new roads. It is strongly recommended to design a planning system for management pavement maintenance of road network in Iraq and develop a particular failure criterion for roads in Iraq.

Asma T. Ibraheem

2011-01-01

198

Interlocking Paving Stones Pavement as a Solution to Marshy Roads  

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Full Text Available This study is focused on the use of interlocking paving stones pavement for marshy roads and high groundwater table terrain. The permeable interlocking paving type of stones was used to combat intrusion of underground/saline water for the road of case study (Akin-Adesola Street, Victoria Island, Lagos. Hydrogeologic data, i.e., groundwater level information for marshy roads terrain including the area of case study was obtained in form of investigation hole/borehole data. Different scientific tests and researches put together show the effectiveness and durability of the modified exfiltration system type of permeable pavement for high ground water table terrain.

Oluwapelumi O. Ojuri

2012-04-01

199

Pavement Image Segmentation Based on FCM Algorithm Using Neighborhood Information  

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Full Text Available Standard FCM algorithm takes the pixel gray-scale information into account only, while ignoring the spatial location of pixels, so the standard FCM algorithm is sensitive to noise. This paper present a pavement image segmentation algorithm based on FCM algorithm using neighborhood information. The presented algorithm introduces neighborhood information into membership function to improve the standard FCM algorithm. It can eliminate noise effectively and retain the boundary information. The experiments by synthetic images and real pavement images show that the presented algorithm in this paper performs more robust to noise than the standard FCM algorithm and retain the boundary information effectively.

Guofeng Qin

2012-11-01

200

Performance of an enhanced pervious pavement system loaded with large volumes of hydrocarbons.  

Science.gov (United States)

Five litres of lubricating oil and two 8.5 litre batches of diesel were deposited on each of two hydraulically isolated experimental enhanced pervious pavement parking bays. The 50 mm aggregate subbases of the two bays were of either recycled concrete or crushed limestone. The bays were constructed in such a way that a near-surface gravity separator was created by the arranging of the outlet pipes such that a permanent pool of water was maintained in the system and water could only enter from below the level of any floating oil. Dissolved/dispersed hydrocarbons were measured at acceptable concentrations when monitoring was carried out over a period of approximately 5 months. The maximum concentration was 7.2 mg/l and of all the samples collected only 3% exceeded the 5 mg/l limit applied in the UK for a class 1 interceptor, and the majority of samples had hydrocarbon concentrations of less than 2 mg/l. Much more significant is the fact that no free product was discharged from either system up to the time the experiment was dismantled 2 years from the first oil application despite the fact that sufficient hydrocarbon had been added to each pavement to produce a film on a water surface of over 500 hectares. PMID:25225930

Newman, Alan P; Puehmeier, Tim; Shuttleworth, Andy; Pratt, Christopher J

2014-01-01

 
 
 
 
201

An elastoplastic model based on the shakedown concept for flexible pavements unbound granular materials  

Science.gov (United States)

Nowadays, the problem of rutting of flexible pavements linked to permanent deformations occurring in the unbound layers is taken into account only by mechanistic empirical formulas. Finite element modelling of realistic boundary value problems with incremental rheological models will lead to unrealistic calculation time for large cycle numbers. The objective of the authors is to present a simplified model which can be used to model the flexible pavements rutting with the finite elements framework. This method is based on the shakedown theory developed by Zarka which is usually associated to materials like steels. It has been adapted for granular materials by introducing a yield surface taking into account the mean stress influence on the mechanical behaviour and a dependency of the hardening modulus with the stress state. The Drucker-Prager yield surface has been used with a non-associated flow rule. Comparisons with repeated load triaxial tests carried out on a subgrade soil have been done. These comparisons underline the capabilities of the model to take into account the cyclic behaviour of unbound materials for roads. Finally, a discussion, dealing with the use of the simplified method within a finite element modelling of a full-scale experiment, is presented.

Habiballah, Taha; Chazallon, Cyrille

2005-05-01

202

Groove depth requirements for tine-textured rigid pavement 5: Durability of tine texturing on PCC pavements  

Science.gov (United States)

The required depth for grooves on new tine textured concrete pavements in order to assure an adequate skid resistance over their entire design life is discussed. Measurements of texture depth and skid resistance, with both ribbed and smooth tires were made on 0 to 5 year-old New York pavements. Initial groove depth needs of 3/16 in. minimum were calculated from two values estimated from the study data: the minimum depth (0.050 in.) to assure adequate skid resistance with a minimally legal treaded tire, and the mean groove wear rate (0.013 in./million vehicle passes). Groove depth measurements on new concrete pavements and bridge decks indicated 21 an 14 percent compliance, respectively, with the proposed new standard of 3/16 in. minimum, and 60 and 44 percent compliance with the current standard of 2/16 in. minimum.

Grady, J. E.; Chamberlin, W. P.

1981-06-01

203

Proportioning of Steel Fibre Reinforced Concrete Mixes for Pavement Construction and Their Impact on Environment and Cost  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Steel fibre reinforced concrete (SFRC) is a construction material investigated for more than 40 years including for pavement applications. A number of studies have demonstrated the technical merits of SFRC pavements over conventional concrete pavements; however little work has been carried out on the environmental and economical impact of SFRC during the pavement’s life cycle. Therefore, extended research was undertaken within the framework of the EU funded project “EcoLanes” to estimat...

Stelios Kallis; Neophytou, Pavlos O.; Kypros Pilakoutas; Kyriacos Neocleous; Diofantos Hadjimitsis; Constantia Achilleos

2011-01-01

204

Functionality enhancement of industrialized optical fiber sensors and system developed for full-scale pavement monitoring.  

Science.gov (United States)

Pavements always play a predominant role in transportation. Health monitoring of pavements is becoming more and more significant, as frequently suffering from cracks, rutting, and slippage renders them prematurely out of service. Effective and reliable sensing elements are thus in high demand to make prognosis on the mechanical properties and occurrence of damage to pavements. Therefore, in this paper, various types of functionality enhancement of industrialized optical fiber sensors for pavement monitoring are developed, with the corresponding operational principles clarified in theory and the performance double checked by basic experiments. Furthermore, a self-healing optical fiber sensing network system is adopted to accomplish full-scale monitoring of pavements. The application of optical fiber sensors assembly and self-healing network system in pavement has been carried out to validate the feasibility. It has been proved that the research in this article provides a valuable method and meaningful guidance for the integrity monitoring of civil structures, especially pavements. PMID:24854060

Wang, Huaping; Liu, Wanqiu; He, Jianping; Xing, Xiaoying; Cao, Dandan; Gao, Xipeng; Hao, Xiaowei; Cheng, Hongwei; Zhou, Zhi

2014-01-01

205

Functionality Enhancement of Industrialized Optical Fiber Sensors and System Developed for Full-Scale Pavement Monitoring  

Directory of Open Access Journals (Sweden)

Full Text Available Pavements always play a predominant role in transportation. Health monitoring of pavements is becoming more and more significant, as frequently suffering from cracks, rutting, and slippage renders them prematurely out of service. Effective and reliable sensing elements are thus in high demand to make prognosis on the mechanical properties and occurrence of damage to pavements. Therefore, in this paper, various types of functionality enhancement of industrialized optical fiber sensors for pavement monitoring are developed, with the corresponding operational principles clarified in theory and the performance double checked by basic experiments. Furthermore, a self-healing optical fiber sensing network system is adopted to accomplish full-scale monitoring of pavements. The application of optical fiber sensors assembly and self-healing network system in pavement has been carried out to validate the feasibility. It has been proved that the research in this article provides a valuable method and meaningful guidance for the integrity monitoring of civil structures, especially pavements.

Huaping Wang

2014-05-01

206

Respiratory distress of the term newborn infant.  

Science.gov (United States)

Respiratory distress is recognised as any signs of breathing difficulties in neonates. In the early neonatal period respiratory distress is common, occurring in up to 7% of newborn infants, resulting in significant numbers of term-born infants being admitted to neonatal units. Many risk factors are involved; the increasing number of term infants delivered by elective caesarean section has also increased the incidence. Additionally the risk decreases with each advancing week of gestation. At 37 weeks, the chances are three times greater than at 39-40 weeks gestation. Multiple conditions can present with features of respiratory distress. Common causes in term newborn infants include transient tachypnoea of the newborn, respiratory distress syndrome, pneumonia, meconium aspiration syndrome, persistent pulmonary hypertension of the neonate and pneumothorax. Early recognition of respiratory distress and initiation of appropriate treatment is important to ensure optimal outcomes. This review will discuss these common causes of respiratory distress in term-born infants. PMID:23347658

Edwards, Martin O; Kotecha, Sarah J; Kotecha, Sailesh

2013-03-01

207

Respiratory Distress Syndrome and its Complications  

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Full Text Available Respiratory distress syndrome in premature babies is one of the most common and most important health problems in newborns. Respiratory distress syndrome of newborn is a syndrome in premature infants caused by developmental insufficiency of surfactant production and structural immaturity in the lungs. Respiratory distress syndrome begins shortly after birth and is manifest by tachypnea, tachycardia, chest wall retractions, expiratory grunting, nasal flaring and cyanosis during breathing efforts. Respiratory distress syndrome or complications caused by respiratory distress syndrome are the most important causes of mortality and morbidity in premature infants. This article briefly reviews respiratory distress syndrome and its complications. [Archives Medical Review Journal 2013; 22(4.000: 615-630

Eren Kale Cekinmez

2013-08-01

208

Respiratory Distress Syndrome and its Complications  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Respiratory distress syndrome in premature babies is one of the most common and most important health problems in newborns. Respiratory distress syndrome of newborn is a syndrome in premature infants caused by developmental insufficiency of surfactant production and structural immaturity in the lungs. Respiratory distress syndrome begins shortly after birth and is manifest by tachypnea, tachycardia, chest wall retractions, expiratory grunting, nasal flaring and cyanosis during breathing effor...

Eren Kale Cekinmez; Hacer Yapicioglu Yildizdas; Ferda Ozlu

2013-01-01

209

Financial Distress Comparison Across Three Global Regions  

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Full Text Available Globalization has precipitated movement of output and employment between regions. We examine factors related to corporate financial distress across three continents. Using a multidimensional definition of financial distress we test three hypotheses to explain financial distress using historical financial data. A null hypothesis of a single global model was rejected in favor of a fully relaxed model which created individual financial distress models for each region. This result suggests that despite other indications of worldwide convergence, international differences in accounting rules, lending practices, managements skill levels, and legal requirements among others has kept corporate decline from becoming commoditized.

Harlan D. Platt

2008-12-01

210

Respiratory distress in the newborn.  

Science.gov (United States)

Respiratory distress presents as tachypnea, nasal flaring, retractions, and grunting and may progress to respiratory failure if not readily recognized and managed. Causes of respiratory distress vary and may not lie within the lung. A thorough history, physical examination, and radiographic and laboratory findings will aid in the differential diagnosis. Common causes include transient tachypnea of the newborn, neonatal pneumonia, respiratory distress syndrome (RDS), and meconium aspiration syndrome (MAS). Strong evidence reveals an inverse relationship between gestational age and respiratory morbidity. (1)(2)(9)(25)(26) Expert opinion recommends careful consideration about elective delivery without labor at less than 39 weeks’ gestation. Extensive evidence, including randomized control trials, cohort studies, and expert opinion, supports maternal group B streptococcus screening, intrapartum antibiotic prophylaxis, and appropriate followup of high-risk newborns according to guidelines established by the Centers for Disease Control and Prevention. (4)(29)(31)(32)(34) Following these best-practice strategies is effective in preventing neonatal pneumonia and its complications. (31)(32)(34). On the basis of strong evidence, including randomized control trials and Cochrane Reviews, administration of antenatal corticosteroids (5) and postnatal surfactant (6) decrease respiratory morbidity associated with RDS. Trends in perinatal management strategies to prevent MAS have changed. There is strong evidence that amnioinfusion, (49) oropharyngeal and nasopharyngeal suctioning at the perineum, (45) or intubation and endotracheal suctioning of vigorous infants (46)(47) do not decrease MAS or its complications. Some research and expert opinion supports endotracheal suctioning of nonvigorous meconium-stained infants (8) and induction of labor at 41 weeks’ gestation (7) to prevent MAS. PMID:25274969

Reuter, Suzanne; Moser, Chuanpit; Baack, Michelle

2014-10-01

211

Nitrogen Transformations in Three Types of Permeable Pavement  

Science.gov (United States)

In 2009, USEPA constructed a 0.4-ha (1-ac) parking lot at the Edison Environmental Center in Edison, NJ, that incorporated three different permeable pavement types - permeable interlocking concrete pavers (PICP), pervious concrete (PC), and porous asphalt (PA). The driving lanes...

212

Coal-tar based pavement sealant toxicity to freshwater macroinvertebrates  

Energy Technology Data Exchange (ETDEWEB)

Non-point-source pollution is a major source of ecological impairment in urban stream systems. Recent work suggests that coal-tar pavement sealants, used extensively to protect parking areas, may be contributing a large portion of the polycyclic aromatic hydrocarbon (PAH) loading seen in urban stream sediments. The hypothesis that dried coal-tar pavement sealant flake could alter the macroinvertebrate communities native to streams in Austin, TX was tested using a controlled outdoor laboratory type approach. The treatment groups were: control, low, medium, and high with total PAH concentrations (TPAH = sum of 16 EPA priority pollutant PAHs) of 0.1, 7.5, 18.4, & 300 mg/kg respectively. The low, medium, and high treatments were created via the addition of dried coal-tar pavement sealant to a sterile soil. At the start of the 24-day exposure, sediment from a minimally impacted local reference site containing a community of live sediment-dwelling benthic macroinvertebrates was added to each replicate. An exposure-dependent response was found for several stream health measures and for several individual taxa. There were community differences in abundance (P = 0.0004) and richness (P < 0.0001) between treatments in addition to specific taxa responses, displaying a clear negative relationship with the amount of coal-tar sealant flake. These results support the hypothesis that coal-tar pavement sealants contain bioavailable PAHs that may harm aquatic environments.

Bryer, P.J.; Scoggins, M.; McClintock, N.L. [Lamar University, Beaumont, TX (United States). Dept. of Biology

2010-05-15

213

A Detailed Study of Cbr Method for Flexible Pavement Design  

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Full Text Available As per IRC recommendation, California Bearing Ratio (CBR value of subgrade is used for design of flexible pavements. California Bearing Ratio (CBR value is an important soil parameter for design of flexible pavements and runway of air fields. It can also be used for determination of sub grade reaction of soil by using correlation. It is one of the most important engineering properties of soil for design of sub grade of roads. CBR value of soil may depends on many factors like maximum dry density (MDD, optimum moisture content (OMC, liquid limit (LL, plastic limit (PL, plasticity index (PI, type of soil, permeability of soil etc. Besides, soaked or unsoaked condition of soil also affects the value. These tests can easily be performed in the laboratory. the estimation of the CBR could be done on the basis of these tests which are quick to perform, less time consuming and cheap, then it will be easy to get the information about the strength of subgrade over the length of roads, By considering this aspect, a number of investigators in the past made their investigations in this field and designed different pavements by determining the CBR value on the basis of results of low cost, less time consuming and easy to perform tests. In this study, attempts have been made to seek the values of CBR of different soil samples and correlate their CBR values for the design purpose of flexible pavement as per guidelines of IRC: SP: 37-2001.

Er. Devendra Kumar Choudhary

2014-06-01

214

Use of seismic pavement analyzer in forensic studies  

Science.gov (United States)

Seismic nondestructive testing technology as used for pavement evaluation has been incorporated in two devices: the Seismic Pavement Analyzer (SPA) and the Portable Seismic Pavement Analyzer (PSPA). A few short-term projects were conducted to learn when and where the use of seismic methods is feasible. The usefulness of the test methods involved in the SPA and PSPA has been to some extent evaluated. In their present states, the SPA and PSPA seem to be emerging as valuable tools in forensic studies and the day-to-day operations of state highway agencies. The devices have been useful in understanding some of the complex mechanisms encountered in a few projects. More experience is needed to fully understand the potential and weaknesses of the devices, and further development of their software is needed. This paper presents a summary of efforts put forth to improve the SPA and PSPA for their incorporation into the activities of the highway community in maintenance, rehabilitation and construction of pavements. Several case studies that demonstrate the usefulness and shortcomings of the two devices and the methodology involved in them are presented.

Yuan, Deren; Nazarian, Soheil; Baker, Mark R.

1999-02-01

215

Evaluating Pavement Cracks with Bidimensional Empirical Mode Decomposition  

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Full Text Available Crack evaluation is essential for effective classification of pavement cracks. Digital images of pavement cracks have been analyzed using techniques such as fuzzy set theory and neural networks. Bidimensional empirical mode decomposition (BEMD, a new image analysis method recently developed, can potentially be used for pavement crack evaluation. BEMD is an extension of the empirical mode decomposition (EMD, which can decompose nonlinear and nonstationary signals into basis functions called intrinsic mode functions (IMFs. IMFs are monocomponent functions that have well-defined instantaneous frequencies. EMD is a sifting process that is nonparametric and data driven; it does not depend on an a priori basis set. It is able to remove noise from signals without complicated convolution processes. BEMD decomposes an image into two-dimensional IMFs. The present paper explores pavement crack detection using BEMD together with the Sobel edge detector. A number of images are filtered with BEMD to remove noise, and the residual image analyzed with the Sobel edge detector for crack detection. The results are compared with results from the Canny edge detector, which uses a Gaussian filter for image smoothing before performing edge detection. The objective is to qualitatively explore how well BEMD is able to smooth an image for more effective edge detection with the Sobel method.

Nii Attoh-Okine

2008-05-01

216

Alternative aircraft loading index for pavement structural analysis  

Energy Technology Data Exchange (ETDEWEB)

The most common practical way to simplify the structural analysis of airfield pavements is the use of equivalent single wheel load models instead of the actual gear of the aircrafts. As the accuracy and reliability of these models strongly affects the design and evaluation of airfield pavements, there is considerable need to investigate both system approaches. The first one, which uses a constant value for the pressure while the radius is variable, is currently under use by the aircraft classification number-pavement classification number method of the International Civil Aviation Organization, but despite this fact it proved to be inadequate to express the aircraft loading in many situations. On the contrary, according to this study, the second model, which has a constant value for the radius while the pressure varies, is more reliable, and it can be an interesting alternative. Thus, based on this model, an aircraft loading index is introduced, which aims to be a simple and reliable factor for expressing the severity of the loading of the aircrafts and a utility for several matters related to the airfield pavement applications.

Loizos, A.; Charonitis, G. [National Technical Univ. of Athens (Greece)

1999-05-01

217

Some experience using a rolling weight deflectometer on airport pavements  

Science.gov (United States)

A laser based deflection tester is being developed by the Swedish National Road Administration. Forty sensors are mounted on a heavy truck to determine two transverse profiles. One profile constitutes an unloaded case. The other profile just behind the rear wheels of the vehicle constitutes the loaded case. The high sampling rate is adequate for filtering the macro texture of the pavement.

Lenngren, Carl A.

1995-07-01

218

Exploring pavement crack evaluation with bidimensional empirical mode decomposition  

Science.gov (United States)

Crack evaluation is essential for effective classification of pavement cracks. Digital images of pavement cracks have been analyzed using techniques such as fuzzy set theory and neural networks. Bidimensional empirical mode decomposition (BEMD), a new image analysis method recently developed, can potentially be used for pavement crack evaluation. BEMD is an extension of the empirical mode decomposition (EMD), which can decompose non-linear and non-stationary signals into basis functions called intrinsic mode functions (IMF). IMFs are monocomponent functions that have well defined instantaneous frequencies. EMD is a sifting process that is non-parametric and data-driven; it does not depend on an a priori basis set. It is able to remove noise from signals without complicated convolution processes. BEMD decomposes an image into two-dimensional IMFs. The present paper explores pavement crack detection using BEMD together with the Sobel edge detector. A number of images are filtered with BEMD to remove noise, and the residual image analyzed with the Sobel edge detector for crack detection. The results are compared with results from the Canny edge detector, which uses a Gaussian filter for image smoothing before performing edge detection. The objective is to qualitatively explore how well BEMD is able to smooth an image for more effective and speedier edge detection with the Sobel method.

Ayenu-Prah, Albert; Attoh-Okine, Nii

2007-04-01

219

Riding Quality Model for Asphalt Pavement Monitoring Using Phase Array Type L-band Synthetic Aperture Radar (PALSAR  

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Full Text Available There are difficulties associated with near-real time or frequent pavement monitoring, because it is time consuming and costly. This study aimed to develop a binary logit model for the evaluation of highway riding quality, which could be used to monitor pavement conditions. The model was applied to investigate the influence of backscattering values of Phase Array type L-band Synthetic Aperture Radar (PALSAR. Training data obtained during 3–7 May 2007 was used in the development process, together with actual international roughness index (IRI values collected along a highway in Ayutthaya province, Thailand. The analysis showed that an increase in the backscattering value in the HH or the VV polarization indicated the poor condition of the pavement surface and, of the two, the HH polarization is more suitable for developing riding quality evaluation. The model developed was applied to analyze highway number 3467, to demonstrate its capability. It was found that the assessment accuracy of the prediction of the highway level of service was 97.00%. This is a preliminary study of the proposed technique and more intensive investigation must be carried out using ALOS/PALSAR images in various seasons.

Kamiya Yoshikazu

2010-11-01

220

Stabilization of Black Cotton Soil With Sand and Cement as a Subgrade for Pavement  

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Full Text Available Expansive soil (Black cotton soil is very weak and does not have enough stability for any type of construction work. In pavement, subgrade layer is the bottommost layer underlying the base course or surface course. To make the subgrade soil stable, by improving its engineering properties is very essential. In the present work, stabilization of subgrade soil by using sand and cement (varying percentage of sand and constant percentage of cement by weight of soil is used to enhance the strength of subgrade soil. The purpose of this study is to determine the optimum dose of the stabilizer, which improves the strength of soil (CBR less than or equal to 2% to more than 7% which is suitable for pavement structure. To evaluate the strength of soil, various test have been performed such as sieve analysis, liquid limit, Plastic limit, Standard proctor test and CBR test in the laboratory. The result shows that the use of sand and cement in combination, increases the California Bearing Ratio values (CBR i.e. the strength of soil to a great extent.

Mrs. Neetu B. Ramteke *1 ,

2014-06-01

 
 
 
 
221

Long-term salt marsh recovery and pavement persistence at {sup M}etula` spill sites  

Energy Technology Data Exchange (ETDEWEB)

Three coastal sites oiled from the 1974 `Metula` oil spill in the Strait of Magellan were revisited in May 1998 to document oiling conditions 23.5 years after the spill. The sites revisited are in the Punta Espora area. Two are salt marshes and the third, an inter-tidal asphalt pavement. It was found that the marshes were still oil covered and bare of vegetation in most sections, although the tilling conducted in 1993 resulted in substantial increases in the number of plants that were able to recolonize. Application of fertilizer without tilling of the surface of the oil had no effect. By 1998 the oil, although still present, was weathered to a rubbery consistency. The large, 550 m. long asphalt pavement that had formed on the mixed-sediment beach remained, and showed relatively little change. Chemical analysis of the asphalt indicated extremely high degradation, including even some of the highly biodegradation-resistant biomarker compounds. The experimental treatment plots that were tilled in 1993 showed the highest level of weathered oil, and the highest degree of plant recolonization, suggesting that recolonization of the marshes could have been accelerated had tilling been conducted on these sites soon after the spill. 15 refs., 5 tabs., 6 figs.

Owens, E. H. [Polaris Applied Sciences, Bainbridge Island, WA (United States); Sergy, G. A. [Environment Canada, Edmonton, AB (Canada); Guzman, M. L. [Instituto de Fomento Pesquero, Punta Arenas (Chile); Wang, Z. [Environment Canada. Ottawa, ON (Canada); Baker, J. [Ruyton-XI-Towns (United Kingdom)

1999-08-01

222

Long-term salt marsh recovery and pavement persistence at Metula' spill sites  

International Nuclear Information System (INIS)

Three coastal sites oiled from the 1974 'Metula' oil spill in the Strait of Magellan were revisited in May 1998 to document oiling conditions 23.5 years after the spill. The sites revisited are in the Punta Espora area. Two are salt marshes and the third, an inter-tidal asphalt pavement. It was found that the marshes were still oil covered and bare of vegetation in most sections, although the tilling conducted in 1993 resulted in substantial increases in the number of plants that were able to recolonize. Application of fertilizer without tilling of the surface of the oil had no effect. By 1998 the oil, although still present, was weathered to a rubbery consistency. The large, 550 m. long asphalt pavement that had formed on the mixed-sediment beach remained, and showed relatively little change. Chemical analysis of the asphalt indicated extremely high degradation, including even some of the highly biodegradation-resistant biomarker compounds. The experimental treatment plots that were tilled in 1993 showed the highest level of weathered oil, and the highest degree of plant recolonization, suggesting that recolonization of the marshes could have been accelerated had tilling been conducted on these sites soon after the spill. 15 refs., 5 tabs., 6 figs

223

Experimental and Numerical Studies of the Effects of Water Sprinkling on Urban Pavement on Heat Island Mitigation  

Science.gov (United States)

One of the main causes of 'heat island phenomeno' is thought to be the artificial covers of the ground surface with asphalt or concrete which reduce greatly inherent cooling effect of water evaporation from soil surface. In this study, as a candidate method of mitigating the heat island the effects of the 'water sprinkling' on the pavements are discussed from field experiments and numerical studies. Three field experiments of water sprinkling on the asphalt/concrete pavements were performed in hot summer days in 2004-2006. For detecting the change in temperatures, the authors developed and used a 3-D measurements system which consists of two vertical planes with 6m high and 16m wide, and has network arrays of 102 thermistors distributed spatially in the planes. The temperatures measured in and around the water sprinkled area indicated that the ground surface temperature decreased 5 to 15 degrees uniformly in the water sprinkled area compared with those in the un-sprinkled area, while the relative decrease of atmospheric temperature was approximately up to 1 degree. The subsurface temperature at a depth of 14cm under the pavement decreased significantly and kept lower than that at the same depth in un-sprinkled area over the next morning. A numerical model was developed and applied to interpret the experimental results. It deals with the heat balance of radiation, sensible/latent heat transfer at the ground surface and heat conduction through the artificial and natural soil layer under ground. temperature and vapor conditions changes at and near ground surface were modeled by using the bulk formula.Good agreements between the calculated time-temperature profiles and the experimental ones were obtained by assuming adequate physical parameters and meteorological conditions. The model could be improved in order to evaluate the changes of temperature and vapor contents in atmosphere near the ground surface caused by aerodynamic turbulent diffusion.

Yoshioka, M.; Tosaka, H.; Nakagawa, K.

2007-12-01

224

Mechanistic modelling of weak interlayers in flexible and semi-flexible road pavements: Part 2  

Scientific Electronic Library Online (English)

Full Text Available SciELO South Africa | Language: English Abstract in english This paper (Part 2 of a two-part set of papers) discusses models and illustrates the adverse effects of weak layers, interlayers, laminations and/or weak interfaces in flexible and semi-flexible pavements, also incorporating lightly cemented layers. The modelling is based on mechanistic analyses for [...] pavement design and evaluation. In Part 1, the effects of these relatively weak layers, interlayers, laminations and/or weak interfaces were discussed. It was shown that methodologies are available to detect and investigate the existence of these weak layers in cemented pavement layers. In Part 2, several cases of the above conditions for different road pavement types are discussed, with field examples. Mechanistic analyses were done on a typical hot mix asphalt (HMA), several cases of a cemented base pavement and a granular base pavement, with and without these weak layers and interface conditions to demonstrate their adverse effects. The analyses focus on the strain energy of distortion (SED) as a pavement response parameter to indicate the potential for structural damage expected within the pavement structure or layer. Generally, the higher the SED, the higher the potential damage in the pavement layer. SED shows some potential for quantifying the relative effects of these weak layers, interlayers, laminations and/or weak interfaces within flexible and semi-flexible pavements.

M, de Beer; J W, Maina; F, Netterberg.

2012-04-01

225

Desempeño de pavimentos estabilizado con asfalto espumado en una prueba de pavimentos a escala real y carga acelerada / Performance of foamed bitumen pavements in accelerated testing facility  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: Spanish Abstract in spanish Uno de los objetivos claves de la gestión de pavimentos es desarrollar e implementar una estrategia de construcción y mantenimiento rentables, con el fin de alcanzar niveles requeridos de servicio y desempeño. Una técnica rentable y sustentable para la rehabilitación de pavimentos es la de estabiliz [...] ación o reciclado con asfalto espumado (AE). Este artículo presenta un estudio sobre el desempeño de pavimentos estabilizados con asfalto espumado en el Canterbury Accelerated Pavement Testing Indoor Facility CAPTIF. CAPTIF es un laboratorio a escala real para pavimentos ubicado en Nueva Zelandia, que permite aplicar un gran número de cargas de tráfico en un breve período de tiempo. Seis secciones de pavimentos con distintos contenidos de asfalto y cemento fueron ensayadas en CAPTIF. Los resultados del experimento mostraron que las deflexiones disminuyen en las secciones con mayor contenido de asfalto espumado. Luego de aplicar más de un millón de ciclos de carga, las secciones estabilizadas sólo con cemento, sólo con asfalto y la sección sin estabilizar mostraron un deterioro significativo en forma de ahuellamiento. Por otro lado, las secciones que fueron estabilizadas con AE y cemento mostraron un buen desempeño, demostrando que el cemento y el AE juntos mejoran significativamente el desempeño del pavimento. Los resultados de ahuellamiento fueron empleados para desarrollar modelos y describir el deterioro estable y acelerado de los pavimentos en estudio, lo que puede ser utilizado para una mejor gestión de los pavimentos estabilizados con asfalto espumado. Abstract in english One of the key principal goals of pavement asset management is to develop and implement cost-effective pavement construction and maintenance strategies that achieve the required levels of service and performance. A sustainable, cost-effective technique for rehabilitating pavements is foamed bitumen [...] stabilization. This paper presents a study on the performance of foamed bitumen pavements tested in the Canterbury Accelerated Pavement Testing indoor Facility (CAPTiF), for full scale testing of pavements. Six pavement sections were tested; the variables were bitumen and cement content; one control section with the untreated unbound material was tested. Results showed that surface deflections decreased at sections with higher bitumen contents. After the application of 5,710,000 Equivalent Standard Axles (ESAs), the sections stabilised with cement only, bitumen only, and the control section all showed large amounts of rutting. Conversely, little rutting was observed in the three sections stabilised with foamed bitumen and 1.0% cement, showing that cement and FB together significantly improve pavement performance. The rutting results were used to develop models to describe the stable and unstable performance of the tested pavements. The paper concludes by outlining some of the practical benefits of utilising this technology in pavement asset management.

Alvaro, Gonzalez; Misko, Cubrinovski; Bryan, Pidwerbesky; David, Alabaster.

226

Desempeño de pavimentos estabilizado con asfalto espumado en una prueba de pavimentos a escala real y carga acelerada / Performance of foamed bitumen pavements in accelerated testing facility  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: Spanish Abstract in spanish Uno de los objetivos claves de la gestión de pavimentos es desarrollar e implementar una estrategia de construcción y mantenimiento rentables, con el fin de alcanzar niveles requeridos de servicio y desempeño. Una técnica rentable y sustentable para la rehabilitación de pavimentos es la de estabiliz [...] ación o reciclado con asfalto espumado (AE). Este artículo presenta un estudio sobre el desempeño de pavimentos estabilizados con asfalto espumado en el Canterbury Accelerated Pavement Testing Indoor Facility CAPTIF. CAPTIF es un laboratorio a escala real para pavimentos ubicado en Nueva Zelandia, que permite aplicar un gran número de cargas de tráfico en un breve período de tiempo. Seis secciones de pavimentos con distintos contenidos de asfalto y cemento fueron ensayadas en CAPTIF. Los resultados del experimento mostraron que las deflexiones disminuyen en las secciones con mayor contenido de asfalto espumado. Luego de aplicar más de un millón de ciclos de carga, las secciones estabilizadas sólo con cemento, sólo con asfalto y la sección sin estabilizar mostraron un deterioro significativo en forma de ahuellamiento. Por otro lado, las secciones que fueron estabilizadas con AE y cemento mostraron un buen desempeño, demostrando que el cemento y el AE juntos mejoran significativamente el desempeño del pavimento. Los resultados de ahuellamiento fueron empleados para desarrollar modelos y describir el deterioro estable y acelerado de los pavimentos en estudio, lo que puede ser utilizado para una mejor gestión de los pavimentos estabilizados con asfalto espumado. Abstract in english One of the key principal goals of pavement asset management is to develop and implement cost-effective pavement construction and maintenance strategies that achieve the required levels of service and performance. A sustainable, cost-effective technique for rehabilitating pavements is foamed bitumen [...] stabilization. This paper presents a study on the performance of foamed bitumen pavements tested in the Canterbury Accelerated Pavement Testing indoor Facility (CAPTiF), for full scale testing of pavements. Six pavement sections were tested; the variables were bitumen and cement content; one control section with the untreated unbound material was tested. Results showed that surface deflections decreased at sections with higher bitumen contents. After the application of 5,710,000 Equivalent Standard Axles (ESAs), the sections stabilised with cement only, bitumen only, and the control section all showed large amounts of rutting. Conversely, little rutting was observed in the three sections stabilised with foamed bitumen and 1.0% cement, showing that cement and FB together significantly improve pavement performance. The rutting results were used to develop models to describe the stable and unstable performance of the tested pavements. The paper concludes by outlining some of the practical benefits of utilising this technology in pavement asset management.

Alvaro, Gonzalez; Misko, Cubrinovski; Bryan, Pidwerbesky; David, Alabaster.

2012-08-01

227

Analysis, testing and verification of the behavior of composite pavements under Florida conditions using a heavy vehicle simulator  

Science.gov (United States)

Whitetopping (WT) is a rehabilitation method to resurface deteriorated asphalt pavements. While some of these composite pavements have performed very well carrying heavy load, other have shown poor performance with early cracking. With the objective of analyzing the applicability of WT pavements under Florida conditions, a total of nine full-scale WT test sections were constructed and tested using a Heavy Vehicle Simulator (HVS) in the APT facility at the FDOT Material Research Park. The test sections were instrumented to monitor both strain and temperature. A 3-D finite element model was developed to analyze the WT test sections. The model was calibrated and verified using measured FWD deflections and HVS load-induced strains from the test sections. The model was then used to evaluate the potential performance of these test sections under critical temperature-load condition in Florida. Six of the WT pavement test sections had a bonded concrete-asphalt interface by milling, cleaning and spraying with water the asphalt surface. This method produced excellent bonding at the interface, with shear strength of 195 to 220 psi. Three of the test sections were intended to have an unbonded concrete-asphalt interface by applying a debonding agent in the asphalt surface. However, shear strengths between 119 and 135 psi and a careful analysis of the strain and the temperature data indicated a partial bond condition. The computer model was able to satisfactorily model the behavior of the composite pavement by mainly considering material properties from standard laboratory tests and calibrating the spring elements used to model the interface. Reasonable matches between the measured and the calculated strains were achieved when a temperature-dependent AC elastic modulus was included in the analytical model. The expected numbers of repetitions of the 24-kip single axle loads at critical thermal condition were computed for the nine test sections based on maximum tensile stresses and fatigue theory. The results showed that 4" slabs can be used for heavy loads only for low-volume traffic. To withstand the critical load without fear of fatigue failure, 6" slabs and 8" slabs would be needed for joint spacings of 4' and 6', respectively.

Tapia Gutierrez, Patricio Enrique

228

Research on the characteristics of temperature field of asphalt pavement in seasonal frozen region  

Science.gov (United States)

The characteristics of climate in seasonal frozen area are low temperature and a large range of temperature variation between day and night in winter. These characteristics often lead to problems of asphalt pavement, especially transverse cracks. To reduce the problems of asphalt pavement, it is necessary to examine the distribution of the temperature range of asphalt pavement. A three-dimensional finite element model was used, taking the SMA asphalt pavement as an example with solid70 and plane55 unit features of ANSYS software. It can obtain the relationship between temperature gradient and time and the relationship between temperature gradient and depth. In addition, a function relation model of stress and time was also established. It can provide a theoretical basis for the prevention and treatment of problems of asphalt pavement in seasonal frozen area. Moreover, it has an important significance for improving asphalt pavement design.

Qiao, Jiangang; Liu, Weizheng

2014-08-01

229

Pathology Case Study: Respiratory Distress  

Science.gov (United States)

This cardiovascular pathology case study, provided by the University of Pittsburgh Department of Pathology, is an excellent resource for students and instructors in the health science fields. A 72-year-old female experiencing respiratory distress is the focus of this case. The patientâÂÂs history, gross description, and microscopic description of test results are provided to aid readers in understanding the patientâÂÂs diagnosis. The official final diagnosis is accompanied by a discussion of the contributing doctorâÂÂs findings and a list of references. This is an excellent resource for students in the health sciences to familiarize themselves with using patient history and laboratory results to diagnose patientâÂÂs conditions.

Ariyanayagam-Baksh, Shashi

2009-05-07

230

Finite element modeling and analysis of accelerated pavement testing devices and rutting phenomenon  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Indiana Department of Transportation/Purdue University accelerated pavement testing facilities (APT and PURWheel) have been utilized in conducting the National Pooled Funds Study (PFS) No. 176, “Validation of SHRP Asphalt Mixture Specifications Using Accelerated Pavement Testing”. Benefit of using the Accelerated Pavement Tester is that early rutting performance could be obtained for Superpave mixtures. ^ In conjunction with the testing, finite element models have been developed for...

Hua, Jianfeng

2000-01-01

231

The influence of construction quality control data variability on pavements evolution  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Predicting pavement evolution is a fundamental component in pavement maintenance and rehabilitation management work. However, it is very complex to carry out due to several drawbacks, namely a common use of inadequate quality control procedures or a lack of reproducibility of quality control data. This paper describes the main conclusions of a study on the influence of construction quality control data on pavement evolution. It was possible to develop a methodology for this purpose based on s...

Freitas, Elisabete F.; Pereira, Paulo A. A.; Santos, Lui?s Picado

2005-01-01

232

Application of CalME incremental-recursive method to the evaluation of the structural condition as asphalt pavements; Aplicacion del metodo recursivo-incremental CalME a la evaluacion del estado estructural de los pavimentos bituminosas  

Energy Technology Data Exchange (ETDEWEB)

CalME procedure represents one of the most advanced tools for the design, of flexible pavements world-wide. It is an incremental-recursive method, which means that pavements service life must be divided into many time intervals where both structural integrity and environmental conditions can be regarded as constants. It also means that the damage calculated at the end of each interval must be considered as initial condition for the next one. The goal of this type of models is the prediction of the evolution of the different distress mechanisms. The advantages of incremental-recursive procedures versus classical analytical design are shown in this paper. Advantages are shown not only in terms of design, but also as a tool in order to support structural evaluation. In particular, the potential of asphalt fatigue model incorporated in CalME is presented. this model is initially calibrated in the laboratory, and it is then re-calibrated based on the actual performance observed from field deflection testing. The model provides a reliable prediction of the future evolution of the damage of the asphalt mixture. Fatigue model validation has been conducted based on the performance from several flexible sections evaluated in CEDEX full-scale pavements test track. (Author) 14 refs.

Mateos Moreno, A.; Perez Ayuso, J.; Cadavid Jauregui, B.; Marron Fernandez, J. O.

2011-07-01

233

Stress Analysis and Determination of Effective k-value for Rigid Pavement  

Digital Repository Infrastructure Vision for European Research (DRIVER)

EverFE is a user-friendly 3D finite-element analysis tool for simulating the response of jointed plain concrete pavement (JPCP) systems to axle loads and environmental effects. EverFE is useful for both concrete pavement researchers and designers who must perform either complex nonlinear or simple linear stress analyses of JPCP.With help of this develop any type of model of rigid pavement considering practical condition thus getting more accurate and advance analysis for rigid pavement. It ca...

Kundan Meshram; Goliya, H. S.; Akhilesh Poddar

2013-01-01

234

Performance of pervious pavement parking bays storing rainwater in the north of Spain.  

Science.gov (United States)

Pervious pavements are drainage techniques that improve urban water management in a sustainable manner. An experimental pervious pavement parking area has been constructed in the north of Spain (Santander), with the aim of harvesting good quality rainwater. Forty-five pervious pavement structures have been designed and constructed to measure stored water quantity and quality simultaneously. Ten of these structures are specifically constructed with different geotextile layers for improving water storage within the pavements. Following the confirmation in previous laboratory experiments that the geotextile influenced on water storage, two different geosynthetics (Inbitex and a One Way evaporation control membrane) and control pervious pavements with no geotextile layers were tested in the field. Weather conditions were monitored in order to find correlations with the water storage within the pervious pavement models tested. During one year of monitoring the three different pervious pavement types tested remained at their maximum storage capacity. The heavy rain events which occurred during the experimental period caused evaporation rates within the pervious pavements to be not significant, but allowed the researchers to observe certain trends in the water storage. Temperature was the most closely correlated weather factor with the level of the water stored within the pervious pavements tested. PMID:20706008

Gomez-Ullate, E; Bayon, J R; Coupe, S; Castro-Fresno, D

2010-01-01

235

Low-cost bicycle path pavements. Final report, September 1, 1975--November 30, 1976  

Energy Technology Data Exchange (ETDEWEB)

The proposed research involves an analytic and experimental investigation to develop realistic design criteria for bicycle path pavements. The research also included evaluation of specific designs and innovative low-cost material systems for use in bicycle path pavements. An extensive literature review of currently existing and experimental bikepath pavement was also included. Results from this report indicate that the strength and durability of Class I bikepath pavements can be improved and the construction cost can be reduced through better design and construction practices and use of low-cost material systems.

Lai, J.S.

1976-12-01

236

Analysis of engineering characteristics of pavement deflection trends  

Energy Technology Data Exchange (ETDEWEB)

This paper describes analysis of pavement deflection data collected by the Transport Research Laboratory at two experimental road sites in England during 1960--1985. Measurements of Benkelman beam deflections together with records of traffic loading were taken at 6 to 12 month intervals. The analysis investigates the deflection trend as a function of road base material and thickness. The deflection trend was represented by a negative exponential curve form. Engineering aspects of the curve form were extracted and statistically analyzed. The results obtained focus on the dependency of deflection progression on both road base material and thickness, which are shown to act either jointly or singly, depending on the engineering characteristic of the pavement deflection trend.

Kerali, H.R.; Lawrance, A.J. [Univ. of Birmingham (United Kingdom)

1999-05-01

237

AN OPTIMAL MAINTENANCE MANAGEMENT MODEL FOR AIRPORT CONCRETE PAVEMENT  

Science.gov (United States)

In this paper, an optimal management model is formulated for the performance-based rehabilitation/maintenance contract for airport concrete pavement, whereby two types of life cycle cost risks, i.e., ground consolidation risk and concrete depreciation risk, are explicitly considered. The non-homogenous Markov chain model is formulated to represent the deterioration processes of concrete pavement which are conditional upon the ground consolidation processes. The optimal non-homogenous Markov decision model with multiple types of risk is presented to design the optimal rehabilitation/maintenance plans. And the methodology to revise the optimal rehabilitation/maintenance plans based upon the monitoring data by the Bayesian up-to-dating rules. The validity of the methodology presented in this paper is examined based upon the case studies carried out for the H airport.

Shimomura, Taizo; Fujimori, Yuji; Kaito, Kiyoyuki; Obama, Kengo; Kobayashi, Kiyoshi

238

Use of Recycled Aggregate and Fly Ash in Concrete Pavement  

Directory of Open Access Journals (Sweden)

Full Text Available Problem statement: Recycled materials aggregate from the demolished concrete structures and fly ash from burning coal shows the possible application as structural and non structural components in concrete structures. This research aims to evaluate the feasibility of using concrete containing recycled concrete aggregate and fly ash in concrete pavement. Approach: Two water cement ratio (0.45 and 0.55 the compressive strength, modulus of electricity and flexural strength for concrete with recycled aggregate and fly ash with 0, 25% replacing cement in mass were considered. Results: The material properties of recycled aggregate concrete with fly ash indicate comparable results with that of concrete with natural aggregate and without fly ash. Conclusion/Recommendations: The recycled materials could be used in concrete pavement and it will promote the sustainability of concrete.

Myle N. James

2011-01-01

239

The improvement of pavement performance using asphalt rubber hot mixes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The need of a better pavement performance has led researchers to develop new road materials, mainly for the asphalt layers, where the modification of the asphalt is the main example. This modification usually forces the use of polymers and fibers and, more recently, the use of crumb rubber from ground tires, where the modified asphalt is known as asphalt rubber. This asphalt rubber used in asphalt mixtures produces a superior performance if compared to the asphalt mixtures with...

Pais, Jorge C.; Pereira, Paulo A. A.

2007-01-01

240

Combined permeable pavement and ground source heat pump systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The PhD thesis focuses on the performance assessment of permeable pavement systems incorporating ground source heat pumps (GSHP). The relatively high variability of temperature in these systems allows for the survival of pathogenic organisms within the sub?base. Salmonella sp, Escherichia coli, Enterococci and total heterotrophic bacteria were analysed in order to assess potential risk to health. Supplementary carbon dioxide monitoring indicated relatively high microbial activity on the geo...

Grabowiecki, Piotr

2010-01-01

 
 
 
 
241

DYNAMIC JOINT LOAD TRANSFER EFFICIENCY OF RIGID PAVEMENT  

Directory of Open Access Journals (Sweden)

Full Text Available the mechanistic analysis presented in this paper is only the beginning of new approach for understanding the real joint load transfer capability on airport and highway concrete pavements. It gives up the two major assumptions those have been popularly adopted by hundreds of published papers: the load is transferred under a wheel with zero speed and with fixed position. The real load transfer in field is always under wheels with non-zero speed and with varied position at any moment. The objective of this study focuses on quantifying the dynamic effects of a moving wheel while it is crossing a joint on a pavement. The analysis is conducted using a model of two-slab system on Kelvin foundation under a moving wheel with variable speed v, different pavement damping Cs, foundation reaction modulus k and foundation damping Ck. The dynamic joint load transfer efficiency is temporarily and empirically defined by the peak strain ratio LTE(S on the two sides of a joint. The primary findings include: (1 The higher speed of a moving wheel leads to the higher LTE(S;(2 The larger the pavement damping Cs leads to the higher LTE(S;(3 The numerical ratio c(=LTE(Sdynamic/ LTE(Sstatic varies in the range 1 to 2 mainly depending on speed v and damping Cs;(4 The LTE(Sdynamic is not sensitive to foundation reaction modulus k and foundation damping Ck. Further researches are needed for appropriate applications of the new model in practice.

YU Xinhua

2011-02-01

242

DYNAMIC JOINT LOAD TRANSFER EFFICIENCY OF RIGID PAVEMENT  

Digital Repository Infrastructure Vision for European Research (DRIVER)

the mechanistic analysis presented in this paper is only the beginning of new approach for understanding the real joint load transfer capability on airport and highway concrete pavements. It gives up the two major assumptions those have been popularly adopted by hundreds of published papers: the load is transferred under a wheel with zero speed and with fixed position. The real load transfer in field is always under wheels with non-zero speed and with varied position at any moment. The object...

Yu, Xinhua; Wu, Xiaochun

2011-01-01

243

User's guide: Hot-mix recycling of asphalt concrete pavements  

Science.gov (United States)

This guide provides the technical information required to implement the application of hot-mix recycling of asphalt concrete pavements. Included are details on application, benefits/advantages, limitations/disadvantages, and costs associated with this technology. Information is provided on three demonstration sites at Fort Gillem, Georgia; Fort Leavenworth, Kansas; and Fort Benjamin Harrison, Indiana. Also provided is information concerning funding, procurement, maintenance, and performance monitoring. A fact sheet on recycling, contract specification example, and references are provided in the appendices.

Shoenberger, James E.

1993-05-01

244

Town of Avon: A Case Study in Pavement Preservation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this session presenters will discuss how the town of Avon has implemented and managed their pavement preservation program. This proactive program which began in the late 1990’s, resulted in good roads, a good overall network rating and an overall reduction in construction costs. Presenters will discuss the assessment of the road network, selection of treatments, and candidate selection. Representatives from the agency, contractor, and engineering firm will be on hand to discuss ideas and...

Moore, Steve; Cannon, Ryan; Hedges, Rex; Strange, Shawn

2013-01-01

245

Identification and conversion of foundation parameters for airport pavement  

Science.gov (United States)

The least squares method has been employed to fit measured and theoretical curves for the deflection of airport pavements, with the aim of identifying modulus of resilience E0 and of reaction K. Using these moduli results in errors generally no larger than 10 percent. A more accurate method of converting E0 into K and vice versa is proposed. The error is generally about 1 percent with maximum error not exceeding 2.7 percent.

Shang, Shiying; Wang, Shangwen

1993-01-01

246

EVALUATION OF TIRE RUBBER DISPOSAL IN CONCRETE FOR PAVEMENTS  

Directory of Open Access Journals (Sweden)

Full Text Available The production of waste by the tire industry has been a growing problem, indicating the need for its reuse. More than thirty million tires are discharged per year in Brazil, where regulation for the environment states that for each four new tires, five unusable ones must be adequately disposed by manufacturers and importers. Paving consumes an extremely large quantity of materials, which can be the source of rational application of waste and rejected materials. Research shows that tire rubber can be added to asphalt, which increases its durability and improves pavement quality and safety conditions by absorbing the rubber elastic properties, and also be used for architectural applications, among others. This study deals with the addition of rubber fibers from tire crushing in concrete for roadway pavements in order to provide proper indication about the alternative material disposal through an evaluation of the mechanical behavior of the modified concrete. Different concrete mixes were produced, within which, part of fine aggregates were substituted by tire rubber and mechanical experiment tests were performed, which show that, due to great resistance losses, the disposal of this alternative material in concrete should be considered for light traffic pavements, with the addition of rubber ranging up to 10% in mass.

Rosa Cristina Cecche Lintz

2009-12-01

247

Reliability-based performance simulation for optimized pavement maintenance  

International Nuclear Information System (INIS)

Roadway pavement maintenance is essential for driver safety and highway infrastructure efficiency. However, regular preventive maintenance and rehabilitation (M and R) activities are extremely costly. Unfortunately, the funds available for the M and R of highway pavement are often given lower priority compared to other national development policies, therefore, available funds must be allocated wisely. Maintenance strategies are typically implemented by optimizing only the cost whilst the reliability of facility performance is neglected. This study proposes a novel algorithm using multi-objective particle swarm optimization (MOPSO) technique to evaluate the cost-reliability tradeoff in a flexible maintenance strategy based on non-dominant solutions. Moreover, a probabilistic model for regression parameters is employed to assess reliability-based performance. A numerical example of a highway pavement project is illustrated to demonstrate the efficacy of the proposed MOPSO algorithms. The analytical results show that the proposed approach can help decision makers to optimize roadway maintenance plans. - Highlights: ?A novel algorithm using multi-objective particle swarm optimization technique. ? Evaluation of the cost-reliability tradeoff in a flexible maintenance strategy. ? A probabilistic model for regression parameters is employed to assess reliability-based performance. ? The proposed approach can help decision makers to optimize roadway maintenance plans.

248

Full scale demonstration of air-purifying pavement  

Energy Technology Data Exchange (ETDEWEB)

Highlights: ? The results of a demonstration project for photocatalytic pavement are shown. ? The photocatalytic performance was studied in a street as well as on lab scale. ? The outdoor monitoring was performed in different seasons and weather conditions. ? The NO{sub x} concentration was in average 19% lowered by the photocatalytic street. ? Under ideal weather conditions the NO{sub x} reduction reached up to 45%. -- Abstract: Experiments concerning a full-scale demonstration of air purifying pavement in Hengelo, The Netherlands, are reported. The full width of the street was provided with concrete pavement containing TiO{sub 2} over a length of 150 m (“DeNO{sub x} street”). Another part of the street, about 100 m, was paved with normal paving blocks (“Control street”). The outdoor monitoring was done during 26 days for a period exceeding one year, and measured parameters included traffic intensity, NO, NO{sub 2} and ozone concentrations, temperature, relative humidity, wind speed and direction, and the visible and UV light irradiance. Prior and parallel to these field measurements, the used blocks were also measured in the lab to assess their performance. The NO{sub x} concentration was, on average, 19% (considering the whole day) and 28% (considering only afternoons) lower than the obtained values in the Control street. Under ideal weather conditions (high radiation and low relative humidity) a NO{sub x} concentration decrease of 45% could be observed.

Ballari, M.M., E-mail: ballari@santafe-conicet.gov.ar [Department of the Built Environment, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Brouwers, H.J.H., E-mail: jos.brouwers@tue.nl [Department of the Built Environment, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands)

2013-06-15

249

Stratified soils under stone pavements as tools for palaeoenvironment reconstruction  

Science.gov (United States)

Stone pavements in climate-sensitive arid environments are often genetically associated with their underlying soil. Such soils are in general accretionary but also show features of stratification, resulting from changing environmental conditions, as well as alteration by pedogenesis. We thus regard soil-sediment profiles under stone pavements as distinctive archives of past geomorphic and pedologic processes. Deciphering the evolution allows reconstruction of landscape dynamics. Cima Volcanic Field, eastern Mojave Desert, California, has been in the focus of several studies. However, a detailed stratigraphic investigation of soils developed on basaltic lava flows of known age has not been conducted. We present descriptions of pedologic, stratigraphic and mineralogic properties of a sequence of soil profiles situated on a basaltic lava flow of middle Pleistocene age. We infer several phases of aeolian, fluvial, mass movement and pedologic activity of different nature. The archive reveals a complex evolution that can be attributed to specific environmental conditions in this climate-sensitive region, though numerical dating is preliminary. However, stratified, cumulic soils associated with desert pavements can be regarded as a unique type of archive, recording processes not traced in any other proxy record.

Dietze, M.; Kleber, A.

2009-04-01

250

Performance of Recycled Asphalt Pavement as Coarse Aggregate in Concrete  

Directory of Open Access Journals (Sweden)

Full Text Available Recycled asphalt pavement (RAP is the reclaimed and reprocessed pavement material containing asphalt and aggregate. Most RAP is recycled back into pavements, and as a result there is a general lack of data pertaining to the mechanical properties for RAP in other possible applications such as Portland cement concrete. In the present study, some mechanical properties of Portland cement concrete containing RAP as coarse aggregate were investigated in the laboratory. Six concrete mixes of widely differing water/cement ratios and mix proportions were made using RAP as coarse aggregate. The properties tested include the physical properties of the RAP aggregate, the compressive and flexural strengths of the concrete. These properties were compared with those of similar concretes made with natural gravel aggregate. Results of the tests suggest that the strength of concrete made from RAP is dependent on the bond strength of the ?asphalt-mortar? (asphalt binder-sand-filler matrix coatings on the aggregates and may not produce concrete with compressive strength above 25 MPa. However, for middle and low strength concrete, the material was found to compare favorably with natural gravel aggregate.

Fidelis O. OKAFOR

2010-12-01

251

In-situ determination of moisture in road pavement by nuclear methods  

International Nuclear Information System (INIS)

The use of neutron moisture probes to determine moisture in compacted pavement layers has been studied on samples representative of those used by the New South Wales Department of Main Roads for roadway construction. The aim of this work was to measure the average moisture content of the upper layer (15-20 cm thick) with minimum interference from moisture in underlying layers. Sub-surface probes using high (?-Be) and low (?-Li) energy neutron sources were examined; conventional ?-Be sources in specially designed compact probes should result in an error due to base moisture and density variations of less than 0.4 wt % moisture. As this error is probably less than those due to sampling and geometry variations in the field, such a probe should be sufficiently accurate for DMR requirements. If less sensitivity to base moisture is required, the ?-Li source will reduce this sensitivity by a factor of about 1.4

252

The impact of light-colored pavements on active layer dynamics revealed by Ground-Penetrating Radar monitoring  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Ground-penetrating radar (GPR) has been used to study the variations in the depth of the frost table throughout a complete thaw-freeze season in Kangerlussuaq Airport, western Greenland. In autumn 2000, three test areas were painted white on the parking area of the airport in order to reduce further development of depressions in the asphalt pavement. One of these areas has been used in the GPR investigations to compare the variations of the frost table underneath a normal dark asphalt surface...

Jørgensen, Anders Stuhr; Ingeman-nielsen, Thomas

2008-01-01

253

GPR used in combination with other NDT methods for assessing pavements in PPP projects  

Science.gov (United States)

In the recent decades, Public-Private Partnerships (PPP) has been adopted for highway infrastructure procurement in many countries. PPP projects typically take the form of a section of highway and connecting roadways which are to be construction and managed for a given concession period. Over the course of the highway concession period, the private agency takes over the pavement maintenance and rehabilitation duties. On this purpose, it is critical to find the most cost effective way to maintain the infrastructure in compliance with the agreed upon performance measures and a Pavement Management Systems (PMS) is critical to the success of this process. For the prosperous operation of a PMS it is necessary to have appropriate procedures for pavement monitoring and evaluation, which is important in many areas of pavement engineering. Non Destructive Testing (NDT) has played a major role in pavement condition monitoring, assessments and evaluation accomplishing continuous and quick collection of pavement data. The analysis of this data can lead to indicators related to trigger values (criteria) that define the pavement condition based on which the pavement "health" is perceived helping decide whether there is the need or not to intervene in the pavement. The accomplished perception appoints required management activities for preserving pavements in favor not only of the involved highway/road agencies but also of users' service. Amongst NDT methods Ground Penetrating Radar (GPR) seems to be a very powerful toll, as it provides a range of condition and construction pavement information. It can support effectively the implementation of PMS activities in the framework of pavement monitoring and evaluation. Given that, the present work aims to the development and adaptation of a protocol for the use of GPR in combination with other NDT methods, such as Falling Weight Deflectometer (FWD), for assessing pavements in PPP projects. It is based on the experience of Laboratory of Pavement Engineering of National Technical University of Athens (NTUA) gained through its research activities in various Greek PPP projects as well its involvement in several related European and International scientific actions. It is suggested that the implementation of such protocol could support the pavement management activities with respect to the needs of a PPP project. This is accomplished through the resulted advantages that include simplicity in application, economic benefits and familiarity that are very important factors towards the optimization of the resources and the utilization of the available information; both of them are required for the orderly operation of a PPP project. Acknowledgments: This work benefited from networking activities carried out within the EU funded COST Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar."

Loizos, Andreas; Plati, Christina

2014-05-01

254

CAUSES OF RESPIRATORY DISTRESS IN CHILDREN  

Directory of Open Access Journals (Sweden)

Full Text Available "nThere is a lack of large, prospective epidemiologic studies concerning acute lung injury (ALI and acute respiratory distress syndrome (ARDS in pediatric population. To determine the different causes of respiratory distress in children, we prepared a retrospective study and included the whole 567 children with respiratory distress referred to 17-Shahrivar Hospital, Rasht, Guilan. Using their medical files, data including age, sex, and causes of respiratory distress were collected. SPSS 13.0 (statistical software applied for statistical analysis. Pneumonia, asthma, and croup were the major causes of ARDS in children with a rate of 38.4, 19.04, and 16.5 percent, respectively. It seems that infectious factors are at the top of the list of ARDS causing factors which can be helpful to approach and manage such patients. We suggest vaccinating these at risk groups against common infectious factors such as H. Influenza and RSV which can cause either pneumonia or inducing asthma.

M M Karambin

2008-11-01

255

Investigation of mechanical properties of pavement through electromagnetic techniques  

Science.gov (United States)

Ground-penetrating radar (GPR) is considered as one of the most flexible geophysical tools that can be effectively and efficiently used in many different applications. In the field of pavement engineering, GPR can cover a wide range of uses, spanning from physical to geometrical inspections of pavements. Traditionally, such inferred information are integrated with mechanical measurements from other traditional (e.g. plate bearing test) or non-destructive (e.g. falling weight deflectometer) techniques, thereby resulting, respectively, in time-consuming and low-significant measurements, or in a high use of technological resources. In this regard, the new challenge of retrieving mechanical properties of road pavements and materials from electromagnetic measurements could represent a further step towards a greater saving of economic resources. As far as concerns unpaved and bound layers it is well-known that strength and deformation properties are mostly affected, respectively, by inter-particle friction and cohesion of soil particles and aggregates, and by bitumen adhesion, whose variability is expressed by the Young modulus of elasticity. In that respect, by assuming a relationship between electromagnetic response (e.g. signal amplitudes) and bulk density of materials, a reasonable correlation between mechanical and electric properties of substructure is therefore expected. In such framework, a pulse GPR system with ground-coupled antennae, 600 MHz and 1600 MHz centre frequencies was used over a 4-m×30-m test site composed by a flexible pavement structure. The horizontal sampling resolution amounted to 2.4×10-2 m. A square regular grid mesh of 836 nodes with a 0.40-m spacing between the GPR acquisition tracks was surveyed. Accordingly, a light falling weight deflectometer (LFWD) was used for measuring the elastic modulus of pavement at each node. The setup of such instrument consisted of a 10-kg falling mass and a 100-mm loading plate so that the influence domain of the elasticity measure could be comparable to that of the radar signal. Good agreement were found between high Young modulus values and repaved zones, whereas damaged areas were characterized by lower values of E. Tomographic maps of amplitudes along the z axis were extracted up to a depth of z

Benedetto, Andrea; Tosti, Fabio; D'Amico, Fabrizio

2014-05-01

256

Cortico-limbic morphology separates tinnitus from tinnitus distress.  

Science.gov (United States)

Tinnitus is a common auditory disorder characterized by a chronic ringing or buzzing "in the ear."Despite the auditory-perceptual nature of this disorder, a growing number of studies have reported neuroanatomical differences in tinnitus patients outside the auditory-perceptual system. Some have used this evidence to characterize chronic tinnitus as dysregulation of the auditory system, either resulting from inefficient inhibitory control or through the formation of aversive associations with tinnitus. It remains unclear, however, whether these "non-auditory" anatomical markers of tinnitus are related to the tinnitus signal itself, or merely to negative emotional reactions to tinnitus (i.e., tinnitus distress). In the current study, we used anatomical MRI to identify neural markers of tinnitus, and measured their relationship to a variety of tinnitus characteristics and other factors often linked to tinnitus, such as hearing loss, depression, anxiety, and noise sensitivity. In a new cohort of participants, we confirmed that people with chronic tinnitus exhibit reduced gray matter in ventromedial prefrontal cortex (vmPFC) compared to controls matched for age and hearing loss. This effect was driven by reduced cortical surface area, and was not related to tinnitus distress, symptoms of depression or anxiety, noise sensitivity, or other factors. Instead, tinnitus distress was positively correlated with cortical thickness in the anterior insula in tinnitus patients, while symptoms of anxiety and depression were negatively correlated with cortical thickness in subcallosal anterior cingulate cortex (scACC) across all groups. Tinnitus patients also exhibited increased gyrification of dorsomedial prefrontal cortex (dmPFC), which was more severe in those patients with constant (vs. intermittent) tinnitus awareness. Our data suggest that the neural systems associated with chronic tinnitus are different from those involved in aversive or distressed reactions to tinnitus. PMID:22493571

Leaver, Amber M; Seydell-Greenwald, Anna; Turesky, Ted K; Morgan, Susan; Kim, Hung J; Rauschecker, Josef P

2012-01-01

257

Cortico-limbic morphology separates tinnitus from tinnitus distress  

Directory of Open Access Journals (Sweden)

Full Text Available Tinnitus is a common auditory disorder characterized by a chronic ringing or buzzing “in the ear.” Despite the auditory-perceptual nature of this disorder, a growing number of studies have reported neuroanatomical differences in tinnitus patients outside the auditory-perceptual system. Some have used this evidence to characterize chronic tinnitus as dysregulation of the auditory system, either resulting from inefficient inhibitory control or through the formation of aversive associations with tinnitus. It remains unclear, however, whether these “non-auditory” anatomical markers of tinnitus are related to the tinnitus signal itself, or merely to negative emotional reactions to tinnitus (i.e., tinnitus distress. In the current study, we used anatomical MRI to identify neural markers of tinnitus, and measured their relationship to a variety of tinnitus characteristics and other factors often linked to tinnitus, such as hearing loss, depression, anxiety, and noise sensitivity. In a new cohort of participants, we confirmed that people with chronic tinnitus exhibit reduced grey matter in ventromedial prefrontal cortex (vmPFC compared to controls matched for age and hearing loss. This effect was driven by reduced cortical surface area, and was not related to tinnitus distress, symptoms of depression or anxiety, noise sensitivity, or other factors. Instead, tinnitus distress was positively correlated with cortical thickness in the anterior insula in tinnitus patients, while symptoms of anxiety and depression were negatively correlated with cortical thickness in subcallosal anterior cingulate cortex (scACC across all groups. Tinnitus patients also exhibited increased gyrification of dorsomedial prefrontal cortex (dmPFC, which was more severe in those patients with constant (vs. intermittent tinnitus. Our data suggest that the neural systems associated with chronic tinnitus are different from those involved in aversive or distressed reactions to tinnitus.

AmberMLeaver

2012-04-01

258

Duty, distress, and organ donation.  

Science.gov (United States)

A man of twenty-two is admitted to an intensive care unit (ICU)after intentionally overdosing on Tylenol. The nurse asks the intensivist on call if someone from the local organ procurement organization should be called in to speak to the family, given a worsening clinical picture and the likelihood that the patient will progress to brain death. The patient's condition is such that multiple organs, including his heart and lungs, could be donated. The intensivist instructs the nurse not to call, as he wishes to have an end-of-life discussion with the parents. He believes that the parents should know that death is imminent and that further interventions will not save their son. He argues that introducing the OPO at this point will cause the family more distress. He wants the parents to be able to give their son a peaceful death without additional stressors. What are the broader implications of not calling the OPO at this juncture? Does the nurse involved have an ethical obligation to override the intensivist's instructions by calling the OPO? Should the fact that multiple healthy organs could be harvested from this patient's body have any bearing on the decision to call the OPO? PMID:25412970

Milliken, Aimee; Wall, Anji

2014-11-01

259

Development of an evaporation-optimized and water-permeable pavement  

Science.gov (United States)

During recent decades, urban areas have been threatened more frequently by flood events. Furthermore, the potential for damage from these events has increased on average. The construction of houses, streets and parking lots has caused this trend by sealing the ground surface, i.e. these water-impermeable areas reduce the natural infiltration and evaporation-rates, and in some cases it is even completely stopped. The consequence is the so called "urban water cycle". Water from precipitation cannot be stored anywhere and so there is an immediate and very high surface run-off effect. Especially after intense rain events, canalisations and sewage-treatment plants are overloaded and this leads to higher costs for water treatment and to environmental damage. A practical solution to this problem is the use of water-permeable pavements. Here higher infiltration rates lead to a groundwater recharge that is greater than that of natural soils. The consequences from using these surfaces are already noticeable in many places through increasing groundwater levels. These increases cause damage to buildings. A second difference from a natural-soil water-balance is a lower evapotranspiration rate. Up to now the evaporation rates for water-permeable pavements has not been established accurately. The aim of the applied research project at the University of Muenster, which is sponsored by the DBU (The German Federal Environmental Foundation), is to gain knowledge of urban evaporation rates and of water-permeable surfaces, especially water-permeable pavements. Water-permeable pavements consist of the paving stone surface and the two sub-base layers below. Pre-investigations show that evaporation can be influenced by the complete sub-base. Therefore, the first step was to investigate which materials are used for sub-base construction. All in all, 27 materials were collected from throughout Germany and these materials were then tested (in terms of physical and hydraulic attributes) in the soil-mechanics laboratory of the University of Muenster. For their street construction useability, and having regard to evaporation, a selection of appropriate materials were built into a test field. The test field consisted of seven hexagonal areas each about 10 m2 large, which are placed in a honeycomb manner. The evaporation measurements are carried out with a WERNER tunnel-evaporation gauge (TUV) which is able to detect the actual evaporation rate. Its functional principle also allows a direct comparison between the middle reference area and one outer area of the test field. Every measuring period lasts one week and after that the TUV is moved to between the next outer area and the reference area. So the TUV rotates over the whole test field and every measuring area is covered by a measurement. In addition, a Hellman rain-gauge near the test field enables the measurement of a direct precipitation-evaporation ratio. Since the start of the measurements in July 2008, the first results collected showed that measureable differences in evaporation rates could be detected after a few measuring periods, i.e. the differences are up to 32% between the reference area and one outer area. In July 2009, the six outer measuring areas of the test field will be replaced and, based on the actual results collected, the sub-base layers will be replaced by an evaporation-optimized sub-base. The new outer measuring areas will only differ in terms of a different paving-stone surface. These paving stones are actually under developement and under laboratory testing (i.e. permeability, porosity, capillary water and evaporationrates), and so they will be evaporation-opimized. The open-air test in the test field is to assure and compare the evaporation rates. As a final result, the evaporation-optimized and water-permeable pavement and the knowledge of its exact drainage ratio will allow city planners or architects to build water-permeable streets with due regard to the respective area-specific conditions. This new developed pavement is an approximation to the water balanc

Starke, P.; Göbel, P.; Coldewey, W. G.

2009-04-01

260

Distress, demoralization and psychopathology: Diagnostic boundaries  

Directory of Open Access Journals (Sweden)

Full Text Available Background and Objectives: The objectives of the manuscript are: (a to review the understanding of demoralization and its assessment; (b to describe its clinical progression; (c to explain the differences between demoralization and other form of psychological distress; (d to propose a set of criteria for future research on demoralization. Methods: A MEDLINE search using the keywords distress, subjective incompetence, depression, demoralization, helplessness, hopelessness and psychopathology was conducted. This was supplemented by a manual search of the literature. Results: Demoralization can be distinguished from passing or transient distress, non-specific distress, sub-threshold depression or anxiety, and certain mental disorders. Demoralization can be a risk factor for the manifestation of psychopathology, the prodromal phase of a mental disorder, or a trigger for exacerbation or recurrence of psychiatric distress symptoms. The domains of distress and demoralization are described and research diagnostic criteria for demoralization are presented. Conclusions: The scales discussed in this article differ in their time frames and have not yet been applied to the same population at the same time. The role of demoralization as a risk factor for mental disorders is just beginning to be understood. The domains and the diagnostic criteria for demoralization presented in this article need to be confirmed by epidemiological and empirical studies. Future research should continue to clarify its role in the pathogenesis of both mental disorders and physical illnesses and identify appropriate interventions for its arrest or prevention.

John M. de Figueiredo

2013-03-01

 
 
 
 
261

/ Distress, demoralization and psychopathology: Diagnostic boundaries  

Scientific Electronic Library Online (English)

Full Text Available SciELO Spain | Language: English Abstract in english Background and Objectives: The objectives of the manuscript are: (a) to review the understanding of demoralization and its assessment; (b) to describe its clinical progression; (c) to explain the differences between demoralization and other form of psychological distress; (d) to propose a set of cri [...] teria for future research on demoralization. Methods: A MEDLINE search using the keywords distress, subjective incompetence, depression, demoralization, helplessness, hopelessness and psychopathology was conducted. This was supplemented by a manual search of the literature. Results: Demoralization can be distinguished from passing or transient distress, non-specific distress, sub-threshold depression or anxiety, and certain mental disorders. Demoralization can be a risk factor for the manifestation of psychopathology, the prodromal phase of a mental disorder, or a trigger for exacerbation or recurrence of psychiatric distress symptoms. The domains of distress and demoralization are described and research diagnostic criteria for demoralization are presented. Conclusions: The scales discussed in this article differ in their time frames and have not yet been applied to the same population at the same time. The role of demoralization as a risk factor for mental disorders is just beginning to be understood. The domains and the diagnostic criteria for demoralization presented in this article need to be confirmed by epidemiological and empirical studies. Future research should continue to clarify its role in the pathogenesis of both mental disorders and physical illnesses and identify appropriate interventions for its arrest or prevention.

John M. de, Figueiredo.

2013-03-01

262

Pulmonary distress following attempted suicidal hanging  

Directory of Open Access Journals (Sweden)

Full Text Available Objective : To assess the incidence of post-hanging pulmonary distress in cases of attempted suicidal hanging and predictors of outcome among these patients. Design : Five-year retrospective analysis. Setting: Tertiary care center in south India. Patients :A total of 335 patients who attempted suicidal hanging, aged above 16 years, were admitted during this period. Thirty-eight of them with pulmonary distress established clinically and with radiological evidence of pulmonary injury post hanging met the inclusion criteria. Measurements : Data from ICU records of 5 years, X-rays and laboratory investigations were reviewed. In patients identified to have post-hanging pulmonary distress, the neurological status, chest x-rays, arterial blood gas values and outcome data were collected and analyzed. Results : Eleven percent (n = 38 of the 335 patients admitted following attempted suicidal hanging were diagnosed to have post-hanging pulmonary distress. The overall mortality among post-hanging patients was 5%, which increased to 34.2% (n = 13 in the presence of pulmonary distress (P ? 0.001. Among the prognostic factors evaluated, a PaO 2 / FiO 2 (P/F ratio of < 100 at admission predicted a poor outcome (P ? 0.001. Conclusion : Post-hanging pulmonary distress is a relatively common complication of hanging and is associated with increased mortality. P/F ratio from arterial blood gas at admission was the only significant predictor of outcome in this group of patients.

Nair Shalini

2009-02-01

263

/ Distress, demoralization and psychopathology: Diagnostic boundaries  

Scientific Electronic Library Online (English)

Full Text Available SciELO Spain | Language: English Abstract in english Background and Objectives: The objectives of the manuscript are: (a) to review the understanding of demoralization and its assessment; (b) to describe its clinical progression; (c) to explain the differences between demoralization and other form of psychological distress; (d) to propose a set of cri [...] teria for future research on demoralization. Methods: A MEDLINE search using the keywords distress, subjective incompetence, depression, demoralization, helplessness, hopelessness and psychopathology was conducted. This was supplemented by a manual search of the literature. Results: Demoralization can be distinguished from passing or transient distress, non-specific distress, sub-threshold depression or anxiety, and certain mental disorders. Demoralization can be a risk factor for the manifestation of psychopathology, the prodromal phase of a mental disorder, or a trigger for exacerbation or recurrence of psychiatric distress symptoms. The domains of distress and demoralization are described and research diagnostic criteria for demoralization are presented. Conclusions: The scales discussed in this article differ in their time frames and have not yet been applied to the same population at the same time. The role of demoralization as a risk factor for mental disorders is just beginning to be understood. The domains and the diagnostic criteria for demoralization presented in this article need to be confirmed by epidemiological and empirical studies. Future research should continue to clarify its role in the pathogenesis of both mental disorders and physical illnesses and identify appropriate interventions for its arrest or prevention.

John M. de, Figueiredo.

264

Active zone impact on deformation state of non-rigid pavement  

Science.gov (United States)

The paper deals with the design of non-rigid pavement, with emphasis on the effect of active zone on its deformation state. The concepts of determination of active zone are described. The results of numerical modelling of pavement laying on elastic subgrade are presented in the paper

Mandula, Ján

2014-06-01

265

Use of Ground-Penetrating Radar for Detecting Voids Underneath a Jointed Concrete Pavement.  

Science.gov (United States)

A survey of a jointed, reinforced concrete pavement with ground-penetrating radar indicated that the equipment provides a nondestructive inspection technique that can be used at a minimum rate of 5 lane miles of pavement per hour and with only minimal int...

G. G. Clemena, M. M. Sprinkel, R. R. Long

1986-01-01

266

Distress vs. Non-Distress Approach and the Personal Space of Masculine, Feminine, and Androgynous Subjects.  

Science.gov (United States)

Examined was the relationship between personal space and sex roles. Feminine females (N=25), androgynous females (N=25) and masculine males (N=25) viewed a film of male and female approaching stimulus persons in distress and non-distress conditions. Subjects marked the Comfortable Interpersonal Distance Scale at the point where they would prefer…

Glisson, Pamela A.; Thomas, Georgelle

267

Design Basis for Fibre Reinforced Concrete (FRC) Pavements  

DEFF Research Database (Denmark)

The paper summarises a Ph.D. project on development of a new design basis for fibre reinforced concrete ground slabs. The stress-crack openingrelationship is a well know basic material property of theso-called fictitious crack model for concrete. In the presentstudy it is shown how the stress-crack opening relationship can beused to descibe the properties of fibre reinforced concrete (FRC) intension and how the stress-crack opening relationship can beapplied in a simple design scheme for pavements. The projectincludes development of design tools, experiments to determine thestress-crack opening relationship by direct tension tests and fullscale tests on FRC-slabs cast on ground.

Bendixen, SØren; Stang, Henrik

1996-01-01

268

Asphaltic concrete overlays of rigid and flexible pavements  

Science.gov (United States)

The development of a mechanistic approach to overlay thickness selection is described. The procedure utilizes a deflection analysis to determine pavement rehabilitation needs. Design guides for selecting the overlay thickness are presented. Tolerable deflection-traffic load relationships and the deflection attenuation properties of asphaltic concrete were developed, representing the subgrade support conditions and properties of materials used in Louisiana. All deflection measurements on asphaltic concrete were corrected for the effect of temperature. Deflection measurements taken before and after overlay were also adjusted to minimize the effects of seasonal subgrade moisture variation.

Kinchen, R. W.; Temple, W. H.

1980-10-01

269

Evaluation of the visco-elastic properties in asphalt rubber in conventional mixtures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Flexible pavements are subjected to a set of degradations on the pavement surface, such as cracks and other specific types of distress which arise from traffic and temperature variations and which are responsible for the users’ unsafety and discomfort. The occurrence of temperature variations in the pavement leads to a severe aggravation of the reflective cracking phenomenon what implies a premature distress of the overlays. In this way, a theoretical study about the influ...

Minhoto, Manuel; Pereira, Paulo; Pais, Jorge

2007-01-01

270

Potential for localized groundwater contamination in a porous pavement parking lot setting in Rhode Island  

Science.gov (United States)

The control of polluted surface runoff and the assessment of possible impacts on groundwater is a concern at the local and regional scale. On this background, a study investigates possible impacts of organic and inorganic pollutants (including bacteria) originating from a permeable asphalt parking lot on the water quality immediately beneath it. The functioning of the permeable pavement, including clogging and restricted vertical percolation, was also evaluated. Four nested sample ports (shallow and deep) were installed below low- and high-traffic areas, including one port outside the parking lot. At least initially there was a good hydraulic connection between the parking surface and the shallow sample ports. The presence of a geotextile layer at the base of the parking lot structure, however, was identified in lab tests as one factor restricting vertical percolation to the deeper ports. Clogging of the permeable surface was most pronounced in heavy traffic areas and below snow pile storage areas. Corroborated by high electric conductivity and chloride measurements, sand brought in by cars during winter was the principal cause for clogging. No bacteria or BOD were found in percolating water. Polycyclic aromatic hydrocarbons (PAH) were present at concentrations near minimum detection limit. Nutrients (nitrate and phosphate) were being leached into the ground via the permeable parking lot surface at annual flux rates of 0.45 0.84 g/m2/year. A multi-species tracer test demonstrated a retention capacity of the permeable parking lot structure of >90% for metals and 27% for nutrients, respectively.

Boving, Thomas B.; Stolt, Mark H.; Augenstern, Janelle; Brosnan, Brian

2008-08-01

271

Continuous highway pavements deflection measurements using a rolling dynamic deflectometer (RDD)  

Science.gov (United States)

Nondestructive testing of pavements plays an important role int he management of pavement infrastructure. A new technique for continuous profiling of pavements is under development. This technique involves the Rolling Dynamic Deflectometer (RDD). The RDD is a large truck on which a servo-hydraulic vibrator is mounted. The vibrator is used to apply large vertical dynamic loads to the pavement. The resulting dynamic displacements are sensed with rolling sensor. A description of the RDD and procedures used to analyze RDD data are discussed herein. The results of continuous RDD profiling of rigid pavements are presented. These results show that continuous stiffness profiles of displacement per given load of origin pavements can be used to characterize: 1) the pavement stiffness and its longitudinal variation; 2) the location of transverse cracks and joints; 3) the efficiency of transverse cracks and joints; 4) the efficiency of longitudinal joints; and 5) the lateral variation in average mid-span stiffness. Two significant benefits of continuous RDD profiles which are clearly shown are: 1) softer versus stiffer areas are clearly delineated and 2) the variation in joint efficiency is readily identified.

Bay, James A.; Stokoe, Kenneth H., II; Hudson, W. R.

1996-11-01

272

Thickness and air voids measurement on asphalt concrete pavements using ground-penetrating radar  

Science.gov (United States)

Layer thickness and air voids are important parameters in quality assurance of newly paved hot mix asphalt (HMA) pavements. A non-destructive testing (NDT) technique was used to collect layer thickness information. The thicknesses estimated by the technique were compared with core thicknesses. Ground penetrating radar (GPR) system with air coupled antennas was used for on-site pavement data collection. Two application softwares - RADAN and ROAD DOCTOR - were used to process the field data for estimating layer thicknesses and air voids along the scanned pavements. 150 mm diameter cores taken from random locations on the pavements were tested in the laboratory to determine layer thickness and air voids. Statistical analyses were conducted to compare thicknesses and generate a regression equation relating air voids and dielectric constant of the pavement material. No significant differences were found between thickness estimates from RADAN and ROAD DOCTOR softwares when compared to the core measurements. However, RADAN and ROAD DOCTOR results are marginally significantly different from each other. ROAD DOCTOR software was used to generate air voids for the pavements scanned. Laboratory results from cores were utilized to determine calibration factors for the air voids -- dielectric equation. A relationship between air voids and dielectric constant is presented. It is concluded that GPR system with air coupled antennas used alongside a reduced core testing has a potential for quality control of newly paved hot mixed asphalt pavements.

Dhakal, Sharad Raj

273

Assessing artificial neural network performance in estimating the layer properties of pavements  

Directory of Open Access Journals (Sweden)

Full Text Available A major concern in assessing the structural condition of existing flexible pavements is the estimation of the mechanical properties of constituent layers, which is useful for the design and decision-making process in road management systems. This parameter identification problem is truly complex due to the large number of variables involved in pavement behavior. To this end, non-conventional adaptive or approximate solutions via Artificial Neural Networks – ANNs – are considered to properly map pavement response field measurements. Previous investigations have demonstrated the exceptional ability of ANNs in layer moduli estimation from non-destructive deflection tests, but most of the reported cases were developed using synthetic deflection data or hypothetical pavement systems. This paper presents further attempts to back-calculate layer moduli via ANN modeling, using a database gathered from field tests performed on three- and four-layer pavement systems. Traditional layer structuring and pavements with a stabilized subbase were considered. A three-stage methodology is developed in this study to design and validate an “optimum” ANN-based model, i.e., the best architecture possible along with adequate learning rules. An assessment of the resulting ANN model demonstrates its forecasting capabilities and efficiency in solving a complex parameter identification problem concerning pavements.

Gloria Inés Beltran

2014-07-01

274

Finite Element Investigation of the Deterioration of Doweled Rigid Pavements  

CERN Document Server

The purpose of this study is to describe the failure of concrete around dowel bars in jointed rigid pavements, and the resulting effect on the pavement performance. In fact, under repetitive vehicle loading, concrete in contact with the dowel bar deteriorates, particularly at the joint face. The degradation of concrete around the dowel negatively affects the latter's performance in terms of transferring wheel loads through vertical shear action. In this context, a nonlinear 3D Finite Element analysis was performed using the commercial FE code Abaqus (v-6.11). The FE model was validated with classical analytical solutions of shear and moment along the dowel. A concrete damaged plasticity model was used for the PCC slab to model the degradation of concrete matrix around the dowels under incremental loading. Results obtained show, among other things, that the degradation of concrete matrix around the dowel was found to initiate at the face of the joint and propagate towards the interior of the dowel. Also, resul...

Ghauch, Ziad G

2011-01-01

275

Sustainable Drainage Practices in Spain, Specially Focused on Pervious Pavements  

Directory of Open Access Journals (Sweden)

Full Text Available The Spanish climate is full of contrasts, with torrential rains and long droughts; under these conditions, appropriate water management is essential. In Spain, until the end of the twentieth century, water management and legislative development lagged behind other more developed countries. Nowadays, great efforts are being made to reverse this situation and improve both water management and legislation in order to control the two main problems related to stormwater management in cities: floods and diffuse pollution. In this context, Sustainable Urban Drainage Systems (SUDS were developed as the main solution to these problems. The study of these techniques started in the 1970s in the USA, but they were not studied in Spain until 1993 when the University of Cantabria and CLABSA started to look into solutions for stormwater management. After 20 years of research and application, sustainable drainage in Spain is still behind other countries in spite of the efforts to change this situation, notably by the University of Cantabria with 10 years of experience in these techniques, mainly regarding pervious pavements, where more than 13 related research projects have been carried out. The future challenges focus on the application of pervious pavements for Urban Hydrological Rehabilitation.

Jorge Rodriguez-Hernandez

2013-01-01

276

An Overview Of Pavement Management System For Industrial Areas  

Science.gov (United States)

ACT With the current surge in national economy the industrial traffic has increased many folds in terms of quantity of load and traffic volume. This results in early deterioration of the roads. Also the serviceability reduces hampering the industry's supply of raw material and transport of finished goods. An efficient road transportation system is of vitally important for smooth operations of industrial units. Construction of new roads needs an enormous investment. However, once constructed the road network system requires huge resources to maintain serviceability and to ensure safe passage at an appropriate speed and with low VOC (Vehicle Operating Cost). Road maintenance is therefore an essential function and should be carried out on a timely basis. The cost of providing and maintaining the roads for the industrial areas at an acceptable serviceability level is quite high. It is therefore essential for a transportation engineer to attempt establishing an acceptable pavement condition level from economic, safety and environmental point of view. In today's economic environment of constrained budgets, as the existing road infrastructure has aged, a more systematic approach towards determining maintenance and rehabilitation needs is necessary. The efficient pavement management system shall provide objective information and useful analysis to ensure consistent and cost effective decisions related to preservation of existing industrial road network in healthy condition.

Hokam, Vivek S.

2012-03-01

277

13 CFR 301.3 - Economic distress levels.  

Science.gov (United States)

...distress criteria: (i) An unemployment rate that is, for the most recent...greater than the national average unemployment rate; (ii) Per capita income...distress levels based upon the unemployment rate or per capita income...

2010-01-01

278

Development of a Distress Alerting and Locating System (DALS).  

Science.gov (United States)

An automated method of determining a distressed vessel's situation and position could be useful in the U. S. Coast Guard's search and rescue mission. Evaluation of commercially available retransmitting equipment, modified for use as a Distress Alerting an...

W. A. DeGeorge, J. R. Lindeblad

1975-01-01

279

Determination of importance of various parameters on performance of rigid pavement joints  

Science.gov (United States)

The effects of various parameters on an experimental concrete pavement were evaluated. Variables included in the pavement were (1) joint spacing, (2) subbase stabilization, (3) coating of dowel bars, (4) configuration of the saw cut, and (5) the use of skewed joints. Both long term and short term horizontal movements caused by temperature and vertical movement of slab ends under known axle loads were measured. A record of cracking and spalling of the pavement is also included. A statistical analysis of both long and short term movements was conducted and recommendations for joint design are included.

Cook, J. P.; Minkarah, I.; McDonough, J. F.

1981-08-01

280

NON-CONTACT, NON-DESTRUCTIVE PAVEMENT PROFILE, TEXTURE AND DEFLECTION MEASUREMENTS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A non-contact, non-destructive method is described that allows the user to measure pavement texture and loaded and unloaded profiles from a moving vehicle.^ The device uses laser distance measuring gages. The gages are arranged such that their readings can be interpreted to give the loaded and unloaded pavement profiles and a measure of its texture. Four gages are mounted on a rigid beam that, in turn, is mounted on the side of a load vehicle. The gages read the distance to the pavement. T...

Elton, David John

1982-01-01

 
 
 
 
281

NOTRA - noise trailer in pavement evolution measurements  

Energy Technology Data Exchange (ETDEWEB)

Reduction of noise emission has become more important issue among automotive industry and road construction. There are lot of different means to affect traffic noise by automotive engineering, road construction and maintenance. Perhaps the most effective means can be found during land use planning but practically in most cases a road and the houses already does exists. Changes in the built environment are always compromises and there is demand to have reliable information about the effect of different noise prevention means and their effects. Reduction of noise means new challenges and at the same time gives new business opportunities. Today the major source of traffic noise is tyre-road interaction. Tyre is a trade off between very complex and also emotionally loaded values like safety features, recycling questions, style (fashion) and noise. This offers opportunities to co-operation in research between automotive and road engineers and national road administrations. The full name of the project is {sup E}volution of road surface and noise from tyre-road interaction{sup .} The HUT NOTRA stands for Helsinki University of Technology, Noise Trailer. The part of NOTRA became the name of the trailer itself and so turned to be also the name of the whole project. It is today a registered trade mark for this kind of trailer. This project was under the umbrella of VTT (Technical Research Centre of Finland) coordinated Mobile 2-project by the support of Finnish Road Administration and Nokian Tyres plc.

Sainio, P.

2003-07-01

282

Long-term salt marsh recovery and pavement persistence at {sup M}etula' spill sites  

Energy Technology Data Exchange (ETDEWEB)

Three coastal sites oiled from the 1974 'Metula' oil spill in the Strait of Magellan were revisited in May 1998 to document oiling conditions 23.5 years after the spill. The sites revisited are in the Punta Espora area. Two are salt marshes and the third, an inter-tidal asphalt pavement. It was found that the marshes were still oil covered and bare of vegetation in most sections, although the tilling conducted in 1993 resulted in substantial increases in the number of plants that were able to recolonize. Application of fertilizer without tilling of the surface of the oil had no effect. By 1998 the oil, although still present, was weathered to a rubbery consistency. The large, 550 m. long asphalt pavement that had formed on the mixed-sediment beach remained, and showed relatively little change. Chemical analysis of the asphalt indicated extremely high degradation, including even some of the highly biodegradation-resistant biomarker compounds. The experimental treatment plots that were tilled in 1993 showed the highest level of weathered oil, and the highest degree of plant recolonization, suggesting that recolonization of the marshes could have been accelerated had tilling been conducted on these sites soon after the spill. 15 refs., 5 tabs., 6 figs.

Owens, E. H. [Polaris Applied Sciences, Bainbridge Island, WA (United States); Sergy, G. A. [Environment Canada, Edmonton, AB (Canada); Guzman, M. L. [Instituto de Fomento Pesquero, Punta Arenas (Chile); Wang, Z. [Environment Canada. Ottawa, ON (Canada); Baker, J. [Ruyton-XI-Towns (United Kingdom)

1999-07-01

283

Study of Sand Characteristics as Bearing and Filler in Joint of Inter-locking Concrete Block Pavement  

Directory of Open Access Journals (Sweden)

Full Text Available The use of interlocking concrete block pavement as a road surface has increased in the road constructionrecently. This study was conducted to envisage the problems occur particularly for the bedding and joint filling sand of the interlocking concrete block pavement. Moreover, the effect of the moisture on the bedding sandwas also studied. Two type of additives namely as palm oil fly ash (POFA and silica fume, which carry thepozzolanic behaviour, were mixed with joint filling sand in order to improve its quality. These materials areindustrial waste compound which can be easily found in Malaysia. Two types of permeability experiments,the constant and falling head tests were conducted to evaluate the permeability of the joint filling sands withthe percentage additives used of 2%, 4%, 6%, 8% and 10%. A physical model was developed to investigatethe degree of compaction and water absorption via sand in joints. Water absorption test was also conductedonto the model with the addition of additives of 0%, 5% and 10% with the joint filling sand for 5 and 10days. Study shown that the incorporation of additives reduced the permeability of joint filling sand withthe optimum values obtained for both POFA and silica fume mixtures both were at 2% respectively.

Rosli Hainin

2009-09-01

284

Happiness and Death Distress: Two Separate Factors  

Science.gov (United States)

The aim of the present study was to explore the relationship between happiness and death distress (death anxiety, death depression, and death obsession) in 275 volunteer Kuwaiti undergraduates. They responded to the Oxford Happiness Inventory, the Death Anxiety Scale, the Arabic Scale of Death Anxiety, the Death Depression Scale-Revised, and the…

Abdel-Khalek, Ahmed M.

2005-01-01

285

Discrimination Distress among Chinese American Adolescents  

Science.gov (United States)

This paper addresses contradictions between common perceptions of Asian Americans as a "model minority" and growing evidence of discrimination and its negative psychological implications for this group. The current study examined Chinese American early adolescents' distress from experiences of discrimination, its relationship with mental health…

Grossman, Jennifer M.; Liang, Belle

2008-01-01

286

The death distress construct and scale.  

Science.gov (United States)

The purpose of this research was to construct a short scale to assess the death distress construct, that is, death anxiety, death depression, and death obsession as derivatives from the already existing scales. A sample of 630 volunteer undergraduates responded to scales of death anxiety, death depression, and death obsession. A Pearson correlation matrix was computed using the 51 individual items of the three scales. A forced three-factor principal components analysis with orthogonal varimax rotation was carried out. Eight items with factor loading > 0.5 on each scale was determined. The eight items with highest factor loadings on Factor I were with "Death obsession," whereas the Factors II and III were labeled: "Death anxiety," and "Death depression." Their alpha reliabilities ranged from 0.83 to 0.93, indicating high internal consistency. One week test retest reliability ranged between 0.76 and 0.91, indicating temporal stability. A single high-loaded factor of death distress was disclosed, demonstrating the discriminant validity of the death distress construct and scale. Women obtained a significantly higher mean scores on all three factors. It was concluded that the aforementioned three factors were sufficiently independent to justify their use in assessing partially distinct sub-constructs as sub-components of the generic high-order factor of death distress, with empirical and clinical implications. PMID:22375351

Abdel-Khalek, Ahmed M

287

Spiritual distress: integrative review of literature  

Directory of Open Access Journals (Sweden)

Full Text Available This study aims to identify concepts and clinical indicators that evidence spiritual distress in patients. Integrative review was the method adopted for the development of the study. In the initial stage, 82 studies were found in the following databases PUBMED, COCHRANE, CINAHL, LILACS and North American Nursing Diagnosis Association Conference Proceedings and 18 were selected. The descriptors used were spirituality and nursing diagnosis in addition to the term spiritual distress. Literature review (38.9% and articles with level of evidence IV (27.8% were the predominant types of study. The analysis of the articles revealed that the identified concepts of spiritual distress presented common and related elements to the human being subjective and individual response to life experiences, which harm the human spiritual dimension. Defining spiritual distress is a complex task since it depends on the perspective of those evaluating it, limiting in this way, its generalization. However, knowledge regarding the constructs that guide the understanding of human spirituality can base the nursing care in its spiritual dimension, thus providing theoretical support for the diagnosis.

Cristina Maria Galvão

2008-07-01

288

Spiritual distress: integrative review of literature  

Directory of Open Access Journals (Sweden)

Full Text Available This study aims to identify concepts and clinical indicators that evidence spiritual distress in patients. Integrative review was the method adopted for the development of the study. In the initial stage, 82 studies were found in the following databases PUBMED, COCHRANE, CINAHL, LILACS and North American Nursing Diagnosis Association Conference Proceedings and 18 were selected. The descriptors used were spirituality and nursing diagnosis in addition to the term spiritual distress. Literature review (38.9% and articles with level of evidence IV (27.8% were the predominant types of study. The analysis of the articles revealed that the identified concepts of spiritual distress presented common and related elements to the human being subjective and individual response to life experiences, which harm the human spiritual dimension. Defining spiritual distress is a complex task since it depends on the perspective of those evaluating it, limiting in this way, its generalization. However, knowledge regarding the constructs that guide the understanding of human spirituality can base the nursing care in its spiritual dimension, thus providing theoretical support for the diagnosis.

Erika Cássia Lopes Chaves

2008-08-01

289

Distress screening in chronic disease: essential for cancer survivors.  

Science.gov (United States)

Distress is a psychological state that is often observed in patients with chronic disease. Many cancers are considered chronic in nature, with patients experiencing long, disease-free states and intervals of metastatic disease. Distress can negatively affect the biopsychosocial balance in cancer survivors and impede their progress along the cancer trajectory. Distress can also affect medical and psychological outcomes and hinder advancement into long-term survivorship. Distress may contribute to disease progression, although despite research findings, health-care providers seldom screen for indications of persistent or unresolved distress. This article discusses research findings related to the prevalence of distress in multiple chronic diseases. Validated instruments used to screen for distress in cancer survivors, such as the Distress Thermometer and symptom checklist from the National Comprehensive Cancer Network, are reviewed. With the availability of brief and concise instruments to screen for distress, providers have the ability to provide holistic and comprehensive care for cancer survivors. The overall financial impact of cancer-related distress is understudied, although similar psychological studies indicate that prevention or elimination of distress is beneficial. Cancer is a lifelong, chronic disease; patients have ongoing needs and varied sources of distress. As the number of cancer survivors exponentially increases, their psychosocial needs will likewise expand. PMID:25032045

Petty, Lorie; Lester, Joanne

2014-03-01

290

Sexual Abuse Victimization and Psychological Distress among Adolescent Offenders.  

Science.gov (United States)

This study focused on sexual abuse victimization and psychological distress among 272 adolescent offenders. Female respondents reported more sexual abuse victimization and psychological distress than did their male counterparts. Furthermore, church attendance moderated the association between sexual abuse victimization and psychological distress

Phan, Debra L.; Kingree, J. B.

2001-01-01

291

Proportioning of Steel Fibre Reinforced Concrete Mixes for Pavement Construction and Their Impact on Environment and Cost  

Directory of Open Access Journals (Sweden)

Full Text Available Steel fibre reinforced concrete (SFRC is a construction material investigated for more than 40 years including for pavement applications. A number of studies have demonstrated the technical merits of SFRC pavements over conventional concrete pavements; however little work has been carried out on the environmental and economical impact of SFRC during the pavement’s life cycle. Therefore, extended research was undertaken within the framework of the EU funded project “EcoLanes” to estimate the environmental and economical loadings of SFRC pavements. The innovative concept of the project is the use of recycled steel tyre-cord wire as concrete fibre reinforcement, which provides additional environmental benefits for tyre recycling over landfilling. Within the project framework a demonstration of a steel-fibre-reinforced roller-compacted concrete (SFR-RCC pavement was constructed in a rural area in Cyprus. In order to assess the economical and environmental picture of the demonstration pavement, life cycle cost analysis (LCCA and life cycle assessment (LCA studies were undertaken, which also compared the under study pavement design with four conventional alternatives. The main output of the studies is that SFR-RCC is more environmentally and economically sustainable than others. In addition, various concrete mix designs were investigated by considering parameters such as fibre type and dosage, cement type, and transportation distances to the construction site. Fibre dosage has been highlighted as a crucial factor compared with economical and environmental loadings in SFR-RCC pavement construction.

Stelios Kallis

2011-07-01

292

Permeable Pavement Research at NRMRL?s Urban Watershed Research Facility (Poster 2)  

Science.gov (United States)

Assess pollutant removal efficiency of porous pavement systems with regard to parking lot runoff. Bench-scale study will examine: Discharge volume Flow rate Total suspended solids (TSS) of influent vs. effluent Use of a geotextile permeable filter fabric...

293

Stress Analysis and Determination of Effective k-value for Rigid Pavement  

Directory of Open Access Journals (Sweden)

Full Text Available EverFE is a user-friendly 3D finite-element analysis tool for simulating the response of jointed plain concrete pavement (JPCP systems to axle loads and environmental effects. EverFE is useful for both concrete pavement researchers and designers who must perform either complex nonlinear or simple linear stress analyses of JPCP.With help of this develop any type of model of rigid pavement considering practical condition thus getting more accurate and advance analysis for rigid pavement. It can also determine effective k-values for different combination of granular sub-base and dry lean concrete. A comparative study is done for two types of loading i.e. single and tandem axle. Edge and Corner stresses are also calculated for Class-AA of loading. Also calculate moment and shear force transfer by dowel bar by EverFE.

Kundan Meshram

2013-03-01

294

Thermal stresses of asphalt pavement under dependence of material characteristics on reference temperature  

Science.gov (United States)

This thesis presents an analytical study of thermal stresses of asphalt pavement under dependence of material characteristics on reference temperature. In the analysis, flexible pavement is regarded as a multi-layered elastic half-space axisymmetrical system. Firstly, thermo-elastic theory is used to describe thermal stresses of a multi-layered system, while the temperature-dependent material characteristics are considered. Then Laplace transformation and Hankel transformation with respect to time and radial, respectively, are utilized for thermo-elastic equations of equilibrium. In addition, the transfer matrix method is applied to derive general solutions for the multi-layered problem. Finally, the resulting formulation is applied to calculate thermal stresses in the low temperature cracking problem of asphalt pavement. Thermal stress is calculated and compared with the case that material characteristics are supposed to be constant to show the remarkable impact of temperature-dependent material characteristics on thermal stresses of asphalt pavement.

Zhong, Yang; Geng, Litao

2009-03-01

295

Theoretical analysis of piezoelectric energy harvesting from traffic induced deformation of pavements  

International Nuclear Information System (INIS)

The problem of energy harvesting using piezoelectric transducers for pavement system applications is formulated with a focus on moving vehicle excitations. The pavement behavior is described by an infinite Bernoulli–Euler beam subjected to a moving line load and resting on a Winkler foundation. A closed-form dynamic response of the pavement is determined by a Fourier transform and the residue theorem. The voltage and power outputs of the piezoelectric harvester embedded in the pavements are then obtained by the direct piezoelectric effect. A comprehensive parametric study is conducted to show the effect of damping, the Winkler modulus, and the velocity of moving vehicles on the voltage and power output of the piezoelectric harvester. It is found that the output increases sharply when the velocity of the vehicle is close to the so-called critical velocity. (paper)

296

Contributions of performance-graded asphalt to low temperature cracking resistance of pavements. Final report  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this research was to study and evaluate the role that asphalt cracking. As part of the Strategic Highway Research Program (SHRP) new specifications for asphalt binders were developed that are based on the performance of the material. The asphalt binder graded and specified according to these new performance-based specifications is called PG binder. These new specifications are commonly referred to as Superpave (Superior Performing Asphalt Pavement) binder specifications. A section of Interstate 64 in southern Indiana was experiencing severe low temperature cracking before it was reconstructed over the summers of 1995 and 1996. The binder used in the new pavement mixes was PG material. Dynamic Shear Rheometer (DSR) tests, Bending Beam Rheometer (BBR) tests, and viscosity tests were performed on this binder. Comparisons were made between test results obtained from the binders in the old pavement and the new pavement. All tests and comparisons were based on the Superpave binder specifications.

Loh, S.W.; Olek, J.

1999-05-01

297

23 CFR 970.208 - Federal lands pavement management system (PMS).  

Science.gov (United States)

...MANAGEMENT SYSTEMS National Park Service Management Systems § 970.208 Federal lands pavement management system (PMS). In addition to the requirements...basic framework for a PMS: (1) A database and an ongoing program for the...

2010-04-01

298

Over the Edge and Back: What to Do If You Drive Off the Pavement Edge  

Science.gov (United States)

... can result from broken pavement, erosion of an unpaved shoulder, inadequate maintenance, or the resurfacing of a ... be fatal relative to other crashes on similar roads.” You may drive, or be forced, off the ...

299

Development of Knowledge-Based Expert System for Flexible Pavement Design  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, the knowledge-based expert system approach was used to design a programmer using shell expert system of KAPPA PC Version 2.4 that is object oriented and displaying higher graphic resolutions. The flexible pavement design based on the accumulation of knowledge from several experts, books and journals results in a modular approach. Normally, the process of flexible pavement design is done by experts. The process was computerized and apply artificial intelligent that is a new technology in providing a system that can design and give the suggestion for user to choices the best and economy of the thickness of pavement layers. The expert system was tested using several design calculation samples. From the test, the success is 100% for pavement design. The expert system has revealed satisfactorily findings in a faster layers design.

Deprizon

2009-01-01

300

Theoretical analysis of piezoelectric energy harvesting from traffic induced deformation of pavements  

Science.gov (United States)

The problem of energy harvesting using piezoelectric transducers for pavement system applications is formulated with a focus on moving vehicle excitations. The pavement behavior is described by an infinite Bernoulli–Euler beam subjected to a moving line load and resting on a Winkler foundation. A closed-form dynamic response of the pavement is determined by a Fourier transform and the residue theorem. The voltage and power outputs of the piezoelectric harvester embedded in the pavements are then obtained by the direct piezoelectric effect. A comprehensive parametric study is conducted to show the effect of damping, the Winkler modulus, and the velocity of moving vehicles on the voltage and power output of the piezoelectric harvester. It is found that the output increases sharply when the velocity of the vehicle is close to the so-called critical velocity.

Xiang, H. J.; Wang, J. J.; Shi, Z. F.; Zhang, Z. W.

2013-09-01

 
 
 
 
301

The use of accelerometers in the pavement performance monitoring and analysis  

International Nuclear Information System (INIS)

This study investigated the use of sensor technology to enhance the management of highway infrastructure. With the help of monitoring data, it is possible to assess the current analytical pavement analysis method, which is based on multi-layered elastic analysis, and, thus enhance the pavement design practices in use. Pavement response was measured using different sensors, installed at various depths. Most promising sensors for the continuous monitoring purposes were the accelerometers. The drawback of these sensors is that the measured quantity is acceleration, which must be converted to the deflection via mathematical integration. In this paper some issues related to the manipulation of accelerometer data is presented and discussed, in addition of the discussion of the calculated and measured pavement response.

302

23 CFR 970.208 - Federal lands pavement management system (PMS).  

Science.gov (United States)

...HIGHWAYS NATIONAL PARK SERVICE MANAGEMENT SYSTEMS National Park Service Management Systems § 970.208 Federal lands pavement management system (PMS). In addition...shoulder information; (ii) A history of project dates and...

2010-04-01

303

The Influence of Waste Carpet on the Structural Soil Characteristics in Pavement Granular Layer  

Directory of Open Access Journals (Sweden)

Full Text Available Solid waste materials can be left out of environment in different ways or can be used again. As an example of waste fiber materials is the fibers reselling from producing carpet which are made in Iran in largest quantity. These materials are added to soil and granular materials and improve their various properties as compressive and tensile strengths. In present study, the result of previous researches are collected and presented, then, they are used to analyses the effect of using from waste materials in subgrade on highway pavement performance. By using analytical software and results of testing, tensile strain under asphalt layer and compressive strain on subgrade of pavement containing these materials are calculated and after that they are compared together. Next the allowable frequencies of loading for different pavement models are calculated by using existing formula. The results indicate that adding 1.5% of waste fiber to pavement subgrade increases the allowable frequency of loading to 15%.

Mohammad M. Khabiri

2011-07-01

304

23 CFR 970.208 - Federal lands pavement management system (PMS).  

Science.gov (United States)

...HIGHWAYS NATIONAL PARK SERVICE MANAGEMENT SYSTEMS National Park Service Management Systems § 970.208 Federal lands pavement management system (PMS). In addition...nature of the transportation network. These different...

2010-04-01

305

Integration and road tests of a self-sensing CNT concrete pavement system for traffic detection  

International Nuclear Information System (INIS)

In this paper, a self-sensing carbon nanotube (CNT) concrete pavement system for traffic detection is proposed and tested in a roadway. Pre-cast and cast-in-place self-sensing CNT concrete sensors were simultaneously integrated into a controlled pavement test section at the Minnesota Road Research Facility (MnROAD), USA. Road tests of the system were conducted by using an MnROAD five-axle semi-trailer tractor truck and a van, respectively, both in the winter and summer. Test results show that the proposed self-sensing pavement system can accurately detect the passing of different vehicles under different vehicular speeds and test environments. These findings indicate that the developed self-sensing CNT concrete pavement system can achieve real-time vehicle flow detection with a high detection rate and a low false-alarm rate. (paper)

306

[Gas exchange in acute respiratory distress syndrome].  

Science.gov (United States)

The hypoxemia of acute respiratory distress syndrome (ARDS) depends chiefly upon shunt and ventilation-perfusion (VA/Q) inequality produced by fluid located in the interstitial space, alveolar collapse and flooding. Variables other tham inspired oxygen fraction and the underlying physiological abnormality can influence arterial oxygen partial pressure (PaO2). Changes in cardiac output, hemoglobin concentration, oxygen consumption and alcalosis can cause changes in PaO2 through their influence on mixed venous PO2. Gas exchange (GE) in ARDS may be studied using the inert gas elimination technique (MIGET) which enables to define the distribution of ventilation and perfusion without necessarily altering the FIO2 differentiating shunt from lung units with low VA/Q ratios and dead space from lung units with high VA/Q ratios. Different ventilatory strategies that increase mean airway pressure (positive end-expiratory pressure, high tidal volumes, inverse inspiratory-expiratory ratio, etc) improve PaO2 through increasing lung volume by recruiting new open alveoli and spreading the intra-alveolar fluid over a large surface area. Also prone-position ventilation would result in a marked improvement in GE enhancing dorsal lung ventilation by the effects on the gravitional distribution of pleural pressure and the reduction in the positive pleural pressure that develops in dorsal regions in ARDS. Inhaled nitric oxide (NO) has been shown to increase PaO2 in ARDS patients by inducing vasodilation predominantly in ventilated areas redistributing pulmonary blood flow away from nonventilated toward ventilated areas of the lung thus resulting in a shunt reduction. On the same way inhaled prostaglandins (PGI2 or PGE1) causes selective pulmonary vasodilation improving pulmonary GE. Intravenous almitrine, a selective pulmonary vasoconstrictor, has been shown to increase PaO2 by increasing hypoxic pulmonary vasoconstriction. A synergistic effect was found between inhaled NO and almitrine. In spite of the improval of GE shown by these different techniques on ARDS, no effect was demonstrated on mortality or duration of mechanical ventilation. PMID:12793087

Raimondi, Guillermo A

2003-01-01

307

Plastic Damage Model to Evaluate the Fracture Size of Semi-Rigid Base Pavement  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A simple supported beam model has been presented to simulate the response of semi-rigid pavement structure, which are consistent of the upper layer, middle layer, bottom layer, base and sub base course, during the cycle vehicle loading. This mechanics model coupled with plastic-damage mechanics model could simulate the limit broken of the pavement structure in condition that soil base layer losing bearing capacity gradually. In the meanwhile, numerical calculations based on preceding mechanic...

Cao Peng; Feng Decheng; Jing Ruxin; Zhao Yin

2013-01-01

308

New-Fangled Approach to Predict the Behaviour of Composite Sandwich Pavements  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The significance of this research lies in the reduction of cost of construction of roads by arriving at an economically feasible pavement. This is accomplished by studying the response of thick composite sandwich plate, supported continuously, for the cyclic loading condition at various stress ratios and is compared with plain slabs placed on similar support condition. A conceptual pavement model was examined using lean cement concrete as the sandwiched material. The behaviour of the plain an...

A K, Shaul Sharafna

2011-01-01

309

Cost effectiveness evaluation of rigid and composite highway pavement routine maintenance  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This dissertation deals with the evaluation of three issues related to routine maintenance of highway pavements. These are: (1) whether and how much routine maintenance has an impact on the pavement's serviceability and/or expected service life; (2) whether seal coating practice is cost-effective, and what is the optimal timing for this activity; and (3) what directions, principles and criteria should be used for chip and sand seal coating activities on Indiana state highway system.^ The f...

Mouaket, Ibrahim Moussa

1990-01-01

310

Utilizationof Hypo Sludge by Eco-Efficient Development of Rigid Pavement in Rural Roads  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The paperproducing industry generates various wastes coming out from the various processes. From the preliminary waste named as hypo sludge, due to its low calcium is taken out to replace the cement in concrete. Major initiatives are needed in India to use these large volumes in construction industry especially in rigid pavement construction and other infrastructure projects. Moreover Use of Hypo Sludge in construction of rigid pavement will improve transportation functionality and ecological...

Prof Jayeshkumar Pitroda, Dr L. B. Zala

2013-01-01

311

Evaluation of test methods for estimating resilient modulus of modules of pavement geomaterials  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Resilient modulus is a key parameter required for the mechanistic empirical pavement design procedures currently being adopted around the world including the recently developed NCHRP 1- 37A design guide in the United States and the current South African Pavement Design Method(SAPDM). The determination of the resilient modulus requires sophisticated equipment and skilled personnel for laboratory and field testing. These requirements have contributed immensely to the proliferation of differe...

Anochie-boateng, J. K.; Paige-green, Philip; Mgangira, M. B.

2009-01-01

312

Preliminary evaluation of the lifecycle costs and market barriers of reflective pavements; TOPICAL  

International Nuclear Information System (INIS)

t-saving features of porous pavements fell outside the boundaries of this study. Resin pavements were found to be only slightly more expensive than conventional AC, but the uncertainties in the cost and performance data were large. The use of light-colored additives in asphalt emulsion seal coats for parking lot pavements was found to be significantly more expensive than conventional AC, reflecting its current niche market of decorative applications. We also proposed two additional approaches to increasing the reflectivity of conventional AC, which we call the chipping and aggregate methods, and calculated their potential life cycle costs. By analyzing the potential for increased pavement durability resulting from these conceptual approaches, we then estimated the incremental costs that would allow them to be cost-effective compared to conventional AC. For our example case of Los Angeles, we found that those allowable incremental costs range from less than dollar 1 to more than dollar 11 per square yard (dollar 1 to dollar 13 per square meter) depending on street type and the condition of the original pavement. Finally, we evaluated the main actors in the pavement market and the existing and potential market barriers associated with reflective pavements. Apart from situations where lifecycle costs are high compared to conventional AC, all reflective paving technologies face a cultural barrier based on the belief that black is better. For PCC, high first costs were found to be the most significant economic barrier, particularly where agencies are cons trained by first cost. Lack of developer standards was found to be a significant institutional barrier to PCC since developers are often not held accountable for the long-term maintenance of roads after initial construction, which creates a misplaced incentive to build low first-cost pavements. PCC also faces site-specific barriers such as poorly compacted base soils and proximity to areas of frequent utility cutting

313

Strength gain and cementation of flexible pavement bases (revised)  

Science.gov (United States)

The strength gain of selected carbonate Florida Department of Transportation (FDOT) flexible pavement base materials is addressed. The gain in strength after aging of base sections constructed in an inside environment and outside environment was measured. Scanning electron microscope (SEM) photographs were also taken and examined to determine changes in structure. The materials investigated were: (1) bank run shell; (2) limerock; and (3) cemented coquina. Strength tests were the Clegg Impact Value (CIV) performed on inside and outside sections and a rigid plate test performed on the inside section. There was a small gain in strength for all three carbonate bases after 22 months. Changes in the matrix particles were observed in the SEM study. The three complementary phases (CIV, plate modulus, and SEM) tend to reinforce each other, indicating a small gain in strength.

Zimpfer, W. H.

1991-02-01

314

Performance of preformed compression sealers in transverse pavement joints  

Science.gov (United States)

Preformed compression sealers, 1-1/4 in. wide and installed in 5/8 in. wide transverse contraction joints in rigid pavements, were observed for up to 10 years. Many joints closed tighter than the 5/8 in. minimum design width. Results of force deflection and recovery tests performed on new sealer samples related to compression set occurring during field service, but not to infiltration. Force deflection and recovery properties of the sealers generally decreased after field aging. Preconditioning sealer samples at elevated (212 F) or reduced (14 and 20 F) temperatures produced changes in force deflection and recovery properties. A laboratory cycle test, which simulates joint infiltration, appeared to relate to field infiltration.

Bryden, J. E.; Lorini, R. A.

1980-03-01

315

Article title misstates the role of pavement sealers.  

Science.gov (United States)

The claim made in the title of Witter et al. (2014) "Coal-tar-based sealcoated pavement: A major PAH source to urban stream sediments" is not supported by the data presented. The author's use of Pearson correlation coefficients is insufficient to indicate causation. The application of spatial analysis and principle component analysis did not include sealer specific inputs, so provides no basis for the claim. To test the hypothesis that sealers are a source of PAHs in the stream studied, EPA's Chemical Mass Balance (CMB) source evaluation model was applied to Witter's sediment data. CMB found an excellent fit (R(2) > 0.999) between measured and modeled PAH concentrations when sealers were not included as a potential source. This finding does not support Witter et al. (2014) claim that sealers are a major source of PAHs. PMID:24373812

O'Reilly, Kirk

2014-08-01

316

Airport pavement roughness evaluation based on aircraft response  

Science.gov (United States)

Runway roughness affects primarily ride quality and dynamic wheel loads. The forces applied onto the airport pavement by aircraft vary instantaneously above and blow the static weight, which in turn increase the runway roughness. One method to effectively assess the ride quality of the airport runway is to measure its longitudinal profile and numerical simulate aircraft response performing a takeoff, landing or taxiing on that profile data. In this study the aircraft responses excited as the aircraft accelerates or moves at a constant speed on the runway during takeoff and taxi are computed by using the improved computer program TAXI. This procedure is capable of taking into account both the effects of discrete runway bumps and runway roughness. Thus, sections of significant dynamic response can be determined, and the maintenance and rehabilitation works for airport runways will be conducted.

Dong, Qinxi; Hachiya, Yoshitaka; Endo, Katsura; Himeno, Kenji; Kawamura, Akira; Matsui, Kunihito

2004-07-01

317

Fatigue Investigation of the Interface Shear Performance in Asphalt Pavement  

Directory of Open Access Journals (Sweden)

Full Text Available This paper shows the interlayer fatigue performance evaluated by the Sapienza shear testing machine. The tests can be performed by placing double layer specimens in several inclinations, in order to reproduce a variety of expected ratios between the normal and the shear stress. The machine manages loads with any kind of waveform and is particularly able to simulate the stress trends expected in field in points located just outside the wheel path. In this experimentation, the machine applies a triangular waveform load computed by a linear elastic multilayer program at the depth of the first pavement interface. A fatigue law is estimated considering the number of repetitions that causes the interface failure. A linear regression in the log-log graph suitably fits the experimental results for the analyzed conditions of temperature and interface type.

Cristina Tozzo

2014-02-01

318

Test of Microstructur Permeable Asphalt Pavement Used Domato Stone (Quarsite Dolomite As Course Agregate for Surface Layer of Road Pavement  

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Full Text Available The experiment works was dividing into two phases, for phase one was developed to investigate the properties of aggregates and straight asphalt qualities. The experiment work for phase two was developed to design the porous asphalt mix. In this phase Japan’s method and Binamarga’s method was used to define optimum asphalt content. In this phase, has result cantabro loss weight 77.10 for asphalt quality 3% and loss weight 9.70 for asphalt quality 5%. asphalt flow down, air void and density values. The experiment work for phase two was developed to investigate the qualities of porous asphalt. In this phase, wheel tracking machine test was used to investigate the dynamic stability of mixes.

Firdaus Chairuddin

2014-06-01

319

Bitumen-cement Stabilized Layer in Pavement Construction Using Indirect Tensile Strength (ITS Method  

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Full Text Available In this study, the objective was to blend and mix Portland cement and bitumen emulsion with soil for enhancing the strength, durability and pertinent properties of the soil. In order to enhance the soil strength and lessen its vulnerability to water, soil stabilization is required to be applied to the soil. In line with this, improved load transfer was added to the pavement foundation by having the cement effect which actually boosts the stiffness and Bitumen emulsion effects which improve resilience and soil permeability of the stabilized layer. The current study is divided into two phases. In the first phase, the optimization of Portland cement and bitumen emulsion was preformed as well as conducting a series of Indirect Tensile Strength (ITS. Furthermore, in order to lessen the pavement’s thickness and to enhance its bearing capacity, alternative roadway sections were scrutinized through the second phase. The results proved that soil stabilization with cement and bitumen enhances the bearing capacity of pavements in two chief areas. Primarily, there was enhancement in pavement’s lifetime and the more efficient construction time is achieved.

Ramez Alezzi Almansob

2013-05-01

320

Continuous monitoring of mining induced strain in a road pavement using fiber Bragg grating sensors  

Science.gov (United States)

This paper describes the application of fiber Bragg grating (FBG) based sensors for monitoring road pavement strains caused by mining induced ground subsidence as a result of underground longwall coal mining beneath a major highway in New South Wales, Australia. After a lengthy planning period, the risks to the highway pavement were successfully managed by the highway authority and the mining company through a technical committee. The technical committee comprised representatives of the mining company, the highway authority and specialists in the fields of pavement engineering, geotechnical engineering and subsidence. An important component of the management strategy is the installation of a total of 840 strain and temperature sensors in the highway pavement using FBG arrays encapsulated in glass-fiber composite cables. The sensors and associated demodulation equipment provide continuous strain measurements along the pavement, enabling on-going monitoring of the effects of mining subsidence on the pavement and timely implementation of planned mitigation and response measures to ensure the safety and serviceability of the highway throughout the mining period.

Nosenzo, Giorgio; Whelan, B. E.; Brunton, M.; Kay, Daryl; Buys, Henk

2013-06-01

 
 
 
 
321

Lead and zinc removal with storage period in porous asphalt pavement  

Scientific Electronic Library Online (English)

Full Text Available SciELO South Africa | Language: English Abstract in english Porous asphalt pavements have been used as an effective technique to overcome road runoff challenges, and to improve efficiency of rainwater utilisation in urban areas. Using porous asphalt pavements with reservoir storage and harvesting facilities is an important consideration for the future. This [...] study monitored changes in water quality indicators, such as pH, conductivity, and concentrations of lead and zinc, for water stored in porous asphalt pavement models with basalt-, limestone- and 'basalt+limestone'-filled reservoir structures. The research discusses findings over a 696-h storage period following artificial rainfall. Total lead and zinc concentrations were remarkably reduced throughout the initial flush, showing, on average, reductions of 90% and 80.5%, respectively. This pattern was consistent throughout the storage period, producing average reductions in lead and zinc of 99.98% and 79%, respectively, over 696 h. Conductivity and pH levels increased in all pavement models after the 696-h storage. The results obtained confirmed the potential of using porous asphalt pavements with reservoir structures to remove heavy metals from road runoff. This can be applied to future research on the removal mechanisms of porous asphalt pavements in relation to heavy metals in road runoff.

Yao, Zhao; Chen, Zhao.

2014-01-01

322

Greenhouse gas emissions of alternative pavement designs: framework development and illustrative application.  

Science.gov (United States)

Pavement rehabilitation is carbon intensive and the choice of pavement type is a critical factor in controlling greenhouse gas (GHG) emissions. The existing body of knowledge is not able to support decision-making on pavement choice due to a lack of consensus on the system boundaries, the functional units and the estimation periods. Excessive data requirements further inhibit the generalization of the existing methodologies for design evaluation at the early planning stage. This study proposes a practical life-cycle GHG estimation approach, which is arguably effective to benchmark pavement emissions given project bid tabulation. A set of case studies conducted for this study suggest that recycled asphalt pavement (e.g., foam stabilized base (FSB), and warm mix asphalt (WMA)) would prevent up to 50% of GHGs from the initial construction phase. However, from a life-cycle perspective, pavement emissions are dictated largely by the traffic characteristics and the analysis period for the use phase. The benefits from using recycled materials (e.g., FSB) are likely to diminish if the recycled products do not perform as well as those properly proportioned with less recycled materials, or if the recycled materials are locally unavailable. When the AADT reaches 10,000, use phase releases more than 97% of the life cycle emissions and the emissions difference among alternative designs will be within 1%. PMID:24333742

Liu, Xiaoyu; Cui, Qingbin; Schwartz, Charles

2014-01-01

323

A TECHNIQUE OF ESTIMATION OF TECHNICAL CONDITION OF RIGID AIRFIELD PAVEMENTS IN THE CONTEXT OF RISK THEORY  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Problem statement. To provide for safe takeoff and landing of modern aviation complexes, specialattention is given to technical condition of artificial pavements of runways which can be serviceableor faulty, efficient or limiting. Available standard methods of an expeditious estimation of an operational-technical condition of airfield pavements are based on general principles of defect graduationand of definition of integrated total generalized indicator of pavement condition and often yield ...

Popov, A. N.; Shashkov, I. G.; Kozlov, A. V.

2012-01-01

324

Synthesis Study on Use of Concrete Recycled from Pavement and Building Rubble in the Indiana Highway System  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The demolition of buildings and highway pavements in the State of Indiana generates a considerable amount of waste materials. The disposal of these materials causes strain on the existing landfills which are rapidly approaching their full capacity. This study is a synthesis of the information on the use of concrete recycled from pavements and building rubble for use in the Indiana highway system. Test results have shown that recycled pavement concrete made chiefly from broken-up and crushed o...

Burke, Thomas T.; Cohen, Menashi D.; Scholer, Charles F.

1992-01-01

325

Acute respiratory distress syndrome with miliary tuberculosis.  

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A 71-year-old man was admitted to the hospital complaining of productive cough and weight loss. Physical examination showed fine bilateral basal crackles. Laboratory findings showed elevated liver enzymes. Tuberculin skin test and sputum smear for acid-fast bacilli were negative. On the fifth day of admission, he deteriorated and developed severe respiratory distress. A chest radiograph demonstrated worsening pulmonary infiltrates. He was electively intubated and was put on a mechanical ventilator. The chest CT scan revealed diffuse bilateral pulmonary nodules and airspace disease. Based upon the clinical suspicion of acute respiratory distress syndrome associated with miliary tuberculosis (TB, empiric treatment with antituberculosis and systemic steroids was started. He was extubated after 6 days. The diagnosis of miliary TB was confirmed by a thoracoscopic lung biopsy. He was discharged with a near normal chest radiograph and was followed up as an outpatient.

Hadeel A. Khadawardi

2012-01-01

326

DESERT PAVEMENTS AND SOILS ON BASALTIC PYROCLASTIC DEPOSITS AT LATHROP WELLS AND RED CONE VOLCANOES, SOUTHERN NEVADA  

Energy Technology Data Exchange (ETDEWEB)

Formation of desert pavement and accretionary soils are intimately linked in arid environments such as the Mojave Desert. Well-sorted fallout scoria lapilli at Lathrop Wells (75-80 ky) and Red Cone ({approx}1 Ma) volcanoes (southern Nevada) formed an excellent starting material for pavement, allowing infiltration of eolian silt and fine sand that first clogs the pore space of underlying tephra and then aggrades and develops vesicular A (Av) horizons. Variations in original pyroclast sizes provide insight into minimum and maximum clast sizes that promote pavement and soil formation: pavement becomes ineffective when clasts can saltate under the strongest winds, while clasts larger than coarse lapilli are unable to form an interlocking pavement that promotes silt accumulation (necessary for Av development). Contrary to predictions that all pavements above altitudes of {approx}400 m would have been ''reset'' in their development after late Pleistocene vegetation advances (about 15 ka), the soils and pavements show clear differences in maturity between the two volcanoes. This indicates that either the pavement soils develop slowly over many 10,000's of years and then are very stable, or that, if they are disrupted by vegetation advances, subsequent pavements are reestablished with successively more mature characteristics.

G.A. Valentine; C.D. Harrington

2005-08-10

327

Corticosteroids in acute respiratory distress syndrome  

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Full Text Available Improving the course and outcome of patients with acute respiratory distress syndrome presents a challenge. By understanding the immune status of a patient, physicians can consider manipulating proinflammatory systems more rationally. In this context, corticosteroids could be a therapeutic tool in the armamentarium against acute respiratory distress syndrome. Corticosteroid therapy has been studied in three situations: prevention in high-risk patients, early treatment with high-dose, short-course therapy, and prolonged therapy in unresolving cases. There are differences between the corticosteroid trials of the past and recent trials: today, treatment starts 2-10 days after disease onset in patients that failed to improve; in the past, the corticosteroid doses employed were 5-140 times higher than those used now. Additionally, in the past treatment consisted of administering one to four doses every 6 h (methylprednisolone, 30 mg/kg versus prolonging treatment as long as necessary in the new trials (2 mg kg-1 day-1 every 6 h. The variable response to corticosteroid treatment could be attributed to the heterogeneous biochemical and molecular mechanisms activated in response to different initial insults. Numerous factors need to be taken into account when corticosteroids are used to treat acute respiratory distress syndrome: the specificity of inhibition, the duration and degree of inhibition, and the timing of inhibition. The major continuing problem is when to administer corticosteroids and how to monitor their use. The inflammatory mechanisms are continuous and cyclic, sometimes causing deterioration or improvement of lung function. This article reviews the mechanisms of action of corticosteroids and the results of experimental and clinical studies regarding the use of corticosteroids in acute respiratory distress syndrome.

A.B.S. Fernandes

2005-02-01

328

Resonance frequency in respiratory distress syndrome  

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AIM—To observe how the resonance frequency changes with the course of respiratory distress syndrome (RDS), by examining the effect of changing static compliance on the resonance frequency in premature infants.?METHODS—In 12 ventilated premature infants with RDS (mean gestational age 26.6 weeks, mean birth weight 0.84 kg), resonance frequency and static compliance were determined serially using phase analysis and single breath mechanics technique respectively in the ...

Lee, S.; Milner, A.

2000-01-01

329

Corticosteroids in acute respiratory distress syndrome  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Improving the course and outcome of patients with acute respiratory distress syndrome presents a challenge. By understanding the immune status of a patient, physicians can consider manipulating proinflammatory systems more rationally. In this context, corticosteroids could be a therapeutic tool in t [...] he armamentarium against acute respiratory distress syndrome. Corticosteroid therapy has been studied in three situations: prevention in high-risk patients, early treatment with high-dose, short-course therapy, and prolonged therapy in unresolving cases. There are differences between the corticosteroid trials of the past and recent trials: today, treatment starts 2-10 days after disease onset in patients that failed to improve; in the past, the corticosteroid doses employed were 5-140 times higher than those used now. Additionally, in the past treatment consisted of administering one to four doses every 6 h (methylprednisolone, 30 mg/kg) versus prolonging treatment as long as necessary in the new trials (2 mg kg-1 day-1 every 6 h). The variable response to corticosteroid treatment could be attributed to the heterogeneous biochemical and molecular mechanisms activated in response to different initial insults. Numerous factors need to be taken into account when corticosteroids are used to treat acute respiratory distress syndrome: the specificity of inhibition, the duration and degree of inhibition, and the timing of inhibition. The major continuing problem is when to administer corticosteroids and how to monitor their use. The inflammatory mechanisms are continuous and cyclic, sometimes causing deterioration or improvement of lung function. This article reviews the mechanisms of action of corticosteroids and the results of experimental and clinical studies regarding the use of corticosteroids in acute respiratory distress syndrome.

A.B.S., Fernandes; W.A., Zin; P.R.M., Rocco.

2005-02-01

330

Acute Respiratory Distress Syndrome in Children  

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Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are an important challenge for pediatric intensive care units. These disorders are characterized by a significant inflammatory response to a local (pulmonary) or remote (systemic) insult resulting in injury to alveolar epithelial and endothelial barriers of the lung, acute inflammation and protein rich pulmonary edema. The reported rates in children vary from 8.5 to 16 cases/1000 pediatric intensive care unit (PICU) admiss...

Dincer Yildizdas; Ozden Ozgur Horoz; Ali Ertug Arslankoylu; Muge Sagiroglu

2009-01-01

331

Psychosocial distress and periodontitis in adolescents  

DEFF Research Database (Denmark)

Periodontitis is an inflammatory disease associated with predominantly gram negative biofilms and characterized by the progressive destruction of the supporting tissues of the teeth. Some studies conducted among adults have found a significant association between periodontitis and dimensions of psychosocial distress and it is unclear whether this association can be found among younger subjects in which destruction of periodontal tissues as a result of periodontitis are less severe. Purpose: The main aim of this study was to assess whether adolescents with periodontitis presented with higher scores for non-psychotic psychosocial disorders than control subjects without periodontitis. Materials and Methods: We used a case control study (n=160) nested in a well-defined adolescent population (n=9,163) and the 28-item Spanish version of the General Health Questionnaire. The inclusion criterion for being a case was clinical attachment level ? 3 mm in at least two teeth. Multiple logistic regression analyses were used to assess the association between periodontitis and psychosocial distress. Results: The response rate was high and 94% of the participants answered all the items of the questionnaire. Similarly, the internal consistency of the instrument was high (Cronbach’s ? = 0.91). The results of multiple logistic regression analyses, adjusted for age and gender, suggested an association between case status and higher total scoring for psychosocial distress (OR=1.69). Among the four subdomains of General Health Questionnaire, the dimensions ‘somatic symptoms’ and ‘severe depression’ appeared positively associated with periodontal case status though not significantly.

Lopez, Rodrigo; Ramírez, Valeria

2012-01-01

332

Distress intolerance in substance dependent patients.  

Science.gov (United States)

This study seeks to extend the literature by examining distress tolerance (DT) levels for a substance dependent group of individuals. Next, it considers the potential relationship of DT levels with substance dependence features and finally, it compares those factors with a healthy control group. This study included 93 individuals (49 substance dependent and 44 healthy controls). Participants were evaluated using the Structured Clinical Interview for DSM-IV Axis I Diagnosis (SCID-I) and given the Distress Tolerance Scale (DTS), Beck Depression Inventory (BDI), and State & Trait Anxiety Inventory (STAI). Consistent with our expectations, the substance dependent group showed higher scores on the BDI and STAI, and lower scores on the DTS. There was no difference between the single drug dependent group and multiple substance-dependent groups, and their DT levels were not correlated with the duration of substance use, nor with the age of first substance use. Instead, DT was strongly correlated with trait anxiety, state anxiety, and depressive symptoms. The DT levels of this group of substance dependent individuals were very low in comparison to controls and to other groups reported in the literature. Our results suggest that distress tolerance may represent a therapeutic target factor in substance dependency treatment. Limitations and future research directions are also discussed. PMID:24439559

Özdel, Kadir; Ekinci, Suat

2014-05-01

333

Severity of Psychological Distress among Adults with and without Disabilities.  

Science.gov (United States)

The aim of this study is to examine psychological distress and its individual symptoms between adults with and without disabilities, and among adults with disabilities, to examine whether an association exists between severity of distress and health-related factors. Cross-sectional data from the 2007 Behavioral Risk Factor Surveillance System were used for this study. Severity of psychological distress was assessed using the Kessler 6 scale of nonspecific psychological distress. Logistic regression analyses were performed to estimate predicted marginals and prevalence ratios. Nine percent of adults had mild to moderate psychological distress and 3.9% had serious psychological distress. The adjusted mean Kessler 6 total scores and individual item scores were higher for adults with disabilities, as was the average number of days that a mental health condition interfered with activities in the past 30 days. Among adults with disabilities, mild to moderate and serious psychological distress were particularly high among those who were unemployed or unable to work. Those who had either mild to moderate or serious psychological distress were significantly more likely than those with no psychological distress to be physically inactive, to smoke, and to report fair or poor health, life dissatisfaction, and inadequate social support. A dose-response relationship exists between categorical severity of psychological distress and examined health-related factors. These findings may inform the design of targeted public health strategies that aim to eliminate health disparities between people with and without disabilities. PMID:25350897

Okoro, Catherine A; Dhingra, Satvinder S

2014-11-10

334

Moss cushions facilitate water and nutrient supply for plant species on bare limestone pavements.  

Science.gov (United States)

Dense moss cushions of different size are distributed across the bare limestone pavements on Øland, SE Sweden. Increasing cushion size is predicted to physically protect and improve performance and colonization by vascular plants. Therefore, we tested water balance, phosphorus supply, and species richness, and evaluated duration of plant activity during desiccation as a function of ground area, for a large collection of moss cushions. We found that lower evaporation and higher water storage contributed equally to extending the desiccation period with increasing cushion size. Evaporation rates declined by the -0.36 power of cushion diameter, and were not significantly different from -0.50 for the square root function previously predicted for the increasing thickness of the boundary layer, with greater linear dimensions for smooth flat objects at low wind velocities. Size dependence vanished under stagnant conditions. One moss species was added to the species pool for every nine-fold increase in cushion area. Vascular plants were absent from the smallest cushions, whereas one or two species, on average, appeared in 375- and 8,500-cm(2) cushions with water available for 6 and 10 days during desiccation. Phosphorus concentrations increased stepwise and four-fold from detritus to surface mosses and to vascular plants, and all three pools increased with cushion size. We conclude that cushion mosses and cushion size play a critical role in this resource-limited limestone environment by offering an oasis of improved water and nutrient supply to colonization and growth of plants. PMID:22481304

Sand-Jensen, Kaj; Hammer, Kathrine Jul

2012-10-01

335

Stresses, strains, and displacements in a poroelastic layered pavement model subject to a moving load  

International Nuclear Information System (INIS)

The response of a layered poroelastic halfspace to a progressing normally distributed load applied at the surface is evaluated for the case in which the constant velocity of the moving load is less than that of the elastic waves in each layer. It is assumed that a steady state exists with respect to the coordinate axes attached to a moving load. A three-dimensional problem for Biot's consolidated equations is then solved by taking Fourier transforms in the horizontal directions to evaluate stresses and displacements at any point in the medium. The analysis is illustrated by numerical examples using an algorithm based on one previously developed to calculate the response to a static load for axisymmetric poroelastic layers. To reduce the amount of computation, attention is restricted to a two-dimensional problem in which the load extends infinitely in the transverse direction. Results are presented for two and three-layered pavement models composed of concrete and gravel over a clay subbase responding to moving traffic, but the method is applicable to any number of layers. The effect of varying the velocity of the load and layer properties is observed

336

Moss cushions facilitate water and nutrient supply for plant species on bare limestone pavements  

DEFF Research Database (Denmark)

Dense moss cushions of different size are distributed across the bare limestone pavements on Øland, SE Sweden. Increasing cushion size is predicted to physically protect and improve performance and colonization by vascular plants. Therefore, we tested water balance, phosphorus supply, and species richness, and evaluated duration of plant activity during desiccation as a function of ground area, for a large collection of moss cushions. We found that lower evaporation and higher water storage contributed equally to extending the desiccation period with increasing cushion size. Evaporation rates declined by the -0.36 power of cushion diameter, and were not significantly different from -0.50 for the square root function previously predicted for the increasing thickness of the boundary layer, with greater linear dimensions for smooth flat objects at low wind velocities. Size dependence vanished under stagnant conditions. One moss species was added to the species pool for every nine-fold increase in cushion area. Vascular plants were absent from the smallest cushions, whereas one or two species, on average, appeared in 375- and 8,500-cm(2) cushions with water available for 6 and 10 days during desiccation. Phosphorus concentrations increased stepwise and four-fold from detritus to surface mosses and to vascular plants, and all three pools increased with cushion size. We conclude that cushion mosses and cushion size play a critical role in this resource-limited limestone environment by offering an oasis of improved water and nutrient supply to colonization and growth of plants.

Jensen, Kaj Sand; Hammer, Kathrine

2012-01-01

337

Influence of mixture composition on the noise and frictional characteristics of flexible pavements  

Science.gov (United States)

Both traffic noise and wet pavement-tire friction are mainly affected by the tire/pavement interaction. Existing laboratory test methods allow for evaluation of polishing resistance of the aggregates only. Currently, there is no generally accepted standardized laboratory test method to address noise related issues and the overall frictional properties of pavements (including macrotexture). In this research, which included both laboratory and field components, friction and noise properties of the flexible (asphalt) pavements were investigated. As a part of this study, a laboratory device to polish asphalt specimens was developed and the procedure to evaluate mixture frictional properties was proposed. Following this procedure, forty-six different Superpave mixtures (each utilizing a different aggregate blends), one stone matrix asphalt (SMA) mixture and one porous friction course (PFC) mixture were tested. Six of the above mixes (four Superpave mixtures, SMA mixture and PFC mixture) were selected for laboratory noise testing. This testing was performed using a one-of-a-kind tester called the Tire/Pavement Test Apparatus (TPTA). In addition, the field sections constructed using Superpave, SMA and PFC mixtures were also periodically tested for friction and noise. Field measurements included testing of total of 23 different asphalt and two concrete pavements. The field friction testing was performed using both portable CTM and DFT devices and the (ASTM E 274) locked wheel friction trailer. The laboratory friction testing was performed using CTM and DFT devices only. The results of both field and laboratory friction measurements were used to develop an International Friction Index (IFI)-based frictional requirement for laboratory friction measurements. The results collected in the course of the study indicate that the IFI-based flag values could be successfully used in place of SN-based flag values to characterize frictional characteristics of pavements.

Kowalski, Karol J.

338

Camiones de alto tonelaje y su impacto en ciclo de vida de pavimentos asfálticos / Heavy load trucks and its impact in life cycle of asphalt pavements  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: Spanish Abstract in spanish En los últimos años se inició el debate sobre la factibilidad técnico-económica de introducir en la flota de transporte de carga configuraciones de alto tonelaje (CAT). Estas configuraciones superan el peso bruto total máximo de 45 t permitido en Chile, distribuyendo la carga sobre un mayor número d [...] e ejes. En Chile no existe experiencia en el uso de este tipo de configuraciones de carga, por lo que es prudente y necesario estudiar el impacto global que tendrían en el sistema de transporte interurbano si se implementan. En este trabajo se analiza en particular el impacto sobre los pavimentos asfálticos. Utilizando un enfoque mecanicista-empírico, se comparó el impacto en el ciclo de vida producido por CAT del tipo bitrén corto y largo, y configuraciones tradicionales del tipo camión-remolque y tracto-semirremolque. En la evaluación se consideraron diferentes estructuras de pavimento, condiciones climáticas y niveles de tránsito solicitante, representativos de la Región del Biobío. La evaluación mecanicista-empírica se realizó utilizando el método de diseño de pavimentos mecanicista francés Alize-LCPC, y los modelos de deterioro desarrollados por el Asphalt Institute. Para comparar distintos métodos de evaluación y modelos de deterioro, el ciclo de vida fue evaluado utilizando la Ley de Miner implementada en la guía de diseño MEPDG de Estados Unidos. Los resultados mostraron que el camión-remolque produce mayor daño en el pavimento, mientras que el tracto-semirremolque es el que produce menor daño, ambos con 45 t de peso bruto total. El bitrén largo de 75 t produce un impacto estructural levemente menor que el bitrén corto de 61 t. Sin embargo, se encontró evidencia teórica de que las CAT producen mayor ahuellamiento superficial en forma proporcional al peso bruto total. Abstract in english In recent years a discussion of the technical-economic feasibility of introduce the heavy load trucks (CAT) in goods transport fleet was started. This truck configurations overpass the maximum gross weight of 45 t permitted in Chile. In Chile there not exist experience of using this type of trucks, [...] whence is relevant to study the global impact of it over the interurban transport system. This paper discusses the impact of heavy load trucks over asphalt pavements. Using a mechanistic-empirical framework, the impact of two types of CAT, long and short bitrén, and a one and two units 45 tons trucks were compared along the life-cycle of the pavement. Assessment considers different pavement configurations, weather conditions and traffic levels, typical of the Bio Bio region. The mechanistic-empirical assessment was performed using the Alize-LCPC pavement design tool and the deterioration models of the Asphalt Institute. For comparing deteriorations, the life-cycle was assessed using the Miner Law implemented in the Mechanist-Empirical Pavement Design Guide, MEPDG. Results show that the one unit truck induces the greater damage over the pavement and that the two unit truck induces the lower damage. The long bitren (75 tons) induce a slightly lower impact than the short bitren. However it was found evidence that the CAT induce the greater rutting in the pavement surface, which increases linearly if the gross weight of the truck increases.

R, Díaz; T, Echaveguren; S, Vargas-Tejeda.

2012-04-01

339

Crumb rubber modifier (CRM) in asphalt pavement: Summary of practices in Arizona, California, and Florida. Interim report, 1 February-30 June 1995  

Energy Technology Data Exchange (ETDEWEB)

Highway agencies have been evaluating crumb rubber modifier (CRM) in hot mix asphalt (HMA) since the 1970`s. Three agencies, Arizona, California, and Florida, currently use CRM in HMA at levels that would approach or exceed the mandate in Section 1038 of the Intermodal Surface Transportation Efficiency Act of 1991. This report documents the use of CRM in HMA in these three States. In particular, it addresses issues including thickness design, materials and mix design, construction procedure, including control, and pavement performance. The report also addresses the following questions: (1) What processes are used, (2) Why are they used, (3) How are they performing.

Hicks, R.G.; Lundy, J.R.; Leahy, R.B.; Hanson, D.; Epps, J.

1995-09-01

340

Reduction of traffic and tire/pavement noise: 1st year results of the Arizona Quiet Pavement Program-Site III  

Science.gov (United States)

The Arizona Quiet Pavement Pilot Program overlaid major freeway segments in the Phoenix area with an Asphalt Rubber Friction Course (ARFC). The overlay was placed on various Portland Cement Concrete Pavement (PCCP) textures. Traffic noise reductions were evaluated by performing wayside traffic noise measurements and tire/pavement source level measurements. First year results for three different study sites are presented in this paper. Depending on the texture of the initial PCCP and microphone locations, reductions of up to 12 dBA in wayside traffic noise levels were measured. Similar reductions of tire/pavement source levels were measured. Results of the two methods are compared. Traffic conditions monitored during the measurements were modeled using the Federal Highway Administration's Traffic Noise Model (TNM 2.5) to compare modeled levels to those measured for PCCP and AFRC overlay conditions. The model under predicted levels for PCCP conditions and over predicted levels for AFRC conditions. The magnitude of under or over prediction varied with distance. The effect of propagation was examined and was aided by simultaneous measurements of wind conditions made by Arizona State University. TNM 2.5 was used to identify sound wall heights that were equivalent to the traffic noise reductions provided by the AFRC overlay.

Reyff, James A.; Donavan, Paul

2005-09-01

 
 
 
 
341

Assessment of Distress Associated to Psychopathology in Children and Adolescents  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this paper was to study the distress associated to psychopathology in children and adolescents. The sample included 330 children aged 8 to 17 years attending outpatient mental health services of the public network in Barcelona(Spain assessed using a structured diagnostic interview. A substantial part of children brought to treatment suffered distress associated to internalizing and externalizing psychological symptoms. Psychological distress was most frequent among girls and among adolescents, and was more frequently reported by children and adolescents than by their parents. It was also a marker of perception of need of psychological help, and it was significantly related to diagnosis, subthreshold conditions and functional impairment. Individual symptoms of depression, dysthymia, generalized anxiety disorder and oppositional defiant disorder were most associated with psychological distress. Given the potential importance of subjective distress as well as impairment for the identification and definition of psychopathology and planning of treatment, diagnostic assessment should include questions related to distress.

Wendy Reich

2009-04-01

342

Financial Distress Prediction in Emerging Market: Empirical Evidences from Iran  

Directory of Open Access Journals (Sweden)

Full Text Available In this article the ability of financial ratios for prediction of financial distress of the listed companies in Tehran Stock Exchange (TES was investigated. For this reason, the multiple regression models were used and a model was presented for prediction of financial distress in listed companies in TES. The assessment of the model was done by utilizing the data of two groups. The first group contained 30 companies which don't have any financial distress, and the second group, similarly, contained 30 companies which have financial distress. The presented model was according to five the ratios, namely; ratios indicate liquidity, profitability, managing of debt and managing of property. The statistical results of the model indicate the validity of that model and the selected ratios. The results of the test of the ability of model prediction indicate the reality that the model designed four years before financial distress in companies; present a correct prediction about the financial distress.

Mahdi Salehi

2009-08-01

343

Psychological and physical distress of cancer patients during radiotherapy  

CERN Document Server

Purpose: patients undergoing radiotherapy have physical and psychological symptoms related to the underlying disease and the treatment. In order to give the best possible support to the patients, more knowledge about the amount and the changing of distress in the course of radiotherapy is of essentially importance. Methods: The distress was measured in a consecutive sample of cancer patients (n=82) undergoing radiotherapy. Each patient was given the EORTC-QLQ-C30, the HADS and a special questionnaire which ascertain radiotherapy-specific items before starting the radiotherapy, at the onset of radiotherapy, in the third week of radiotherapy and 3 weeks after the end of radiotherapy. Results: within the first week of treatment the psychological distress of the patients is increasing; 98.8 % of the patients are 'moderate distressed', 46 % 'severe distressed'. General physical symptoms seem not to be affected by the radiotherapy, there is no changing. The distress caused by the organization of the radiotherapy is...

König, A

2001-01-01

344

Framing the Issues: Moral Distress in Health Care  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Moral distress in health care has been identified as a growing concern and a focus of research in nursing and health care for almost three decades. Researchers and theorists have argued that moral distress has both short and long-term consequences. Moral distress has implications for satisfaction, recruitment and retention of health care providers and implications for the delivery of safe and competent quality patient care. In over a decade of research on ethical practice, registered nurses a...

Pauly, Bernadette M.; Storch, Jan

2012-01-01

345

Accuracy of the Danish version of the 'distress thermometer'  

DEFF Research Database (Denmark)

Objective: Short screening instruments have been suggested to improve the detection of psychological symptoms. We examined the accuracy of the Danish version of the 'Distress Thermometer'. Methods: Between October 2008 and October 2009, 426 women with newly diagnosed primary breast cancer who were operated at the Breast Surgery Clinic of the Rigshospitalet, Copenhagen, were eligible for this study. Of these, 357 participated (84%) and 333 completed a questionnaire. The distress thermometer was evaluated against the 'hospital anxiety and depression scale' (HADS). We also examined the women's wish for referral for psychological support. Results: A cut-off score of 6 vs 7 (low:?6, high:?7) on the distress thermometer was optimal for confirming distress, with a sensitivity of 42%, a specificity of 93%, a positive predictive value (PPV) of 78% and a negative predictive value (NPV) of 73%. A cut-off score of 2 vs 3 was optimal for screening, with a sensitivity of 99%, a specificity of 36%, a PPV of 47% and a NPV of99%. Of those who were distressed using the cut-off score of 2 vs 3 on the distress thermometer, 17% (n = 41) wished to be referred for psychological support and 57% (n = 140) potentially wanted a later referral. Conclusion: The distress thermometer performed satisfactorily relative to the HADS in detecting distress in our study. A screening procedure in which application of the distress thermometer is a first step could be useful for identifying persons in need of support. Copyright © 2011 John Wiley & Sons, Ltd.

Rottmann, Nina; Johansen, Christoffer

2012-01-01

346

Utilizationof Hypo Sludge by Eco-Efficient Development of Rigid Pavement in Rural Roads  

Directory of Open Access Journals (Sweden)

Full Text Available The paperproducing industry generates various wastes coming out from the various processes. From the preliminary waste named as hypo sludge, due to its low calcium is taken out to replace the cement in concrete. Major initiatives are needed in India to use these large volumes in construction industry especially in rigid pavement construction and other infrastructure projects. Moreover Use of Hypo Sludge in construction of rigid pavement will improve transportation functionality and ecological sustainability and results in improved traffic safety and reduced life-cycle cost. Use of Hypo Sludge in construction of rigid pavement will benefit urban growth, public health and surrounding communities by encouraging smart growth by integrating and guiding future growth. It is also needed to reduce the cost of concrete pavement for rural development in India. So our study is concerned with eco-efficient utilization of Hypo sludge as partial replacement of cement in concrete for development of low cost rigid pavement of rural road infrastructure.The Hypo sludge was replaced within the range of 10-40% by weight of cement. In the present study, 5 different mixes of Hypo Sludge are tested for parameters like: compressive strength, flexural strength and cost

Prof. Jayeshkumar Pitroda1 , Dr. L.B.Zala2 , Dr.F.S.Umrigar

2013-09-01

347

Reflectance of interurban-road pavements from radar-based measurements  

Science.gov (United States)

Reflectance measurements in interurban-road typical pavements are essential for traffic security. The reflectance of interurban-road pavements presents high variability due to such variables as climatic and atmospheric conditions and the presence of foreign materials on the road (e.g. dirt, fuel or oil). For this reason, the recording of real-time measurements for these kinds of pavements is a complex task. However, its critical importance in traffic safety demands precise measurements under all the possible conditions. In this context, the use of remote-sensing systems working in the radar spectral range is of great interest. With active sensors that receive their own radar signal, the reflectance measurements made by the remote-sensing system are not influenced by the atmospheric conditions. In this work, we present a radar-based methodology to develop real-time measurements of the reflectance in typical interurban-road pavements. We are engaged in extending this new method to study the reflectance of interurban-road pavements within the visible spectrum.

Fernandez, Paz; Peña-García, Antonio; Poyatos-Martínez, David; Escot-Bocanegra, David; Fernández-Oliveras, Alicia

2013-11-01

348

Guidelines and specifications for the use of reclaimed aggregates in pavement. Final report  

Energy Technology Data Exchange (ETDEWEB)

The project focused on evaluating the performance of recycled concrete for use as a base material under hot mix asphalt pavements and as an aggregate in Portland cement concrete pavements. In order to meet this objective, several goals were established. First, published literature on RCA was reviewed and a survey of State Highway Agencies (SHA) was performed to determine the extent of use of RCA in highway projects. Second, the RCA was tested at the FDOT Material Lab in Gainesville, Florida, to determine the material properties. Third, by using the output from the falling weight deflectometer test along with the KENSLABS and KENLAYER computer programs (Huang, 1993), a theoretical analysis was performed to predict the number of repetitions before the pavements failed in both the fatigue and permanent deformation criteria. Lastly, nine design sections involving HMA and PCC pavements were constructed at the University of Central Florida`s Circular Accelerated Test Track (UCF-CATT) to evaluate the response of the pavement sections made with RCA under actual dual-wheel loading.

Chini, S.A.; Kuo, S.S.; Duxbury, J.P.; Monteiro, F.M.B.R.; Mbwambo, W.J.

1998-08-01

349

Life Cycle Assessment of Pavements: A Critical Review of Existing Literature and Research  

Energy Technology Data Exchange (ETDEWEB)

This report provides a critical review of existing literature and modeling tools related to life-cycle assessment (LCA) applied to pavements. The review finds that pavement LCA is an expanding but still limited research topic in the literature, and that the existing body of work exhibits methodological deficiencies and incompatibilities that serve as barriers to the widespread utilization of LCA by pavement engineers and policy makers. This review identifies five key issues in the current body of work: inconsistent functional units, improper system boundaries, imbalanced data for asphalt and cement, use of limited inventory and impact assessment categories, and poor overall utility. This review also identifies common data and modeling gaps in pavement LCAs that should be addressed in future work. These gaps include: the use phase (rolling resistance, albedo, carbonation, lighting, leachate, and tire wear and emissions), asphalt fumes, feedstock energy of bitumen, traffic delay, the maintenance phase, and the end-of-life phase. This review concludes with a comprehensive list of recommendations for future research, which shed light on where improvements in knowledge can be made that will benefit the accuracy and comprehensiveness of pavement LCAs moving forward.

Santero, Nicholas; Masanet, Eric; Horvath, Arpad

2010-04-20

350

Evaluating the Infiltration Performance of Eight Dutch Permeable Pavements Using a New Full-Scale Infiltration Testing Method  

Directory of Open Access Journals (Sweden)

Full Text Available Permeable pavements are a type of sustainable urban drainage system (SUDS technique that are used around the world to infiltrate and treat urban stormwater runoff and to minimize runoff volumes. Urban stormwater runoff contains significant concentrations of suspended sediments that can cause clogging and reduce the infiltration capacity and effectiveness of permeable pavements. It is important for stormwater managers to be able to determine when the level of clogging has reached an unacceptable level, so that they can schedule maintenance or replacement activities as required. Newly-installed permeable pavements in the Netherlands must demonstrate a minimum infiltration capacity of 194 mm/h (540 l/s/ha. Other commonly used permeable pavement guidelines in the Netherlands recommend that maintenance is undertaken on permeable pavements when the infiltration falls below 0.50 m/d (20.8 mm/h. This study used a newly-developed, full-scale infiltration test procedure to evaluate the infiltration performance of eight permeable pavements in five municipalities that had been in service for over seven years in the Netherlands. The determined infiltration capacities vary between 29 and 342 mm/h. Two of the eight pavements show an infiltration capacity higher than 194 mm/h, and all infiltration capacities are higher than 20.8 mm/h. According to the guidelines, this suggests that none of the pavements tested in this study would require immediate maintenance.

Floris Boogaard

2014-07-01

351

Challenges confronting road freight transport and the use of vehicle-pavement interaction analysis in addressing these challenges  

Scientific Electronic Library Online (English)

Full Text Available SciELO South Africa | Language: English Abstract in english Traditional arguments for maintaining riding quality of pavement are expanded in this paper to examine the effects of deteriorating riding quality on vehicle operating costs, freight damage and logistics. The objectives of this paper are to analyse the effects of different levels of riding quality o [...] n a truck and its freight, and to discuss potential applications of the analysis in terms of effectiveness of the freight transport system. The paper discusses needs and drivers influencing freight transport costs, vehicle-pavement interaction concepts, and the potential physical effects and costs from roads with deteriorating riding quality. A case study is presented analysing vehicle-pavement interaction for selected roadways in California. It is concluded that investments in pavement and freight transport industry improvements can be investigated by applying vehicle-pavement interaction analysis to evaluate damage to pavement, vehicle and freight that would result from alternative levels of pavement riding quality. The paper recommends that existing concepts, tools and resources such as dedicated truck lanes and vehicle-pavement interaction analysis can help to improve the freight transport system. A framework is proposed to better understand the scale of potential impacts of riding quality from localised effects to larger-scale influences, including costs to customers and global competitiveness.

W J vd M, Steyn; C L, Monismith; W A, Nokes; J T, Harvey; T J, Holland; N, Burmas.

2012-04-01

352

Acute respiratory distress caused by Neosartorya udagawae  

Science.gov (United States)

We describe the first reported case of acute respiratory distress syndrome (ARDS) attributed to Neosartorya udagawae infection. This mold grew rapidly in cultures of multiple respiratory specimens from a previously healthy 43-year-old woman. Neosartorya spp. are a recently recognized cause of invasive disease in immunocompromised patients that can be mistaken for their sexual teleomorph, Aspergillus fumigatus. Because the cultures were sterile, phenotypic identification was not possible. DNA sequencing of ITS, calmodulin and ?-tubulin genes supported identification of Neosartorya udagawae. Our case is the first report of ARDS associated with Neosartorya sp. infection and defines a new clinical entity. PMID:25379388

Farrell, John J.; Kasper, Douglas J.; Taneja, Deepak; Baman, Sudhakar; O?Rourke, Lindsay M.; Lowery, Kristin S.; Sampath, Rangarajan; Bonomo, Robert A.; Peterson, Stephen W.

2014-01-01

353

Adult respiratory distress syndrome: CT findings  

International Nuclear Information System (INIS)

Adult respiratory distress syndrome (ARDS) is associated with a mortality in excess of 50%. The authors performed CT examinations on 26 patients with ARDS. The test was needed to rule out intra-abdominal abscesses, empyemas, or additional pathology not imaged on chest radiographs. The pattern of lung disease was analyzed according to distribution. Diffuse consolidation, multifocal patch involvement, and lobar or segmental disease were detected. Over half of the patients developed cystic lung spaces. Pleural effusions, pneumothoraces, and unexpected abscesses and empyemas were discovered. The authors conclude that CT in ARDS can disclose additional complications not visible on bedside chest radiographs, thus improving the management of selected patients

354

Surfactant treatment for acute respiratory distress syndrome  

Digital Repository Infrastructure Vision for European Research (DRIVER)

OBJECTIVE—To determine prospectively the efficacy of surfactant in acute respiratory distress syndrome.?STUDY DESIGN—Twenty patients, 1 month to 16 years of age, diagnosed with an acute pulmonary disease with severe hypoxaemia (PaO2/FiO2 < 100) (13 with systemic or pulmonary disease and seven with cardiac disease) were treated with one to six doses of 50-200 mg/kg of porcine surfactant administered directly into the trachea. The surfactant was considered to be ef...

Lopez-herce, J.; Lucas, N.; Carrillo, A.; Bustinza, A.; Moral, R.

1999-01-01

355

Acute Respiratory Distress Syndrome in Lemierre's Syndrome.  

Science.gov (United States)

Lemierre's syndrome is an infectious disease defined by the presence of septic thrombophlebitis with associated embolic phenomenon, most commonly to the lungs. Here we present two cases from a single institution of acute respiratory distress syndrome (ARDS) developing as a result of Lemierre's syndrome in previously healthy young adult men. ARDS can occur as a consequence of pulmonary septic emboli and sepsis, both of which are well-described consequences of Lemierre's syndrome. We describe important diagnostic and management considerations in the care of patients with hypoxemic respiratory failure and Lemierre's syndrome. Essential components of management include prompt antibiotic therapy, lung-protective ventilation strategies, and supportive care. PMID:25143837

Hein, Paul N; Soghikian, Maida V; Bhangoo, Munveer S

2014-01-01

356

Acute respiratory distress syndrome and pneumothorax.  

Science.gov (United States)

Acute respiratory distress syndrome (ARDS) can occur during the treatment of several diseases and in several interventional procedures as a complication. It is a difficult situation to handle and special care should be applied to the patients. Mechanical ventilation is used for these patients and several parameters are changed constantly until compliance is achieved. However, a complication that is observed during the application of positive airway pressure is pneumothorax. In our current work we will present definition and causes of pneumothorax in the setting of intensive care unit (ICU). We will identify differences and similarities of this situation and present treatment options. PMID:25337400

Terzi, Eirini; Zarogoulidis, Konstantinos; Kougioumtzi, Ioanna; Dryllis, Georgios; Kioumis, Ioannis; Pitsiou, Georgia; Machairiotis, Nikolaos; Katsikogiannis, Nikolaos; Lampaki, Sofia; Papaiwannou, Antonis; Tsiouda, Theodora; Madesis, Athanasios; Karaiskos, Theodoros; Zaric, Bojan; Branislav, Perin; Zarogoulidis, Paul

2014-10-01

357

A Statistical Analysis to Predict Financial Distress  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this study is to apply the statistical inference to identify if a firm is likely to become financially distressed in the short term. To do this, we decided to collect data from the firms’ financial statements. The analyses performed were based on a group of 45 financial ratios observed from a sample of 86 firms operating in Argentina. First, we used the principal component analysis to turn the information in the 45 original ratios into two new global variables named as ?Risk and ?Return. In this way, we can easily represent and compare in a graph the firms’ risk and return variations. By the computation of these new variables it is possible to quickly financially categorize a certain firm based on the risk the company has with regard to the nature of its business and the risk involved in the amount of debt it has taken in comparison to the profits that were generated during the last two fiscal years. Second, we performed a logistic regression analysis to estimate the probability that a firm becomes financially distressed in the short term. The model finally selected managed to successfully identify 85% of the companies from the sample and it explains 65% of the total sample variability. The model is represented by the following variables: 1 Current Debt Ratio, 2 Total Cost of Debt, 3 Operating Profit Margin, and 4 ?ROE. The outcomes from this study are two tools that were developed based on the statistical inference from which we can quickly asses the financial status of a firm based on its risks and return’s variation as well as to estimate the probability that a firm becomes financially distressed in the short term. There are different ways of taking these tools into practice such as: 1 to control and follow up the financial performance of a company, 2 to support the decision of lending money to a company, 3 to support the decision of investing money or the decision of merging with a company, 4 to support market analysis from a financial perspective, and 5 to support actions or decisions related to the financial assessment of a company that declares itself to be financially distressed.

Nicolas Emanuel Monti

2010-09-01

358

Predicting financial distress in teaching hospitals.  

Science.gov (United States)

Despite the prestige and reputation of teaching hospitals, as a group they are in financial distress. If this trend continues, one would expect to see a higher incidence of mergers and acquisitions or divestitures of assets and services, and other strategies designed to combat failing businesses. Nearly one out of every six teaching hospitals sampled was predicted to be near immediate bankruptcy, and the overwhelming majority was not far behind. It will take a significant effort for these hospitals to continue to treat their operations as a clinical and research "business," but they must do just that if they are to survive the continually turbulent market. PMID:19175242

Langabeer, Jim

2006-01-01

359

Making the Grade but Feeling Distressed: Gender Differences in Academic Performance and Internal Distress.  

Science.gov (United States)

There is disagreement over whether girls or boys are at risk in the context of school. Girls outperform boys in school, particularly in stereotypically feminine subjects. However, girls are also more vulnerable to internal distress than boys are. The aim of this research was to understand this pattern of gender differences. (Author)

Pomerantz, Eva M.; Altermatt, Ellen Rydell; Saxon, Jill L.

2002-01-01

360

GPR abilities in investigation of the pavement transversal cracks  

Science.gov (United States)

This paper describes the results of an investigation into the capabilities of the GPR technique within the field of pavement crack diagnostics. Initially, laboratory tests were performed on prototypes simulating idealized cracks. Next, long-term visual observation and repeated GPR scanning were performed, on three roads of semi-rigid construction, several hundreds of meters long and subjected to heavy traffic. Furthermore, a road of rigid construction was tested, having a more than 70-year history of use. In several cases the cracks were probed by drillings, in order to recognize structures responsible for signal generation, or to explain reasons of signal lacking. The main result of this work is a list of GPR indications of cracks, which can be noticed on echograms. It was created through a correlation of the visually-observed cracks with the corresponding echograms, with decimeter accuracy. Several types of GPR responses were classified and linked to possible categories of crack structures, or to processes associated with the presence of cracks (as crumbling, erosion, and lithological alterations). The poor visibility of cracks was also studied, due to small crack size, or to the blurred character of the damaged area, or else to masking effects related to coarse grains in the asphalt mixture. The efficiency of the proposed method for the identification and localization of cracks is higher when a long-term GPR observation is performed.

Krysi?ski, Lech; Sudyka, Jacek

2013-10-01

 
 
 
 
361

Recycling of radioactive oil sludge waste into pavement brick  

International Nuclear Information System (INIS)

Malaysia produces about 1450 tons of radioactive oil sludge waste per year and there is an urgent need to find a permanent solution to the storage and disposal of this radioactive waste problem. Several treatment methods such bacteria farming, ultracentrifuge, steam reforming and incineration are currently being used but the core issue of the radioactive material in the oil sludge had not been solved. The paper relates a study on utilizing the radioactive component of the oil sludge and turning them into pavement brick. Characteristic study of this radioactive component by XRD and XRF show that it mainly comprised of quartz and anorthite minerals. While the radioactivity analysis by gamma technique shows that more than 90 % of this radioactivity comes from this soil component with Ra-226 and Ra-228 as the main radionuclides. A vitrified brick was then produced from this sediment by mixing it with low radioactive local red clay. The result also shows that the formation of the vitrified layer may be due high content of K in the red clay. Tensile test on the brick shows that it has more than four times the strength of commercial clay brick. Long duration leaching test on the brick also shows that there is no dissolution of radionuclide from the brick. (author)

362

Prediction of Airport Flexible Pavement Critical Responses from Non-destructive Test Data Using ANN-based Structural Models  

Directory of Open Access Journals (Sweden)

Full Text Available This study describes the development of Artificial Neural Network (ANN based pavement response prediction models for rapid structural analysis of airport flexible pavements based on Non-destructive Test (NDT data. A finite element based pavement structural model, which can accommodate stress-sensitive geomaterial stiffness models, was used to generate the ANN training and testing dataset. The goal was to establish ANN models for predicting critical responses (stresses and strains from routine NDT airfield pavement structural evaluation data. The developed ANN models predicted the critical pavement responses obtained from the finite element model with good accuracy. Further research is required to achieve increased prediction accuracies and validate the ANN models using actual field data.

Kasthurirangan Gopalakrishnan

2006-01-01

363

Solar Reflectance Index of Pedestrian Pavements and Their Response to Aging  

Directory of Open Access Journals (Sweden)

Full Text Available Due to the impact of the optical characteristics of the materials composing the urban envelopes on the energy balance of cities, their categorization according to their ability to decrease urban temperatures is an indispensable tool for sustainable development. This work presents the evaluation results of the thermal performance of the different pedestrian pavements available in the region, so as to classify them according to the Solar Reflectance Index (SRI. The study was carried out during a 2-year period, involving the analysis of the behaviour of 28 pavements in widely used compositions, shapes and colours. Additionally, the aging effect of the material was quantified over the SRI. The results show that 74% of pavements diminished their initial ability for decreasing temperatures, while 50% of the dark material, with initial negative performances, improved their thermal behavior.

N. L. Alchapar

2013-10-01

364

Plastic Damage Model to Evaluate the Fracture Size of Semi-Rigid Base Pavement  

Directory of Open Access Journals (Sweden)

Full Text Available A simple supported beam model has been presented to simulate the response of semi-rigid pavement structure, which are consistent of the upper layer, middle layer, bottom layer, base and sub base course, during the cycle vehicle loading. This mechanics model coupled with plastic-damage mechanics model could simulate the limit broken of the pavement structure in condition that soil base layer losing bearing capacity gradually. In the meanwhile, numerical calculations based on preceding mechanics model, using the FEM software ABAQUS, have been used to define the broken size of beam. The results indicated that: when the size of simple supported beam expanded to 10 m, brittle damage could happen immediately, Just the standard vehicle loading (about 0.7 Mpa has been implement once. Objective of this study is to provide a physical and rather concrete explanation for the style and concept of the semi-rigid pavement brittle broken.

Cao Peng

2013-01-01

365

Monitoring the performance of geosynthetic materials within pavement systems using MEMS  

Science.gov (United States)

Geosynthetic materials have found useful applications when unbound aggregates have been placed on cohesive soil with very weak subgrade. They have also been successfully used in retarding reflective cracking in both flexible and composite pavements. There are many applications of geosynthetics in pavement engineering yet there is considerable lack of understanding in the behavior of the material. Geosynthetic materials exhibit very peculiar properties in the area of tensile strength and reinforcement. MEMS are miniature sensing or actuating devices that can interact with other environments (provided no adverse reaction occurs) to either obtain information or alter it. With remote query capability, it appears such devices can be embedded in pavement systems as testing and monitoring tools. The aim of this paper is to propose both field and laboratory methods for monitoring geotextile performance using MEMS.

Attoh-Okine, Nii O.; Ayenu-Prah, Albert Y.; Mensah, Stephen A.

2005-05-01

366

47 CFR 80.335 - Procedures for canceling false distress alerts.  

Science.gov (United States)

...distress alert. (a) VHF Digital Selective Calling. (1...distress alert. (b) MF Digital Selective Calling. (1...distress alert. (c) HF Digital Selective Calling; (1...registration number, and INMARSAT identity with the cancelled alert...

2010-10-01

367

Relaxation Training and Expectation in the Treatment of Postpartum Distress.  

Science.gov (United States)

Examined the effectiveness of relaxation training in reducing postpartum distress for 48 first-time mothers-to-be via a treatment-component strategy. Compared with nonrelaxation conditions, relaxation treatments reduced reported postpartal distress. Expectations about treatment effectiveness were not significant factors in treatment outcome.…

Halonen, Jane S.; Passman, Richard H.

1985-01-01

368

[Distress during end-of-life: Ethical questions about sedation].  

Science.gov (United States)

Distress and suffering are words currently used in the medical vocabulary, the first carrying a more acute and dramatic feature, while suffering is more subjective. They may concern the somatic, psychic, social, and spiritual domains, with interactions such as excrutiating and unrelieved pain causing psychological distress. Distress during the end of life is induced by the threatening of an unavoidable death, more or less foreseen by the patient. It may correspond to an existential distress, with loss of the meaning of life, and of the social role, along with metaphysical anxiety. Patient's next of kin and carers can also be involved by the distress, either by empathic transmission, or due to specific factors. Palliative care and anticipation should allow to prevent or relieve distress and suffering. This imply to ask for palliative care on due time, and to anticipate the foreseeable situations, trying meanwhile to identify the patient's preferences. Pharmacologic sedation is becoming a frequent practice during terminal phase of diseases, raising ethical questioning on its motives and aims. Deep continuous sedation maintained until death may be viewed as a psychic and social euthanasia, ethically questionable, and should be foreseen only in case of intractable distress. A controlled and reversible sedation, when needed, should be preferred, always with the agreement of the patient or his/her proxy. Existential distress by itself should not justify a deep continuous sedation. PMID:21376509

Zittoun, Robert

2011-05-01

369

Child Rearing and Children's Prosocial Initiations toward Victims of Distress.  

Science.gov (United States)

Investigates the relation between maternal rearing behavior and the ways children aged 1 1/2 to 2 1/2 years cope with emotions of distress in others. Specifically examined children's reparation for transgression when they were the cause of distress and their altruism when they were bystanders. (JMB)

Zahn-Waxler, Carolyn; And Others

1979-01-01

370

Examining Victimization and Psychological Distress in Transgender College Students  

Science.gov (United States)

Treatment-seeking and non-treatment-seeking transgender college students were examined with regard to victimization and psychological distress. Findings showed that transgender college students had elevated rates of distress as compared with college students who identified as men or women. Results indicated that treatment-seeking and non-treatment…

Effrig, Jessica C.; Bieschke, Kathleen J.; Locke, Benjamin D.

2011-01-01

371

Somatic, Affective and Behavioral Distress Reactions across Cultures  

Science.gov (United States)

The purpose of the present study was to compare the expression and frequency of somatic, affective and cognitive symptoms of distress across Turkish and U.S. university students. An open-ended free-list question was used to elicit distress responses from 827 Turkish and U.S. participants. The coding was done using classical content analysis. It…

Canel-Cinarbas, Deniz; Aegisdottir, Stefania

2010-01-01

372

Differences in Distress among Adult Children of Alcoholics.  

Science.gov (United States)

Investigated psychological distress, social support, and hardiness among 79 adult children of alcoholics (ACAs) compared to 67 ACAs not involved in support groups. Group members reported higher levels of psychological distress, lower levels of hardiness, and less satisfaction with perceived social support than did nonmembers. For both groups,…

Kashubeck, Susan; Christensen, Sue A.

1992-01-01

373

Partnership Transitions and Mental Distress: Investigating Temporal Order  

Science.gov (United States)

The study uses 15 waves of the British Household Panel Survey and the General Health Questionnaire to investigate changes in mental distress over several years surrounding transitions both into and out of marital partnerships (marriages and cohabitations) using fixed effects models. Entering marital partnerships is associated with reduced distress

Blekesaune, Morten

2008-01-01

374

Routine screening for psychosocial distress following hematopoietic stem cell transplantation.  

Science.gov (United States)

The diagnosis and treatment of cancer is often associated with high levels of psychosocial distress, yet exploration of these issues is rarely included in routine oncologic care. We conducted a pilot study to evaluate the feasibility of screening for psychosocial distress after autologous and allogeneic stem cell transplantation. A total of 80 adults were enrolled in Boston, MA, USA. Subjects completed self-administered assessments prior to hospital admission, at their first clinic visit after hospital discharge, and at 100 days post transplant. Assessments included validated instruments assessing psychosocial distress and quality of life (QOL). Elevated levels of anxiety and/or depression were detected in 55% of those providing pre-transplant assessments and were associated with compromised QOL. Post transplant screening was successfully performed in 69% of subjects and identified that 44% had symptoms of depression, anxiety or post traumatic stress disorder. Pre-transplant distress was associated with detection of distress after transplantation (81 vs 13%, P< 0.0001). In summary, we detected high levels of distress in transplant patients using self-administered tools. Pre-transplant distress appears to be highly predictive of distress post transplant and is a feasible marker to target screening and intervention programs. PMID:15502851

Lee, S J; Loberiza, F R; Antin, J H; Kirkpatrick, T; Prokop, L; Alyea, E P; Cutler, C; Ho, V T; Richardson, P G; Schlossman, R L; Fisher, D C; Logan, B; Soiffer, R J

2005-01-01

375

Design of concrete pavements : design criteria for plain and lean concrete  

Digital Repository Infrastructure Vision for European Research (DRIVER)

New road infrastructure projects are important and constitute of large investments that have to serve the society for a long time. The investments have to be durable at the lowest life cycle cost and the pavements have to sustain loads from increasing traffic intensity and heavy traffic loads. In Sweden less than 1 ‰ of the national road network consists of concrete pavements. In parts of Europe and in the U.S., on the other hand, concrete roads are used to a large extent for highways as we...

So?derqvist, Johan

2006-01-01

376

Optical fiber based sensing system design for the health monitoring of multi-layered pavement structure  

Science.gov (United States)

This paper introduces an optical fiber based sensing system design for multi-layered pavement structural health monitoring. The co-line and integration design of FBG (Fiber Bragg Gating) sensors and BOTDR (Brillouin Optical Time Domain Reflectometry) sensors will ensure the large scale damage monitoring and local high accurate strain measurement. The function of pavement structure multi-scale shape measurement will provide real time subgrade settlement and rutting information. The sensor packaging methodology and strain transfer problem of the system will also be discussed in this paper. Primary lab tests prove the potential and feasibility of the practical application of the sensing system.

Liu, Wanqiu; Wang, Huaping; Zhou, Zhi; Li, Shiyu; Ni, Yuanbao; Wang, Geng

2011-11-01

377

A framework for developing optimal pavement life-cycle activity profiles  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Highway pavement managers seek cost-effective maintenance and rehabilitation (M&R) profiles over the pavement life-cycle. The benefits of each profile, which can be measured as the service life, increase in average performance compared to the do-nothing profile, or the area bounded by the performance curve that corresponds to the profile, may be monetized or un-monetized. The cost of each profile comprises the agency costs (of construction and maintenance) and the user costs during work zone ...

Irfan, Muhammad

2010-01-01

378

Profiles of distress in sheltered battered women: implications for intervention.  

Science.gov (United States)

Heterogeneity in patterns of distress and psychological functioning was investigated using a person-oriented approach to data analysis in two diverse samples of battered women in shelters. In order to provide some empirically derived guidance to clinicians, scores on measures of depressive symptoms as well as state and trait anxiety were cluster analyzed. A four-cluster solution provided the best fit for both samples of women, and despite the demographic differences in the women, generally similar clusters were found in both samples. One cluster contained women with minimal distress; another, those who were mildly anxious; in a third cluster, the women were moderately to highly depressed and anxious; and in a fourth cluster, the women were reporting severe levels of distress. Implications for treatment include the importance of providing individually tailored interventions for the women, based on differential combinations of depression and anxiety, especially for women whose distress levels are in the high and severe ranges of distress. PMID:21882668

Hughes, Honore M; Cangiano, Claudine; Hopper, Elizabeth K

2011-01-01

379

Enhancing the resolution of gpr spectra for pavement engineering applications  

Science.gov (United States)

Ground Penetrating Radar (GPR) is a geophysical method that uses radar pulses to image the subsurface. This non-destructive method uses electromagnetic radiation and detects the reflected signals from subsurface structures. It can detect objects, changes in material, and voids and cracks. GPR has many applications in a number of fields. In the field of civil engineering one of the most advanced technologies used for road pavement monitoring is based on the deployment of advanced GPR systems. One of the most relevant causes of road pavement damage is often referable to water intrusion in structural layers. In this context, GPR has been recently proposed as a method to estimate moisture content in a porous medium without preventive calibration. Hence, the development of methods to obtain an estimate of the moisture content is a crucial research field involving economic, social and strategic aspects in road safety for a great number of public and private Agencies. In particular, a recent new approach was proposed to estimate moisture content in a porous medium basing on the theory of Rayleigh scattering, showing a shift of the frequency peak of the GPR spectrum towards lower frequencies as the moisture content increases in the soil. The weakness characterizing this approach is represented by the needs of high resolution signals, whereas GPR spectra are affected by low resolution. Hence, the rising requirement for high resolution leads to specific demands for improved prediction methods. Recently, a new technique combining the response of the conventional fast Fourier transform (FFT, well known for its high-precision receiving signal level) with that of the MUSIC (multiple signal classification) algorithm, well known for its super-resolution capacity has been proposed. This combined method has been proved to obtain a high precision level in quantifying the shift of the frequency peak of the GPR spectrum. This combined method can perform a reliable coarse estimate of the (abscissa of the) frequency peak. Unfortunately, whereas resolution affecting the GPR spectra has been enhanced, we still need a sensible increasing of the moisture content to appreciate a visible frequency shift. Hence, sub-sample resolution techniques are needed to obtain a resolution better than the sample period. Addressing some of these issues, this work proposes a sub-sample resolution technique exploiting a fast parabolic interpolator, running on three samples of the GPR spectrum in the neighborhood of the frequency peak (i.e. the coarse estimation). More in details, the new detector searches for the (abscissa of the) vertex of the parabola fitted over three GPR samples: the coarse estimate of the frequency peak, and one sample before and after this estimation. The rationale behind the new fast parabolic approach is as follows. We expect the method to obtain a finer estimation of the (abscissa of the) frequency peak because we are now interpolating a parabola in the neighborhood of the same maximum (i.e the coarse estimate), but with a narrow variance thus increasing the estimation accuracy. No noteworthy increase of computational complexity and processing throughput is required to implement the new approach. In fact, near the totality of the amount of the required computation is due to the former stage (i.e. FFT and/or MUSIC implementation to evaluate the coarse estimate of the frequency peak), and the latter logic (i.e. the interpolation function) is negligible from implementation and computational point of view. Experimental results confirm the effectiveness of the proposed approach to evidence and quantify moisture content in soil. In fact, the proposed sub-sample super resolution technique can resolve a frequency shift in the GPR spectrum even for a corresponding amount of moisture less than 2-3%.

Benedetto, F.; Benedetto, A.

2012-04-01

380

Techno- Economical Study of Rigid Pavement by Using the Used Foundry Sand  

Directory of Open Access Journals (Sweden)

Full Text Available Indian road network of almost 3.5 million km comprising both paved and unpaved surfaces is the world’s second largest. Indian roads are presently constructed with not the right choice of material. The two major types of materials, bitumen and concrete are used in road construction in the country. A very small share of roads in the country is made of concrete. Though, it is superior on many counts as a medium for road buildings. The use of large amount of by-product materials as powder or fines not only avoids the requirement of landfills but also reduce the environmental problems. It is most essential to develop profitable building materials from used foundry sand. The innovative use of used foundry sand in concrete formulations as a fine aggregate replacement material was tested as an alternative to traditional concrete. The fine aggregate has been replaced by used foundry sand accordingly in the range of 0%, 10%, 30% & 50% by weight for M-20 grade concrete. Concrete mixtures were produced, tested and compared in terms of compressive and flexural strength with the conventional concrete. These tests were carried out to evaluate the mechanical properties for 7, 14 and 28 days. This research work is to investigate the behaviour of concrete while replacing used foundry sand in different proportion in concrete. This low cost concrete with good strength is used in rigid pavement for 3000 commercial vehicles per day (cvpd and Dry Lean Concrete (DLC 100mm thick for national highway to make it eco-friendly.

Vipul D. Prajapati1 , Nilay Joshi2 , Prof. Jayeshkumar Pitroda

2013-05-01

 
 
 
 
381

A study of sound absorption by street canyon boundaries and asphalt rubber concrete pavement  

Science.gov (United States)

A sound field model, based on a classical diffusion equation, is extended to account for sound absorption in a diffusion parameter used to model sound energy in a narrow street canyon. The model accounts for a single sound absorption coefficient, separate accommodation coefficients and a combination of separate absorption and accommodation coefficients from parallel canyon walls. The new expressions are compared to the original formula through numerical simulations to reveal the effect of absorption on sound diffusion. The newly established analytical formulae demonstrate satisfactory agreement with their predecessor under perfect reflection. As well, the influence of the extended diffusion parameter on normalized sound pressure levels in a narrow street canyon is in agreement with experimental data. The diffusion parameters are used to model sound energy density in a street canyon as a function of the sound absorption coefficient of the street canyon walls. The acoustic and material properties of conventional and asphalt rubber concrete (ARC) pavement are also studied to assess how the crumb rubber content influences sound absorption in street canyons. The porosity and absolute permeability of compacted specimens of asphalt rubber concrete are measured and compared to their normal and random incidence sound absorption coefficients as a function of crumb rubber content in the modified binder. Nonlinear trends are found between the sound absorption coefficients, porosity and absolute permeability of the compacted specimens and the percentage of crumb rubber in the modified binders. The cross-sectional areas of the air voids on the surfaces of the compacted specimens are measured using digital image processing techniques and a linear relationship is obtained between the average void area and crumb rubber content. The measured material properties are used to construct an empirical formula relating the average porosity, normal incidence noise reduction coefficients and percentage of crumb rubber in the modified binder of the compacted specimens.

Drysdale, Graeme Robert

382

Politics, economic distress mark Rmoga sessions  

International Nuclear Information System (INIS)

This paper reports that election year energy politics clashed with economic distress at Rocky Mountain Oil and Gas Association's annual meeting in Denver early this month. Energy Sec. James D Watkins used the occasion to hail omnibus energy legislation passed by a House-Senate conference committee just hours before he spoke. But not all producers and refiners in the audience shared his enthusiasm for the energy bill, a hard-won Bush administration goal that many Rmoga members doubt will help this industry much. Several of them privately expressed dismay over Watkins' praise, delivered to a beleaguered oil and gas group, of Department of Energy research programs boosting clean coal technology and battery powered vehicles

383

Peripheral intravenous cannulation: managing distress and anxiety.  

Science.gov (United States)

It is recognised that peripheral intravenous (IV) cannulation is an increasingly performed procedure within the hospital setting. This invasive, yet necessary, procedure often causes patients considerable anxiety and distress, especially those patients who have to endure multiple and possibly painful and difficult cannulations. Nurses can play a valuable role in minimising the associated physical discomfort and complications that patients may experience as a result of having a peripheral cannula inserted through maintaining their knowledge and skills in relation to patient preparation, assessment and the care and management of the cannula. However, nurses also play an equally valuable role in recognising the potential psychological complications that are associated with peripheral IV cannulation. Demonstrating a knowledge and understanding of the effective methods that are used to manage and minimise these complications can ensure patients' confidence is maintained and their experience of cannulation is positive. PMID:25345479

McGowan, Donna

2014-10-22

384

Surfactant alteration and replacement in acute respiratory distress syndrome  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract The acute respiratory distress syndrome (ARDS is a frequent, life-threatening disease in which a marked increase in alveolar surface tension has been repeatedly observed. It is caused by factors including a lack of surface-active compounds, changes in the phospholipid, fatty acid, neutral lipid, and surfactant apoprotein composition, imbalance of the extracellular surfactant subtype distribution, inhibition of surfactant function by plasma protein leakage, incorporation of surfactant phospholipids and apoproteins into polymerizing fibrin, and damage/inhibition of surfactant compounds by inflammatory mediators. There is now good evidence that these surfactant abnormalities promote alveolar instability and collapse and, consequently, loss of compliance and the profound gas exchange abnormalities seen in ARDS. An acute improvement of gas exchange properties together with a far-reaching restoration of surfactant properties was encountered in recently performed pilot studies. Here we summarize what is known about the kind and severity of surfactant changes occuring in ARDS, the contribution of these changes to lung failure, and the role of surfactant administration for therapy of ARDS.

Walmrath Dieter

2001-10-01

385

Permeable Pavement Research at NRMRL?s Urban Watershed Research Facility  

Science.gov (United States)

The results of a bench-scale study of a porous pavement parking lot. Flow rates and total suspended solids (TSS) removal are discussed for systems with a geotextile filter fabric liner in place and those without. The systems with a liner have ~20% better TSS removal performance a...

386

78 FR 26847 - Including Specific Pavement Types in Federal-aid Highway Traffic Noise Analyses  

Science.gov (United States)

...to the Federal eRulemaking portal at http://www.regulations...through the Federal eRulemaking portal at: http://www.regulations...page at: http://www.archives.gov and the Government Printing...Quieter Pavement Systems in Europe,'' and funded several...

2013-05-08

387

Assessment of the performance of rigid pavement back-calculation through finite element modeling  

Science.gov (United States)

This study focuses on examining the behavior of rigid pavement layers during the Falling Weight Deflectometer (FWD) test. Factors affecting the design of a concrete slab, such as whether the joints are doweled or undoweled and the spacing between the transverse joints, were considered in this study. Explicit finite element analysis was employed to investigate pavement layers' responses to the action of the impulse of the FWD test. Models of various dimensions were developed to satisfy the factors under consideration. The accuracy of the finite element models developed in this investigation was verified by comparing the finite element- generated deflection basin with that experimentally measured during an actual test. The results showed that the measured deflection basin can be reproduced through finite element modeling of the pavement structure. The resulting deflection basins from the use FE modeling was processed in order to backcalculate pavement layer moduli. This approach provides a method for the evaluation of the performance of existing backcalculation programs which are based on static elastic layer analysis. Based upon the previous studies conducted for the selection of software, three different backcalculation programs were chosen for the evaluation: MODULUS5.0, EVERCALC4.0, and MODCOMP3. The results indicate that ignoring the dynamic nature of the load may lead to crude results, especially during backcalculation procedures.

Shoukry, Samir N.; William, Gergis W.; Martinelli, David R.

1999-02-01

388

23 CFR 973.208 - Indian lands pavement management system (PMS).  

Science.gov (United States)

...nationwide and tribal PMSs may be based on the concepts described in the AASHTO's “Pavement...basic framework for a PMS: (1) A database and an ongoing program for the collection...to support the PMS. The minimum PMS database shall include: (i) An...

2010-04-01

389

23 CFR 971.208 - Federal lands pavement management system (PMS).  

Science.gov (United States)

... (b) The PMS may be based on the concepts described in the AASHTO's “Pavement...basic framework for a PMS: (1) A database and an ongoing program for the collection...to support the PMS. The minimum PMS database shall include: (i) An...

2010-04-01

390

23 CFR 972.208 - Federal lands pavement management system (PMS).  

Science.gov (United States)

... (b) The PMS may be based on the concepts described in the AASHTO's “Pavement...basic framework for a PMS: (1) A database and an ongoing program for the collection...to support the PMS. The minimum PMS database shall include: (i) An...

2010-04-01

391

Automatic processing and modeling of GPR data for pavement thickness and properties  

Science.gov (United States)

A GSSI SIR-8 with 1 GHz air-launched horn antennas has been modified to acquire data from a moving vehicle. Algorithms have been developed to acquire the data, and to automatically calibrate, position, process, and full waveform model it without operator intervention. Vehicle suspension system bounce is automatically compensated (for varying antenna height). Multiple scans are modeled by full waveform inversion that is remarkably robust and relatively insensitive to noise. Statistical parameters and histograms are generated for the thickness and dielectric permittivity of concrete or asphalt pavements. The statistical uncertainty with which the thickness is determined is given with each thickness measurement, along with the dielectric permittivity of the pavement material and of the subgrade material at each location. Permittivities are then converted into equivalent density and water content. Typical statistical uncertainties in thickness are better than 0.4 cm in 20 cm thick pavement. On a Pentium laptop computer, the data may be processed and modeled to have cross-sectional images and computed pavement thickness displayed in real time at highway speeds.

Olhoeft, Gary R.; Smith, Stanley S., III

2000-04-01

392

Re-Evaluation of the AASHTO-Flexible Pavement Design Equation with Neural Network Modeling.  

Science.gov (United States)

Here we establish that equivalent single-axle loads values can be estimated using artificial neural networks without the complex design equality of American Association of State Highway and Transportation Officials (AASHTO). More importantly, we find that the neural network model gives the coefficients to be able to obtain the actual load values using the AASHTO design values. Thus, those design traffic values that might result in deterioration can be better calculated using the neural networks model than with the AASHTO design equation. The artificial neural network method is used for this purpose. The existing AASHTO flexible pavement design equation does not currently predict the pavement performance of the strategic highway research program (Long Term Pavement Performance studies) test sections very accurately, and typically over-estimates the number of equivalent single axle loads needed to cause a measured loss of the present serviceability index. Here we aimed to demonstrate that the proposed neural network model can more accurately represent the loads values data, compared against the performance of the AASHTO formula. It is concluded that the neural network may be an appropriate tool for the development of databased-nonparametric models of pavement performance. PMID:25397962

Ti?demir, Mesut

2014-01-01

393

Response of pavement to freeze-thaw cycles: Lebanon, New Hampshire, regional airport  

Science.gov (United States)

In 1978 reconstruction was begun on the runway of the Lebanon Regional Airport, Lebanon, New Hampshire. The runway had experienced severe differential frost heaving and cracking during the previous three winters, which had resulted in closure of the facility during periods of extreme roughness. Temperature sensors were placed within the newly constructed pavement sections, and during the winters of 1979, 1980, and 1982 temperature data were recorded, and level surveys and repeated plate bearing tests were performed in order to provide data for the investigation. The three pavement sections were constructed to investigate the effect of section thickness on the level of frost protection provided. The sections consisted of 4 in. of asphalt concrete, 6 in. of crushed gravel and 22,30 dn 38 in. of well-graded sand subbase material. The 48-in section provided the highest level of frost protection to the subgrade. However, all three pavement sections maintained resilient stiffness values during the spring thaw period on the order of two to three times that of the pavement before reconstruction. Also, frost heave in all sections was reduced to levels that would not cause difficulty for aircraft using the facility.

Allen, Wendy L.; Quinn, William F.; Keller, Donald; Eaton, Robert A.

1989-01-01

394

EVALUATION OF RUTTING DEPTH IN FLEXIBLE PAVEMENTS BY USING FINITE ELEMENT ANALYSIS AND LOCAL EMPIRICAL MODEL  

Directory of Open Access Journals (Sweden)

Full Text Available The objective of this research is to predict rut depth in local flexible pavements. Predication model in pavement performance is the process that used to estimate the parameter values which related to pavement structure, environmental condition and traffic loading. The different local empirical models have been used to calculate permanent deformation which include environmental and traffic conditions. Finite element analysis through ANSYS computer software is used to analyze two dimensional linear elastic plane strain problem through (Plane 82 elements. Standard Axle Load (ESAL of 18 kip (80 kN loading on an axle with dual set of tires, the wheel spacing is 13.5 in (343 mm with tire contact pressure of 87 psi (0.6 MPa is used. The pavement system is assumed to be an elastic multi-layers system with each layer being isotropic, homogeneous with specified resilient modulus and Poisson ratio. Each layer is to extend to infinity in the horizontal direction and have a finite thickness except the bottom layer. The analysis of results show that, although, the stress level decrease 14% in the leveling course and 27% in the base course, the rut depth is increased by 12 and 28% in that layers respectively because the material properties is changed.

Alaa H. Abed

2012-01-01

395

Psychological distress among Thai migrant workers in Israel.  

Science.gov (United States)

The purpose of this cross-sectional study was to examine the associations between migration stressors and psychological distress among Thai migrant agricultural workers in Israel, and to examine the direct and indirect contribution of socio-cultural variables to this relationship. Two hundred and twenty-one Thai male workers were interviewed using a structured questionnaire that included demographic variables and occupational exposures to organophosphate pesticides (as control variables), migration stressors, intervening variables (traditional health beliefs, social support, drinking behavior, and utilization of medical services), and a psychological distress scale. In multivariate analysis, migration stressors, the migrants' traditional health beliefs, quality of current social relationships, drinking behavior, as well as age and occupational exposure were significantly associated with psychological distress. Workers who reported higher migration stressors (perceived the migration to be difficult, and often felt homesick), those with higher levels of traditional health beliefs, those whose social relationships with other Thai co-workers were poor, those who consumed either no alcohol or large amounts of alcohol, and those who reported 'problem drinking' had significantly higher levels of psychological distress. A moderating effect of the quality of social relationships with co-workers on the association between homesickness and psychological distress was found. Additionally, migrants aged 28-34 and those who were experiencing eye irritation from chemicals at work had significantly increased levels of distress. The findings demonstrate the focal role of specific migration stressors and the current socio-cultural context on psychological distress of migrant workers. PMID:12850104

Griffin, Jennifer; Soskolne, Varda

2003-09-01

396

Symptom distress of Jordanian patients with cancer receiving chemotherapy.  

Science.gov (United States)

The purpose of this study was to explore the prevalence of symptom distress among Jordanian patients with cancer who are receiving chemotherapy. A total of 112 patients with cancer were evaluated using the Distress Thermometer and clinical symptom problem list, and Demographic and Clinical Characteristic Data Sheet. Patients in the sample were mostly female, and recently diagnosed with cancer during the past 6 months, with a variety of types of cancer with breast cancer being the most common. Patients reported several symptoms with nausea, fatigue, anorexia and daily activity disorder being reported most frequently. Most of the patients (71%) reported distress at a clinically significant level. Distress was correlated with clinical characteristics as treatment number and time. Problems in the areas of family relationships, emotional functioning and physical functioning were associated with higher reports of distress. Identification of the presence of distress is the first step towards referral and treatment of the symptoms that may contribute to the distress of the patient with cancer. PMID:22435975

Omran, Suha; Saeed, Ahmad Mohamad Ahmad; Simpson, Jennifer

2012-04-01

397

Improvements to the materials characterization and fatigue life prediction methods of the Texas rigid pavement overlay design procedure  

Science.gov (United States)

Certain improvements to the Texas Rigid Pavement Overlay Procedure (RPOD2) with regard to materials characterization and fatigue life predictions are presented. Suggestions are made for characterizing rigid pavement layers from Dynaflect deflections and material tests, and some guidelines for selecting design sections along the length of a road are presented. Finite element analysis is used to quantify the effect of pavement discontinuities on the tresses obtained from layered theory. Further finite element analysis is used in an attempt to relate the critical reflection stresses in an ac overlay to deflection measurements obtained before overlaying.

Taute, A.; McCullough, B. F.; Hudon, W. R.

1981-11-01

398

Effects of diurnal temperature dynamics on curing of cold-emulsion reclaimed asphalt pavements  

Directory of Open Access Journals (Sweden)

Full Text Available Strength development in Cold-Emulsion Reclaimed Asphalt Pavements is gradual and largely dependent on the rate at which curing proceeds. Its early life strength is therefore low and presents a major challenge in material specification for mechanistic pavement design. The solution has been to subject a sample of the mixture to be used in the pavement to accelerated laboratory curing to the attainment of Equilibrium Moisture Content (EMC condition. Fatigue and Stiffness parameters of the mix along with the chemical properties of the binder can be determined from the cured samples and results incorporated into the pavement design process. The emphasis is in the choice of a laboratory curing protocol that adequately simulates expected curing trends in the field. Protocols in popular use employ steady state curing temperatures to predict long term behaviour of Reclaimed Asphalt Pavements. This project set out to investigate the likely effects of seasonal variations and diurnal cycles in ambient temperatures on the engineering properties of Reclaimed Asphalt and the incorporated binders. To simulate the above phenomena, a predictive model was adopted in computation of high and low temperature peaks that can be expected in two pavements, one in the tropics and the other in a temperate region. The resulting sets of temperatures were used to cyclically cure Reclaimed Asphalt Pavement cores that were manufactured by artificially aging Dense Bitumen Macadam (DBM in the laboratory and mixing it with a cationic bitumen emulsion. Another set of cores were subjected to steady temperatures as is the current practice. This acted as a control for the two cyclic temperatures under study. Use was made of a suite of tests available in the Nottingham Asphalt Tester (NAT to determine stiffness and fatigue properties of the mix under the three treatments. Bitumen binders recovered at the end of curing was tested for penetration, softening point temperatures and percentage of Asphaltenes. The findings pointed at a likelihood of severe treatment of asphalt samples by the existing laboratory curing protocols. Curing at a steady temperature led to a lower fatigue life, over estimation of early life strength and underestimation of long term strength of the cold asphalt. Low penetration values, high softening point temperatures and high percentages of Asphaltenes in bitumen from the cured samples attest to severe aging of the samples.

Kiplagat Chelelgo

2010-11-01

399

Preschoolers' responses to peers' distress and beliefs about bystander intervention.  

Science.gov (United States)

The spontaneous responses of 27 3-5-yr-olds to the distress of their peers were recorded in the classroom. Individual interviews were also conducted to assess the children's understanding of social norms governing bystander intervention. Findings indicated that the children often paid attention to distressed peers, and many were capable of active intervention. Overall, however, a low rate of prosocial responding was observed. The interviews revealed that the children held systematic beliefs about how to aid a distressed companion, but did not believe they were supposed to help when competent adult caregivers were present. PMID:2708463

Caplan, M Z; Hay, D F

1989-03-01

400